Prometheus metrics improvements (#2398)

- Enabled metrics in storagesvc, buildermgr and controller.
- Added a middleware in storagesvc, router, executor and controller to monitor total number of http requests, each request's duration and number of requests that are currently being served. These requests can be filtered on their path, method or statuscode.
- Removed functionCallDuration and functionCallResponseSize metrics from router.
- Removed funcAliveSummary, funcIsAlive, funcReapTime and idleTime metrics.
- Replaced function calls for collecting metrics to direct metric calls.

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
Co-authored-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/executor/metrics/metrics.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2022 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	// function_name: the function's name
+	// function_uid: the function's version id
+	// function_address: the address of the pod from which the function was called
+	functionLabels = []string{"function_name", "function_namespace"}
+	ColdStarts     = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "fission_function_cold_starts_total",
+			Help: "How many cold starts are made by function_name, function_uid.",
+		},
+		functionLabels,
+	)
+	FuncRunningSummary = promauto.NewSummaryVec(
+		prometheus.SummaryOpts{
+			Name:       "fission_function_running_seconds",
+			Help:       "The running time (last access - create) in seconds of the function.",
+			Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
+		},
+		functionLabels,
+	)
+	FuncError = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "fission_function_cold_start_errors_total",
+			Help: "Count of fission cold start errors",
+		},
+		functionLabels,
+	)
+)