> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vertracloud.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Find Out Why Your Application Crashes

> Read the logs, recognise out-of-memory kills, crash loops and silent exits, and fix the causes behind most failed deploys.

When an application goes to **Error** or keeps restarting, the answer is almost always in its output.
This guide shows where to look and how to read what you find.

## Where the logs are

* **Dashboard**: the application's **Logs** tab shows the live output, including the dependency
  installation and the build.
* **CLI**: `vertra logs -f` follows the output from the terminal. See [CLI](/cli).
* **API**: [Get Logs](/api-reference/endpoint/apps/logs).

Always read from the **first** error line, not the last: the last line is usually a consequence.

## What the platform does when the app crashes

Auto-restart is always on. An exit with code `0` is treated as a normal stop and isn't restarted;
any other exit is. If the application crashes **5 times in 10 minutes**, auto-restart is paused for
24 hours and the application stays stopped: fix the cause and start it by hand.

## Match the symptom

<AccordionGroup>
  <Accordion title="The process stops right away, with no error">
    Exit code `0`: the program simply finished. A server must keep listening and a bot must stay
    logged in. Check the entry point in **Config** points to the right file.
  </Accordion>

  <Accordion title="It dies without a stack trace, often under load">
    That's an out-of-memory kill. Watch the memory graph on the **Overview** tab: if it climbs to the limit
    before each crash, raise the RAM in **Config** or reduce what the process holds in memory. Java,
    headless browsers and big caches need 512 MB or more.
  </Accordion>

  <Accordion title="Cannot find module / ModuleNotFoundError">
    The dependency isn't declared. Node.js: it's in `devDependencies` or missing from `package.json`.
    Python: missing from `requirements.txt`. The container only installs what the manifest lists.
  </Accordion>

  <Accordion title="The deploy fails before the app starts">
    `INSTALL_TIMEOUT` means dependency installation passed 15 minutes; `BUILD_FAILED` means your build
    command exited with an error (the build output is in the logs); `BUILD_TIMEOUT` means it passed
    10 minutes.
  </Accordion>

  <Accordion title="Online, but the site doesn't answer">
    The server listens on `localhost` or a fixed port. Listen on `0.0.0.0` and read `PORT`:

    ```javascript theme={null}
    app.listen(process.env.PORT || 80, '0.0.0.0');
    ```
  </Accordion>

  <Accordion title="A variable is undefined">
    `.env` files aren't read at runtime. Set the variable in **Config** and restart: a changed variable
    only reaches the process after a restart.
  </Accordion>

  <Accordion title="Works locally, fails here">
    Compare runtime versions (set `VERSION` in [Configuration](/configuration)), don't upload
    `node_modules`/`venv` built on your machine, and remember file names are case-sensitive on Linux:
    `./Config.js` and `./config.js` are different files.
  </Accordion>
</AccordionGroup>

## Check before you deploy

`vertra doctor` inspects the current directory for the most common problems before anything is sent.
The full list of error codes is in [Common errors](/common-errors).