overleaf/overleaf · error

mongo health check failed, error present

Error message

mongo health check failed, error present

What it means

Dedicated Mongo health endpoint: the callback-style getUserEmail query returned a non-null err, so the Mongo driver itself failed (connection, timeout, or query error). Unlike the 'no email' variant, this indicates a transport/query-level failure rather than missing data.

Source

Thrown at services/web/app/src/Features/HealthCheck/HealthCheckController.mjs:69

  },

  checkRedis(req, res, next) {
    return rclient.healthCheck(function (error) {
      if (error != null) {
        logger.err({ err: error }, 'failed redis health check')
        return res.sendStatus(500)
      } else {
        return res.sendStatus(200)
      }
    })
  },

  checkMongo(req, res, next) {
    return UserGetter.getUserEmail(
      settings.smokeTest.userId,
      function (err, email) {
        if (err != null) {
          logger.err({ err }, 'mongo health check failed, error present')
          return res.sendStatus(500)
        } else if (email == null) {
          logger.err(
            { err },
            'mongo health check failed, no emai present in find result'
          )
          return res.sendStatus(500)
        } else {
          return res.sendStatus(200)
        }
      }
    )
  },
}

View on GitHub (pinned to 28ad3b03b7)

Solutions

1. Check Mongo connection strings and replica set health
2. Look at the logged err for the specific driver error (e.g. MongoNetworkError, MongoTimeoutError)
3. Scale or tune connection pool sizes if the health check times out under load

When it happens

Trigger: Thrown at services/web/app/src/Features/HealthCheck/HealthCheckController.mjs:69 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of overleaf/overleaf@28ad3b03b7 (2026-09-03). Data as JSON: /api/errors/9e1852762df69dc5. Report an issue: GitHub.