[Bug]: go.d/docker: removing a container also removes the charts of every container whose name starts with the same string #24230

Bug description

When a container is removed, the go.d docker collector also removes the per-container charts of any other container whose name begins with the removed container's name. For example, removing foo also removes foo-bar's charts. Those charts are never re-created while the Netdata plugin keeps running, so foo-bar silently drops out of docker.container_state, docker.container_health_status and docker.container_writable_layer_size. Its docker_container_down and docker_container_unhealthy alerts go to REMOVED.

Cause (v2.12.0, unchanged on master and in v2.12.1):

charts.go#L166-L174 matches chart IDs by prefix without a separator:

func (c *Collector) removeContainerCharts(name string) {
	px := fmt.Sprintf("container_%s", name)

	for _, chart := range *c.Charts() {
		if strings.HasPrefix(chart.ID, px) {
			chart.MarkRemove()
			chart.MarkNotCreated()
		}
	}
}

So container_foo matches container_foo-bar_state, container_foo-bar_health_status and container_foo-bar_writable_layer_size.

collect.go#L188-L193 deletes only foo from c.containers, and collect.go#L162-L165 adds charts only for names that are not already in c.containers. foo-bar stays in the map, so its charts are never added again.

Expected behavior

Removing container foo removes only foo's charts. foo-bar's charts and alerts stay in place while it keeps running.

Steps to reproduce

1. With the go.d docker collector enabled, start two containers:
   docker run -d --name foo-bar alpine sleep infinity and docker run -d --name foo alpine sleep infinity
2. Wait for both containers' charts to appear (for example docker.container_state for foo and for foo-bar).
3. docker rm -f foo
4. After the next collection, foo-bar's charts are gone (marked obsolete) even though foo-bar is still running. They do not come back.
5. Restart Netdata (or the go.d plugin): foo-bar's charts come back.

Installation method

docker

System info

$ uname -srvmo
Linux 6.8.0-146-generic #146-Ubuntu SMP PREEMPT_DYNAMIC Thu Sep  3 16:12:30 UTC 2026 x86_64 GNU/Linux
$ grep -HvE "^#|URL" /etc/*release
/etc/lsb-release:DISTRIB_ID=Ubuntu
/etc/lsb-release:DISTRIB_RELEASE=24.04
/etc/lsb-release:DISTRIB_CODENAME=noble
/etc/lsb-release:DISTRIB_DESCRIPTION="Ubuntu 24.04.5 LTS"
/etc/os-release:PRETTY_NAME="Ubuntu 24.04.5 LTS"
/etc/os-release:VERSION_ID="24.04"
/etc/os-release:VERSION_CODENAME=noble
/etc/os-release:ID=ubuntu
/etc/os-release:ID_LIKE=debian
Docker Engine 29.8.2

Netdata build info

Packaging:
    Netdata Version ____________________________________________ : v2.12.0
    Installation Type __________________________________________ : binpkg-deb
    Package Architecture _______________________________________ : x86_64
    Package Distro _____________________________________________ : ubuntu 24.04
Operating System:
    Kernel _____________________________________________________ : Linux
    Kernel Version _____________________________________________ : 6.8.0-146-generic
    Operating System ___________________________________________ : Ubuntu
    Operating System ID ________________________________________ : ubuntu
    Operating System ID Like ___________________________________ : debian
    Operating System Version ___________________________________ : 24.04.5 LTS (Noble Numbat)
    Operating System Version ID ________________________________ : 24.04
    Detection __________________________________________________ : /etc/os-release
(netdata -W buildinfo, Packaging and Operating System sections)

Additional info

Suggested fix: add the separator:

px := fmt.Sprintf("container_%s_", name)

This fixes the foo / foo-bar case. Container names may also contain _, though, so container_foo_ would still match a container named foo_state (container_foo_state_state). Matching the exact IDs built from the per-container chart templates avoids that, for example:

func (c *Collector) removeContainerCharts(name string) {
	ids := make(map[string]bool)
	for _, tmpl := range containerChartsTmpl {
		ids[fmt.Sprintf(tmpl.ID, name)] = true
	}
	for _, chart := range *c.Charts() {
		if ids[chart.ID] {
			chart.MarkRemove()
			chart.MarkNotCreated()
		}
	}
}

(containerChartsTmpl is the template set that addContainerCharts uses, charts.go#L92-L96.)

Some other go.d collectors use the same unsuffixed HasPrefix(chart.ID, ...) removal on master, for example ntpd (peer_%s), nvme (device_%s), wireguard (device_%s, peer_%s), logstash ("pipeline_"+id), upsd, proxysql (mysql_user_, mysql_command_) and k8s_state (pod_%s, node_%s, deployment_%s, cronjob_%s). I have not checked whether each of those can actually collide.