Christian Schwarz
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
48 lines
833 B
Go
48 lines
833 B
Go
package trace
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import (
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"encoding/base64"
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"math/rand"
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"os"
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"strings"
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"time"
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"github.com/zrepl/zrepl/util/envconst"
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)
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var genIdPRNG = rand.New(rand.NewSource(1))
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func init() {
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genIdPRNG.Seed(time.Now().UnixNano())
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genIdPRNG.Seed(int64(os.Getpid()))
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}
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var genIdNumBytes = envconst.Int("ZREPL_TRACE_ID_NUM_BYTES", 3)
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func init() {
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if genIdNumBytes < 1 {
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panic("trace node id byte length must be at least 1")
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}
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}
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func genID() string {
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var out strings.Builder
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enc := base64.NewEncoder(base64.RawStdEncoding, &out)
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buf := make([]byte, genIdNumBytes)
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for i := 0; i < len(buf); {
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n, err := genIdPRNG.Read(buf[i:])
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if err != nil {
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panic(err)
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}
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i += n
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}
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n, err := enc.Write(buf[:])
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if err != nil || n != len(buf) {
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panic(err)
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}
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if err := enc.Close(); err != nil {
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panic(err)
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}
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return out.String()
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}
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