Distinguish between connect timeout and read timeout

[tanmaybinaykiya]

Feature request: Throw identifiable exceptions for read timeout and connect timeout.
We wish to retry on connect timeout errors and not on read timeouts. The okHttp client throws the same exception in both cases. The only way to distinguish between the two is the through the error message, which is not clean or reliable.

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)

[wu1178279937]

we meet the same issue!

[MartyIX]

I would appreciate this feature very much. I would like to help a little, so I tried to simulate both scenarios on the latest version of okhttp (3.10.0).

Connect timeout

To simulate connection timeout, I tried to connect to http://10.255.255.1 (see) and the exception I get is:

java.net.ConnectException: Failed to connect to /10.255.255.1:80

	at okhttp3.internal.connection.RealConnection.connectSocket(RealConnection.java:242)
	at okhttp3.internal.connection.RealConnection.connect(RealConnection.java:160)
	at okhttp3.internal.connection.StreamAllocation.findConnection(StreamAllocation.java:257)
	at okhttp3.internal.connection.StreamAllocation.findHealthyConnection(StreamAllocation.java:135)
	at okhttp3.internal.connection.StreamAllocation.newStream(StreamAllocation.java:114)
	at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:42)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:126)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:200)
	at okhttp3.RealCall.execute(RealCall.java:77)
	at com.project.shared.utils.http.Client.send(Client.java:85)
	at com.project.shared.utils.http.ClientTest.Send(ClientTest.groovy:13)
Caused by: java.net.ConnectException: Connection timed out: connect
	at java.base/java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
	at java.base/java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:400)
	at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:243)
	at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:225)
	at java.base/java.net.PlainSocketImpl.connect(PlainSocketImpl.java:148)
	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:402)
	at java.base/java.net.Socket.connect(Socket.java:591)
	at okhttp3.internal.platform.Platform.connectSocket(Platform.java:129)
	at okhttp3.internal.connection.RealConnection.connectSocket(RealConnection.java:240)
	... 19 more

Read timeout

For read timeout, the exception is as follows:

java.net.SocketTimeoutException: Read timed out

	at java.base/java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
	at java.base/java.net.SocketInputStream.read(SocketInputStream.java:171)
	at java.base/java.net.SocketInputStream.read(SocketInputStream.java:141)
	at okio.Okio$2.read(Okio.java:140)
	at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)
	at okio.RealBufferedSource.indexOf(RealBufferedSource.java:355)
	at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:227)
	at okhttp3.internal.http1.Http1Codec.readHeaderLine(Http1Codec.java:215)
	at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189)
	at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:88)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:126)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
	at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
	at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:200)
	at okhttp3.RealCall.execute(RealCall.java:77)
	at com.project.shared.utils.http.Client.send(Client.java:85)
	at com.project.shared.utils.http.ClientTest.read timeout(ClientTest.groovy:27)

(I set readTimeout(10, TimeUnit.MILLISECONDS) to simulate this)

My environment:

• okhttp 3.10
• java 9.0.4

[chefdd]

how to solve this problem?

[swankjesse]

I’m not 100% sure we’re going to be able to solve this problem in a satisfying way. We can differentiate between whether we’ve send the request bytes or not, but we can’t differentiate between whether or not the server has received them.

I’d love to learn more about what your application will do differently on connect vs. read timeouts.

[swankjesse]

... this is especially true as we migrate towards QUIC which doesn’t have a distinct “connected” phase.

[tanmaybinaykiya]

A read timeout implies that the network is intact and the server is still processing the request.
A connect timeout would mean that the server didn't receive the request. We'd want to retry the request in this case

[swankjesse]

Yeah, but how do we know whether the server received the request? The only reliable way is to receive a response back from the server.

[tanmaybinaykiya]

As per my understanding, the transport layer library throws a java.net.ConnectException: Connection timed out: connect if it does not receive an ACK during the connect timeout.
Refer to the exception provided in #3318 (comment)

[swankjesse]

@tanmaybinaykiya that’s true but you shouldn’t make application behavior depend upon it. If any part of your route between client and web server has a proxy (client-side proxy, server-side load balancer, etc.) then the connect timeout tells you whether it successfully connected to that proxy, and not whether your actual webserver received any data.