resultChanged() crashes on undefined result and permanently prevents triggers from firing after transient registry errors #923
Description
Summary
When a transient registry error (502, socket hang up, etc.) occurs during findNewVersion() on the first check after restart, the container's result is left as undefined. This causes resultChanged() to throw TypeError: Cannot read properties of undefined (reading 'tag'), which prevents mapContainerToContainerReport() from producing a valid report. As a consequence, triggers never fire for that container's update — even after subsequent watch cycles successfully detect the update.
The only recovery is restarting WUD.
Environment
- WUD version: 8.1.1
- Trigger types: command (with
WUD_TRIGGER_COMMAND_<commandname>_ONCE=true) and SMTP
Sequence of Events
- WUD watches a container for the first time (or after restart).
findNewVersion()fails with a transient error (e.g., registry returns 502) on the first check.- Container is inserted into the store with
result = undefined. mapContainerToContainerReportsetschanged = true(first-time path), butupdateAvailableisfalse(becauseresultis undefined), so the trigger does not fire (which is to be expected at this point).- On the next watch cycle,
findNewVersion()succeeds. Nowresultis populated andupdateAvailableistrue. containerInDb.resultChanged(containerReport.container)is called.containerInDbwas saved in step 3 without aresult, sothis.resultisundefined.this.result.tagthrowsTypeError: Cannot read properties of undefined (reading 'tag').- The exception propagates,
changedis never set totrue, and the trigger never fires. - The store is then updated with the valid result, so on the next cycle
resultChanged()sees no change, sochanged = falseand the trigger still doesn't fire. - The container shows as "update available" on the dashboard, but no trigger ever runs for it.
Observed Behavior
On my system, when the transient error occurred, the WUD log showed:
11:01:07 WARN whats-up-docker/watcher.docker.local: Error when processing (502 - "<html><body><h1>502 Bad Gateway</h1>...") (container=local_vikunja)
Then an hour later when the cron caused the system to watch again, I got:
12:00:11.611 INFO whats-up-docker/watcher.docker.local: Cron started (0 * * * *)
12:00:12.162 WARN whats-up-docker/watcher.docker.local: Error when processing some containers (Cannot read properties of undefined (reading 'tag'))
After that, the vikunja container showed an update available on the dashboard, but none of the triggers I had associated with it ever fired. Manually triggering from the dashboard worked fine.
Root Cause
In app/model/container.js, resultChanged does not guard against this.result or otherContainer.result being undefined:
function resultChangedFunction(otherContainer) {
return (
otherContainer === undefined ||
this.result.tag !== otherContainer.result.tag || // crashes if this.result is undefined
this.result.digest !== otherContainer.result.digest ||
this.result.created !== otherContainer.result.created
);
}In app/watchers/providers/docker/Docker.js, watchContainer() deletes result at the start of each cycle and only sets it on success:
delete containerWithResult.result; // result is now undefined
try {
containerWithResult.result = await this.findNewVersion(container, logContainer);
} catch (e) {
containerWithResult.error = { message: e.message };
// result stays undefined
}The container is then saved to the store without a result, and subsequent calls to resultChanged() crash.
Suggested Fix
Add null guards in resultChanged():
function resultChangedFunction(otherContainer) {
if (otherContainer === undefined) return true;
if (!this.result || !otherContainer.result) return true; // treat missing result as changed
return (
this.result.tag !== otherContainer.result.tag ||
this.result.digest !== otherContainer.result.digest ||
this.result.created !== otherContainer.result.created
);
}When either side has no result, the function should return true (changed) so that triggers can fire once a valid result appears.
Related Issues
This appears to be the root cause behind multiple open issues reporting the same error:
- Error when processing some containers #422 - Error when processing some containers
- Error when processing #470 - Error when processing
- Error self-updating wud #484 - Error self-updating wud
- Getting 404 - Undefined #490 - Getting 404 - Undefined
- what to do with "socket hang up" and "read properties of undefined" #551 - "socket hang up" and "read properties of undefined"
- Error when processing (Error: socket hang up) #620 - Error when processing (Error: socket hang up)