Smithy-go's HTTP metrics are prone to data races

[alexandrupitis1]

Smithy-go's HTTP metrics use httptrace.ClientTrace. To quote the docs:

ClientTrace is a set of hooks to run at various stages of an outgoing HTTP request. Any particular hook may be nil. Functions may be called concurrently from different goroutines and some may be called after the request has completed or failed.

However, current implementation is not safe to call concurrently, as there are write-write data races on various methods ( for example ConnectStart ). This in turn trips data race detection.

[abraithwaite]

Just ran into this myself:

==================
WARNING: DATA RACE
Write at 0x00c000578390 by goroutine 59:
  github.com/aws/smithy-go/transport/http.(*httpMetrics).ConnectStart()
      /Users/abraithwaite/Projects/golang/pkg/mod/github.com/aws/[email protected]/transport/http/metrics.go:122 +0x6c
  github.com/aws/smithy-go/transport/http.(*httpMetrics).ConnectStart-fm()
      <autogenerated>:1 +0x20
  net.(*sysDialer).dialSingle()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:657 +0x108
  net.(*sysDialer).dialSerial()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:635 +0x1bc
  net.(*sysDialer).dialParallel.func1()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:555 +0xb4
  net.(*sysDialer).dialParallel.gowrap4()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:581 +0x58

Previous write at 0x00c000578390 by goroutine 56:
  github.com/aws/smithy-go/transport/http.(*httpMetrics).ConnectStart()
      /Users/abraithwaite/Projects/golang/pkg/mod/github.com/aws/[email protected]/transport/http/metrics.go:122 +0x6c
  github.com/aws/smithy-go/transport/http.(*httpMetrics).ConnectStart-fm()
      <autogenerated>:1 +0x20
  net.(*sysDialer).dialSingle()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:657 +0x108
  net.(*sysDialer).dialSerial()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:635 +0x1bc
  net.(*sysDialer).dialParallel.func1()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:555 +0xb4
  net.(*sysDialer).dialParallel.gowrap2()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:570 +0x58

Goroutine 59 (running) created at:
  net.(*sysDialer).dialParallel()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:581 +0x6dc
  net.(*Dialer).DialContext()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:527 +0x878
  net.(*Dialer).DialContext-fm()
      <autogenerated>:1 +0x64
  github.com/aws/aws-sdk-go-v2/aws/transport/http.(*BuildableClient).GetTransport.defaultHTTPTransport.traceDialContext.func1()
      /Users/abraithwaite/Projects/golang/pkg/mod/github.com/aws/[email protected]/aws/transport/http/client.go:207 +0xb4
  net/http.(*Transport).dial()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1226 +0x90
  net/http.(*Transport).dialConn()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1728 +0xa3c
  net/http.(*Transport).dialConnFor()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1563 +0xb8
  net/http.(*Transport).startDialConnForLocked.func1()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1545 +0x38

Goroutine 56 (running) created at:
  net.(*sysDialer).dialParallel()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:570 +0x310
  net.(*Dialer).DialContext()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/dial.go:527 +0x878
  net.(*Dialer).DialContext-fm()
      <autogenerated>:1 +0x64
  github.com/aws/aws-sdk-go-v2/aws/transport/http.(*BuildableClient).GetTransport.defaultHTTPTransport.traceDialContext.func1()
      /Users/abraithwaite/Projects/golang/pkg/mod/github.com/aws/[email protected]/aws/transport/http/client.go:207 +0xb4
  net/http.(*Transport).dial()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1226 +0x90
  net/http.(*Transport).dialConn()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1728 +0xa3c
  net/http.(*Transport).dialConnFor()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1563 +0xb8
  net/http.(*Transport).startDialConnForLocked.func1()
      /opt/homebrew/Cellar/go/1.23.3/libexec/src/net/http/transport.go:1545 +0x38
==================

[rjeczalik]

Just did a quick research, and found that this:

smithy-go/transport/http/metrics.go

Lines 121 to 123 in bed421c

	func (m *httpMetrics) ConnectStart(string, string) {
	m.connectStart = now()
	}

Can be called concurrently if transport is dual-stack:

https://github.com/golang/go/blob/6293a0683171e3a08e275884fddeaa2b57a861f6/src/internal/nettrace/nettrace.go#L36-L45

Due to this:

https://github.com/golang/go/blob/6293a0683171e3a08e275884fddeaa2b57a861f6/src/net/http/httptrace/trace.go#L43-L46

[rjeczalik]

#555