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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
54 lines
1.2 KiB
Go
54 lines
1.2 KiB
Go
package trace
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import (
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"fmt"
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"strings"
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"sync"
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"github.com/willf/bitset"
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)
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type uniqueConcurrentTaskNamer struct {
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mtx sync.Mutex
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active map[string]*bitset.BitSet
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}
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// bitvecLengthGauge may be nil
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func newUniqueTaskNamer() *uniqueConcurrentTaskNamer {
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return &uniqueConcurrentTaskNamer{
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active: make(map[string]*bitset.BitSet),
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}
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}
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// appends `#%d` to `name` such that until `done` is called,
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// it is guaranteed that `#%d` is not returned a second time for the same `name`
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func (namer *uniqueConcurrentTaskNamer) UniqueConcurrentTaskName(name string) (uniqueName string, done func()) {
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if strings.Contains(name, "#") {
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panic(name)
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}
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namer.mtx.Lock()
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act, ok := namer.active[name]
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if !ok {
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act = bitset.New(64) // FIXME magic const
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namer.active[name] = act
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}
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id, ok := act.NextClear(0)
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if !ok {
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// if !ok, all bits are 1 and act.Len() returns the next bit
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id = act.Len()
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// FIXME unbounded growth without reclamation
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}
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act.Set(id)
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namer.mtx.Unlock()
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return fmt.Sprintf("%s#%d", name, id), func() {
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namer.mtx.Lock()
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defer namer.mtx.Unlock()
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act, ok := namer.active[name]
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if !ok {
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panic("must be initialized upon entry")
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}
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act.Clear(id)
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}
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}
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