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HTTP 503 Service Unavailable

The server cannot handle the request right now. Free reference, no signup.

503 Service Unavailable

MeaningThe server cannot handle the request right now.
WhenThe app is overloaded, deploying, or in maintenance.
CausesNo healthy upstream, a full worker pool, or a maintenance window.
FixRestore capacity or wait out the deploy. Honor Retry-After when it is present.
RetryRetry with backoff.
Alert?Yes. Users and jobs are being turned away.

Runs in your browser. Nothing you enter is stored.

Get pinged when your API starts returning 503s

Users and jobs are being turned away.

curl -sS -X POST https://api.trigv.com/v1/events \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "Authorization: Bearer $TRIGV_API_KEY" \
  -d '{"channel":"ops","title":"HTTP 503","level":"error"}'
Get an API key All status codes

How to use it

  1. Read what 503 means before changing a retry loop.
  2. Check the common causes against the response body and the server log.
  3. Follow the retry note. Retrying a 400 with the same body will fail again.
  4. If this is your API, use the snippet to hear about it.

About this tool

HTTP 503 Service Unavailable means The server cannot handle the request right now. Servers send it when The app is overloaded, deploying, or in maintenance.

Common causes: No healthy upstream, a full worker pool, or a maintenance window. The practical fix is: Restore capacity or wait out the deploy. Honor Retry-After when it is present.

Retry: Retry with backoff.

Alert on it? Yes. Users and jobs are being turned away.

Trigv is a push for the moment a status starts mattering, not a log of every response. If the code is one you should hear about, the snippet posts a single event with level error or warning. The status page itself does not call your API.

Questions

What is HTTP 503?

The server cannot handle the request right now.

Should the client retry?

Retry with backoff.

Should I alert on it?

Yes. Users and jobs are being turned away.

How is this different from reading the spec?

The page adds a plain retry note and an alert verdict for people running the service, not only for people parsing the response.

500 Internal Server Error The server hit an unexpected error. 501 Not Implemented The server does not support this feature. 502 Bad Gateway A proxy got an invalid response from the upstream server. Cron Job Alert Script Wrap a command so a failed, slow, or finished cron job sends a Trigv alert.