Alright, let’s talk about this thing I wrestled with yesterday. It wasn’t pretty, but got it sorted. There was this weird glitch in the reporting tool, you know? Every so often, maybe twice a day, it’d just hang when generating the daily summary. Super annoying because folks rely on that.
Figuring Out the Mess
So, first thing, I jumped into the logs. Standard procedure, right? Checked the application logs, server logs, database logs… nothing obvious. Just the process stopping. No big error message screaming “I’m broken!”. That’s always the worst. Makes you feel like you’re chasing ghosts.
Spent a good hour just staring at timestamps, trying to correlate the freeze with maybe a database backup or some other scheduled task. Nope. Seemed random. Ran some basic diagnostics, checked server resources like memory and CPU when it usually happened – looked fine, nothing maxed out.
Breaking it Down – The Chop
Okay, plan B. Time to really break this thing down. I call it the ‘chop’ method sometimes. Just slice the problem into smaller bits until you find the rotten part. I decided to isolate the report generation piece entirely.
Here’s kinda what I did:
- Pulled the exact query the report uses. Ran it manually against the database. Worked perfectly fine, and fast too. So, not a database issue directly.
- Looked at the code section that calls the query and then processes the data. It’s old code, been there forever.
- Started adding extra logging. Like, really detailed logging. Logged before the query, after the query, before processing each chunk of data, after processing.
- Triggered the report manually, again and again. Watching the logs like a hawk.
This took ages. Run, wait, check logs. Run, wait, check logs. Felt like I was going cross-eyed.
The “Aha!” Moment
Then, finally, I saw it. It wasn’t hanging during the data processing. It was hanging right before it started processing, but only sometimes. And the extra logging showed me it was getting stuck trying to create a temporary file it uses during the summary calculation. Why only sometimes? That was the next puzzle.
Dug into the temp file creation logic. Turns out, the way it generated the filename wasn’t guaranteed to be unique under heavy load. If two reports tried to run at the exact same millisecond (rare, but possible!), they could try creating the same temp file. One would succeed, the other would just hang, waiting for a file lock that never released because the first process finished cleanly without the second one ever getting the lock. Dumb, right? A classic race condition, hidden away.
Fixing and Testing
The fix was pretty simple once I knew the cause. Changed the temp filename generation. Added a timestamp plus a random string. Much safer. Deployed the change to the staging server first.
Then I just hammered it. Triggered the report generation like crazy, maybe 50 times back-to-back. No hangs. Let it soak for a few hours, running automatically. Still solid.
Pushed it to production late last night. Checked this morning, reports generated fine overnight and the first one today went smooth too. Fingers crossed, but I think that ghost is busted. Felt good to finally nail it down after chasing shadows for a bit. Just needed to chop the problem down methodically.
