Logs

Web services and workers have a Logs page that streams what your app writes to standard output and standard error as it happens. Anything your app prints is captured, with nothing to install or configure.

Read logs

Open the web service or worker and choose Logs in its sidebar. The status at the top left shows Live once the stream is connected. New lines appear at the bottom as your app writes them, and scrolling up loads older lines.

Filter

Use the buttons in the toolbar to show one kind of line:

Warning and Error come from the text of each line, so a line counts as an error when it contains a word like error or exception. If your app writes JSON log lines, their level, severity or levelname field decides instead.

Search

Type in Search logs… to show only lines that contain your text.

Copy

Click the copy icon in the toolbar to copy the lines currently shown to your clipboard.

Crashes and memory

When your service stops unexpectedly, a System line says what happened:

• Service ran out of memory and was restarted. Consider a larger size.
• Service crashed (exit code …) and was restarted.
• Service exited (exit code 0) and was restarted.

The output of the run that stopped stays in the log after the restart, so you can read the error that caused it. If you see the out-of-memory line, give the service more memory. See Memory and sizing.

Build output

While a web service is building, its Logs page shows the build's output. Before its first build starts, the page shows No logs yet.

How far back logs go

Logs cover the service's current run, plus the run before it after a crash. A deploy or restart starts the log again from that point. To keep logs for longer, send them from your app to a logging service.

Databases, key value stores, cron jobs and storage services don't have a Logs page. Their Events pages show what happened to them.