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cmd/prometheus: fix flaky TestQueryLog race condition (#17933)

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Add waitForQueryLog helper that polls for query log entries to appear
before asserting, rather than reading the file immediately after making
a query. This fixes a race condition where the query log wasn't flushed
to disk before the test read the file.

The helper uses a 5 second timeout with 100ms polling intervals, which
is generous enough to handle slow CI environments while keeping the test
responsive.

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>
This commit is contained in:
Arve Knudsen 2026-01-27 10:02:16 +01:00 committed by GitHub
parent 5e66c9305f
commit a5f86c3fb6
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GPG key ID: B5690EEEBB952194
1 changed files with 20 additions and 4 deletions
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24
cmd/prometheus/query_log_test.go
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@ -334,7 +334,8 @@ func (p *queryLogTest) run(t *testing.T) {
p.query(t)
ql := readQueryLog(t, queryLogFile.Name())
// Wait for query log entry to be written (avoid race with file I/O).
ql := waitForQueryLog(t, queryLogFile.Name(), 1)
qc := len(ql)
if p.exactQueryCount() {
require.Equal(t, 1, qc)
@ -361,7 +362,8 @@ func (p *queryLogTest) run(t *testing.T) {
p.query(t)
qc++
ql = readQueryLog(t, queryLogFile.Name())
// Wait for query log entry to be written (avoid race with file I/O).
ql = waitForQueryLog(t, queryLogFile.Name(), qc)
if p.exactQueryCount() {
require.Len(t, ql, qc)
} else {
@ -392,7 +394,8 @@ func (p *queryLogTest) run(t *testing.T) {
qc++
ql = readQueryLog(t, newFile.Name())
// Wait for query log entry to be written (avoid race with file I/O).
ql = waitForQueryLog(t, newFile.Name(), qc)
if p.exactQueryCount() {
require.Len(t, ql, qc)
} else {
@ -404,7 +407,8 @@ func (p *queryLogTest) run(t *testing.T) {
p.query(t)
ql = readQueryLog(t, queryLogFile.Name())
// Wait for query log entry to be written (avoid race with file I/O).
ql = waitForQueryLog(t, queryLogFile.Name(), 1)
qc = len(ql)
if p.exactQueryCount() {
require.Equal(t, 1, qc)
@ -446,6 +450,18 @@ func readQueryLog(t *testing.T, path string) []queryLogLine {
return ql
}
// waitForQueryLog waits for the query log to contain at least minEntries entries,
// polling at regular intervals until the timeout is reached.
func waitForQueryLog(t *testing.T, path string, minEntries int) []queryLogLine {
t.Helper()
var ql []queryLogLine
require.Eventually(t, func() bool {
ql = readQueryLog(t, path)
return len(ql) >= minEntries
}, 5*time.Second, 100*time.Millisecond, "timed out waiting for query log to have at least %d entries, got %d", minEntries, len(ql))
return ql
}
func TestQueryLog(t *testing.T) {
if testing.Short() {
t.Skip("skipping test in short mode.")