lib/promscrape/discovery/consul: expose service tags in individual labels __meta_consul_tag_<tagname>

This simplifies copying service tags to target labels with the following relabeling rule:

- action: labelmap
  regex: __meta_consul_tag_(.+)

See https://stackoverflow.com/questions/44339461/relabeling-in-prometheus

docs/CHANGELOG.md

@@ -17,6 +17,12 @@ The following tip changes can be tested by building VictoriaMetrics components f
 
 * FEATURE: support overriding of `-search.latencyOffset` value via URL param `latency_offset` when performing requests to [/api/v1/query](https://docs.victoriametrics.com/keyConcepts.html#instant-query) and [/api/v1/query_range](https://docs.victoriametrics.com/keyConcepts.html#range-query). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3481).
 * FEATURE: allow changing field names in JSON logs if VictoriaMetrics components are started with `-loggerFormat=json` command-line flags. The field names can be changed with the `-loggerJSONFields` command-line flag. For example `-loggerJSONFields=ts:timestamp,msg:message` would rename `ts` and `msg` fields on the output JSON to `timestamp` and `message` fields. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2348). Thanks to @michal-kralik for [the pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3488).
+* FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): expose `__meta_consul_tag_<tagname>` and `__meta_consul_tagpresent_<tagname>` labels for targets discovered via [consul_sd_configs](https://docs.victoriametrics.com/sd_configs.html#consul_sd_configs). This simplifies converting [Consul service tags](https://developer.hashicorp.com/consul/docs/discovery/services#service-definition) to target labels with a simple [relabeling rule](https://docs.victoriametrics.com/vmagent.html#relabeling):
+```yml
+- action: labelmap
+  regex: __meta_consul_tag_(.+)
+```
+This resolves [this StackOverflow question](https://stackoverflow.com/questions/44339461/relabeling-in-prometheus).
 
 * BUGFIX: properly return query results for time series, which stop receiving new samples after the rotation of `indexdb`. Previously such time series could be missing in query results. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3502). The issue has been introduced in [v1.83.0](https://docs.victoriametrics.com/CHANGELOG.html#v1830).
 * BUGFIX: allow specifying values bigger than 2GiB to the following command-line flag values on 32-bit architectures (`386` and `arm`): `-storage.minFreeDiskSpaceBytes` and `-remoteWrite.maxDiskUsagePerURL`. Previously values bigger than 2GiB were incorrectly truncated on these architectures.

docs/sd_configs.md

@@ -140,6 +140,7 @@ scrape_configs:
 
     # tag_separate is an optional string by which Consul tags are joined into the __meta_consul_tags label.
     # By default "," is used as a tag separator.
+    # Individual tags are also available via __meta_consul_tag_<tagname> labels - see below.
     # tag_separator: "..."
 
     # allow_stale is an optional config, which allows stale Consul results.
@@ -166,7 +167,9 @@ The following meta labels are available on discovered targets during [relabeling
 * `__meta_consul_service_port`: the service port of the target
 * `__meta_consul_service`: the name of the service the target belongs to
 * `__meta_consul_tagged_address_<key>`: each node tagged address key value of the target
-* `__meta_consul_tags`: the list of tags of the target joined by the tag separator
+* `__meta_consul_tag_<tagname>`: the value for the given <tagname> tag of the target
+* `__meta_consul_tagpresent_<tagname>`: "true" for every <tagname> tag of the target
+* `__meta_consul_tags`: the list of tags of the target joined by the tag_separator
 
 
 ## digitalocean_sd_configs
@@ -631,7 +634,7 @@ The following meta labels are available on discovered targets during [relabeling
 * `__meta_gce_project`: the GCP project in which the instance is running
 * `__meta_gce_public_ip`: the public IP address of the instance, if present
 * `__meta_gce_subnetwork`: the subnetwork URL of the instance
-* `__meta_gce_tags`: comma separated list of instance tags
+* `__meta_gce_tags`: list of instance tags separated by tag_separator
 * `__meta_gce_zone`: the GCE zone URL in which the instance is running
 
 

lib/promscrape/discovery/consul/service_node.go

@@ -95,6 +95,24 @@ func (sn *ServiceNode) appendTargetLabels(ms []*promutils.Labels, serviceName, t
 	// in relabeling rules don't have to consider tag positions.
 	m.Add("__meta_consul_tags", tagSeparator+strings.Join(sn.Service.Tags, tagSeparator)+tagSeparator)
 
+	// Expose individual tags via __meta_consul_tag_* labels, so users could move all the tags
+	// into the discovered scrape target with the following relabeling rule in the way similar to kubernetes_sd_configs:
+	//
+	// - action: labelmap
+	//   regex: __meta_consul_tag_(.+)
+	//
+	// This solves https://stackoverflow.com/questions/44339461/relabeling-in-prometheus
+	for _, tag := range sn.Service.Tags {
+		k := tag
+		v := ""
+		if n := strings.IndexByte(tag, '='); n >= 0 {
+			k = tag[:n]
+			v = tag[n+1:]
+		}
+		m.Add(discoveryutils.SanitizeLabelName("__meta_consul_tag_"+k), v)
+		m.Add(discoveryutils.SanitizeLabelName("__meta_consul_tagpresent_"+k), "true")
+	}
+
 	for k, v := range sn.Node.Meta {
 		m.Add(discoveryutils.SanitizeLabelName("__meta_consul_metadata_"+k), v)
 	}

lib/promscrape/discovery/consul/service_node_test.go

@@ -43,7 +43,7 @@ func TestParseServiceNodesSuccess(t *testing.T) {
     "Service": {
       "ID": "redis",
       "Service": "redis",
-      "Tags": ["primary"],
+      "Tags": ["primary","foo=bar"],
       "Address": "10.1.10.12",
       "TaggedAddresses": {
         "lan": {
@@ -124,7 +124,11 @@ func TestParseServiceNodesSuccess(t *testing.T) {
 			"__meta_consul_service_port":                   "8000",
 			"__meta_consul_tagged_address_lan":             "10.1.10.12",
 			"__meta_consul_tagged_address_wan":             "10.1.10.12",
-			"__meta_consul_tags":                           ",primary,",
+			"__meta_consul_tag_foo":                        "bar",
+			"__meta_consul_tag_primary":                    "",
+			"__meta_consul_tagpresent_foo":                 "true",
+			"__meta_consul_tagpresent_primary":             "true",
+			"__meta_consul_tags":                           ",primary,foo=bar,",
 		}),
 	}
 	discoveryutils.TestEqualLabelss(t, labelss, expectedLabelss)