HTTP 400: Data decoding error / Data validation erroredit
The most likely cause for this error is using incompatible versions of APM agent and APM Server. See the agent/server compatibility matrix to verify compatibility.
HTTP 400: Event too largeedit
APM agents communicate with the APM server by sending events in an HTTP request. Each event is sent as its own line in the HTTP request body. If events are too large, you should consider increasing the Max event size setting in the APM integration, and adjusting relevant settings in the agent.
HTTP 401: Invalid tokenedit
HTTP 403: Forbidden requestedit
Either you are sending requests to a RUM endpoint without RUM enabled, or a request is coming from an origin not specified in the APM integration settings. See the Allowed origins setting for more information.
HTTP 503: Request timed out waiting to be processededit
This happens when APM Server exceeds the maximum number of requests that it can process concurrently. To alleviate this problem, you can try to: reduce the sample rate and/or reduce the collected stack trace information. See Reduce storage for more information.
Another option is to increase processing power. This can be done by either migrating your Elastic Agent to a more powerful machine or adding more APM Server instances.