zrepl/zfs/zfscmd/zfscmd_context.go
Christian Schwarz 10a14a8c50 [#307] add package trace, integrate it with logging, and adopt it throughout zrepl
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
2020-05-19 11:30:02 +02:00

33 lines
594 B
Go

package zfscmd
import (
"context"
"github.com/zrepl/zrepl/daemon/logging"
"github.com/zrepl/zrepl/logger"
)
type contextKey int
const (
contextKeyJobID contextKey = 1 + iota
)
type Logger = logger.Logger
func WithJobID(ctx context.Context, jobID string) context.Context {
return context.WithValue(ctx, contextKeyJobID, jobID)
}
func getJobIDOrDefault(ctx context.Context, def string) string {
ret, ok := ctx.Value(contextKeyJobID).(string)
if !ok {
return def
}
return ret
}
func getLogger(ctx context.Context) Logger {
return logging.GetLogger(ctx, logging.SubsysZFSCmd)
}