Feat/pubsub v2 otel

[Josemaralves]

Summary

Migration of Pub/Sub to the cloud.google.com/go/pubsub/v2 SDK with native OpenTelemetry tracing support, a comprehensive OTEL infrastructure overhaul (signal-specific exporters, Prometheus, runtime metrics, sampling), and opt-in MongoDB monitoring, alongside dependency upgrades across the board.

Key Changes

Pub/Sub v2 Migration (factory/contrib/cloud.google.com/pubsub/v1)

• Switched from pubsub.NewClient to pubsub.NewClientWithConfig with EnableOpenTelemetryTracing: true ? native OTel tracing via the SDK
• Attached otelgrpc.NewClientHandler() and gRPC experimental metrics dial options, wired to the boost OTel MeterProvider
• Helper.Start() now uses fire-and-forget goroutines (dropped sync.WaitGroup coordination)
• Extracted generateCloudEvent to a standalone message.go

OpenTelemetry Overhaul (factory/contrib/go.opentelemetry.io/otel/v1)

• Signal-specific endpoints: metric.endpoint, metric.protocol, trace.endpoint, trace.protocol, trace.ratio ? resolution order follows the OTel env-var spec
• Prometheus exporter: registered alongside the periodic OTLP reader in StartMetricProvider
• Runtime instrumentation: runtime.Start(...) runs automatically (5s memory stats interval)
• Sampling: AlwaysSample() ? TraceIDRatioBased(options.Trace.Ratio), defaulting to 1.0
• Env parsing: NewOptions now reads OTEL_RESOURCE_ATTRIBUTES, OTEL_EXPORTER_OTLP_TIMEOUT, OTEL_TRACES_SAMPLER_ARG
• Provider lifecycle: removed noop initializers ? providers are now only set when explicitly started; plugins no longer auto-start them

MongoDB Opt-in Monitoring (factory/contrib/go.mongodb.org/mongo-driver/v2)

• Command/pool monitors gated behind Log.Enabled (default false), extracted to setLogMonitor
• OTel plugin now passes WithMeterProvider alongside the tracer provider

gRPC Client OTel (factory/contrib/google.golang.org/grpc/v1)

• ~20 experimental gRPC metrics enabled (subchannel, pick_first, RLS, WRR, outlier detection, xDS client) via oteltelemetry.DialOption

Function Middleware

• OTel middleware: holds a Tracer instance, uses c.Tracer.Start instead of creating a new tracer per invocation; sync.Once-guarded lazy meter init
• Logger middleware: simplified log adapter signature from func(format string, args ...interface{}) to func(string); default level changed from "INFO" to "DEBUG"

New FX Modules

• fx/modules/factory/contrib/go.opentelemetry.io/otel/v1 ? starts tracer and meter providers at app startup
• fx/modules/bootstrap/function/middleware/opentelemetry ? provides OpenTelemetry[T] via fx.Provide, gated by config flag

Dependency Upgrades

• Go 1.26.0 ? 1.26.4
• Nearly all dependencies bumped (Datadog agent, AWS SDK v2, OTel stack, Echo, NATS, gRPC, etc.)
• Added: go.opentelemetry.io/contrib/instrumentation/runtime, go.opentelemetry.io/otel/exporters/prometheus
• Removed two replace directives (gnostic-models, kube-openapi)

Test Plan

• Verify Pub/Sub subscriber receives and acknowledges messages with OTel tracing enabled
• Confirm OTEL signal-specific endpoints work independently for traces and metrics
• Validate Prometheus /metrics endpoint is exposed correctly
• Check MongoDB monitors are not attached when Log.Enabled is false (default)
• Run go build ./... and go test ./... green

Breaking Changes

• Pub/Sub adapter backoff default changed from true to false
• Logger middleware adapter signature changed from func(format string, args ...interface{}) to func(string)