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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
41 lines
751 B
Go
41 lines
751 B
Go
package semaphore
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import (
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"context"
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"github.com/zrepl/zrepl/daemon/logging/trace"
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wsemaphore "golang.org/x/sync/semaphore"
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)
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type S struct {
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ws *wsemaphore.Weighted
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}
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func New(max int64) *S {
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return &S{wsemaphore.NewWeighted(max)}
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}
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type AcquireGuard struct {
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s *S
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released bool
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}
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// The returned AcquireGuard is not goroutine-safe.
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func (s *S) Acquire(ctx context.Context) (*AcquireGuard, error) {
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defer trace.WithSpanFromStackUpdateCtx(&ctx)()
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if err := s.ws.Acquire(ctx, 1); err != nil {
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return nil, err
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} else if err := ctx.Err(); err != nil {
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return nil, err
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}
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return &AcquireGuard{s, false}, nil
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}
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func (g *AcquireGuard) Release() {
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if g == nil || g.released {
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return
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}
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g.released = true
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g.s.ws.Release(1)
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}
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