The DefaultRetryPolicy method retry() doesn't do what it is intended to do.

[Ericliu001]

Hi, I was going to through the code on the retry mechanism today and came across the RetryPolicy. The following code is from the class DefaultRetryPolicy.

/**
 * Prepares for the next retry by applying a backoff to the timeout.
 * @param error The error code of the last attempt.
 */
@Override
public void retry(VolleyError error) throws VolleyError {
    mCurrentRetryCount++;
    mCurrentTimeoutMs += (mCurrentTimeoutMs * mBackoffMultiplier);
    if (!hasAttemptRemaining()) {
        throw error;
    }
}

Under the circumstance where the NetworkDispatcher wants to retry a request, it calls retry() on the RetryPolicy instance of that request. I would assume that the same request should be added to the RequestQueue as an retry attempt.

But the retry() method actually doesn't do much other than updating a few values, which doesn't schedule another call to fire the failed request again.

If we look at the test case in BasicNetworkTest, it seems that we should assume that a retry request has been made as long as the retry() method of the RetryPolicy instance is called. But the currently implementation of DefaultRetryPolicy doesn't really do that.

@Test public void serverError_enableRetries() throws Exception {
    for (int i = 500; i <= 599; i++) {
        MockHttpStack mockHttpStack = new MockHttpStack();
        BasicHttpResponse fakeResponse =
                new BasicHttpResponse(new ProtocolVersion("HTTP", 1, 1), i, "");
        mockHttpStack.setResponseToReturn(fakeResponse);
        BasicNetwork httpNetwork =
                new BasicNetwork(mockHttpStack, new ByteArrayPool(4096));
        Request<String> request = buildRequest();
        request.setRetryPolicy(mMockRetryPolicy);
        request.setShouldRetryServerErrors(true);
        doThrow(new VolleyError()).when(mMockRetryPolicy).retry(any(VolleyError.class));
        try {
            httpNetwork.performRequest(request);
        } catch (VolleyError e) {
            // expected
        }
        // should retry all 500 errors
        verify(mMockRetryPolicy).retry(any(ServerError.class));
        reset(mMockRetryPolicy);
    }
} 

[xesam]

DefaultRetryPolicy#retry() will not add a new(or the same) request to the current RequestQueue .this method just swallowed the 'VolleyError', so BasicNetwork#performRequest(request) can continue the 'while(true)' loop

[Ericliu001]

Thank you for explaining. @xesam