trace

package
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 Go to latest Published: Dec 6, 2024 License: Apache-2.0 Imports: 35 Imported by: 1

Documentation

Overview

Package trace wraps standard tracing for outreach.

This package wraps honeycomb tracing

Trace Initialization

Applications should call `trace.StartTracing(serviceName)` and `trace.StopTracing()` in their `main` like so: 

func main() {
     trace.StartTracing("example")
     defer trace.StopTracing()

     ... main app logic ...
}

See https://github.com/grevych/gobox/blob/master/cmd/example/main.go.

Servers and incoming requests

The httpx/pkg/handlers package wraps the required trace header parsing logic and so applications that use `handlers.Endpoint` do not have to do anything special here.

Custom http servers should wrap their request handling code like so: 

		trace.NewHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) *roundtripperState {
		  trace.StartSpan(r.Context(), "my endpoint")
		  defer trace.End(r.Context())
		  ... do actual request handling ...
     }), "my endpoint")

Non-HTTP servers should wrap their request handling like so: 

ctx = trace.StartSpan(ctx, "my endpoint")
defer trace.End(ctx)
... do actual request handling ...

Clients should use a Client with the provided transport like so: 

ctx = trace.StartSpan(ctx, "my call")
defer trace.End(ctx)
client := http.Client{Transport: trace.NewTransport(nil)}
... do actual call using the new client ...

Tracing calls

Any interesting function (such as model fetches or redis fetches) should use the following pattern: 

func MyInterestingRedisFunction(ctx context.Context, ...) error {
    ctx = trace.StartCall(ctx, "redis", RedisInfo{...})
    defer trace.EndCall(ctx)

    .... actual work ...
    trace.AddInfo(ctx, xyzInfo)

    return trace.SetCallStatus(ctx, err)
}

This automatically updates metrics ("call_request_secconds" is the counter with "redis" as the name label), writes to debug/error logs and also writes traces to our tracing infrastructure

Trace calls can be nested.

Creating spans

Spans should rarely be needed but are available for when the metrics or default logging is not sufficient.

Spans are automatically considered `children` of the current trace or span (based on the `context`). The redis example above would look like so: 

ctx = trace.StartSpan(ctx, "redis")
defer trace.End(ctx)
.... do actual redis call...

Adding tags

Tags can be added to the `current` span (or trace or call) by simply calling `trace.AddInfo`. Note that this accepts the same types that logging accepts. For instance, to record an error with redis: 

result, err := redis.Call(....)
if err != nil {
   // if you are using trace.Call, then do trace.SetCallStatus
   // instead.
   return trace.Error(ctx, err)
}

Index

Constants

View Source 
const (
	// Header that enforces the tracing for particular request
	HeaderForceTracing = "X-Force-Trace"
	// Header used by OpenTelemetry to propagate traces
	OtelPropagationHeader = "Traceparent"
)

Variables

This section is empty.

Functions

func AddInfo 

func AddInfo(ctx context.Context, args ...log.Marshaler)

AddInfo updates the current span with the provided fields. If a call exists, it updates the call info args with the passed in log marshalers

This is not propagated to child spans automatically.

It does nothing if there isn't a current span.

func AddSpanInfo 

func AddSpanInfo(ctx context.Context, args ...log.Marshaler)

AddSpanInfo updates the current span with the provided fields.

It does nothing if there isn't a current span.

func AsGRPCCall 

func AsGRPCCall() call.Option

AsGRPCCall changes the call type to gRPC. This SHOULD NOT be used for outbound calls to external services. Use AsOutboundCall instead.

func AsHTTPCall 

func AsHTTPCall() call.Option

AsHTTPCall changes the call type to HTTP. This SHOULD NOT be used for outbound calls to external services. Use AsOutboundCall instead.

func AsOutboundCall 

func AsOutboundCall() call.Option

AsOutboundCall changes the call type to Outbound. This is meant for calls to external services, such as a client making a call to a server.

func CloseTracer 

func CloseTracer(ctx context.Context)

CloseTracer stops all tracing and sends any queued traces.

This should be called when an application is exiting, or when you want to terminate the tracer.

func CommonProps 

func CommonProps() log.Marshaler

CommonProps sets up common properties for traces in cli apps

func End 

func End(ctx context.Context)

End ends a span (or a trace started via StartTrace).

func EndCall 

func EndCall(ctx context.Context)

EndCall calculates the duration of the call, writes to metrics, standard logs and closes the trace span.

This call should always be right after the StartCall in a defer pattern. See StartCall for the right pattern of usage.

EndCall, when called within a defer, catches any panics and rethrows them. Any panics are converted to errors and cause error logging to happen (as do any SetCallStatus calls)

func EndTracing deprecated 

func EndTracing()

Deprecated: Use CloseTracer() instead. EndTracing stops the tracing infrastructure.

This should be called at the exit of the application.

func Error 

func Error(ctx context.Context, err error) error

Error is a convenience for attaching an error to a span.

func ForceTracing 

func ForceTracing(ctx context.Context) context.Context

ForceTracing will enforce tracing for processing started with returned context and all downstream services that will be invoken on the way.

func FromHeaders 

func FromHeaders(ctx context.Context, hdrs map[string][]string, name string) context.Context

FromHeaders fetches trace info from a headers map and starts a new Span on top of the extracted span context (which can be either local or remote). You must end this context with End.

Only use for GRPC. Prefer NewHandler for http calls.

func GetTraceStateSampleRate 

func GetTraceStateSampleRate(ts trace.TraceState) (uint, bool)

GetTraceStateSampleRate fetches the sample rate from the tracestate.

The second return value is an `ok` bool that is false if the fetch fails.

func ID 

func ID(ctx context.Context) string

ID returns an ID for use with external services to propagate tracing context. The ID returned will be the honeycomb trace ID (if honeycomb is enabled) or an empty string if neither are enabled.

func IDs 

func IDs(ctx context.Context) log.Marshaler

IDs returns a log-compatible tracing scope (IDs) data built from the context suitable for logging.

func InitTracer 

func InitTracer(_ context.Context, serviceName string) error

InitTracer starts all tracing infrastructure.

This needs to be called before sending any traces otherwise they will not be published.

func NewForceTraceHeaderSampler 

func NewForceTraceHeaderSampler(delegate sdktrace.Sampler) sdktrace.Sampler

NewForceTraceHeaderSampler wraps an existing sampler with support for the X-Force-Trace header, with the help of the `isTracingForced` context flag.

func NewHandler 

func NewHandler(handler http.Handler, operation string) http.Handler

NewHandler creates a new handlers which reads propagated headers from the current trace context.

Usage: 

	  trace.NewHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) *roundtripperState {
		trace.StartSpan(r.Context(), "my endpoint")
		defer trace.End(r.Context())
		... do actual request handling ...
   }), "my endpoint")

func NewHoneycombDeterministicSampler 

func NewHoneycombDeterministicSampler(sampleRate uint) sdktrace.Sampler

NewHoneycombDeterministicSampler returns a sampler that mimics the deterministic sampler behavior from Honeycomb's beeline libraries. This was formerly our primary sampler, but now we use it only for new local traces.

Our exact choice of sampling algorithm shouldn't matter in a world where every service respects parent-based sampling. However, we have a lot of old services that still have this HC deterministic sampler hard-coded, and so using this as our sampler reduces the odds of broken traces.

In the longer term, when every service supports parent-based sampling, we can stop caring which sampler we use for this case.

func NewLogFileExporter 

func NewLogFileExporter(port int) (sdktrace.SpanExporter, error)

NewLogFileExporter Creates a new exporter that sends all spans to the passed in port on localhost.

func NewLogFileTracer 

func NewLogFileTracer(ctx context.Context, serviceName string, config *Config) (tracer, error)

NewLogFileTracer initializes a tracer that sends traces to a log file.

func NewOtelTracer 

func NewOtelTracer(ctx context.Context, serviceName string, config *Config) (tracer, error)

NewOtelTracer creates and initializes a new otel tracer.

func NewSampleRateTaggingSampler 

func NewSampleRateTaggingSampler(defaultSampleRate uint) sdktrace.Sampler

NewSampleRateTaggingSampler is a sampler that doesn't actually make sampling decisions. It simply inherits the decision from its parent. We used it not for decision-making, but to ensure all sampled spans include an appropriate "SampleRate" tag that Honeycomb can use for sample rate adjustment.

This is a hack. We hope that one day we can move to an official OpenTelemetry head-based sampling mechanism that handles this more cleanly. [1] At the time of writing, this part of the standard is in flux and not all OpenTelemetry libraries support it.

[1] https://opentelemetry.io/docs/specs/otel/trace/tracestate-probability-sampling/

func NewTransport 

func NewTransport(old http.RoundTripper) http.RoundTripper

NewTransport creates a new transport which propagates the current trace context.

Usage: 

client := &http.Client{Transport: trace.NewTransport(nil)}
resp, err := client.Get("/ping")

For most cases, use the httpx/pkg/fetch package as it also logs the request, updates latency metrics and adds traces with full info

Note: the request context must be derived from StartSpan.

func RegisterSpanProcessor 

func RegisterSpanProcessor(s sdktrace.SpanProcessor)

func SetCallError 

func SetCallError(ctx context.Context, err error) error

SetCallError is deprecated and will directly call into SetCallStatus for backward compatibility

func SetCallStatus 

func SetCallStatus(ctx context.Context, err error) error

SetCallStatus can be optionally called to set status of the call. When the error occurs on the current call, the error will be traced. When the error is nil, no-op from this function

func SetCallTypeGRPC deprecated 

func SetCallTypeGRPC(ctx context.Context) context.Context

Deprecated: use AsGrpcCall call.Option instead SetTypeGRPC is meant to set the call type to GRPC on a context that has already been initialized for tracing via StartCall or StartExternalCall.

func SetCallTypeHTTP deprecated 

func SetCallTypeHTTP(ctx context.Context) context.Context

Deprecated: use AsHttpCall call.Option instead SetTypeHTTP is meant to set the call type to HTTP on a context that has already been initialized for tracing via StartCall or StartExternalCall.

func SetCallTypeOutbound deprecated 

func SetCallTypeOutbound(ctx context.Context) context.Context

Deprecated: use AsOutboundCall call.Option instead SetCallTypeOutbound is meant to set the call type to Outbound on a context that has already been initialized for tracing via StartCall or StartExternalCall.

func SetCustomCallKind 

func SetCustomCallKind(ctx context.Context, ck metrics.CallKind)

SetCustomCallKind is meant to alter the Kind property of a traced call. This can be useful as a service specific dimension to slice, e.g. grpc_request_handled metric based on additional context.

func SetSpanProcessorHook 

func SetSpanProcessorHook(hook func([]attribute.KeyValue))

SetSpanProcessorHook sets a hook to run when a span ends

func SetTraceStateSampleRate 

func SetTraceStateSampleRate(ts trace.TraceState, sampleRate uint) trace.TraceState

SetTraceStateSampleRate sets the sample rate in the tracestate.

func SpanID 

func SpanID(ctx context.Context) string

SpanID returns the root tracing SpanID for use when it is needed to correlate the logs belonging to same flow. The SpanID returned will be the honeycomb trace SpanID (if honeycomb is enabled) or an empty string if neither are enabled

func StartCall 

func StartCall(ctx context.Context, cType string, args ...log.Marshaler) context.Context

StartCall is used to start an internal call. For external calls please use StartExternalCall.

This takes care of standard logging, metrics and tracing for "calls"

Typical usage: 

ctx = trace.StartCall(ctx, "sql", SQLEvent{Query: ...})
defer trace.EndCall(ctx)

return trace.SetCallStatus(ctx, sqlCall(...));

The callType should be broad category (such as "sql", "redis" etc) as as these are used for metrics and cardinality issues come into play. Do note that commonly used call types are exported as constants in this package and should be used whenever possible. The most common call types are http (trace.CallTypeHTTP) and grpc (trace.CallTypeGRPC).

Use the extra args to add stuff to traces and logs and these can have more information as needed (including actual queries for instance).

The log includes a initial Debug entry and a final Error entry if the call failed (but no IDs entry if the call succeeded). Success or failure is determined by whether there was a SetCallStatus or not. (Panics detected in EndCall are considered errors).

StartCalls can be nested.

func StartSpan 

func StartSpan(ctx context.Context, name string, args ...log.Marshaler) context.Context

StartSpan starts a new span.

Use trace.End to end this.

func StartSpanAsync deprecated 

func StartSpanAsync(ctx context.Context, name string, args ...log.Marshaler) context.Context

Deprecated: use StartSpan() instead. It will handle async traces automatically. StartSpanAsync starts a new async span.

An async span does not have to complete before the parent span completes.

Use trace.End to end this.

func StartSpanWithOptions 

func StartSpanWithOptions(ctx context.Context, name string, opts []SpanStartOption, args ...log.Marshaler) context.Context

StartSpanWithOptions starts a new span, with extra start options (such as links to external spans).

Use trace.End to end this.

func StartTrace deprecated 

func StartTrace(ctx context.Context, name string) context.Context

Deprecated: use StartSpan() instead. It will start a trace automatically if the context does not contain one already. StartTrace starts a new root span/trace.

Use trace.End to end this.

func StartTracing deprecated 

func StartTracing(serviceName string) error

Deprecated: Use InitTracer() instead. StartTracing starts the tracing infrastructure.

This should be called at the start of the application.

func ToHeaders 

func ToHeaders(ctx context.Context) map[string][]string

ToHeaders writes the current trace context into a headers map

Only use for GRPC. Prefer NewTransport for http calls.

func WithCallOptions 

func WithCallOptions(ctx context.Context, opts CallOptions)

SetCallOptions sets the provided call options on the current call in the provided context. The provided options replace any existing options. Call options are not preserved across application boundaries.

Example: 

ctx = trace.StartCall(ctx, "http", trace.WithCallOptions(ctx, trace.CallOptions{DisableInfoLogging: true}))

func WithInfoLoggingDisabled 

func WithInfoLoggingDisabled() call.Option

WithInfoLoggingDisabled disables info logging on the current call.

Note that the default behavior is configurable. If the info logs were already disabled by default, this will be a no-op.

Example: 

ctx = trace.StartCall(ctx, "http", trace.WithInfoLoggingDisabled())

func WithInfoLoggingEnabled 

func WithInfoLoggingEnabled() call.Option

WithInfoLoggingEnabled enables info logging on the current call

Note that the default behavior is configurable. If the info logs were already enabled by default, this will be a no-op.

Example: 

ctx = trace.StartCall(ctx, "http", trace.WithInfoLoggingEnabled())

func WithScheduledTime 

func WithScheduledTime(t time.Time) call.Option

WithScheduledTime sets the call scheduled time to the provided time. Normally, this is set automatically by StartCall.

Example: 

ctx = trace.StartCall(ctx, "http", log.F{"query": query}, trace.WithScheduledTime(time.Now()))

Types

type Annotator 

type Annotator struct {
	// contains filtered or unexported fields
}

Annotator is a SpanProcessor that adds service-level tags on every span

func (Annotator) ForceFlush 

func (a Annotator) ForceFlush(context.Context) error

func (Annotator) OnEnd 

func (a Annotator) OnEnd(s sdktrace.ReadOnlySpan)

func (Annotator) OnStart 

func (a Annotator) OnStart(_ context.Context, s sdktrace.ReadWriteSpan)

func (Annotator) Shutdown 

func (a Annotator) Shutdown(context.Context) error

type CallOptions 

type CallOptions call.Options

CallOptions contains options for all tracing calls. See call.Options for more information.

type Config 

type Config struct {
	Otel       `yaml:"OpenTelemetry"`
	LogFile    LogFile `yaml:"LogFile"`
	GlobalTags `yaml:"GlobalTags,omitempty"`

	// LogCallByDefault determines info logs for non-error instances of
	// `trace.StartCall`.  The behavior can be overridden by providing
	// explicit options to specific `trace.StartCall` invocations.  A
	// `trace.StartCall` that ends in an error will always be logged.
	LogCallsByDefault bool `yaml:"LogCallsByDefault"`
}

Config is the tracing config that gets read from trace.yaml

func (*Config) Load 

func (c *Config) Load() error

Load loads the configuration from trace.yaml

type GlobalTags 

type GlobalTags struct {
	DevEmail string `yaml:"DevEmail,omitempty"`
}

GlobalTags are tags that get included with every span

func (*GlobalTags) MarshalLog 

func (g *GlobalTags) MarshalLog(addField func(key string, v interface{}))

MarshalLog ensures that GlobalTags have a valid value included

type Handler 

type Handler struct {
	// contains filtered or unexported fields
}

func (*Handler) ServeHTTP 

func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request)
type Link struct {
	// contains filtered or unexported fields
}

Link implements SpanStartOption 

func WithLink(traceHeaders map[string][]string) Link

WithLink links an external span to the current one. The link can only happen when trace span starts (they cannot be attached mid-span lifetime).

The caller should not modify the argument traceHeaders map after calling WithLink.

The method accepts trace headers as a map: assumption is current 'context' hosts the parent span and the linked contexts come from 'outside' by other means (e.g. clerk system event headers). In case you need to link trace with a span and you have direct access to that Span's context, you can use trace.ToHeaders to extract the same headers map.

func (Link) SpanID 

func (l Link) SpanID() string

SpanID returns the span ID from the linked context or empty if such is unavailable

func (Link) TraceID 

func (l Link) TraceID() string

TraceID returns the trace ID from the linked context or empty if such is unavailable

type LogFile 

type LogFile struct {
	// Enabled determines whether to turn on tracing to a log file
	Enabled bool `yaml:"Enabled"`

	// Port is the port used by the the logfile trace server
	Port int `yaml:"Port"`
}

LogFile is the configuration for log file based tracing

type LogFileSpanExporter 

type LogFileSpanExporter struct {
	// contains filtered or unexported fields
}

LogFileSpanExporter an exporter that sends all traces across the configured connection.

func (*LogFileSpanExporter) ExportSpans 

func (se *LogFileSpanExporter) ExportSpans(ctx context.Context, spans []sdktrace.ReadOnlySpan) error

ExportSpans exports all the provided spans.

func (*LogFileSpanExporter) Shutdown 

func (se *LogFileSpanExporter) Shutdown(_ context.Context) error

Shutdown cleans up when the exporter close by ensuring that the connection gets closed.

type Otel 

type Otel struct {
	// Enabled determines whether to turn on tracing
	Enabled bool `yaml:"Enabled"`
	// Endpoint for the tracing backend
	Endpoint string `yaml:"Endpoint"`
	// CollectorEndpoint endpoint for the opentelemetry collector for tracing
	CollectorEndpoint string `yaml:"CollectorEndpoint"`
	// Dataset the honeycomb grouping of traces
	Dataset string `yaml:"Dataset"`
	// SamplePercent the rate at which to sample
	SamplePercent float64 `yaml:"SamplePercent"`
	// Debug allows printing debug statements for traces
	Debug bool `yaml:"Debug"`
	// Stdout also outputs traces to stdout
	Stdout bool `yaml:"Stdout"`
	// APIKey used for authentication with the backend at Endpoint
	APIKey cfg.Secret `yaml:"APIKey"`
}

Otel is the configuration for OpenTelemetry based tracing

type SpanStartOption 

type SpanStartOption interface {
	// contains filtered or unexported methods
}

SpanStartOption is an interface for various options to be provided during span creation (StartSpan).

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