Retry more errors in Volley's BasicNetwork.

Always retry I/O errors while reading the HTTP response entity.
Furthermore, if a client opts in, retry HTTP 500 errors indicating
something went wrong on the server.

This resolves a longstanding TODO to only throw a ServerError on 5xx
errors by adding a ClientError for 4xx errors. For backwards
compatibility, this extends ServerError.

Note that Volley already may retry a request that reached the server
if the connection times out, which means that lack of idempotency
shouldn't be a concern here if it wasn't already. But if we wanted to
be even safer, we could require clients to opt into the additional
retry cases, at the cost of a somewhat more polluted API.

Add unit tests for most failure scenarios.

Bug: 23152983
Change-Id: I92cf35c66ccf98a1682adf41654afeb8634911db

1 files changed, 20 insertions, 1 deletions

diff --git a/src/main/java/com/android/volley/Request.java b/src/main/java/com/android/volley/Request.java
index 5b42d1f..8200f6e 100644
--- a/src/main/java/com/android/volley/Request.java
+++ b/src/main/java/com/android/volley/Request.java
@@ -20,7 +20,6 @@ import android.net.TrafficStats;
 import android.net.Uri;
 import android.os.Handler;
 import android.os.Looper;
-import android.os.SystemClock;
 import android.text.TextUtils;
 
 import com.android.volley.VolleyLog.MarkerLog;
@@ -90,6 +89,9 @@ public abstract class Request<T> implements Comparable<Request<T>> {
     /** Whether or not a response has been delivered for this request yet. */
     private boolean mResponseDelivered = false;
 
+    /** Whether the request should be retried in the event of an HTTP 5xx (server) error. */
+    private boolean mShouldRetryServerErrors = false;
+
     /** The retry policy for this request. */
     private RetryPolicy mRetryPolicy;
 
@@ -474,6 +476,23 @@ public abstract class Request<T> implements Comparable<Request<T>> {
     }
 
     /**
+     * Sets whether or not the request should be retried in the event of an HTTP 5xx (server) error.
+     *
+     * @return This Request object to allow for chaining.
+     */
+    public final Request<?> setShouldRetryServerErrors(boolean shouldRetryServerErrors) {
+        mShouldRetryServerErrors = shouldRetryServerErrors;
+        return this;
+    }
+
+    /**
+     * Returns true if this request should be retried in the event of an HTTP 5xx (server) error.
+     */
+    public final boolean shouldRetryServerErrors() {
+        return mShouldRetryServerErrors;
+    }
+
+    /**
      * Priority values.  Requests will be processed from higher priorities to
      * lower priorities, in FIFO order.
      */