Retry-After support

okhttp-tests/src/test/java/okhttp3/CallTest.java

@@ -1583,6 +1583,22 @@ private void postBodyRetransmittedAfterAuthorizationFail(String body) throws Exc
     assertEquals("Body", response.body().string());
   }
 
+  @Test public void getClientRequestTimeoutWithBackPressure() throws Exception {
+    server.enqueue(new MockResponse()
+        .setSocketPolicy(SocketPolicy.DISCONNECT_AT_END)
+        .setResponseCode(408)
+        .setHeader("Connection", "Close")
+        .setHeader("Retry-After", "1")
+        .setBody("You took too long!"));
+
+    Request request = new Request.Builder()
+        .url(server.url("/"))
+        .build();
+    Response response = client.newCall(request).execute();
+
+    assertEquals("You took too long!", response.body().string());
+  }
+
   @Test public void requestBodyRetransmittedOnClientRequestTimeout() throws Exception {
     server.enqueue(new MockResponse()
         .setSocketPolicy(SocketPolicy.DISCONNECT_AT_END)
@@ -1649,6 +1665,48 @@ private void postBodyRetransmittedAfterAuthorizationFail(String body) throws Exc
     assertEquals(2, server.getRequestCount());
   }
 
+  @Test public void maxUnavailableTimeoutRetries() throws IOException {
+    server.enqueue(new MockResponse()
+        .setSocketPolicy(SocketPolicy.DISCONNECT_AT_END)
+        .setResponseCode(503)
+        .setHeader("Connection", "Close")
+        .setHeader("Retry-After", "0")
+        .setBody("You took too long!"));
+    server.enqueue(new MockResponse()
+        .setSocketPolicy(SocketPolicy.DISCONNECT_AT_END)
+        .setResponseCode(503)
+        .setHeader("Connection", "Close")
+        .setHeader("Retry-After", "0")
+        .setBody("You took too long!"));
+
+    Request request = new Request.Builder()
+        .url(server.url("/"))
+        .build();
+    Response response = client.newCall(request).execute();
+
+    assertEquals(503, response.code());
+    assertEquals("You took too long!", response.body().string());
+
+    assertEquals(2, server.getRequestCount());
+  }
+
+  @Test public void retryOnUnavailableWith0RetryAfter() throws IOException {
+    server.enqueue(new MockResponse()
+        .setSocketPolicy(SocketPolicy.DISCONNECT_AT_END)
+        .setResponseCode(503)
+        .setHeader("Connection", "Close")
+        .setHeader("Retry-After", "0")
+        .setBody("You took too long!"));
+    server.enqueue(new MockResponse().setBody("Body"));
+
+    Request request = new Request.Builder()
+        .url(server.url("/"))
+        .build();
+    Response response = client.newCall(request).execute();
+
+    assertEquals("Body", response.body().string());
+  }
+
   @Test public void propfindRedirectsToPropfindAndMaintainsRequestBody() throws Exception {
     // given
     server.enqueue(new MockResponse()

okhttp/src/main/java/okhttp3/internal/http/RetryAndFollowUpInterceptor.java

@@ -49,6 +49,7 @@
 import static java.net.HttpURLConnection.HTTP_PROXY_AUTH;
 import static java.net.HttpURLConnection.HTTP_SEE_OTHER;
 import static java.net.HttpURLConnection.HTTP_UNAUTHORIZED;
+import static java.net.HttpURLConnection.HTTP_UNAVAILABLE;
 import static okhttp3.internal.Util.closeQuietly;
 import static okhttp3.internal.http.StatusLine.HTTP_PERM_REDIRECT;
 import static okhttp3.internal.http.StatusLine.HTTP_TEMP_REDIRECT;
@@ -359,13 +360,47 @@ private Request followUpRequest(Response userResponse) throws IOException {
           return null;
         }
 
+        if (retryAfter(userResponse, 0) > 0) {
+          return null;
+        }
+
         return userResponse.request();
 
+      case HTTP_UNAVAILABLE:
+        if (userResponse.priorResponse() != null
+            && userResponse.priorResponse().code() == HTTP_UNAVAILABLE) {
+          // We attempted to retry and got another timeout. Give up.
+          return null;
+        }
+
+        if (retryAfter(userResponse, Integer.MAX_VALUE) == 0) {
+          // specifically received an instruction to retry without delay
+          return userResponse.request();
+        }
+
+        return null;
+
       default:
         return null;
     }
   }
 
+  private int retryAfter(Response userResponse, int defaultDelay) {
+    String header = userResponse.header("Retry-After");
+
+    if (header == null) {
+      return defaultDelay;
+    }
+
+    // https://tools.ietf.org/html/rfc7231#section-7.1.3
+    // currently ignores a HTTP-date, and assumes any non int 0 is a delay
+    if (header.matches("\\d+")) {
+      return Integer.valueOf(header);
+    }
+
+    return Integer.MAX_VALUE;
+  }
+
   /**
    * Returns true if an HTTP request for {@code followUp} can reuse the connection used by this
    * engine.