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WAL watcher: improve comments

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Clarify in the first comment that it is `watch()` that waits, and reduce
verbiage.

The second comment was slightly contradictory to the first and otherwise
didn't seem to add much, since `currentSegment` was incremented just a
few lines later.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2024-02-22 09:32:46 +00:00
parent a975a83079
commit 6ed56c9f04
1 changed files with 2 additions and 4 deletions
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6
tsdb/wlog/watcher.go
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@ -290,8 +290,8 @@ func (w *Watcher) Run() error {
for !isClosed(w.quit) { for !isClosed(w.quit) {
w.currentSegmentMetric.Set(float64(currentSegment)) w.currentSegmentMetric.Set(float64(currentSegment))
// Reset the value of lastSegment each iteration, this is to avoid having to wait too long for // Re-check on each iteration in case a new segment was added,
// between reads if we're reading a segment that is not the most recent segment after startup. // because watch() will wait for notifications on the last segment.
_, lastSegment, err := w.firstAndLast() _, lastSegment, err := w.firstAndLast()
if err != nil { if err != nil {
return fmt.Errorf("wal.Segments: %w", err) return fmt.Errorf("wal.Segments: %w", err)
@ -299,8 +299,6 @@ func (w *Watcher) Run() error {
tail := currentSegment >= lastSegment tail := currentSegment >= lastSegment
level.Debug(w.logger).Log("msg", "Processing segment", "currentSegment", currentSegment, "lastSegment", lastSegment) level.Debug(w.logger).Log("msg", "Processing segment", "currentSegment", currentSegment, "lastSegment", lastSegment)
// On start, after reading the existing WAL for series records, we have a pointer to what is the latest segment.
// On subsequent calls to this function, currentSegment will have been incremented and we should open that segment.
if err := w.watch(currentSegment, tail); err != nil && !errors.Is(err, ErrIgnorable) { if err := w.watch(currentSegment, tail); err != nil && !errors.Is(err, ErrIgnorable) {
return err return err
} }