Okhttp: Android AGP 4.0, R8 - Http2Writer NPE Okhttp v4.3.0

[wezley98]

Seeing the following crashes on Android with Okhttp v4.3.0, not happening on v4.2.2

• Using http2 rest endpoints with retrofit and rxjava.

Fatal Exception: m0.a
       at okio.Buffer.writableSegment$okio(Buffer.java:1812)
       at okio.Buffer.writeByte(Buffer.java:1662)
       at okio.RealBufferedSink.writeByte(RealBufferedSink.java:197)
       at okhttp3.internal.Util.writeMedium(Util.java:309)
       at okhttp3.internal.http2.Http2Writer.frameHeader(Http2Writer.java:261)
       at okhttp3.internal.http2.Http2Writer.settings(Http2Writer.java:173)
       at okhttp3.internal.http2.Http2Connection.start(Http2Connection.java:496)
       at okhttp3.internal.http2.Http2Connection.start$default(Http2Connection.java:493)
       at okhttp3.internal.connection.RealConnection.startHttp2(RealConnection.java:329)
       at okhttp3.internal.connection.RealConnection.establishProtocol(RealConnection.java:312)
       at okhttp3.internal.connection.RealConnection.connect(RealConnection.java:182)
       at okhttp3.internal.connection.ExchangeFinder.findConnection(ExchangeFinder.java:238)
       at okhttp3.internal.connection.ExchangeFinder.findHealthyConnection(ExchangeFinder.java:111)
       at okhttp3.internal.connection.ExchangeFinder.find(ExchangeFinder.java:79)
       at okhttp3.internal.connection.Transmitter.newExchange$okhttp(Transmitter.java:163)
       at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:35)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:112)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:87)
       at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:82)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:112)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:87)
       at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:84)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:112)
       at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:71)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:112)
       at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:87)
       at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:194)
       at okhttp3.RealCall$AsyncCall.run(RealCall.java:138)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
       at java.lang.Thread.run(Thread.java:919)

and

Fatal Exception: m0.a
       at okio.Segment.pop(Segment.java:89)
       at okio.Buffer.skip(Buffer.java:1478)
       at okio.RealBufferedSource.skip(RealBufferedSource.java:431)
       at okhttp3.internal.http2.Http2Connection$ReaderRunnable.data(Http2Connection.java:643)
       at okhttp3.internal.http2.Http2Reader.readData(Http2Reader.java:178)
       at okhttp3.internal.http2.Http2Reader.nextFrame(Http2Reader.java:117)
       at okhttp3.internal.http2.Http2Connection$ReaderRunnable.run(Http2Connection.java:614)
       at java.lang.Thread.run(Thread.java:919)

[swankjesse]

I’m running a pretty extensive stress test to try to shake out this regression, but I’ve been unsuccessful at reproducing thus far.

Typically these kinds of crashes indicate thread-unsafe operations on Okio buffers. Unfortunately the crashes can sometimes occur far away from the bad unsafe code, because the unsafe code corrupts Okio’s segment pool.

I’d like to create a special build of Okio to help root out these bugs. When that’s ready I hope you’ll be able to run it.

[wezley98]

@swankjesse thanks, I'll will test as soon as you have something ready.

[Stonos]

Are you using AGP 4.0.0 with R8? I've had similar exceptions with that combination.

I've opened an issue on the R8 issue tracker, which also includes a project where you can reproduce the issue: https://issuetracker.google.com/issues/147411673

[swankjesse]

Wow, great find @Stonos!

[wezley98]

@Stonos Yes, AGP 4.0.0-alpha07 with R8, thanks for logging it.

[Stonos]

Update from the R8 issue tracker: They're working on a fix. For now, adding the following keep rule seems to resolve the issue:

-keep class okio.SegmentPool { *; }

[JakeWharton]

Make you sure you put a big # TODO Remove once R8 fixes <issue link> so that rule doesn't stay in your rules forever!

[swankjesse]

Fixed in R8 on Jan 16. I suspect this probably made it into 4.0.0-alpha09. Update your Android Gradle Plugin and you should be good.