[BEAM-4832] Concurrent Writes in Data channels

• Type: Bug
• Status: Resolved
• Priority: P2
• Resolution: Fixed
• Fix Version/s: Not applicable
• Component/s: sdk-go
• Assignee: Robert Burke
• Reporter: Robert Burke
• Created: 19/Jul/18 20:24
• Updated: 24/Jul/20 20:10
• Resolved: 24/Jul/18 16:01

Description

A user was having issue with streaming Go pipelines on Dataflow. Investigation yeilded the panic below, which triggered concurrent modifications of the data channel maps.

 

The fix is properly guarding all writes to the Data channel maps, in particular:

 
func (c *DataChannel) removeReader([id|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&gs=kythe%253A%252F%252Fgoogle3%253Flang%253Dgo%253Fpath%253Dthird_party%252Fgolang%252Fapache_beam%252Fpkg%252Fbeam%252Fcore%252Fruntime%252Fharness%252Fharness%2523param%252520DataChannel.removeReader%25253Aid&gsn=id&ct=xref_usages] string)

{ delete([c|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&ct=xref_jump_to_def&gsn=c&rcl=205012539].[readers|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=93&ct=xref_jump_to_def&gsn=readers&rcl=205012539], [id|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&ct=xref_jump_to_def&gsn=id&rcl=205012539])}

Should be
 
func (c *DataChannel) removeReader([id|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&gs=kythe%253A%252F%252Fgoogle3%253Flang%253Dgo%253Fpath%253Dthird_party%252Fgolang%252Fapache_beam%252Fpkg%252Fbeam%252Fcore%252Fruntime%252Fharness%252Fharness%2523param%252520DataChannel.removeReader%25253Aid&gsn=id&ct=xref_usages] string)

{ [c|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=198&ct=xref_jump_to_def&gsn=c&rcl=205012539].[mu|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=96&ct=xref_jump_to_def&gsn=mu&rcl=205012539].[Lock|https://cs.corp.google.com/piper///depot/google3/third_party/go/gc/src/sync/mutex.go?l=72&ct=xref_jump_to_def&gsn=Lock&rcl=205012539]() delete([c|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&ct=xref_jump_to_def&gsn=c&rcl=205012539].[readers|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=93&ct=xref_jump_to_def&gsn=readers&rcl=205012539], [id|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=212&ct=xref_jump_to_def&gsn=id&rcl=205012539]) [c|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=198&ct=xref_jump_to_def&gsn=c&rcl=205012539].[mu|https://cs.corp.google.com/piper///depot/google3/third_party/golang/apache_beam/pkg/beam/core/runtime/harness/datamgr.go?l=96&ct=xref_jump_to_def&gsn=mu&rcl=205012539].[Unlock|https://cs.corp.google.com/piper///depot/google3/third_party/go/gc/src/sync/mutex.go?l=175&ct=xref_jump_to_def&gsn=Unlock&rcl=205012539]() }

 

 

I fatal error: concurrent map writes
I
I goroutine 3277 [running]:
I runtime.throw(0xf880d0, 0x15)
I GOROOT/src/runtime/panic.go:616 +0x81 fp=0xc4212eb6d8 sp=0xc4212eb6b8 pc=0x42be31
I runtime.mapdelete_faststr(0xe18160, 0xc4202ba7b0, 0xc4213dc0e0, 0x20)
I GOROOT/src/runtime/hashmap_fast.go:892 +0x28d fp=0xc4212eb738 sp=0xc4212eb6d8 pc=0x40e45d
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness.(*DataChannel).removeReader(...)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness/datamgr.go:213
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness.(*dataReader).Close(0xc420ba8c80, 0xc42031e0c0, 0xf)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness/datamgr.go:241 +0x6e fp=0xc4212eb768 sp=0xc4212eb738 pc=0xc5059e
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec.(*DataSource).Process(0xc4203ae540, 0x10708c0, 0xc420464e70, 0x0, 0x0)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec/datasource.go:156 +0x1302 fp=0xc4212ebbd8 sp=0xc4212eb768 pc=0x894612
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec.(Root).Process-fm(0x10708c0, 0xc420464e70, 0xc420b7bc58, 0x0)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec/plan.go:112 +0x43 fp=0xc4212ebc10 sp=0xc4212ebbd8 pc=0x8a4c23
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec.callNoPanic(0x10708c0, 0xc420464e70, 0xc420b7bcc8, 0x0, 0x0)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec/util.go:42 +0x6c fp=0xc4212ebc40 sp=0xc4212ebc10 pc=0x8a37ac
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec.(*Plan).Execute(0xc420030770, 0x10708c0, 0xc420464e70, 0xc4201a85e8, 0x5, 0x1064720, 0xc4202097e0, 0xfb5320, 0xc4206ff940)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec/plan.go:112 +0x3bd fp=0xc4212ebd58 sp=0xc4212ebc40 pc=0x89d4ed
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness.(*control).handleInstruction(0xc4201a7820, 0x10708c0, 0xc420464e10, 0xc420d5e340, 0xc420038018)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness/harness.go:193 +0x729 fp=0xc4212ebf40 sp=0xc4212ebd58 pc=0xc51ef9
I google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness.Main.func2(0x1070840, 0xc420038018, 0xc420d5e340)
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness/harness.go:113 +0x167 fp=0xc4212ebfc8 sp=0xc4212ebf40 pc=0xc54b17
I runtime.goexit()
I bazel-out/k8-fastbuild/bin/external/io_bazel_rules_go/linux_amd64_stripped/stdlib~/src/runtime/asm_amd64.s:2361 +0x1 fp=0xc4212ebfd0 sp=0xc4212ebfc8 pc=0x45a591
I created by google/vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness.Main
I vendor/github.com/apache/beam/sdks/go/pkg/beam/core/runtime/harness/harness.go:126 +0x5cc
I

Issue Links

• links to: GitHub Pull Request #6003