use istio client-go library instead of knative (#1661)

use istio client-go library instead of knative
bump kubernetes dependency version
change code coverage to codecov

vendor/k8s.io/component-base/metrics/processstarttime.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2019 The Kubernetes 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/procfs"
+	"k8s.io/klog"
+	"os"
+	"time"
+)
+
+var processStartTime = prometheus.NewGaugeVec(
+	prometheus.GaugeOpts{
+		Name: "process_start_time_seconds",
+		Help: "Start time of the process since unix epoch in seconds.",
+	},
+	[]string{},
+)
+
+// Registerer is an interface expected by RegisterProcessStartTime in order to register the metric
+type Registerer interface {
+	Register(prometheus.Collector) error
+}
+
+// RegisterProcessStartTime registers the process_start_time_seconds to
+// a prometheus registry. This metric needs to be included to ensure counter
+// data fidelity.
+func RegisterProcessStartTime(registrationFunc func(prometheus.Collector) error) error {
+	start, err := getProcessStart()
+	if err != nil {
+		klog.Errorf("Could not get process start time, %v", err)
+		start = float64(time.Now().Unix())
+	}
+	processStartTime.WithLabelValues().Set(start)
+	return registrationFunc(processStartTime)
+}
+
+func getProcessStart() (float64, error) {
+	pid := os.Getpid()
+	p, err := procfs.NewProc(pid)
+	if err != nil {
+		return 0, err
+	}
+
+	if stat, err := p.NewStat(); err == nil {
+		return stat.StartTime()
+	}
+	return 0, err
+}