# One crash a day, and no error at all

Cloud galaxy · Cédric Merlin, CTO · https://merlin-cedric.fr/en/cloud/monolithe/

A daily crash with no trace in the logs: a hidden memory reservation pushed the machine past its capacity.

## The problem

Once a day, the system abruptly killed the application. No error in the logs.

## The constraint

The memory the application actually used was far below the machine’s capacity. The culprit was elsewhere.

## What I did

1. **A hidden reservation.** The application reserved a huge share of memory in one go, in an area the usual tools do not show.
2. **More than the machine.** Together with the search engine and the other services, we went over the machine’s memory.
3. **A setting that survives.** I reduce that reservation, add swap space, and record the setting in the automation so it survives the next deployment.
4. **The real culprit.** I measure process by process: web traffic was flat, the spikes came from a batch job.

## The result

Not a single crash since the fix, and a clear map of what to split out first.

Figure: 0 crash a day since the fix.

## Stack

Linux, Memory analysis, Automation, Monitoring

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Page: https://merlin-cedric.fr/en/cloud/monolithe/ · Contact: contact@merlin-cedric.fr