Distinguish between Connect Timeout and Read Timeout with okhttp

Question

I am using okhttp with ribbon using spring. I wish to retry on another service instance on connect timeout but not on read timeout(for obvious reasons). This retry will be handled by a custom ribbon retry handler. But to do the above, I need to distinguish between read and connect timeouts. The behaviour with okhttp is as follows:

• On read timeout:

   java.net.SocketTimeoutException: timeout at okio.Okio$3.newTimeoutException(Okio.java:212) at okio.AsyncTimeout.exit(AsyncTimeout.java:288) at okio.AsyncTimeout$2.read(AsyncTimeout.java:242) at okio.RealBufferedSource.indexOf(RealBufferedSource.java:325) at okio.RealBufferedSource.indexOf(RealBufferedSource.java:314) at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:210) at okhttp3.internal.http.Http1xStream.readResponse(Http1xStream.java:184) at okhttp3.internal.http.Http1xStream.readResponseHeaders(Http1xStream.java:125) at okhttp3.internal.http.HttpEngine.readNetworkResponse(HttpEngine.java:775) at okhttp3.internal.http.HttpEngine.access$200(HttpEngine.java:86) at okhttp3.internal.http.HttpEngine$NetworkInterceptorChain.proceed(HttpEngine.java:760) at okhttp3.internal.http.HttpEngine.readResponse(HttpEngine.java:613) at okhttp3.RealCall.getResponse(RealCall.java:244) at okhttp3.RealCall$ApplicationInterceptorChain.proceed(RealCall.java:201) at com.bluejeans.sample.test.OkHttpConnect$1.intercept(OkHttpConnect.java:25) at okhttp3.RealCall$ApplicationInterceptorChain.proceed(RealCall.java:190) at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:163) at okhttp3.RealCall.execute(RealCall.java:57) at com.bluejeans.sample.test.OkHttpConnect.main(OkHttpConnect.java:39) Caused by: java.net.SocketTimeoutException: Read timed out at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:170) at java.net.SocketInputStream.read(SocketInputStream.java:141) at okio.Okio$2.read(Okio.java:140) at okio.AsyncTimeout$2.read(AsyncTimeout.java:238) ... 16 more 

• On connect timeout:

    java.net.SocketTimeoutException: connect timed out at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:589) at okhttp3.internal.Platform.connectSocket(Platform.java:121) at okhttp3.internal.io.RealConnection.connectSocket(RealConnection.java:185) at okhttp3.internal.io.RealConnection.buildConnection(RealConnection.java:170) at okhttp3.internal.io.RealConnection.connect(RealConnection.java:111) at okhttp3.internal.http.StreamAllocation.findConnection(StreamAllocation.java:187) at okhttp3.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:123) at okhttp3.internal.http.StreamAllocation.newStream(StreamAllocation.java:93) at okhttp3.internal.http.HttpEngine.connect(HttpEngine.java:296) at okhttp3.internal.http.HttpEngine.sendRequest(HttpEngine.java:248) at okhttp3.RealCall.getResponse(RealCall.java:243) at okhttp3.RealCall$ApplicationInterceptorChain.proceed(RealCall.java:201) at com.bluejeans.sample.test.OkHttpConnect$1.intercept(OkHttpConnect.java:25) at okhttp3.RealCall$ApplicationInterceptorChain.proceed(RealCall.java:190) at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:163) at okhttp3.RealCall.execute(RealCall.java:57) at com.bluejeans.sample.test.OkHttpConnect.main(OkHttpConnect.java:39) 

Deciding based on the exception message doesn't seem like a good idea. What is the recommended way to achieve this?

Answer 1

If you do not want to rely on the message you may also choose the following options. However both of them need JUnit coverage because the developers of OkHttp may change their implementation in future.

1. Use the cause of the exception to decide how to treat the request:

    try { ... } catch (SocketTimeoutException e) { if (e.getCause() != null && e.getCause() instanceof SocketTimeoutException) { // read timeout } else { // socket timeout } } 

2. Loop through the stack trace:

    try { ... } catch (SocketTimeoutException e) { boolean isConnectException = false; for (StackTraceElement elem : e.getStackTrace()) { if ("java.net.Socket".equals(elem.getClassName()) && "connect".equals(elem.getMethodName())) { isConnectException = true; break; } } ... }