Files
zrepl/util/semaphore/semaphore.go
Christian Schwarz 1ae087bfcf [WIP] add and use tracing API as part of package logging
- 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
- introduce the concept of tasks and spans, also tracked as linked list within ctx
    - [ ] TODO automatic logging of span begins and ends, with a unique
      ID stack that makes it easy to follow a series of log entries in
      concurrent code
    - 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 )
2020-04-25 11:16:59 +02:00

42 lines
748 B
Go

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