Address review comments

Refactor code, move metricsprovider to internal

Signed-off-by: Abdul Qadeer <aqadeer@paypal.com>

README.md

@@ -47,18 +47,13 @@ GET /watcher
 
 This will return metrics for all nodes. A query parameter to filter by host can be added with `host`.
 
-## Third Party Client Configuration
-- To use the Kubernetes metric server client, please configure environment varirables `METRIC_CLIENT=k8s` and your `KUBE_CONFIG` to your 
-kubernetes client configuration file path if running out of cluster.
-
-- To use the prometheus client, please configure environment variables as `METRIC_CLIENT=prometheus`, and configure 
-  `METRIC_HOST` and `METRIC_AUTH_TOKEN` to  your Prometheus endpoint and token. Please ignore `PROM_TOKEN` as empty string if no authentication 
-  is needed to access the Prometheus APIs. When using the prometheus in a cluster, the default endpoint is
-  `http://prometheus-k8s.monitoring.svc.cluster.local:9090`. You need to  configure `PROM_HOST` if your Prometheus endpoint is different.
-
-- To use the signalFx client, please configure environment variables as `METRIC_CLIENT=signalfx`, and configure
-  `METRIC_HOST` and `METRIC_AUTH_TOKEN` to  your signalFx endpoint and token. Please ignore `METRIC_AUTH_TOKEN` as empty string if no authentication
-  is needed to access the signalFx APIs.
+## Metrics Provider Configuration
+- By default Kubernetes Metrics Server client is configured. Set `KUBE_CONFIG` env var to your kubernetes client configuration file path if running out of cluster.
+
+- To use the Prometheus client, please configure environment variables `METRICS_PROVIDER_NAME`, `METRICS_PROVIDER_ADDRESS` and `METRICS_PROVIDER_TOKEN` to `Prometheus`, Prometheus address and auth token. Please do not set `METRICS_PROVIDER_TOKEN` if no authentication 
+  is needed to access the Prometheus APIs. Default value of address set is `http://prometheus-k8s:9090` for Prometheus client.
+
+- To use the SignalFx client, please configure `METRICS_PROVIDER_NAME`, `METRICS_PROVIDER_ADDRESS` and `METRICS_PROVIDER_TOKEN` to `SignalFx`, SignalFx address and auth token respectively. Default value of address set is `https://api.signalfx.com` for Prometheus client.
 
 ## Deploy `load-watcher` as a service
 To deploy `load-watcher` as a monitoring service in your Kubernetes cluster, you can run the following.

main.go

@@ -17,21 +17,22 @@ limitations under the License.
 package main
 
 import (
-	"log"
-
-	"github.com/paypal/load-watcher/pkg/client"
-	"github.com/paypal/load-watcher/pkg/utils"
 	"github.com/paypal/load-watcher/pkg/watcher"
+	"github.com/paypal/load-watcher/pkg/watcher/api"
+	log "github.com/sirupsen/logrus"
 )
 
-
 func main() {
-	utils.InitEnvVars()
-	cl, err := client.NewFetcherClient(utils.MetricProviderType, utils.MetricEndpoint, utils.MetricAuthToken)
+	client, err := api.NewLibraryClient(watcher.EnvMetricProviderOpts)
 	if err != nil {
-		log.Fatalf("unable to create new client: %v", err)
+		log.Fatalf("unable to create client: %v", err)
 	}
-	w := watcher.NewWatcher(cl.Fetcher)
-	w.StartWatching()
+	metrics, err := client.GetLatestWatcherMetrics()
+	if err != nil {
+		log.Errorf("unable to get watcher metrics: %v", err)
+	}
+	log.Infof("received metrics: %v", metrics)
+
+	// Keep the watcher server up
 	select {}
-}
+}

manifests/load-watcher-deployment.yaml

@@ -20,7 +20,7 @@ spec:
       - name: watcher
         image: chenw/load-watcher:latest
         env:
-        - name: METRIC_CLIENT
+        - name: METRICS_PROVIDER_NAME
           value: prometheus
         ports:
         - containerPort: 2020
@@ -34,12 +34,10 @@ metadata:
   labels:
     app: load-watcher
 spec:
-  externalTrafficPolicy: Local
   ports:
   - name: http
     port: 2020
     protocol: TCP
     targetPort: 2020
   selector:
-    app: load-watcher
-  type: LoadBalancer
+    app: load-watcher

pkg/watcher/fetcher.go → pkg/watcher/api/api.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2020 PayPal
+Copyright 2021 PayPal
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,14 +14,12 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package watcher
+package api
 
-// Interface to be implemented by any metrics provider client to interact with Watcher
-type FetcherClient interface {
-	// Return the client name
-	Name() string
-	// Fetch metrics for given host
-	FetchHostMetrics(host string, window *Window) ([]Metric, error)
-	// Fetch metrics for all hosts
-	FetchAllHostsMetrics(window *Window) (map[string][]Metric, error)
+import "github.com/paypal/load-watcher/pkg/watcher"
+
+// Watcher Client API
+type Client interface {
+	// Returns latest metrics present in load Watcher cache
+	GetLatestWatcherMetrics() (*watcher.WatcherMetrics, error)
 }