feat: add new metrics

add info metrics about providers, enterprises, organizations,
repositories and pools.

Also expose most of the configurable pool information as metric like
e.g. max Runners as garm_pool_max_runners

Signed-off-by: Mario Constanti <mario.constanti@mercedes-benz.com>

metrics/instance.go

@@ -0,0 +1,79 @@
+package metrics
+
+import (
+	"log"
+
+	"github.com/cloudbase/garm/auth"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// CollectInstanceMetric collects the metrics for the runner instances
+// reflecting the statuses and the pool they belong to.
+func (c *GarmCollector) CollectInstanceMetric(ch chan<- prometheus.Metric, hostname string, controllerID string) {
+	ctx := auth.GetAdminContext()
+
+	instances, err := c.runner.ListAllInstances(ctx)
+	if err != nil {
+		log.Printf("cannot collect metrics, listing instances: %s", err)
+		return
+	}
+
+	pools, err := c.runner.ListAllPools(ctx)
+	if err != nil {
+		log.Printf("listing pools: %s", err)
+		return
+	}
+
+	type poolInfo struct {
+		Name         string
+		Type         string
+		ProviderName string
+	}
+
+	poolNames := make(map[string]poolInfo)
+	for _, pool := range pools {
+		if pool.EnterpriseName != "" {
+			poolNames[pool.ID] = poolInfo{
+				Name:         pool.EnterpriseName,
+				Type:         string(pool.PoolType()),
+				ProviderName: pool.ProviderName,
+			}
+		} else if pool.OrgName != "" {
+			poolNames[pool.ID] = poolInfo{
+				Name:         pool.OrgName,
+				Type:         string(pool.PoolType()),
+				ProviderName: pool.ProviderName,
+			}
+		} else {
+			poolNames[pool.ID] = poolInfo{
+				Name:         pool.RepoName,
+				Type:         string(pool.PoolType()),
+				ProviderName: pool.ProviderName,
+			}
+		}
+	}
+
+	for _, instance := range instances {
+
+		m, err := prometheus.NewConstMetric(
+			c.instanceMetric,
+			prometheus.GaugeValue,
+			1,
+			instance.Name,                           // label: name
+			string(instance.Status),                 // label: status
+			string(instance.RunnerStatus),           // label: runner_status
+			poolNames[instance.PoolID].Name,         // label: pool_owner
+			poolNames[instance.PoolID].Type,         // label: pool_type
+			instance.PoolID,                         // label: pool_id
+			hostname,                                // label: hostname
+			controllerID,                            // label: controller_id
+			poolNames[instance.PoolID].ProviderName, // label: provider
+		)
+
+		if err != nil {
+			log.Printf("cannot collect runner metric: %s", err)
+			continue
+		}
+		ch <- m
+	}
+}