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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
92 lines
1.8 KiB
Go
92 lines
1.8 KiB
Go
package hooks
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import (
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"bufio"
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"bytes"
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"context"
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"sync"
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"github.com/zrepl/zrepl/daemon/logging"
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"github.com/zrepl/zrepl/logger"
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"github.com/zrepl/zrepl/util/envconst"
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)
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type Logger = logger.Logger
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func GetLogger(ctx context.Context) Logger { return getLogger(ctx) }
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func getLogger(ctx context.Context) Logger {
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return logging.GetLogger(ctx, logging.SubsysHooks)
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}
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const MAX_HOOK_LOG_SIZE_DEFAULT int = 1 << 20
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type logWriter struct {
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/*
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Mutex prevents:
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concurrent writes to buf, scanner in Write([]byte)
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data race on scanner vs Write([]byte)
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and concurrent write to buf (call to buf.Reset())
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in Close()
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(Also, Close() should generally block until any Write() call completes.)
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*/
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mtx *sync.Mutex
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buf bytes.Buffer
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scanner *bufio.Scanner
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logger Logger
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level logger.Level
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field string
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}
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func NewLogWriter(mtx *sync.Mutex, logger Logger, level logger.Level, field string) *logWriter {
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w := new(logWriter)
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w.mtx = mtx
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w.scanner = bufio.NewScanner(&w.buf)
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w.logger = logger
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w.level = level
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w.field = field
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return w
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}
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func (w *logWriter) log(line string) {
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w.logger.WithField(w.field, line).Log(w.level, "hook output")
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}
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func (w *logWriter) logUnreadBytes() error {
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for w.scanner.Scan() {
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w.log(w.scanner.Text())
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}
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if w.buf.Cap() > envconst.Int("ZREPL_MAX_HOOK_LOG_SIZE", MAX_HOOK_LOG_SIZE_DEFAULT) {
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w.buf.Reset()
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}
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return nil
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}
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func (w *logWriter) Write(in []byte) (int, error) {
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w.mtx.Lock()
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defer w.mtx.Unlock()
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n, bufErr := w.buf.Write(in)
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if bufErr != nil {
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return n, bufErr
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}
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err := w.logUnreadBytes()
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if err != nil {
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return n, err
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}
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// Always reset the scanner for the next Write
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w.scanner = bufio.NewScanner(&w.buf)
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return n, nil
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}
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func (w *logWriter) Close() (err error) {
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w.mtx.Lock()
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defer w.mtx.Unlock()
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return w.logUnreadBytes()
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}
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