Potential failure on CallServerInterceptor if writeRequestHeader fails

[gdrehmer]

Unfortunately this bug is hard to replicate and to create a failing test.
But I hope it still gets attention.

We've noticed that there is a big number of crashes in our customer base after upgrading from OkHttp 4.9.3 to version 4.12.0, as per stacktrace below.

We've also noticed a change in 4.11 could be related to that:

Read the response even if writing the request fails (#6295) (#7453)

e46a200

It seems that a change has been introduced in CallServerInterceptor which moved the exchange.write* operations into a try/catch block (I suppose by design, to fix the issue as referenced in the commit).

However, the effect of that could be that the following block, the exchange.readResponseHeaders might be executed with state set to 0 (IDLE, not initalised), if the previous exchange.writeRequestHeaders(request) operation failed for any reason apart from ConnectionShutdownException. The readResponseHeaders has a guard statement which would throw an exception if state == 0.

I couldn't find a way which could cause the exchange.writeRequestHeaders call to raise an exception, but we are observing many cases (it is our top crash, affecting thousands of customers in a couple of days after rollout).

It is important to note that we also updated from Okio 3.0.0 to 3.7.0 in the same release.

Stacktrace:

Exception java.lang.IllegalStateException: state: 0
  at okhttp3.internal.http1.Http1ExchangeCodec.readResponseHeaders (Http1ExchangeCodec.kt)
  at okhttp3.internal.connection.Exchange.readResponseHeaders (Exchange.kt)
  at okhttp3.internal.http.CallServerInterceptor.intercept (CallServerInterceptor.kt)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at okhttp3.internal.connection.ConnectInterceptor.intercept (ConnectInterceptor.kt)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at okhttp3.internal.cache.CacheInterceptor.intercept (CacheInterceptor.kt)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at okhttp3.internal.http.BridgeInterceptor.intercept (BridgeInterceptor.kt)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept (RetryAndFollowUpInterceptor.kt)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at my.company.SomeInterceptor 
  (...)
  at okhttp3.internal.http.RealInterceptorChain.proceed (RealInterceptorChain.kt)
  at okhttp3.internal.connection.RealCall.getREsponseWithInterceptorChain$okhttp (RealCall.kt)
  at okhttp3.internal.connection.RealCall$AsyncCall.run (RealCall.kt)
  at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1145)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:644)
  at java.lang.Thread.run (Thread.java:1012)

[yschimke]

Probably a dupe of #6853

I'll take a look again on the weekend.