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avoid scheduling duplicate repeating tasks when task times out #10

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Merged
vkarpov15 merged 1 commit into from
May 7, 2026
Merged

avoid scheduling duplicate repeating tasks when task times out #10

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64 changes: 40 additions & 24 deletions src/taskSchema.js
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Original file line number Diff line number Diff line change
Expand Up @@ -175,7 +175,9 @@ taskSchema.statics.expireTimedOutTasks = async function expireTimedOutTasks(opti
const task = await Task.findOneAndUpdate(
{
status: 'in_progress',
timeoutAt: { $exists: true, $lte: now }
// If task is still in_progress 10 minutes after it was supposed
// to time out, assume the task is stuck and mark it as timed_out
timeoutAt: { $exists: true, $lte: now.valueOf() - 10 * 60 * 1000 }
},
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{
$set: {
Expand Down Expand Up @@ -219,31 +221,35 @@ taskSchema.statics.registerHandler = async function registerHandler(name, fn) {
};

async function _handleRepeatingTask(Task, task) {
let scheduledAt;
if (task.nextScheduledAt != null) {
const scheduledAt = new Date(task.nextScheduledAt);
return Task.create({
name: task.name,
scheduledAt,
repeatAfterMS: task.repeatAfterMS,
params: task.params,
previousTaskId: task._id,
originalTaskId: task.originalTaskId || task._id,
timeoutMS: task.timeoutMS,
schedulingTimeoutAt: scheduledAt.valueOf() + 10 * 60 * 1000
});
scheduledAt = new Date(task.nextScheduledAt);
} else if (task.repeatAfterMS != null) {
const scheduledAt = new Date(task.scheduledAt.valueOf() + task.repeatAfterMS);
return Task.create({
scheduledAt = new Date(task.scheduledAt.valueOf() + task.repeatAfterMS);
} else {
return;
}

return Task.updateOne(
{
name: task.name,
scheduledAt,
repeatAfterMS: task.repeatAfterMS,
params: task.params,
previousTaskId: task._id,
originalTaskId: task.originalTaskId || task._id,
timeoutMS: task.timeoutMS,
schedulingTimeoutAt: scheduledAt.valueOf() + 10 * 60 * 1000
});
}
previousTaskId: task._id
},
Comment on lines +234 to +238
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@chatgpt-codex-connector chatgpt-codex-connector Bot May 7, 2026

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P2 Badge Add a unique key for repeat-task upserts

When two workers enter _handleRepeatingTask() concurrently for the same timed-out or scheduling-timed-out task, both updateOne(..., { upsert: true }) calls can evaluate this filter before either insert is visible and both insert a repeat task; the schema only declares a non-unique { status, scheduledAt } index, so MongoDB has no unique constraint to collapse that race. The new sequential tests pass, but the production race this change targets still remains unless these fields are backed by a unique index or another atomic guard.

Useful? React with 👍 / 👎.

{
$setOnInsert: {
name: task.name,
scheduledAt,
repeatAfterMS: task.repeatAfterMS,
params: task.params,
previousTaskId: task._id,
originalTaskId: task.originalTaskId || task._id,
timeoutMS: task.timeoutMS,
schedulingTimeoutAt: scheduledAt.valueOf() + 10 * 60 * 1000
}
},
{ upsert: true }
);
Comment on lines +233 to +252
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@vkarpov15 vkarpov15 May 7, 2026

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This is a reasonable concern, but highly unlikely given the buffer we give for hanging tasks. Will consider improving this for the future.

}

taskSchema.statics.registerHandlers = async function registerHandlers(obj, prefix) {
Expand Down Expand Up @@ -337,7 +343,10 @@ taskSchema.statics.execute = async function(task, options = {}) {
this._handlers.get(task.name).call(task, task.params, task)
),
new Promise((_, reject) => {
timeoutId = setTimeout(() => reject(new Error(`Task timed out after ${task.timeoutMS} ms`)), task.timeoutMS);
timeoutId = setTimeout(
() => reject(new TimeoutError(`Task timed out after ${task.timeoutMS} ms`)),
task.timeoutMS
);
})
]).finally(() => clearTimeout(timeoutId));
} else {
Expand All @@ -350,7 +359,7 @@ taskSchema.statics.execute = async function(task, options = {}) {
task.result = result;
await task.save();
} catch (error) {
task.status = 'failed';
task.status = error instanceof TimeoutError ? 'timed_out' : 'failed';
task.error.message = error.message;
task.error.stack = error.stack;
task.finishedRunningAt = currentTime();
Expand Down Expand Up @@ -379,4 +388,11 @@ taskSchema.statics.schedule = async function schedule(name, scheduledAt, params,
});
};

class TimeoutError extends Error {
constructor(message) {
super(message);
this.name = 'TimeoutError';
}
}

module.exports = taskSchema;
82 changes: 75 additions & 7 deletions test/task.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -299,7 +299,7 @@ describe('Task', function() {

task = await Task.findById(task._id);
assert.ok(task);
assert.equal(task.status, 'failed');
assert.equal(task.status, 'timed_out');
assert.equal(task.error.message, 'Task timed out after 50 ms');
assert.equal(task.finishedRunningAt.valueOf(), now.valueOf());
clearTimeout(handlerTimeout);
Expand Down Expand Up @@ -329,8 +329,8 @@ describe('Task', function() {
// Now simulate time after timeoutAt
sinon.restore();
sinon.stub(time, 'now').callsFake(() =>
// now after the timeoutAt
new Date(timeoutAt.valueOf() + 1000)
// now after the timeoutAt plus the expiry buffer
new Date(timeoutAt.valueOf() + 10 * 60 * 1000 + 1000)
);

// Directly call expireTimedOutTasks instead of polling
Expand Down Expand Up @@ -361,7 +361,7 @@ describe('Task', function() {
// We should advance the fake clock further to catch this one too
sinon.restore();
sinon.stub(time, 'now').callsFake(() =>
new Date(timeoutAt.valueOf() + 2000)
new Date(timeoutAt.valueOf() + 10 * 60 * 1000 + 2000)
);

await Task.expireTimedOutTasks();
Expand All @@ -377,14 +377,82 @@ describe('Task', function() {
assert.ok(repeated.scheduledAt.valueOf() === repeatTaskObj.scheduledAt.valueOf() + 60000);
});

it('does not duplicate a repeating task when timeout expiry races with polling', async function() {
const scheduledAt = time.now();
const startedRunningAt = new Date(scheduledAt.valueOf() - 20 * 60 * 1000);
const timeoutAt = new Date(scheduledAt.valueOf() - 10 * 60 * 1000 - 1000);
const repeatAfterMS = 60000;
const nextScheduledAt = new Date(scheduledAt.valueOf() + repeatAfterMS);

const timedOutTask = await Task.create({
name: 'dedupeTimedOutRepeat',
scheduledAt,
startedRunningAt,
timeoutAt,
status: 'in_progress',
repeatAfterMS,
params: { foo: 'bar' }
});

await Task.create({
name: 'dedupeTimedOutRepeat',
scheduledAt: nextScheduledAt,
repeatAfterMS,
params: { foo: 'bar' },
previousTaskId: timedOutTask._id,
originalTaskId: timedOutTask._id,
status: 'pending',
schedulingTimeoutAt: nextScheduledAt.valueOf() + 10 * 60 * 1000
});

await Task.expireTimedOutTasks();

const repeatedTasks = await Task.find({
name: 'dedupeTimedOutRepeat',
scheduledAt: nextScheduledAt,
previousTaskId: timedOutTask._id
});
assert.equal(repeatedTasks.length, 1);

const expiredTask = await Task.findById(timedOutTask._id);
assert.equal(expiredTask.status, 'timed_out');
});

it('does not duplicate a repeating task when scheduling timeout is handled twice', async function() {
Task.registerHandler('dedupeSchedulingRepeat', async () => {
return 'should not be run';
});

const scheduledAt = time.now();
const nextScheduledAt = new Date(scheduledAt.valueOf() + 100000);
const task = await Task.create({
name: 'dedupeSchedulingRepeat',
scheduledAt,
schedulingTimeoutAt: new Date(scheduledAt.valueOf() - 1000),
status: 'pending',
params: { foo: 'bar' },
nextScheduledAt
});

await Task.execute(task);
await Task.execute(task);

const repeatedTasks = await Task.find({
name: 'dedupeSchedulingRepeat',
scheduledAt: nextScheduledAt,
previousTaskId: task._id
});
assert.equal(repeatedTasks.length, 1);
});

it('creates a retry task when a timed out task has retryOnTimeoutCount', async function() {
Task.registerHandler('timeoutRetry', async () => {
// handler intentionally does nothing (we'll simulate a timeout)
});

const scheduledAt = new Date(now.valueOf() - 5000);
const startedRunningAt = new Date(now.valueOf() - 20000);
const timeoutAt = new Date(now.valueOf() - 1000);
const scheduledAt = new Date(now.valueOf() - 11 * 60 * 1000);
const startedRunningAt = new Date(now.valueOf() - 20 * 60 * 1000);
const timeoutAt = new Date(now.valueOf() - 10 * 60 * 1000 - 1000);

let timedOutTask = await Task.create({
name: 'timeoutRetry',
Expand Down
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