Expected value for ruler external_url

[james-callahan]

Currently for the ruler external_url I tried putting in the URL of our Grafana installation: e.g. external_url: "https://grafana.example.com".
This bubbled through to alertmanager so that the "Source" link leads to https://grafana.example.com/graph?g0.expr=%28sum+by%28thing%29%28count_over_time%28%7Bnamespace%3D%22foo%22%7D+%7C+json+%7C+bar%3D%22maxRetries%22%5B5m%5D%29%29+%3E+0%29&g0.tab=1, which isn't valid.

This url templating (via "/graph?g0.expr=%s&g0.tab=1") appears to be coming via TableLinkForExpression in vendor/github.com/prometheus/prometheus/util/strutil/strconv.go.
I don't think this url format makes any sense for Loki ruler alerts.

--> What should be in the the external_url field?
My first thought is that it should bring up the Grafana Explore view.

[cstyan]

@dannykopping any thoughts here? AFAICT we're not setting this value for our loki clusters.

In our Cortex clusters we set external_url to the Prometheus instance we have running in that k8s cluster.

[dannykopping]

It's a good question. It should probably go directly to Explore as @james-callahan suggests. I checked one of our alerts sent by the ruler and the source is indeed useless when going to /graph?g0.expr=%s&g0.tab=1.

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[james-callahan]

Anyone got ideas on how to address this?

[pschulten]

One could rewrite the expression to grafana-syntax in the fronting http server, e.g. with nginx and lua. But this is probably super complicated.

I'm also very interested. We use Cortex as a remote_write target for multiple Prometheis and the same thing applies there, as well.

I think, I'll just rewrite the /graph.* to something generic like https://grafana.example.com/alerting/list for now, which is maybe more helpful than a broken link.

[parkedwards]

yeah we've run into this as well - right now, we've had to leave external_url undefined (and since there isn't a dedicated Loki UI, as there is with Prometheus, we don't have a ton of options as to where we might direct recipients to)

additionally, the way that alertmanager auto-affixes the path route /graph makes it so that we can't send folks to a landing page....especially if /graph doesn't exist in the route tree :(

[chewrocca]

Mimir has grafanaExploreURL in 2.6.0-rc.0. Do you think that could be implemented?

[ChristianOps]

We're having this issue too and trying to find a way to work around this problem.

Not sure what may be different in loki-ruler compared to alert rules added in Grafana managed alerts that also uses our external Alertmanager. Links are properly linking to "Alert rules / View rule" page in Grafana and they are both using the same receiver template in Alertmanager (with GeneratorURL set). Loki-ruler should be able to achieve the same unless I'm missing something here? Anyone knows how that works?

[stringang]

I found the working mechanism of external_url in the source code of version v2.8.2, and it works with recording rules.

loki/pkg/ruler/base/ruler.go

Lines 79 to 82 in 9f809ed

	// Config is the configuration for the recording rules server.
	type Config struct {
	// This is used for template expansion in alerts; must be a valid URL.
	ExternalURL flagext.URLValue `yaml:"external_url"`

[lyz-code]

Did anyone get around this issue?

[Rohlik]

We also came across this issue and we are waiting for some fix/workaround.