Add logging for prometheus operator in TargetAllocator's config gener…

…ator (open-telemetry#2329)

* add logging for prometheus operator

* adding yaml for changelog

* Adding tracking issue

.chloggen/target-allocator-prometheus-operator-logging.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. operator, target allocator, github action)
+component: target allocator
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add logging for prometheus operator in TargetAllocator's config generator
+
+# One or more tracking issues related to the change
+issues: [2348]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

cmd/otel-allocator/watcher/promOperator.go

@@ -17,9 +17,11 @@ package watcher
 import (
 	"context"
 	"fmt"
+	"os"
 	"time"
 
 	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
 	"github.com/go-logr/logr"
 	monitoringv1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1"
 	promv1alpha1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1alpha1"
@@ -67,7 +69,9 @@ func NewPrometheusCRWatcher(logger logr.Logger, cfg allocatorconfig.Config) (*Pr
 		},
 	}
 
-	generator, err := prometheus.NewConfigGenerator(log.NewNopLogger(), prom, true) // TODO replace Nop?
+	promOperatorLogger := level.NewFilter(log.NewLogfmtLogger(os.Stderr), level.AllowWarn())
+	generator, err := prometheus.NewConfigGenerator(promOperatorLogger, prom, true)
+
 	if err != nil {
 		return nil, err
 	}