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https://github.com/zrepl/zrepl.git
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10a14a8c50
package trace:
- introduce the concept of tasks and spans, tracked as linked list within ctx
- see package-level docs for an overview of the concepts
- **main feature 1**: unique stack of task and span IDs
- makes it easy to follow a series of log entries in concurrent code
- **main feature 2**: ability to produce a chrome://tracing-compatible trace file
- either via an env variable or a `zrepl pprof` subcommand
- this is not a CPU profile, we already have go pprof for that
- but it is very useful to visually inspect where the
replication / snapshotter / pruner spends its time
( fixes #307 )
usage in package daemon/logging:
- goal: every log entry should have a trace field with the ID stack from package trace
- make `logging.GetLogger(ctx, Subsys)` the authoritative `logger.Logger` factory function
- the context carries a linked list of injected fields which
`logging.GetLogger` adds to the logger it returns
- `logging.GetLogger` also uses package `trace` to get the
task-and-span-stack and injects it into the returned logger's fields
75 lines
1.8 KiB
Go
75 lines
1.8 KiB
Go
package trace
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import (
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"context"
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"fmt"
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"runtime"
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"strings"
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"sync"
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)
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// use like this:
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//
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// defer WithSpanFromStackUpdateCtx(&existingCtx)()
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//
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//
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func WithSpanFromStackUpdateCtx(ctx *context.Context) DoneFunc {
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childSpanCtx, end := WithSpan(*ctx, getMyCallerOrPanic())
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*ctx = childSpanCtx
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return end
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}
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// derive task name from call stack (caller's name)
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func WithTaskFromStack(ctx context.Context) (context.Context, DoneFunc) {
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return WithTask(ctx, getMyCallerOrPanic())
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}
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// derive task name from call stack (caller's name) and update *ctx
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// to point to be the child task ctx
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func WithTaskFromStackUpdateCtx(ctx *context.Context) DoneFunc {
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child, end := WithTask(*ctx, getMyCallerOrPanic())
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*ctx = child
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return end
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}
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// create a task and a span within it in one call
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func WithTaskAndSpan(ctx context.Context, task string, span string) (context.Context, DoneFunc) {
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ctx, endTask := WithTask(ctx, task)
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ctx, endSpan := WithSpan(ctx, fmt.Sprintf("%s %s", task, span))
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return ctx, func() {
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endSpan()
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endTask()
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}
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}
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// create a span during which several child tasks are spawned using the `add` function
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func WithTaskGroup(ctx context.Context, taskGroup string) (_ context.Context, add func(f func(context.Context)), waitEnd DoneFunc) {
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var wg sync.WaitGroup
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ctx, endSpan := WithSpan(ctx, taskGroup)
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add = func(f func(context.Context)) {
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wg.Add(1)
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defer wg.Done()
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ctx, endTask := WithTask(ctx, taskGroup)
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defer endTask()
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f(ctx)
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}
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waitEnd = func() {
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wg.Wait()
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endSpan()
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}
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return ctx, add, waitEnd
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}
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func getMyCallerOrPanic() string {
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pc, _, _, ok := runtime.Caller(2)
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if !ok {
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panic("cannot get caller")
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}
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details := runtime.FuncForPC(pc)
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if ok && details != nil {
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const prefix = "github.com/zrepl/zrepl"
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return strings.TrimPrefix(strings.TrimPrefix(details.Name(), prefix), "/")
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}
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return ""
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}
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