adds retrying example details in README, revert change to gradle wrap…

…per properties

examples/README.md

@@ -87,6 +87,36 @@ before trying out the examples.
 
 </details>
 
+- <details>
+  <summary>Retrying</summary>
+
+  The [retrying example](src/main/java/io/grpc/examples/retrying) provides a HelloWorld GRPC client & 
+  server which demos the effect of client retry policy configured on the [ManagedChannel](
+  ../api/src/main/java/io/grpc/ManagedChannel.java) via [GRPC ServiceConfig](
+  ../core/src/main/java/io/grpc/internal/ManagedChannelServiceConfig.java). Retry policy implementation & 
+  configuration details are outlined in the [proposal](https://github.com/grpc/proposal/blob/master/A6-client-retries.md).
+
+  This retrying example is very similar to the [hedging example](src/main/java/io/grpc/examples/hedging) in its setup. 
+  The [RetryingHelloWorldServer](src/main/java/io/grpc/examples/retrying/RetryingHelloWorldServer.java) responds with
+  a status UNAVAILABLE error response to a specified percentage of requests to simulate server resource exhaustion and 
+  general flakiness. The [RetryingHelloWorldClient](src/main/java/io/grpc/examples/retrying/RetryingHelloWorldClient.java) makes 
+  a number of sequential requests to the server, several of which will be retried depending on the configured policy in 
+  [retrying_service_config.json](src/main/resources/io/grpc/examples/retrying/retrying_service_config.json). Although 
+  the requests are blocking unary calls for simplicity, these could easily be changed to future unary calls in order to 
+  test the result of request concurrency with retry policy enabled.
+
+  One can experiment with the [RetryingHelloWorldServer](src/main/java/io/grpc/examples/retrying/RetryingHelloWorldServer.java)
+  failure conditions to simulate server throttling, as well as alter policy values in the [retrying_service_config.json](
+  src/main/resources/io/grpc/examples/retrying/retrying_service_config.json) to see their effects. To disable retrying 
+  entirely, set environment variable `DISABLE_RETRYING_IN_RETRYING_EXAMPLE=true` before running the client. 
+  Disabling the retry policy should produce many more failed GRPC calls as seen in the output log.
+
+  See [the section below](#to-build-the-examples) for how to build and run the example. The
+  executables for the server and the client are `retrying-hello-world-server` and
+  `retrying-hello-world-client`.
+
+</details>
+
 ### <a name="to-build-the-examples"></a> To build the examples
 
 1. **[Install gRPC Java library SNAPSHOT locally, including code generation plugin](../COMPILING.md) (Only need this step for non-released versions, e.g. master HEAD).**

examples/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Tue Jun 02 23:49:09 PDT 2020
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-all.zip
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

examples/src/main/java/io/grpc/examples/retrying/RetryingHelloWorldClient.java

@@ -39,7 +39,7 @@
  * A client that requests a greeting from the {@link RetryingHelloWorldServer} with a retrying policy.
  */
 public class RetryingHelloWorldClient {
-  static final String ENV_DISABLE_RETRIES = "DISABLE_RETRIES_IN_RETRIES_EXAMPLE";
+  static final String ENV_DISABLE_RETRYING = "DISABLE_RETRYING_IN_RETRYING_EXAMPLE";
 
   private static final Logger logger = Logger.getLogger(RetryingHelloWorldClient.class.getName());
 
@@ -117,17 +117,17 @@ private void printSummary() {
       logger.log(
           Level.INFO,
           "Retrying enabled. To disable retries, run the client with environment variable {0}=true.",
-          ENV_DISABLE_RETRIES);
+          ENV_DISABLE_RETRYING);
     } else {
       logger.log(
           Level.INFO,
           "Retrying disabled. To enable retries, unset environment variable {0} and then run the client.",
-          ENV_DISABLE_RETRIES);
+          ENV_DISABLE_RETRYING);
     }
   }
 
   public static void main(String[] args) throws Exception {
-    boolean enableRetries = !Boolean.parseBoolean(System.getenv(ENV_DISABLE_RETRIES));
+    boolean enableRetries = !Boolean.parseBoolean(System.getenv(ENV_DISABLE_RETRYING));
     final RetryingHelloWorldClient client = new RetryingHelloWorldClient("localhost", 50051, enableRetries);
     ForkJoinPool executor = new ForkJoinPool();