Panic in the Garden #1501
Description
Using the same environment as detailed in #1424 (I don't know if it's related), running Concourse 3.4.0 from Docker images, workers stall after an hour or two on busy pipelines with the following:
2017/08/18 12:34:43 http: panic serving 127.0.0.1:56260: runtime error: invalid memory address or nil pointer dereference
goroutine 271183 [running]:
net/http.(*conn).serve.func1(0xc4201585a0)
/usr/local/go/src/net/http/server.go:1721 +0xd0
panic(0xf913c0, 0xfc9e090)
/usr/local/go/src/runtime/panic.go:489 +0x2cf
code.cloudfoundry.org/garden/server/streamer.(*Streamer).serve(0xc420432db0, 0xc4202fd727, 0x4, 0xfcc16e0, 0xc42000f128, 0x1)
/tmp/build/9674af12/concourse/src/code.cloudfoundry.org/garden/server/streamer/streamer.go:70 +0x64
code.cloudfoundry.org/garden/server/streamer.(*Streamer).ServeStderr(0xc420432db0, 0xc4202fd727, 0x4, 0xfcc16e0, 0xc42000f128)
/tmp/build/9674af12/concourse/src/code.cloudfoundry.org/garden/server/streamer/streamer.go:64 +0x5c
code.cloudfoundry.org/garden/server/streamer.(*Streamer).ServeStderr-fm(0xc4202fd727, 0x4, 0xfcc16e0, 0xc42000f128)
/tmp/build/9674af12/concourse/src/code.cloudfoundry.org/garden/server/server.go:93 +0x52
code.cloudfoundry.org/garden/server/streamer.HandlerFunc.ServeHTTP(0xc420422a20, 0xfccee60, 0xc4228b1340, 0xc420d65100)
/tmp/build/9674af12/concourse/src/code.cloudfoundry.org/garden/server/streamer/http_handling.go:21 +0x144
github.com/bmizerany/pat.(*PatternServeMux).ServeHTTP(0xc420418fa0, 0xfccee60, 0xc4228b1340, 0xc420d65100)
/tmp/build/9674af12/concourse/src/github.com/bmizerany/pat/mux.go:117 +0x63f
code.cloudfoundry.org/garden/server.New.func1(0xfccee60, 0xc4228b1340, 0xc420d65100)
/tmp/build/9674af12/concourse/src/code.cloudfoundry.org/garden/server/server.go:112 +0x4d
net/http.HandlerFunc.ServeHTTP(0xc420419060, 0xfccee60, 0xc4228b1340, 0xc420d65100)
/usr/local/go/src/net/http/server.go:1942 +0x44
net/http.serverHandler.ServeHTTP(0xc4200976b0, 0xfccee60, 0xc4228b1340, 0xc420d65100)
/usr/local/go/src/net/http/server.go:2568 +0x92
net/http.(*conn).serve(0xc4201585a0, 0xfcd0060, 0xc422065c00)
/usr/local/go/src/net/http/server.go:1825 +0x612
created by net/http.(*Server).Serve
/usr/local/go/src/net/http/server.go:2668 +0x2ce
NAME STATUS AGE VERSION EXTERNAL-IP OS-IMAGE KERNEL-VERSION
ip-IP.eu-west-1.compute.internal Ready 4h v1.7.0 IP Ubuntu 16.04.3 LTS 4.10.0-28-generic
ip-IP.eu-west-1.compute.internal Ready 17d v1.7.0 IP Ubuntu 16.04.3 LTS 4.10.0-28-generic
ip-IP.eu-west-1.compute.internal Ready 4h v1.7.0 IP Ubuntu 16.04.3 LTS 4.10.0-28-generic
Despite the various issues with 3.x, I've never seen this particular problem prior to Concourse 3.4.0 upgrade.