examples: add Android client side caching example app

19 files changed, 1520 insertions, 0 deletions

diff --git a/examples/android/clientcache/app/build.gradle b/examples/android/clientcache/app/build.gradle
new file mode 100644
index 000000000..5c0c647dc
--- /dev/null
+++ b/examples/android/clientcache/app/build.gradle
@@ -0,0 +1,67 @@
+apply plugin: 'com.android.application'
+apply plugin: 'com.google.protobuf'
+
+android {
+    compileSdkVersion 25
+    buildToolsVersion "25.0.2"
+
+    defaultConfig {
+        applicationId "io.grpc.android.clientcacheexample"
+        minSdkVersion 19
+        targetSdkVersion 25
+        multiDexEnabled true
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    buildTypes {
+        release {
+            minifyEnabled true
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+    lintOptions {
+        disable 'InvalidPackage', 'HardcodedText'
+        textReport true
+        textOutput "stdout"
+    }
+}
+
+protobuf {
+    protoc {
+        artifact = 'com.google.protobuf:protoc:3.4.0'
+    }
+    plugins {
+        javalite {
+            artifact = "com.google.protobuf:protoc-gen-javalite:3.0.0"
+        }
+        grpc {
+            artifact = 'io.grpc:protoc-gen-grpc-java:1.9.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+        }
+    }
+    generateProtoTasks {
+        all().each { task ->
+            task.plugins {
+                javalite {}
+                grpc {
+                    // Options added to --grpc_out
+                    option 'lite'
+                }
+            }
+        }
+    }
+}
+
+dependencies {
+    compile 'com.android.support:appcompat-v7:25.0.0'
+
+    // You need to build grpc-java to obtain these libraries below.
+    compile 'io.grpc:grpc-okhttp:1.9.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    compile 'io.grpc:grpc-protobuf-lite:1.9.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    compile 'io.grpc:grpc-stub:1.9.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    compile 'javax.annotation:javax.annotation-api:1.2'
+
+    testCompile 'junit:junit:4.12'
+    testCompile 'com.google.truth:truth:0.28'
+    testCompile 'io.grpc:grpc-testing:1.9.0-SNAPSHOT'
+}
diff --git a/examples/android/clientcache/app/proguard-rules.pro b/examples/android/clientcache/app/proguard-rules.pro
new file mode 100644
index 000000000..1507a5267
--- /dev/null
+++ b/examples/android/clientcache/app/proguard-rules.pro
@@ -0,0 +1,17 @@
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in $ANDROID_HOME/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+-dontwarn com.google.common.**
+# Ignores: can't find referenced class javax.lang.model.element.Modifier
+-dontwarn com.google.errorprone.annotations.**
+-dontwarn javax.naming.**
+-dontwarn okio.**
+-dontwarn sun.misc.Unsafe
diff --git a/examples/android/clientcache/app/src/main/AndroidManifest.xml b/examples/android/clientcache/app/src/main/AndroidManifest.xml
new file mode 100644
index 000000000..d31cbd940
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/AndroidManifest.xml
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="io.grpc.clientcacheexample" >
+
+    <uses-permission android:name="android.permission.INTERNET" />
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:theme="@style/Base.V7.Theme.AppCompat.Light" >
+        <activity
+            android:name="io.grpc.clientcacheexample.ClientCacheExampleActivity"
+            android:label="@string/app_name" >
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>
diff --git a/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/ClientCacheExampleActivity.java b/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/ClientCacheExampleActivity.java
new file mode 100644
index 000000000..831c1030a
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/ClientCacheExampleActivity.java
@@ -0,0 +1,152 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.clientcacheexample;
+
+import android.content.Context;
+import android.os.AsyncTask;
+import android.os.Bundle;
+import android.support.v7.app.AppCompatActivity;
+import android.text.TextUtils;
+import android.text.method.ScrollingMovementMethod;
+import android.util.Log;
+import android.view.View;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.Button;
+import android.widget.CheckBox;
+import android.widget.EditText;
+import android.widget.TextView;
+import io.grpc.CallOptions;
+import io.grpc.Channel;
+import io.grpc.ClientInterceptors;
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.MethodDescriptor;
+import io.grpc.examples.helloworld.GreeterGrpc;
+import io.grpc.examples.helloworld.HelloReply;
+import io.grpc.examples.helloworld.HelloRequest;
+import io.grpc.stub.ClientCalls;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.concurrent.TimeUnit;
+
+public final class ClientCacheExampleActivity extends AppCompatActivity {
+  private static final int CACHE_SIZE_IN_BYTES = 1 * 1024 * 1024; // 1MB
+  private static final String TAG = "grpcCacheExample";
+  private Button mSendButton;
+  private EditText mHostEdit;
+  private EditText mPortEdit;
+  private EditText mMessageEdit;
+  private TextView mResultText;
+  private CheckBox getCheckBox;
+  private CheckBox noCacheCheckBox;
+  private CheckBox onlyIfCachedCheckBox;
+  private SafeMethodCachingInterceptor.Cache cache;
+
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    setContentView(R.layout.activity_clientcacheexample);
+    mSendButton = (Button) findViewById(R.id.send_button);
+    mHostEdit = (EditText) findViewById(R.id.host_edit_text);
+    mPortEdit = (EditText) findViewById(R.id.port_edit_text);
+    mMessageEdit = (EditText) findViewById(R.id.message_edit_text);
+    getCheckBox = (CheckBox) findViewById(R.id.get_checkbox);
+    noCacheCheckBox = (CheckBox) findViewById(R.id.no_cache_checkbox);
+    onlyIfCachedCheckBox = (CheckBox) findViewById(R.id.only_if_cached_checkbox);
+    mResultText = (TextView) findViewById(R.id.grpc_response_text);
+    mResultText.setMovementMethod(new ScrollingMovementMethod());
+
+    cache = SafeMethodCachingInterceptor.newLruCache(CACHE_SIZE_IN_BYTES);
+  }
+
+  /** Sends RPC. Invoked when app button is pressed. */
+  public void sendMessage(View view) {
+    ((InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE))
+        .hideSoftInputFromWindow(mHostEdit.getWindowToken(), 0);
+    mSendButton.setEnabled(false);
+    new GrpcTask().execute();
+  }
+
+  private class GrpcTask extends AsyncTask<Void, Void, String> {
+    private String host;
+    private String message;
+    private int port;
+    private ManagedChannel channel;
+
+    @Override
+    protected void onPreExecute() {
+      host = mHostEdit.getText().toString();
+      message = mMessageEdit.getText().toString();
+      String portStr = mPortEdit.getText().toString();
+      port = TextUtils.isEmpty(portStr) ? 0 : Integer.valueOf(portStr);
+      mResultText.setText("");
+    }
+
+    @Override
+    protected String doInBackground(Void... nothing) {
+      try {
+        channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext(true).build();
+        Channel channelToUse =
+            ClientInterceptors.intercept(
+                channel, SafeMethodCachingInterceptor.newSafeMethodCachingInterceptor(cache));
+        HelloRequest message = HelloRequest.newBuilder().setName(this.message).build();
+        HelloReply reply;
+        if (getCheckBox.isChecked()) {
+          MethodDescriptor<HelloRequest, HelloReply> safeCacheableUnaryCallMethod =
+              GreeterGrpc.getSayHelloMethod().toBuilder().setSafe(true).build();
+          CallOptions callOptions = CallOptions.DEFAULT;
+          if (noCacheCheckBox.isChecked()) {
+            callOptions =
+                callOptions.withOption(SafeMethodCachingInterceptor.NO_CACHE_CALL_OPTION, true);
+          }
+          if (onlyIfCachedCheckBox.isChecked()) {
+            callOptions =
+                callOptions.withOption(
+                    SafeMethodCachingInterceptor.ONLY_IF_CACHED_CALL_OPTION, true);
+          }
+          reply =
+              ClientCalls.blockingUnaryCall(
+                  channelToUse, safeCacheableUnaryCallMethod, callOptions, message);
+        } else {
+          GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(channelToUse);
+          reply = stub.sayHello(message);
+        }
+        return reply.getMessage();
+      } catch (Exception e) {
+        Log.e(TAG, "RPC failed", e);
+        StringWriter sw = new StringWriter();
+        PrintWriter pw = new PrintWriter(sw);
+        e.printStackTrace(pw);
+        pw.flush();
+        return String.format("Failed... : %n%s", sw);
+      }
+    }
+
+    @Override
+    protected void onPostExecute(String result) {
+      if (channel != null) {
+        try {
+          channel.shutdown().awaitTermination(1, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+          Thread.currentThread().interrupt();
+        }
+      }
+      mResultText.setText(result);
+      mSendButton.setEnabled(true);
+    }
+  }
+}
diff --git a/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptor.java b/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptor.java
new file mode 100644
index 000000000..4ae0c01c5
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptor.java
@@ -0,0 +1,300 @@
+package io.grpc.clientcacheexample;
+
+import android.util.Log;
+import android.util.LruCache;
+import com.google.common.base.Splitter;
+import com.google.protobuf.MessageLite;
+import io.grpc.CallOptions;
+import io.grpc.Channel;
+import io.grpc.ClientCall;
+import io.grpc.ClientInterceptor;
+import io.grpc.Deadline;
+import io.grpc.ForwardingClientCall;
+import io.grpc.ForwardingClientCallListener;
+import io.grpc.Metadata;
+import io.grpc.MethodDescriptor;
+import io.grpc.Status;
+import java.util.Objects;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * An example of an on-device cache for Android implemented using the {@link ClientInterceptor} API.
+ *
+ * <p>Client-side cache-control directives are not directly supported. Instead, two call options can
+ * be added to the call: no-cache (always go to the network) or only-if-cached (never use network;
+ * if response is not in cache, the request fails).
+ *
+ * <p>This interceptor respects the cache-control directives in the server's response: max-age
+ * determines when the cache entry goes stale. no-cache, no-store, and no-transform entirely skip
+ * caching of the response. must-revalidate is ignored, as the cache does not support returning
+ * stale responses.
+ *
+ * <p>Note: other response headers besides cache-control (such as Expiration, Varies) are ignored by
+ * this implementation.
+ */
+final class SafeMethodCachingInterceptor implements ClientInterceptor {
+  static CallOptions.Key<Boolean> NO_CACHE_CALL_OPTION = CallOptions.Key.of("no-cache", false);
+  static CallOptions.Key<Boolean> ONLY_IF_CACHED_CALL_OPTION =
+      CallOptions.Key.of("only-if-cached", false);
+  private static final String TAG = "grpcCacheExample";
+
+  public static final class Key {
+    private final String fullMethodName;
+    private final MessageLite request;
+
+    public Key(String fullMethodName, MessageLite request) {
+      this.fullMethodName = fullMethodName;
+      this.request = request;
+    }
+
+    @Override
+    public boolean equals(Object object) {
+      if (object instanceof Key) {
+        Key other = (Key) object;
+        return Objects.equals(this.fullMethodName, other.fullMethodName)
+            && Objects.equals(this.request, other.request);
+      }
+      return false;
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(fullMethodName, request);
+    }
+  }
+
+  public static final class Value {
+    private final MessageLite response;
+    private final Deadline maxAgeDeadline;
+
+    public Value(MessageLite response, Deadline maxAgeDeadline) {
+      this.response = response;
+      this.maxAgeDeadline = maxAgeDeadline;
+    }
+
+    @Override
+    public boolean equals(Object object) {
+      if (object instanceof Value) {
+        Value other = (Value) object;
+        return Objects.equals(this.response, other.response)
+            && Objects.equals(this.maxAgeDeadline, other.maxAgeDeadline);
+      }
+      return false;
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(response, maxAgeDeadline);
+    }
+  }
+
+  public interface Cache {
+    void put(Key key, Value value);
+
+    Value get(Key key);
+
+    void remove(Key key);
+
+    void clear();
+  }
+
+  /**
+   * Obtain a new cache with a least-recently used eviction policy and the specified size limit. The
+   * backing caching implementation is provided by {@link LruCache}. It is safe for a single cache
+   * to be shared across multiple {@link SafeMethodCachingInterceptor}s without synchronization.
+   */
+  public static Cache newLruCache(final int cacheSizeInBytes) {
+    return new Cache() {
+      private final LruCache<Key, Value> lruCache =
+          new LruCache<Key, Value>(cacheSizeInBytes) {
+            protected int sizeOf(Key key, Value value) {
+              return value.response.getSerializedSize();
+            }
+          };
+
+      @Override
+      public void put(Key key, Value value) {
+        lruCache.put(key, value);
+      }
+
+      @Override
+      public Value get(Key key) {
+        return lruCache.get(key);
+      }
+
+      @Override
+      public void remove(Key key) {
+        lruCache.remove(key);
+      }
+
+      @Override
+      public void clear() {
+        lruCache.evictAll();
+      }
+    };
+  }
+
+  public static SafeMethodCachingInterceptor newSafeMethodCachingInterceptor(Cache cache) {
+    return newSafeMethodCachingInterceptor(cache, DEFAULT_MAX_AGE_SECONDS);
+  }
+
+  public static SafeMethodCachingInterceptor newSafeMethodCachingInterceptor(
+      Cache cache, int defaultMaxAge) {
+    return new SafeMethodCachingInterceptor(cache, defaultMaxAge);
+  }
+
+  private static int DEFAULT_MAX_AGE_SECONDS = 3600;
+
+  private static final Metadata.Key<String> CACHE_CONTROL_KEY =
+      Metadata.Key.of("cache-control", Metadata.ASCII_STRING_MARSHALLER);
+
+  private static final Splitter CACHE_CONTROL_SPLITTER =
+      Splitter.on(',').trimResults().omitEmptyStrings();
+
+  private final Cache internalCache;
+  private final int defaultMaxAge;
+
+  private SafeMethodCachingInterceptor(Cache cache, int defaultMaxAge) {
+    this.internalCache = cache;
+    this.defaultMaxAge = defaultMaxAge;
+  }
+
+  @Override
+  public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
+      final MethodDescriptor<ReqT, RespT> method, final CallOptions callOptions, Channel next) {
+    // Currently only unary methods can be marked safe, but check anyways.
+    if (!method.isSafe() || method.getType() != MethodDescriptor.MethodType.UNARY) {
+      return next.newCall(method, callOptions);
+    }
+
+    final String fullMethodName = method.getFullMethodName();
+
+    return new ForwardingClientCall.SimpleForwardingClientCall<ReqT, RespT>(
+        next.newCall(method, callOptions)) {
+      private Listener<RespT> interceptedListener;
+      private Key requestKey;
+      private boolean cacheResponse = true;
+      private volatile String cacheOptionsErrorMsg;
+
+      @Override
+      public void start(Listener<RespT> responseListener, Metadata headers) {
+        interceptedListener =
+            new ForwardingClientCallListener.SimpleForwardingClientCallListener<RespT>(
+                responseListener) {
+              private Deadline deadline;
+              private int maxAge = -1;
+
+              @Override
+              public void onHeaders(Metadata headers) {
+                Iterable<String> cacheControlHeaders = headers.getAll(CACHE_CONTROL_KEY);
+                if (cacheResponse && cacheControlHeaders != null) {
+                  for (String cacheControlHeader : cacheControlHeaders) {
+                    for (String directive : CACHE_CONTROL_SPLITTER.split(cacheControlHeader)) {
+                      if (directive.equalsIgnoreCase("no-cache")) {
+                        cacheResponse = false;
+                        break;
+                      } else if (directive.equalsIgnoreCase("no-store")) {
+                        cacheResponse = false;
+                        break;
+                      } else if (directive.equalsIgnoreCase("no-transform")) {
+                        cacheResponse = false;
+                        break;
+                      } else if (directive.toLowerCase().startsWith("max-age")) {
+                        String[] parts = directive.split("=");
+                        if (parts.length == 2) {
+                          try {
+                            maxAge = Integer.parseInt(parts[1]);
+                          } catch (NumberFormatException e) {
+                            Log.e(TAG, "max-age directive failed to parse", e);
+                            continue;
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+                if (cacheResponse) {
+                  if (maxAge > -1) {
+                    deadline = Deadline.after(maxAge, TimeUnit.SECONDS);
+                  } else {
+                    deadline = Deadline.after(defaultMaxAge, TimeUnit.SECONDS);
+                  }
+                }
+                super.onHeaders(headers);
+              }
+
+              @Override
+              public void onMessage(RespT message) {
+                if (cacheResponse && !deadline.isExpired()) {
+                  Value value = new Value((MessageLite) message, deadline);
+                  internalCache.put(requestKey, value);
+                }
+                super.onMessage(message);
+              }
+
+              @Override
+              public void onClose(Status status, Metadata trailers) {
+                if (cacheOptionsErrorMsg != null) {
+                  // UNAVAILABLE is the canonical gRPC mapping for HTTP response code 504 (as used
+                  // by the built-in Android HTTP request cache).
+                  super.onClose(
+                      Status.UNAVAILABLE.withDescription(cacheOptionsErrorMsg), new Metadata());
+                } else {
+                  super.onClose(status, trailers);
+                }
+              }
+            };
+        delegate().start(interceptedListener, headers);
+      }
+
+      @Override
+      public void sendMessage(ReqT message) {
+        boolean noCache = callOptions.getOption(NO_CACHE_CALL_OPTION);
+        boolean onlyIfCached = callOptions.getOption(ONLY_IF_CACHED_CALL_OPTION);
+
+        if (noCache) {
+          if (onlyIfCached) {
+            cacheOptionsErrorMsg = "Unsatisfiable Request (no-cache and only-if-cached conflict)";
+            super.cancel(cacheOptionsErrorMsg, null);
+            return;
+          }
+          cacheResponse = false;
+          super.sendMessage(message);
+          return;
+        }
+
+        // Check the cache
+        requestKey = new Key(fullMethodName, (MessageLite) message);
+        Value cachedResponse = internalCache.get(requestKey);
+        if (cachedResponse != null) {
+          if (cachedResponse.maxAgeDeadline.isExpired()) {
+            internalCache.remove(requestKey);
+          } else {
+            cacheResponse = false; // already cached
+            interceptedListener.onMessage((RespT) cachedResponse.response);
+            Metadata metadata = new Metadata();
+            interceptedListener.onClose(Status.OK, metadata);
+            return;
+          }
+        }
+
+        if (onlyIfCached) {
+          cacheOptionsErrorMsg =
+              "Unsatisfiable Request (only-if-cached set, but value not in cache)";
+          super.cancel(cacheOptionsErrorMsg, null);
+          return;
+        }
+        super.sendMessage(message);
+      }
+
+      @Override
+      public void halfClose() {
+        if (cacheOptionsErrorMsg != null) {
+          // already canceled
+          return;
+        }
+        super.halfClose();
+      }
+    };
+  }
+}
diff --git a/examples/android/clientcache/app/src/main/proto/helloworld.proto b/examples/android/clientcache/app/src/main/proto/helloworld.proto
new file mode 100644
index 000000000..7469e1e47
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/proto/helloworld.proto
@@ -0,0 +1,45 @@
+// Copyright 2015, gRPC Authors
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// 
+//     http://www.apache.org/licenses/LICENSE-2.0
+// 
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.grpc.examples.helloworld";
+option java_outer_classname = "HelloWorldProto";
+option objc_class_prefix = "HLW";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+
+  rpc SayAnotherHello (HelloRequest) returns (HelloReply) {}
+
+}
+
+service AnotherGreeter {
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}
diff --git a/examples/android/clientcache/app/src/main/res/layout/activity_clientcacheexample.xml b/examples/android/clientcache/app/src/main/res/layout/activity_clientcacheexample.xml
new file mode 100644
index 000000000..2e48e8a27
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/layout/activity_clientcacheexample.xml
@@ -0,0 +1,73 @@
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
+              android:layout_height="match_parent"
+              tools:context=".MainActivity"
+              android:orientation="vertical" >
+
+    <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal">
+        <EditText
+                android:id="@+id/host_edit_text"
+                android:layout_weight="2"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:hint="Enter Host" />
+        <EditText
+                android:id="@+id/port_edit_text"
+                android:layout_weight="1"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:inputType="numberDecimal"
+                android:hint="Enter Port" />
+    </LinearLayout>
+
+
+    <EditText
+            android:id="@+id/message_edit_text"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="Enter message to send" />
+
+    <CheckBox android:id="@+id/get_checkbox"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Use GET"
+        />
+
+    <CheckBox android:id="@+id/no_cache_checkbox"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Cache-control: no-cache (only for GET)"
+        />
+
+    <CheckBox android:id="@+id/only_if_cached_checkbox"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Cache-control: only-if-cached (only for GET)"
+        />
+
+    <Button
+            android:id="@+id/send_button"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:onClick="sendMessage"
+            android:text="Send Grpc Request" />
+
+    <TextView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:paddingTop="12dp"
+            android:paddingBottom="12dp"
+            android:textSize="16sp"
+            android:text="Response:" />
+
+    <TextView
+            android:id="@+id/grpc_response_text"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:scrollbars = "vertical"
+            android:textSize="16sp" />
+
+</LinearLayout>
diff --git a/examples/android/clientcache/app/src/main/res/mipmap-hdpi/ic_launcher.png b/examples/android/clientcache/app/src/main/res/mipmap-hdpi/ic_launcher.png
new file mode 100644
index 000000000..cde69bccc
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/mipmap-hdpi/ic_launcher.png
diff --git a/examples/android/clientcache/app/src/main/res/mipmap-mdpi/ic_launcher.png b/examples/android/clientcache/app/src/main/res/mipmap-mdpi/ic_launcher.png
new file mode 100644
index 000000000..c133a0cbd
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/mipmap-mdpi/ic_launcher.png
diff --git a/examples/android/clientcache/app/src/main/res/mipmap-xhdpi/ic_launcher.png b/examples/android/clientcache/app/src/main/res/mipmap-xhdpi/ic_launcher.png
new file mode 100644
index 000000000..bfa42f0e7
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/mipmap-xhdpi/ic_launcher.png
diff --git a/examples/android/clientcache/app/src/main/res/mipmap-xxhdpi/ic_launcher.png b/examples/android/clientcache/app/src/main/res/mipmap-xxhdpi/ic_launcher.png
new file mode 100644
index 000000000..324e72cdd
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/mipmap-xxhdpi/ic_launcher.png
diff --git a/examples/android/clientcache/app/src/main/res/values/strings.xml b/examples/android/clientcache/app/src/main/res/values/strings.xml
new file mode 100644
index 000000000..0f8d82d95
--- /dev/null
+++ b/examples/android/clientcache/app/src/main/res/values/strings.xml
@@ -0,0 +1,3 @@
+<resources>
+    <string name="app_name">GrpcClientCacheExample</string>
+</resources>
diff --git a/examples/android/clientcache/app/src/test/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptorTest.java b/examples/android/clientcache/app/src/test/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptorTest.java
new file mode 100644
index 000000000..4fd5bdb0c
--- /dev/null
+++ b/examples/android/clientcache/app/src/test/java/io/grpc/clientcacheexample/SafeMethodCachingInterceptorTest.java
@@ -0,0 +1,557 @@
+package io.grpc.clientcacheexample;
+
+import com.google.common.truth.Truth;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.fail;
+
+import io.grpc.CallOptions;
+import io.grpc.Channel;
+import io.grpc.ClientInterceptors;
+import io.grpc.ForwardingServerCall;
+import io.grpc.ManagedChannel;
+import io.grpc.Metadata;
+import io.grpc.MethodDescriptor;
+import io.grpc.ServerCall;
+import io.grpc.ServerCallHandler;
+import io.grpc.ServerInterceptor;
+import io.grpc.ServerInterceptors;
+import io.grpc.Status;
+import io.grpc.StatusRuntimeException;
+import io.grpc.examples.helloworld.AnotherGreeterGrpc;
+import io.grpc.examples.helloworld.GreeterGrpc;
+import io.grpc.examples.helloworld.HelloReply;
+import io.grpc.examples.helloworld.HelloRequest;
+import io.grpc.stub.ClientCalls;
+import io.grpc.stub.StreamObserver;
+import io.grpc.testing.GrpcServerRule;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+public class SafeMethodCachingInterceptorTest {
+  private static final Metadata.Key<String> CACHE_CONTROL_METADATA_KEY =
+      Metadata.Key.of("cache-control", Metadata.ASCII_STRING_MARSHALLER);
+
+  @Rule public final GrpcServerRule grpcServerRule = new GrpcServerRule().directExecutor();
+
+  private final GreeterGrpc.GreeterImplBase greeterServiceImpl =
+      new GreeterGrpc.GreeterImplBase() {
+        private int count = 1;
+
+        @Override
+        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+          HelloReply reply =
+              HelloReply.newBuilder().setMessage("Hello " + req.getName() + " " + count++).build();
+          responseObserver.onNext(reply);
+          responseObserver.onCompleted();
+        }
+
+        @Override
+        public void sayAnotherHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+          HelloReply reply =
+              HelloReply.newBuilder()
+                  .setMessage("Hello again " + req.getName() + " " + count++)
+                  .build();
+          responseObserver.onNext(reply);
+          responseObserver.onCompleted();
+        }
+      };
+
+  private final AnotherGreeterGrpc.AnotherGreeterImplBase anotherGreeterServiceImpl =
+      new AnotherGreeterGrpc.AnotherGreeterImplBase() {
+        private int count = 1;
+
+        @Override
+        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+          HelloReply reply =
+              HelloReply.newBuilder().setMessage("Hey " + req.getName() + " " + count++).build();
+          responseObserver.onNext(reply);
+          responseObserver.onCompleted();
+        }
+      };
+
+  private final List<String> cacheControlDirectives = new ArrayList<String>();
+  private ServerInterceptor injectCacheControlInterceptor =
+      new ServerInterceptor() {
+        @Override
+        public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
+            ServerCall<ReqT, RespT> call,
+            final Metadata requestHeaders,
+            ServerCallHandler<ReqT, RespT> next) {
+          return next.startCall(
+              new ForwardingServerCall.SimpleForwardingServerCall<ReqT, RespT>(call) {
+                @Override
+                public void sendHeaders(Metadata headers) {
+                  for (String cacheControlDirective : cacheControlDirectives) {
+                    headers.put(CACHE_CONTROL_METADATA_KEY, cacheControlDirective);
+                  }
+                  super.sendHeaders(headers);
+                }
+              },
+              requestHeaders);
+        }
+      };
+
+  private final HelloRequest message = HelloRequest.newBuilder().setName("Test Name").build();
+  private final MethodDescriptor<HelloRequest, HelloReply> safeGreeterSayHelloMethod =
+      GreeterGrpc.getSayHelloMethod().toBuilder().setSafe(true).build();
+  private final TestCache cache = new TestCache();
+
+  private ManagedChannel baseChannel;
+  private Channel channelToUse;
+
+  @Before
+  public void setUp() throws Exception {
+    grpcServerRule
+        .getServiceRegistry()
+        .addService(
+            ServerInterceptors.intercept(greeterServiceImpl, injectCacheControlInterceptor));
+    grpcServerRule.getServiceRegistry().addService(anotherGreeterServiceImpl);
+    baseChannel = grpcServerRule.getChannel();
+
+    SafeMethodCachingInterceptor interceptor =
+        SafeMethodCachingInterceptor.newSafeMethodCachingInterceptor(cache);
+
+    channelToUse = ClientInterceptors.intercept(baseChannel, interceptor);
+  }
+
+  @After
+  public void tearDown() {
+    baseChannel.shutdown();
+  }
+
+  @Test
+  public void safeCallsAreCached() {
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertSame(reply1, reply2);
+  }
+
+  @Test
+  public void safeCallsAreCachedWithCopiedMethodDescriptor() {
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse,
+            safeGreeterSayHelloMethod.toBuilder().build(),
+            CallOptions.DEFAULT,
+            message);
+
+    assertSame(reply1, reply2);
+  }
+
+  @Test
+  public void requestWithNoCacheOptionSkipsCache() {
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse,
+            safeGreeterSayHelloMethod,
+            CallOptions.DEFAULT.withOption(SafeMethodCachingInterceptor.NO_CACHE_CALL_OPTION, true),
+            message);
+    HelloReply reply3 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    assertSame(reply1, reply3);
+  }
+
+  @Test
+  public void requestWithOnlyIfCachedOption_unavailableIfNotInCache() {
+    try {
+      ClientCalls.blockingUnaryCall(
+          channelToUse,
+          safeGreeterSayHelloMethod,
+          CallOptions.DEFAULT.withOption(
+              SafeMethodCachingInterceptor.ONLY_IF_CACHED_CALL_OPTION, true),
+          message);
+      fail("Expected call to fail");
+    } catch (StatusRuntimeException sre) {
+      assertEquals(Status.UNAVAILABLE.getCode(), sre.getStatus().getCode());
+      assertEquals(
+          "Unsatisfiable Request (only-if-cached set, but value not in cache)",
+          sre.getStatus().getDescription());
+    }
+  }
+
+  @Test
+  public void requestWithOnlyIfCachedOption_usesCache() {
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse,
+            safeGreeterSayHelloMethod,
+            CallOptions.DEFAULT.withOption(
+                SafeMethodCachingInterceptor.ONLY_IF_CACHED_CALL_OPTION, true),
+            message);
+
+    assertSame(reply1, reply2);
+  }
+
+  @Test
+  public void requestWithNoCacheAndOnlyIfCached_fails() {
+    try {
+      ClientCalls.blockingUnaryCall(
+          channelToUse,
+          safeGreeterSayHelloMethod,
+          CallOptions.DEFAULT
+              .withOption(SafeMethodCachingInterceptor.NO_CACHE_CALL_OPTION, true)
+              .withOption(SafeMethodCachingInterceptor.ONLY_IF_CACHED_CALL_OPTION, true),
+          message);
+      fail("Expected call to fail");
+    } catch (StatusRuntimeException sre) {
+      assertEquals(Status.UNAVAILABLE.getCode(), sre.getStatus().getCode());
+      assertEquals(
+          "Unsatisfiable Request (no-cache and only-if-cached conflict)",
+          sre.getStatus().getDescription());
+    }
+  }
+
+  @Test
+  public void responseNoCacheDirective_notCached() throws Exception {
+    cacheControlDirectives.add("no-cache");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void responseNoStoreDirective_notCached() throws Exception {
+    cacheControlDirectives.add("no-store");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void responseNoTransformDirective_notCached() throws Exception {
+    cacheControlDirectives.add("no-transform");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void responseMustRevalidateDirective_isIgnored() throws Exception {
+    cacheControlDirectives.add("must-revalidate");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertSame(reply1, reply2);
+  }
+
+  @Test
+  public void responseMaxAge_caseInsensitive() throws Exception {
+    cacheControlDirectives.add("MaX-aGe=0");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void responseNoCache_caseInsensitive() throws Exception {
+    cacheControlDirectives.add("No-CaCHe");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void combinedResponseCacheControlDirectives_parsesWithoutError() throws Exception {
+    cacheControlDirectives.add("max-age=1,no-store , no-cache");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void separateResponseCacheControlDirectives_parsesWithoutError() throws Exception {
+    cacheControlDirectives.add("max-age=1");
+    cacheControlDirectives.add("no-store , no-cache");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void afterResponseMaxAge_cacheEntryInvalidated() throws Exception {
+    cacheControlDirectives.add("max-age=1");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    assertSame(reply1, reply2);
+
+    // Wait for cache entry to expire
+    sleepAtLeast(1001);
+
+    assertNotEquals(
+        reply1,
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message));
+    Truth.assertThat(cache.removedKeys).hasSize(1);
+    assertEquals(
+        new SafeMethodCachingInterceptor.Key(
+            GreeterGrpc.getSayHelloMethod().getFullMethodName(), message),
+        cache.removedKeys.get(0));
+  }
+
+  @Test
+  public void invalidResponseMaxAge_usesDefault() throws Exception {
+    SafeMethodCachingInterceptor interceptorWithCustomMaxAge =
+        SafeMethodCachingInterceptor.newSafeMethodCachingInterceptor(cache, 1);
+    channelToUse = ClientInterceptors.intercept(baseChannel, interceptorWithCustomMaxAge);
+    cacheControlDirectives.add("max-age=-10");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    assertEquals(reply1, reply2);
+
+    // Wait for cache entry to expire
+    sleepAtLeast(1001);
+
+    assertNotEquals(
+        reply1,
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message));
+    Truth.assertThat(cache.removedKeys).hasSize(1);
+    assertEquals(
+        new SafeMethodCachingInterceptor.Key(
+            GreeterGrpc.getSayHelloMethod().getFullMethodName(), message),
+        cache.removedKeys.get(0));
+  }
+
+  @Test
+  public void responseMaxAgeZero_notAddedToCache() throws Exception {
+    cacheControlDirectives.add("max-age=0");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+    Truth.assertThat(cache.internalCache).isEmpty();
+    Truth.assertThat(cache.removedKeys).isEmpty();
+  }
+
+  @Test
+  public void cacheHit_doesNotResetExpiration() throws Exception {
+    cacheControlDirectives.add("max-age=1");
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    sleepAtLeast(1001);
+
+    HelloReply reply3 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+
+    assertSame(reply1, reply2);
+    assertNotEquals(reply1, reply3);
+    Truth.assertThat(cache.internalCache).hasSize(1);
+    Truth.assertThat(cache.removedKeys).hasSize(1);
+  }
+
+  @Test
+  public void afterDefaultMaxAge_cacheEntryInvalidated() throws Exception {
+    SafeMethodCachingInterceptor interceptorWithCustomMaxAge =
+        SafeMethodCachingInterceptor.newSafeMethodCachingInterceptor(cache, 1);
+    channelToUse = ClientInterceptors.intercept(baseChannel, interceptorWithCustomMaxAge);
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    assertSame(reply1, reply2);
+
+    // Wait for cache entry to expire
+    sleepAtLeast(1001);
+
+    assertNotEquals(
+        reply1,
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message));
+    Truth.assertThat(cache.removedKeys).hasSize(1);
+    assertEquals(
+        new SafeMethodCachingInterceptor.Key(
+            GreeterGrpc.getSayHelloMethod().getFullMethodName(), message),
+        cache.removedKeys.get(0));
+  }
+
+  @Test
+  public void unsafeCallsAreNotCached() {
+    GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(channelToUse);
+
+    HelloReply reply1 = stub.sayHello(message);
+    HelloReply reply2 = stub.sayHello(message);
+
+    assertNotEquals(reply1, reply2);
+  }
+
+  @Test
+  public void differentMethodCallsAreNotConflated() {
+    MethodDescriptor<HelloRequest, HelloReply> anotherSafeMethod =
+        GreeterGrpc.getSayAnotherHelloMethod().toBuilder().setSafe(true).build();
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, anotherSafeMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+  }
+
+  @Test
+  public void differentServiceCallsAreNotConflated() {
+    MethodDescriptor<HelloRequest, HelloReply> anotherSafeMethod =
+        AnotherGreeterGrpc.getSayHelloMethod().toBuilder().setSafe(true).build();
+
+    HelloReply reply1 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, safeGreeterSayHelloMethod, CallOptions.DEFAULT, message);
+    HelloReply reply2 =
+        ClientCalls.blockingUnaryCall(
+            channelToUse, anotherSafeMethod, CallOptions.DEFAULT, message);
+
+    assertNotEquals(reply1, reply2);
+  }
+
+  private static void sleepAtLeast(long millis) throws InterruptedException {
+    long delay = TimeUnit.MILLISECONDS.toNanos(millis);
+    long end = System.nanoTime() + delay;
+    while (delay > 0) {
+      TimeUnit.NANOSECONDS.sleep(delay);
+      delay = end - System.nanoTime();
+    }
+  }
+
+  private static class TestCache implements SafeMethodCachingInterceptor.Cache {
+    private Map<SafeMethodCachingInterceptor.Key, SafeMethodCachingInterceptor.Value>
+        internalCache =
+            new HashMap<SafeMethodCachingInterceptor.Key, SafeMethodCachingInterceptor.Value>();
+    private List<SafeMethodCachingInterceptor.Key> removedKeys =
+        new ArrayList<SafeMethodCachingInterceptor.Key>();
+
+    @Override
+    public void put(
+        SafeMethodCachingInterceptor.Key key, SafeMethodCachingInterceptor.Value value) {
+      internalCache.put(key, value);
+    }
+
+    @Override
+    public SafeMethodCachingInterceptor.Value get(SafeMethodCachingInterceptor.Key key) {
+      return internalCache.get(key);
+    }
+
+    @Override
+    public void remove(SafeMethodCachingInterceptor.Key key) {
+      removedKeys.add(key);
+      internalCache.remove(key);
+    }
+
+    @Override
+    public void clear() {}
+  }
+}
diff --git a/examples/android/clientcache/build.gradle b/examples/android/clientcache/build.gradle
new file mode 100644
index 000000000..be0b49fe9
--- /dev/null
+++ b/examples/android/clientcache/build.gradle
@@ -0,0 +1,21 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+
+buildscript {
+    repositories {
+        jcenter()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:2.3.1'
+        classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.1"
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        jcenter()
+        mavenLocal()
+    }
+}
diff --git a/examples/android/clientcache/gradle/wrapper/gradle-wrapper.jar b/examples/android/clientcache/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 000000000..36823b7ec
--- /dev/null
+++ b/examples/android/clientcache/gradle/wrapper/gradle-wrapper.jar
diff --git a/examples/android/clientcache/gradle/wrapper/gradle-wrapper.properties b/examples/android/clientcache/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 000000000..37c7766f3
--- /dev/null
+++ b/examples/android/clientcache/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Tue Jul 11 13:59:44 PDT 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip
diff --git a/examples/android/clientcache/gradlew b/examples/android/clientcache/gradlew
new file mode 100755
index 000000000..cccdd3d51
--- /dev/null
+++ b/examples/android/clientcache/gradlew
@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"
diff --git a/examples/android/clientcache/gradlew.bat b/examples/android/clientcache/gradlew.bat
new file mode 100644
index 000000000..e95643d6a
--- /dev/null
+++ b/examples/android/clientcache/gradlew.bat
@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off

+@rem ##########################################################################

+@rem

+@rem  Gradle startup script for Windows

+@rem

+@rem ##########################################################################

+

+@rem Set local scope for the variables with windows NT shell

+if "%OS%"=="Windows_NT" setlocal

+

+set DIRNAME=%~dp0

+if "%DIRNAME%" == "" set DIRNAME=.

+set APP_BASE_NAME=%~n0

+set APP_HOME=%DIRNAME%

+

+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.

+set DEFAULT_JVM_OPTS=

+

+@rem Find java.exe

+if defined JAVA_HOME goto findJavaFromJavaHome

+

+set JAVA_EXE=java.exe

+%JAVA_EXE% -version >NUL 2>&1

+if "%ERRORLEVEL%" == "0" goto init

+

+echo.

+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

+echo.

+echo Please set the JAVA_HOME variable in your environment to match the

+echo location of your Java installation.

+

+goto fail

+

+:findJavaFromJavaHome

+set JAVA_HOME=%JAVA_HOME:"=%

+set JAVA_EXE=%JAVA_HOME%/bin/java.exe

+

+if exist "%JAVA_EXE%" goto init

+

+echo.

+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%

+echo.

+echo Please set the JAVA_HOME variable in your environment to match the

+echo location of your Java installation.

+

+goto fail

+

+:init

+@rem Get command-line arguments, handling Windows variants

+

+if not "%OS%" == "Windows_NT" goto win9xME_args

+

+:win9xME_args

+@rem Slurp the command line arguments.

+set CMD_LINE_ARGS=

+set _SKIP=2

+

+:win9xME_args_slurp

+if "x%~1" == "x" goto execute

+

+set CMD_LINE_ARGS=%*

+

+:execute

+@rem Setup the command line

+

+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar

+

+@rem Execute Gradle

+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%

+

+:end

+@rem End local scope for the variables with windows NT shell

+if "%ERRORLEVEL%"=="0" goto mainEnd

+

+:fail

+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of

+rem the _cmd.exe /c_ return code!

+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1

+exit /b 1

+

+:mainEnd

+if "%OS%"=="Windows_NT" endlocal

+

+:omega

diff --git a/examples/android/clientcache/settings.gradle b/examples/android/clientcache/settings.gradle
new file mode 100644
index 000000000..e7b4def49
--- /dev/null
+++ b/examples/android/clientcache/settings.gradle
@@ -0,0 +1 @@
+include ':app'