Tracing putTag

[hweawer]

This pull request adds OpenTelemetry distributed tracing support to the build-index tag server's putTag operation. The changes enable tracing of Docker push operations through the system, making it easier to debug and monitor performance.

1. Request Entry Point (Build-Index Server)

• otelhttp.NewMiddleware automatically creates the root span from incoming HTTP request
• Extracts trace context from headers if present (for distributed traces), or generates new Trace ID
• Span name: HTTP-level (e.g., PUT /tags/:tag)

2. Business Logic Span (putTagHandler)

• Creates child span: build_index.put_tag
• Custom attributes added:
  • tag: The Docker image tag
  • digest: The blob digest (sha256:...)
  • replicate: Whether replication was requested
  • dependency_count: Number of dependencies (layers + manifest)
  • success: Final operation status

[Copilot]

Pull request overview

This pull request adds OpenTelemetry distributed tracing support to the build-index tag server's putTag operation. The changes enable tracing of Docker push operations through the system, making it easier to debug and monitor performance.

Changes:

• Adds a new WithTraceContext logging utility function that extracts trace_id and span_id from context
• Implements OpenTelemetry tracing in the putTagHandler with span lifecycle management and error recording
• Updates dependencies to include OpenTelemetry packages (v1.21.0 for core, v0.46.0 for HTTP instrumentation)

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
utils/log/log.go	Adds WithTraceContext helper function to include trace_id and span_id in logs
build-index/tagserver/server.go	Adds tracer field to Server struct, applies tracing middleware to PUT endpoint, implements span management in putTagHandler with attributes and error recording
build-index/cmd/cmd.go	Initializes OpenTelemetry tracer and passes it to the server
build-index/tagserver/server_test.go	Updates test setup to use noop tracer for compatibility
go.mod	Adds OpenTelemetry dependencies and upgrades testify to v1.8.4
go.sum	Updates checksums for new and upgraded dependencies

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