When the agent fails to post metrics to Mackerel, the following error message is output to the log.

Failed to post metrics value (will retry): <reason>

Cause

The specific cause of the error is described in the latter part of the error message.

A common scenario is that the network became temporarily unstable, resulting in a timeout.

Action Required

If the error is temporary, no action is required. Metrics that failed to post will be buffered by the agent and automatically retried.

If the error persists, action is required. Please check the error message content and whether communication with Mackerel can be performed normally.

Reference

• Check connectivity on port 443 to the IP addresses listed in What is Mackerel's IP address and port number?.
• If you are using a proxy server, verify that it is operating correctly.