buildscripts,travis: fetch from mvn with retries (#4140)

A band aid for #3284, to make its symptoms less noticeable. 

15 files changed, 67 insertions, 23 deletions

diff --git a/all/build.gradle b/all/build.gradle
index 138795323..95942b4dd 100644
--- a/all/build.gradle
+++ b/all/build.gradle
@@ -4,7 +4,10 @@ description = "gRPC: All"
 
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath 'org.kt3k.gradle.plugin:coveralls-gradle-plugin:2.0.1'
diff --git a/alts/build.gradle b/alts/build.gradle
index c73a9a082..601ebb486 100644
--- a/alts/build.gradle
+++ b/alts/build.gradle
@@ -5,7 +5,10 @@ targetCompatibility = 1.7
 
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/benchmarks/build.gradle b/benchmarks/build.gradle
index 221dd95ad..11d943ddb 100644
--- a/benchmarks/build.gradle
+++ b/benchmarks/build.gradle
@@ -1,6 +1,9 @@
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/build.gradle b/build.gradle
index f2856893e..7e5d0096f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,5 @@
 buildscript {
   repositories {
-    mavenCentral()
     mavenLocal()
     maven {
       url "https://plugins.gradle.org/m2/"
@@ -59,11 +58,11 @@ subprojects {
     targetCompatibility = 1.6
 
     repositories {
-        mavenCentral()
-        mavenLocal()
         maven {
-          url "https://oss.sonatype.org/content/repositories/snapshots/"
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
         }
+        mavenLocal()
     }
 
     [compileJava, compileTestJava, compileJmhJava].each() {
diff --git a/compiler/build.gradle b/compiler/build.gradle
index 803370b80..1fef805fa 100644
--- a/compiler/build.gradle
+++ b/compiler/build.gradle
@@ -5,7 +5,10 @@ description = 'The protoc plugin for gRPC Java'
 
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+          // The google mirror is less flaky than mavenCentral()
+          url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
         mavenLocal()
     }
     dependencies {
diff --git a/examples/build.gradle b/examples/build.gradle
index 02236461e..d98b8f2c8 100644
--- a/examples/build.gradle
+++ b/examples/build.gradle
@@ -3,7 +3,10 @@ apply plugin: 'com.google.protobuf'
 
 buildscript {
   repositories {
-    mavenCentral()
+    maven {
+      // The google mirror is less flaky than mavenCentral()
+      url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+    }
   }
   dependencies {
     // ASSUMES GRADLE 2.12 OR HIGHER. Use plugin version 0.7.5 with earlier
@@ -13,7 +16,10 @@ buildscript {
 }
 
 repositories {
-  mavenCentral()
+  maven {
+      // The google mirror is less flaky than mavenCentral()
+    url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+  }
   mavenLocal()
 }
 
diff --git a/gae-interop-testing/gae-jdk7/build.gradle b/gae-interop-testing/gae-jdk7/build.gradle
index 216e16bfb..4a1b71f9b 100644
--- a/gae-interop-testing/gae-jdk7/build.gradle
+++ b/gae-interop-testing/gae-jdk7/build.gradle
@@ -16,7 +16,10 @@ description = 'gRPC: gae interop testing (jdk7)'
 buildscript {    // Configuration for building
   repositories {
     jcenter()    // Bintray's repository - a fast Maven Central mirror & more
-    mavenCentral()
+    maven {
+      // The google mirror is less flaky than mavenCentral()
+      url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+    }
   }
   dependencies {
     classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.3'
@@ -27,10 +30,10 @@ buildscript {    // Configuration for building
 repositories {   // repositories for Jar's you access in your code
   mavenLocal()
   maven {
-    url 'https://maven-central.storage.googleapis.com'             // Google's mirror of Maven Central
+    // The google mirror is less flaky than mavenCentral()
+    url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
   }
   jcenter()
-  mavenCentral()
 }
 
 apply plugin: 'java'                              // standard Java tasks
diff --git a/gae-interop-testing/gae-jdk8/build.gradle b/gae-interop-testing/gae-jdk8/build.gradle
index 951d476ad..8e57fe570 100644
--- a/gae-interop-testing/gae-jdk8/build.gradle
+++ b/gae-interop-testing/gae-jdk8/build.gradle
@@ -16,7 +16,10 @@ description = 'gRPC: gae interop testing (jdk8)'
 buildscript {    // Configuration for building
   repositories {
     jcenter()    // Bintray's repository - a fast Maven Central mirror & more
-    mavenCentral()
+    maven {
+      // The google mirror is less flaky than mavenCentral()
+      url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+    }
   }
   dependencies {
     classpath 'com.google.cloud.tools:appengine-gradle-plugin:1.3.3'
@@ -27,10 +30,10 @@ buildscript {    // Configuration for building
 repositories {   // repositories for Jar's you access in your code
   mavenLocal()
   maven {
-    url 'https://maven-central.storage.googleapis.com'             // Google's mirror of Maven Central
+    // The google mirror is less flaky than mavenCentral()
+    url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
   }
   jcenter()
-  mavenCentral()
 }
 
 apply plugin: 'java'                              // standard Java tasks
diff --git a/grpclb/build.gradle b/grpclb/build.gradle
index cf54dfbfb..921a14ca6 100644
--- a/grpclb/build.gradle
+++ b/grpclb/build.gradle
@@ -2,7 +2,10 @@ description = "gRPC: GRPCLB LoadBalancer plugin"
 
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/interop-testing/build.gradle b/interop-testing/build.gradle
index 3f87b76f4..0fb71a1c7 100644
--- a/interop-testing/build.gradle
+++ b/interop-testing/build.gradle
@@ -6,7 +6,10 @@ startScripts.enabled = false
 // Add dependency on the protobuf plugin
 buildscript {
   repositories {
-    mavenCentral()
+      maven {
+          // The google mirror is less flaky than mavenCentral()
+          url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+      }
   }
   dependencies {
     classpath libraries.protobuf_plugin
diff --git a/protobuf-lite/build.gradle b/protobuf-lite/build.gradle
index 30b235569..e7342be75 100644
--- a/protobuf-lite/build.gradle
+++ b/protobuf-lite/build.gradle
@@ -1,6 +1,9 @@
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
         mavenLocal()
     }
     dependencies {
diff --git a/protobuf-nano/build.gradle b/protobuf-nano/build.gradle
index ea629d3b6..03ef6e89f 100644
--- a/protobuf-nano/build.gradle
+++ b/protobuf-nano/build.gradle
@@ -1,7 +1,10 @@
 // Add dependency on the protobuf plugin
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/protobuf/build.gradle b/protobuf/build.gradle
index 9ce87b9ab..2d4a8a8c5 100644
--- a/protobuf/build.gradle
+++ b/protobuf/build.gradle
@@ -2,7 +2,10 @@ description = 'gRPC: Protobuf'
 
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/services/build.gradle b/services/build.gradle
index 3322b895a..6f7924863 100644
--- a/services/build.gradle
+++ b/services/build.gradle
@@ -1,7 +1,10 @@
 // Add dependency on the protobuf plugin
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin
diff --git a/testing-proto/build.gradle b/testing-proto/build.gradle
index 84f651af4..d28992127 100644
--- a/testing-proto/build.gradle
+++ b/testing-proto/build.gradle
@@ -3,7 +3,10 @@ description = "gRPC: Testing Protos"
 // Add dependency on the protobuf plugin
 buildscript {
     repositories {
-        mavenCentral()
+        maven {
+            // The google mirror is less flaky than mavenCentral()
+            url "https://maven-central.storage-download.googleapis.com/repos/central/data/"
+        }
     }
     dependencies {
         classpath libraries.protobuf_plugin