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When using HTTP alert sources, only JSON objects are accepted at the root level. JSON arrays at the top level are not supported and will cause issues with alert processing.

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What happens when you send a JSON array?

If you send a JSON array as the root payload to an HTTP alert source, you may experience the following behavior:
  • Your transform function will have no effect
  • An empty alert will be created with no data
This is because we don’t expect an array here, so the processing fails when trying to map the payload.

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Supported JSON structure

HTTP alert sources expect a single JSON object at the root level, like this: 
{
  "alert_name": "Server Down",
  "severity": "critical",
  "message": "Web server is not responding"
}
Arrays at the root level are not supported : 
[
  {
    "title": "Database Connection Failed",
    "status": "firing",
    "description": "Unable to connect to primary database",
    "severity": "critical"
  },
  {
    "title": "High Memory Usage", 
    "status": "firing",
    "description": "Memory usage above 90%",
    "severity": "warning"
  }
]

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Workarounds

If your monitoring service sends JSON arrays (like updown.io), you’ll need to:
  • Check if your monitoring service offers an alternative webhook format that sends single objects
  • Use a middleware service to transform the array into individual object requests
This limitation affects services that send arrays “for future use” where multiple alerts might be included in a single request, even if they currently only send one alert at a time.