Allow tuning client-side vmagent process.

General

Escalation

General

Escalation

Description

We should allow modifying vmagent process configurations in use. In particular it will be needed for changing remoteWrite.maxDiskUsagePerURL, which is 1Gb by default in current PMM client versions:

/usr/local/percona/pmm2/exporters/vmagent -envflag.enable=true -httpListenAddr=127.0.0.1:42001 -loggerLevel=INFO -promscrape.config=/tmp/vm_agent/agent_id/78474bd8-94e3-443c-8934-504dde1242bd/vmagentscrapecfg -remoteWrite.maxDiskUsagePerURL=1073741824 -remoteWrite.tlsInsecureSkipVerify=true -remoteWrite.tmpDataPath=/tmp/vmagent-temp-dir -remoteWrite.url=https://10.124.33.55:443/victoriametrics/api/v1/write

This variable governs how much disk space can be used in the event of a disconnection with the server. It seems to be innocuous, but in the case were many PMM client instances are running sharing mountpoint for /tmp/, for example, it may cause issues. This is particularly true in k8s environments, where disk space is shared between many services.

How to test

add VMAGENT_remoteWrite_maxDiskUsagePerURL=52428800 to PMM Server

Check that vmagents on client size is using it.
Useful article https://www.baeldung.com/linux/process-environment-variables for it. Also vmagent logs can be checked if any mention of it there exist

How to document

VMAGENT_ env variables passed to PMM Server will be passed to all PMM Clients connected. How to create env variable to override flag is mentioned in this link
https://docs.victoriametrics.com/#environment-variables
List of all available flags https://docs.victoriametrics.com/#list-of-command-line-flags