Fix valkey-benchmark hanging in single-thread duration mode by yzc-yzc · Pull Request #3079 · valkey-io/valkey

yzc-yzc · 2026-01-20T08:52:26Z

In single-thread mode with --duration, the benchmark could hang indefinitely after the duration elapsed.

Root Cause

Consider the following scenario:

Step 1 (T = 0.99s, duration = 1s):

readHandler receives response, calls clientDone()
isBenchmarkFinished() returns false (0.99s < 1s)
clientDone() calls resetClient()

Step 2 (T = 1.01s):

writeHandler is called
isBenchmarkFinished() returns true (1.01s >= 1s)
writeHandler returns early, no request sent, no read event registered

Result:

readHandler never triggers → clientDone() never called → no aeStop()
showThroughput() checks num_threads && isBenchmarkFinished(), skipping single-thread mode
Event loop never terminates

Fixes #2893, fixes #2843

Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com>

yzc-yzc · 2026-01-20T08:59:03Z

One way to reliably trigger this bug is to add the following code in writeHandler() before the isBenchmarkFinished() check:

/* Initialize request when nothing was written. */
if (c->written == 0) {
    // DEBUG: Force duration to expire
    static bool flag = true;
    if (flag) {
        config.start -= 1000;  // Simulate 1 second has passed
        flag = false;
    }
    
    int requests_issued = atomic_fetch_add_explicit(...);
    if (isBenchmarkFinished(requests_issued)) {
        c->pending = 0; 
        return;
    }
    ...
}

Then test with --duration 1.

codecov · 2026-01-20T09:11:32Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.30%. Comparing base (0b1f99d) to head (b1a43af).
⚠️ Report is 2 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #3079      +/-   ##
============================================
- Coverage     74.33%   74.30%   -0.04%     
============================================
  Files           129      129              
  Lines         71009    71009              
============================================
- Hits          52784    52762      -22     
- Misses        18225    18247      +22

Files with missing lines	Coverage Δ
src/valkey-benchmark.c	`61.50% <100.00%> (ø)`

... and 22 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com>

zuiderkwast

LGTM, thanks.

@rainsupreme PTAL.

dvkashapov

LGTM

sarthakaggarwal97

Thank you! This will help daily CI run green.

rainsupreme

haha wow I didn't see that earlier! good catch 👍

…o#3079) In single-thread mode with --duration, the benchmark could hang indefinitely after the duration elapsed. ## Root Cause Consider the following scenario: **Step 1** (T = 0.99s, duration = 1s): - `readHandler` receives response, calls `clientDone()` - `isBenchmarkFinished()` returns `false` (0.99s < 1s) - `clientDone()` calls `resetClient()` **Step 2** (T = 1.01s): - `writeHandler` is called - `isBenchmarkFinished()` returns `true` (1.01s >= 1s) - `writeHandler` returns early, **no request sent, no read event registered** **Result**: - `readHandler` never triggers → `clientDone()` never called → no `aeStop()` - `showThroughput()` checks `num_threads && isBenchmarkFinished()`, skipping single-thread mode - **Event loop never terminates** Fixes valkey-io#2893, fixes valkey-io#2843 --------- Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com> Signed-off-by: arshidkv12 <arshidkv12@gmail.com>

zuiderkwast · 2026-01-29T11:35:36Z

#2581 was not included in 9.0 so we should not backport this fix.

…o#3079) In single-thread mode with --duration, the benchmark could hang indefinitely after the duration elapsed. ## Root Cause Consider the following scenario: **Step 1** (T = 0.99s, duration = 1s): - `readHandler` receives response, calls `clientDone()` - `isBenchmarkFinished()` returns `false` (0.99s < 1s) - `clientDone()` calls `resetClient()` **Step 2** (T = 1.01s): - `writeHandler` is called - `isBenchmarkFinished()` returns `true` (1.01s >= 1s) - `writeHandler` returns early, **no request sent, no read event registered** **Result**: - `readHandler` never triggers → `clientDone()` never called → no `aeStop()` - `showThroughput()` checks `num_threads && isBenchmarkFinished()`, skipping single-thread mode - **Event loop never terminates** Fixes valkey-io#2893, fixes valkey-io#2843 --------- Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com>

…o#3079) In single-thread mode with --duration, the benchmark could hang indefinitely after the duration elapsed. ## Root Cause Consider the following scenario: **Step 1** (T = 0.99s, duration = 1s): - `readHandler` receives response, calls `clientDone()` - `isBenchmarkFinished()` returns `false` (0.99s < 1s) - `clientDone()` calls `resetClient()` **Step 2** (T = 1.01s): - `writeHandler` is called - `isBenchmarkFinished()` returns `true` (1.01s >= 1s) - `writeHandler` returns early, **no request sent, no read event registered** **Result**: - `readHandler` never triggers → `clientDone()` never called → no `aeStop()` - `showThroughput()` checks `num_threads && isBenchmarkFinished()`, skipping single-thread mode - **Event loop never terminates** Fixes valkey-io#2893, fixes valkey-io#2843 --------- Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com> Signed-off-by: Harkrishn Patro <bunty.hari@gmail.com>

Fix valkey-benchmark hanging in single-thread duration mode

610bde1

Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com>

github-actions Bot assigned yzc-yzc Jan 20, 2026

yzc-yzc requested review from rainsupreme, sarthakaggarwal97 and zuiderkwast January 20, 2026 08:52

yzc-yzc marked this pull request as draft January 20, 2026 09:23

Fix the SEGV crash

b1a43af

Signed-off-by: yzc-yzc <96833212+yzc-yzc@users.noreply.github.com>

yzc-yzc marked this pull request as ready for review January 20, 2026 13:51

zuiderkwast approved these changes Jan 20, 2026

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zuiderkwast added this to Valkey 9.0 Jan 20, 2026

zuiderkwast moved this to In Progress in Valkey 9.0 Jan 20, 2026

zuiderkwast linked an issue Jan 20, 2026 that may be closed by this pull request

[TEST-FAILURE] warmup and duration are cumulative in tests/integration/valkey-benchmark.tcl #2843

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dvkashapov approved these changes Jan 20, 2026

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sarthakaggarwal97 approved these changes Jan 20, 2026

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zuiderkwast merged commit 8fdc9e6 into valkey-io:unstable Jan 20, 2026
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github-project-automation Bot moved this from In Progress to To be backported in Valkey 9.0 Jan 20, 2026

rainsupreme approved these changes Jan 20, 2026

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zuiderkwast removed this from Valkey 9.0 Jan 29, 2026

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Fix valkey-benchmark hanging in single-thread duration mode#3079

Fix valkey-benchmark hanging in single-thread duration mode#3079
zuiderkwast merged 2 commits into
valkey-io:unstablefrom
yzc-yzc:fix-benchmark-duration-hang

yzc-yzc commented Jan 20, 2026 •

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