fix(tracing): direct OTel SDK setup for chain-coherent sampling #2756
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,156 @@ | ||
| package tracing | ||
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| import ( | ||
| "context" | ||
| "os" | ||
| "strconv" | ||
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| "go.opentelemetry.io/otel" | ||
| "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc" | ||
| "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp" | ||
| "go.opentelemetry.io/otel/propagation" | ||
| "go.opentelemetry.io/otel/sdk/resource" | ||
| sdktrace "go.opentelemetry.io/otel/sdk/trace" | ||
| semconv "go.opentelemetry.io/otel/semconv/v1.40.0" | ||
| "go.opentelemetry.io/otel/trace/noop" | ||
| "go.uber.org/zap" | ||
| knativetracing "knative.dev/pkg/observability/tracing" | ||
| ) | ||
|
|
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| const ( | ||
| EnvOTLPEndpoint = "OTEL_EXPORTER_OTLP_ENDPOINT" | ||
| EnvOTLPProtocol = "OTEL_EXPORTER_OTLP_PROTOCOL" | ||
| EnvOTLPTracesProtocol = "OTEL_EXPORTER_OTLP_TRACES_PROTOCOL" | ||
| EnvTracesSampler = "OTEL_TRACES_SAMPLER" | ||
| EnvTracesSamplerArg = "OTEL_TRACES_SAMPLER_ARG" | ||
|
|
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| protocolGRPC = "grpc" | ||
| protocolHTTP = "http/protobuf" | ||
| ) | ||
|
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| type TracerProvider struct { | ||
| shutdown func(context.Context) error | ||
| } | ||
|
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| func New(logger *zap.SugaredLogger) *TracerProvider { | ||
| otelConfigured := os.Getenv(EnvOTLPEndpoint) != "" && os.Getenv(EnvTracesSampler) != "" | ||
| if otelConfigured && !globalIsNoop() { | ||
| logger.Warn("OpenTelemetry and Knative tracing both configured; spans go through OpenTelemetry, Knative's tracer is unused. Set `tracing-protocol: none` in `pipelines-as-code-config-observability` to disable Knative, or unset `OTEL_EXPORTER_OTLP_ENDPOINT` to disable OpenTelemetry.") | ||
| } | ||
|
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| if os.Getenv(EnvOTLPEndpoint) == "" { | ||
| logger.Info("OpenTelemetry not configured (OTLP endpoint missing)") | ||
| return passthroughProvider() | ||
| } | ||
| if os.Getenv(EnvTracesSampler) == "" { | ||
| logger.Info("OpenTelemetry not configured (sampler missing)") | ||
| return passthroughProvider() | ||
| } | ||
|
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| proto := protocolFromEnv() | ||
| exporter, err := newExporter(context.Background(), logger, proto) | ||
|
Member
There was a problem hiding this comment. as per some AI review, does timeout handling needed here??
Contributor
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There was a problem hiding this comment. No - |
||
| if err != nil { | ||
| logger.Errorw("failed to create OTLP exporter", "error", err) | ||
| return passthroughProvider() | ||
| } | ||
|
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| res, err := resource.Merge( | ||
| resource.Default(), | ||
| resource.NewWithAttributes( | ||
| semconv.SchemaURL, | ||
| semconv.ServiceName(TracerName), | ||
| ), | ||
| ) | ||
| if err != nil { | ||
| logger.Errorw("failed to create resource", "error", err) | ||
| res = resource.Default() | ||
| } | ||
|
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| tp := sdktrace.NewTracerProvider( | ||
| sdktrace.WithBatcher(exporter), | ||
| sdktrace.WithResource(res), | ||
| sdktrace.WithSampler(samplerFromEnv(logger)), | ||
| ) | ||
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| otel.SetTracerProvider(tp) | ||
| otel.SetTextMapPropagator(propagation.TraceContext{}) | ||
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| logger.Infow("tracing initialized", "endpoint", os.Getenv(EnvOTLPEndpoint), "protocol", proto) | ||
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| return &TracerProvider{shutdown: tp.Shutdown} | ||
| } | ||
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| func passthroughProvider() *TracerProvider { | ||
| return &TracerProvider{shutdown: func(context.Context) error { return nil }} | ||
| } | ||
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| func globalIsNoop() bool { | ||
| tp := otel.GetTracerProvider() | ||
| if _, ok := tp.(noop.TracerProvider); ok { | ||
| return true | ||
| } | ||
| // Knative wraps noop in its own TracerProvider when tracing-protocol is none/absent. | ||
| if knativeProvider, ok := tp.(*knativetracing.TracerProvider); ok { | ||
| _, isNoop := knativeProvider.TracerProvider.(noop.TracerProvider) | ||
| return isNoop | ||
| } | ||
| return false | ||
| } | ||
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| func protocolFromEnv() string { | ||
| if v := os.Getenv(EnvOTLPTracesProtocol); v != "" { | ||
| return v | ||
| } | ||
| if v := os.Getenv(EnvOTLPProtocol); v != "" { | ||
| return v | ||
| } | ||
| return protocolGRPC | ||
| } | ||
|
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| func newExporter(ctx context.Context, logger *zap.SugaredLogger, proto string) (sdktrace.SpanExporter, error) { | ||
| endpoint := os.Getenv(EnvOTLPEndpoint) | ||
| switch proto { | ||
| case protocolHTTP: | ||
| return otlptracehttp.New(ctx, otlptracehttp.WithEndpointURL(endpoint)) | ||
| case protocolGRPC: | ||
| return otlptracegrpc.New(ctx, otlptracegrpc.WithEndpointURL(endpoint)) | ||
| default: | ||
| logger.Errorw("unsupported OTLP protocol; falling back to grpc", "protocol", proto) | ||
| return otlptracegrpc.New(ctx, otlptracegrpc.WithEndpointURL(endpoint)) | ||
| } | ||
| } | ||
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| func (tp *TracerProvider) Shutdown(ctx context.Context) error { | ||
| if tp.shutdown != nil { | ||
| return tp.shutdown(ctx) | ||
| } | ||
| return nil | ||
| } | ||
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| func samplerFromEnv(logger *zap.SugaredLogger) sdktrace.Sampler { | ||
| name := os.Getenv(EnvTracesSampler) | ||
| argStr := os.Getenv(EnvTracesSamplerArg) | ||
| arg, err := strconv.ParseFloat(argStr, 64) | ||
| if err != nil && argStr != "" { | ||
| logger.Errorw("ignoring malformed sampler argument; defaulting to 0% sampling", "env", EnvTracesSamplerArg, "value", argStr) | ||
| } | ||
| if argStr == "" && (name == "traceidratio" || name == "parentbased_traceidratio") { | ||
| logger.Infow("ratio sampler selected without "+EnvTracesSamplerArg+"; defaulting to 0% sampling", "env", EnvTracesSampler, "value", name) | ||
| } | ||
| switch name { | ||
| case "always_on": | ||
| return sdktrace.AlwaysSample() | ||
| case "always_off": | ||
| return sdktrace.NeverSample() | ||
| case "traceidratio": | ||
| return sdktrace.TraceIDRatioBased(arg) | ||
| case "parentbased_always_on": | ||
| return sdktrace.ParentBased(sdktrace.AlwaysSample()) | ||
| case "parentbased_always_off": | ||
| return sdktrace.ParentBased(sdktrace.NeverSample()) | ||
| case "parentbased_traceidratio": | ||
| return sdktrace.ParentBased(sdktrace.TraceIDRatioBased(arg)) | ||
| } | ||
| logger.Warnw("unrecognized OTEL_TRACES_SAMPLER value; falling back to never sample", "value", name) | ||
| return sdktrace.NeverSample() | ||
| } | ||
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While the configmap keys are removed, I see no change in controller. Does that mean the configmap based tracing continue to work even with these changes?
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The Knative tracing wrapper that consumed these
_examplekeys is replaced; the new tracer inpkg/tracing/provider.goreads the OTel-standard env vars directly. The_exampleblock was just documentation for keys nothing reads anymore.This is not the same ConfigMap as
pipelines-as-code(the main one), which holds thetracing-label-action|application|componentoperator label-name mappings.On the "no change in controller" observation - we verified end-to-end that with neither
OTEL_EXPORTER_OTLP_ENDPOINTnorOTEL_TRACES_SAMPLERset, PaC falls back to a noop tracer and emits no spans. If you're seeing tracing behavior unchanged from the pre-PR state, could you share how to reproduce so we can dig in?There was a problem hiding this comment.
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By changes in controller, I intended to ask if the knative base (eventing/adapter) that pac uses, reads these observability configmap keys for any arbitrary configuration/operations. Ref.
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Yes - the Knative eventing-adapter still consumes
config-observabilityfor non-tracing observability (metrics/profiling/etc. viaevadapter.NewObservabilityConfiguratorFromConfigMap()at the line you linked, logging is read fromconfig-loggingseparately). What this PR changes is specifically the tracing portion: PaC's old Knative tracing wrapper (added in bd9f468) readtracing-protocol/tracing-endpoint/tracing-sampling-ratefrom this ConfigMap; the newpkg/tracing/provider.goreads the OTel-standard env vars directly and that wrapper is gone, so those three keys went with the_exampleblock. The Knative-base reads for non-tracing observability are unchanged.There was a problem hiding this comment.
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@ci-operator as it looks breaking change and @theakshaypant is considerate about, can't we introduce env based configuration as fallback to configmap so that we're keeping both, considering other users may want to use configmap?
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If we read those keys, the
tracing-sampling-ratevalue would have to map to eithertraceidratio(which preserves the flat-sampling behavior this PR is fixing) orparentbased_traceidratio(which silently changes existing users' behavior). It's a breaking change either way - a ConfigMap fallback wouldn't actually preserve the old behavior. We're going env-vars-only and calling out the break in the tracing doc.Uh oh!
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What happens if a user still sets these keys in their configmap?
IIUC knative's
sharedmain.SetupObservabilityOrDieis still called by the watcher which starts tracing. Ref sharedmain, Ref watcherHow would these "conflicting" tracing configs be running? Would this cause a leak or is it a functional bug? Or have I completely missed the mark 🤨
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Yeah, this would be an issue. Both tracers initialize when an operator has set the Knative tracing keys. OpenTelemetry's setup runs after Knative's and overrides the global tracer provider, so spans flow through OpenTelemetry; Knative's tracer is configured but receives no spans.
There's now a startup warning when both are configured, the
noopProviderhelper was renamed topassthroughProvider(it never installed a noop globally), and the info-log messages no longer claim otherwise. The docs cover all this in a newWhen both are configuredsubsection.Whether a leak or a functional bug, a tracer receiving no spans is wasted-resource either way. There's now a startup warning, the log messages are clearer, and the docs have a dedicated section for this case.