Add metrics API endpoint and CLI command

cmd/system/command.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/jrasell/sherpa/cmd/system/health"
 	"github.com/jrasell/sherpa/cmd/system/info"
+	"github.com/jrasell/sherpa/cmd/system/metrics"
 	"github.com/sean-/sysexits"
 	"github.com/spf13/cobra"
 )
@@ -37,5 +38,9 @@ func registerCommands(rootCmd *cobra.Command) error {
 		return err
 	}
 
+	if err := metrics.RegisterCommand(rootCmd); err != nil {
+		return err
+	}
+
 	return health.RegisterCommand(rootCmd)
 }

cmd/system/metrics/command.go

@@ -0,0 +1,76 @@
+package metrics
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/jrasell/sherpa/pkg/api"
+	clientCfg "github.com/jrasell/sherpa/pkg/config/client"
+	"github.com/ryanuber/columnize"
+	"github.com/sean-/sysexits"
+	"github.com/spf13/cobra"
+)
+
+const (
+	outputHeader = "Name|Type|Value"
+)
+
+func RegisterCommand(rootCmd *cobra.Command) error {
+	cmd := &cobra.Command{
+		Use:   "metrics",
+		Short: "Retrieve metrics from a Sherpa server",
+		Run: func(cmd *cobra.Command, args []string) {
+			runInfo(cmd, args)
+		},
+	}
+	rootCmd.AddCommand(cmd)
+
+	return nil
+}
+
+func runInfo(_ *cobra.Command, _ []string) {
+	clientConfig := clientCfg.GetConfig()
+	mergedConfig := api.DefaultConfig(&clientConfig)
+
+	client, err := api.NewClient(mergedConfig)
+	if err != nil {
+		fmt.Println("Error setting up Sherpa client:", err)
+		os.Exit(sysexits.Software)
+	}
+
+	metrics, err := client.System().Metrics()
+	if err != nil {
+		fmt.Println("Error calling server metrics:", err)
+		os.Exit(sysexits.Software)
+	}
+
+	out := []string{outputHeader}
+
+	for i := range metrics.Gauges {
+		out = append(out, fmt.Sprintf("%s|%s|%v",
+			metrics.Gauges[i].Name, "Gauge", metrics.Gauges[i].Value))
+	}
+
+	for i := range metrics.Counters {
+		out = append(out, fmt.Sprintf("%s|%s|%v",
+			metrics.Counters[i].Name, "Counter", metrics.Counters[i].Mean))
+	}
+
+	for i := range metrics.Samples {
+		out = append(out, fmt.Sprintf("%s|%s|%v",
+			metrics.Samples[i].Name, "Counter", metrics.Samples[i].Mean))
+	}
+
+	// If there are no metrics to print (happens during initial server startup)
+	// then we don't want to just print the header so perform a check so the
+	// CLI is nice and tidy.
+	if len(out) > 1 {
+		fmt.Println(formatList(out))
+	}
+}
+
+func formatList(in []string) string {
+	columnConf := columnize.DefaultConfig()
+	columnConf.Empty = "<none>"
+	return columnize.Format(in, columnConf)
+}

docs/api/system.md

@@ -51,3 +51,72 @@ $ curl \
   "StrictPolicyChecking": false
 }
 ```
+
+## Get Server Metrics
+
+This endpoint can be used to query the Sherpa server for its latest telemetry data.
+
+| Method   | Path                         |
+| :--------------------------- | :--------------------- |
+| `GET`    | `/v1/system/metrics`              | `200 application/binary` |
+
+
+### Sample Request
+
+```
+$ curl \
+    http://127.0.0.1:8000/v1/system/metrics
+```
+
+### Sample Response
+
+```json
+{
+  "Timestamp": "2019-05-14 20:41:30 +0000 UTC",
+  "Gauges": [
+    {
+      "Name": "sherpa.runtime.alloc_bytes",
+      "Value": 1745680,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.free_count",
+      "Value": 230471,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.heap_objects",
+      "Value": 17573,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.malloc_count",
+      "Value": 248044,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.num_goroutines",
+      "Value": 5,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.sys_bytes",
+      "Value": 72810744,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.total_gc_pause_ns",
+      "Value": 660024,
+      "Labels": {}
+    },
+    {
+      "Name": "sherpa.runtime.total_gc_runs",
+      "Value": 13,
+      "Labels": {}
+    }
+  ],
+  "Points": [],
+  "Counters": [],
+  "Samples": []
+}
+```

docs/commands/system.md

@@ -14,6 +14,11 @@ Show configuration details of the running server:
 $ sherpa system info
 ```
 
+Output the latest metric data points for the running server:
+```bash
+$ sherpa system metrics
+```
+
 ## Usage
 ```bash
 Usage:
@@ -23,4 +28,5 @@ Usage:
 Available Commands:
   health      Retrieve health information of a Sherpa server
   info        Retrieve information about a Sherpa server
+  metrics     Retrieve metrics from a Sherpa server
 ```

go.mod

@@ -3,39 +3,26 @@ module github.com/jrasell/sherpa
 go 1.12
 
 require (
+	github.com/BurntSushi/toml v0.3.1 // indirect
 	github.com/armon/go-metrics v0.0.0-20190430140413-ec5e00d3c878
-	github.com/beorn7/perks v1.0.0 // indirect
-	github.com/davecgh/go-spew v1.1.1
-	github.com/go-logfmt/logfmt v0.4.0 // indirect
-	github.com/gogo/protobuf v1.2.1 // indirect
-	github.com/golang/protobuf v1.3.1 // indirect
 	github.com/gorilla/mux v1.7.1
 	github.com/hashicorp/consul/api v1.1.0
 	github.com/hashicorp/go-cleanhttp v0.5.1
 	github.com/hashicorp/go-rootcerts v1.0.0
 	github.com/hashicorp/golang-lru v0.5.1 // indirect
 	github.com/hashicorp/nomad/api v0.0.0-20190508234936-7ba2378a159e
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/kisielk/errcheck v1.2.0 // indirect
-	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/mattn/go-isatty v0.0.7
 	github.com/pkg/errors v0.8.1
-	github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90 // indirect
-	github.com/prometheus/common v0.4.0 // indirect
-	github.com/prometheus/procfs v0.0.0-20190507164030-5867b95ac084 // indirect
 	github.com/rs/zerolog v1.14.3
 	github.com/ryanuber/columnize v2.1.0+incompatible
 	github.com/sean-/sysexits v0.0.0-20171026162210-598690305aaa
-	github.com/sirupsen/logrus v1.4.1 // indirect
 	github.com/spf13/cobra v0.0.3
 	github.com/spf13/viper v1.3.2
-	github.com/stretchr/objx v0.2.0 // indirect
 	github.com/stretchr/testify v1.3.0
 	golang.org/x/crypto v0.0.0-20190513172903-22d7a77e9e5f // indirect
 	golang.org/x/net v0.0.0-20190514140710-3ec191127204 // indirect
 	golang.org/x/sys v0.0.0-20190514135907-3a4b5fb9f71f // indirect
 	golang.org/x/text v0.3.2 // indirect
-	golang.org/x/tools v0.0.0-20190514143549-2d081dbd584e // indirect
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
-	gopkg.in/square/go-jose.v2 v2.3.1
 )