Make linters happy and disable deprecated exhaustivestruct.

Expect pipeline to fail.

.drone.yml

@@ -0,0 +1,31 @@
+---
+kind: pipeline
+type: docker
+name: build
+
+steps:
+  - name: lint
+    image: code.pztrn.name/containers/mirror/golangci/golangci-lint:v1.46.2
+    environment:
+      CGO_ENABLED: 0
+    commands:
+      - golangci-lint run
+
+  - name: test
+    image: code.pztrn.name/containers/mirror/golang:1.18.3-alpine
+    environment:
+      CGO_ENABLED: 0
+    commands:
+      - go test ./...
+
+  - name: docker
+    image: code.pztrn.name/containers/mirror/plugins/docker:20.13.0
+    when:
+      branch: ["master"]
+    settings:
+      registry: code.pztrn.name
+      username: drone
+      password:
+        from_secret: drone_secret
+      repo: code.pztrn.name/apps/metricator
+      auto_tag: true

.gitignore

@@ -1,3 +1,5 @@
 ._bin
 .vscode
 metricator.yaml
+.idea
+*DS_Store*

.golangci.yml

@@ -3,23 +3,30 @@ run:
 linters:
   enable-all: true
   disable:
-    # Because globals might exist, but according to our codestyle they
-    # should be lowercased and considered as unexported.
-    - gochecknoglobals
     # While it might be useful it'll create more problems that will solve.
     - gocritic
-    # Complains about main() lengths, which isn't an issue.
-    - funlen
     # Magic numbers might be everywhere. Disabled for now.
     - gomnd
-    # ToDos everywhere
-    - godox
     # Why? WHY? WHY _test???
     - testpackage
+    # Structs will contain some context.Context.
+    - containedctx
+    # Deprecated
+    - exhaustivestruct
 linters-settings:
   lll:
     line-length: 120
-  gocyclo:
+  cyclop:
-    min-complexity: 40
+    max-complexity: 40
   gocognit:
     min-complexity: 40
+  funlen:
+    lines: 200
+    statements: 100
+
+issues:
+  exclude-rules:
+    # There will be some ToDos.
+    - linters:
+        - godox
+      text: "TODO"

Dockerfile

@@ -1,4 +1,4 @@
-FROM registry.gitlab.pztrn.name/containers/mirror/golang:1.15.5-alpine AS build
+FROM code.pztrn.name/containers/mirror/golang:1.18.3-alpine AS build
 
 WORKDIR /go/src/gitlab.pztrn.name/pztrn/metricator
 COPY . .
@@ -11,11 +11,13 @@ ARG CI_COMMIT_TAG
 ENV CGO_ENABLED=0
 RUN apk add bash git make
 RUN make metricatord-build
+RUN make metricator-client-build
 
-FROM registry.gitlab.pztrn.name/containers/mirror/golang:1.15.5-alpine
+FROM code.pztrn.name/containers/mirror/golang:1.18.3-alpine
 LABEL maintainer="Stanislav N. <pztrn@pztrn.name>"
 
 COPY --from=build /go/src/gitlab.pztrn.name/pztrn/metricator/._bin/metricatord /usr/local/bin/metricatord
+COPY --from=build /go/src/gitlab.pztrn.name/pztrn/metricator/._bin/metricator-client /usr/local/bin/metricator-client
 
 RUN apk add tzdata
 

Makefile

@@ -14,11 +14,20 @@ help: Makefile
 check-build-dir:
 	@if [ ! -d "._bin" ]; then mkdir ._bin; fi
 
+## metricator-client-build: builds metricator client and places into ${PWD}/._bin.
+metricator-client-build: check-build-dir
+	@if [ -f ./._bin/metricator-client ]; then rm ./._bin/metricator-client; fi
+	@scripts/build.sh metricator-client
+
 ## metricatord-build: builds metricator daemon and places into ${PWD}/._bin.
 metricatord-build: check-build-dir
-	@rm ./._bin/metricatord || true
+	@if [ -f ./._bin/metricatord ]; then rm ./._bin/metricatord; fi
 	@scripts/build.sh metricatord
 
+## metricator-client-run: starts metricator client. Use ARGS to supply args.
+metricator-client-run: metricator-client-build
+	@./._bin/metricator-client -config ${CONFIG} $(ARGS)
+
 ## metricatord-run: starts metricator daemon.
 metricatord-run: metricatord-build
 	./._bin/metricatord -config ${CONFIG}

VERSION

@@ -0,0 +1 @@
+0.2.0

cmd/metricator-client/main.go

@@ -0,0 +1,159 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"go.dev.pztrn.name/metricator/internal/common"
+	"go.dev.pztrn.name/metricator/internal/configuration"
+	"go.dev.pztrn.name/metricator/internal/logger"
+	"go.dev.pztrn.name/metricator/pkg/client"
+	"go.dev.pztrn.name/metricator/pkg/schema"
+)
+
+// nolint:gochecknoglobals
+var (
+	application       = flag.String("application", "", "Application to query.")
+	appsList          = flag.Bool("apps-list", false, "Show application's list registered at Metricator.")
+	metricatorHost    = flag.String("metricator-host", "", "IP address or domain on which Metricator is available")
+	metricatorTimeout = flag.Int("metricator-timeout", 5, "Timeout for requests sent to Metricator.")
+	metricsList       = flag.Bool("metrics-list", false, "Show metrics list. Requires 'application' parameter.")
+	metric            = flag.String("metric", "", "Metric data to retrieve. Requires 'application' parameter.")
+	output            = flag.String("output", "json", "Output format. Can be 'json' or 'plain-by-line'.")
+)
+
+// This function uses fmt.Println to print lines without timestamps to make it easy
+// to parse output, so:
+// nolint:forbidigo
+func main() {
+	config := configuration.NewConfig()
+
+	// Parse configuration.
+	flag.Parse()
+
+	err := config.Parse()
+	if err != nil {
+		log.Fatalln("Failed to parse configuration:", err.Error())
+	}
+
+	logger := logger.NewLogger(config.Logger)
+
+	logger.Debugf("Starting Metricator client, version %s from branch %s (build #%s, commit hash %s)\n",
+		common.Version,
+		common.Branch,
+		common.Build,
+		common.CommitHash,
+	)
+
+	// Check configuration.
+	// We cannot work at all if host isn't defined.
+	if *metricatorHost == "" {
+		logger.Infoln("Host isn't defined.")
+
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	// If nothing is requested - show error message.
+	if !*appsList && !*metricsList && *metric == "" {
+		logger.Infoln("No action specified.")
+
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	// When asking to metrics list we need application to be defined.
+	if *metricsList && *application == "" {
+		logger.Infoln("Getting metrics list requires 'application' parameter to be filled.")
+
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	// When asking for specific metric we need application to be defined.
+	if *metric != "" && *application == "" {
+		logger.Infoln("Getting metric data requires 'application' parameter to be filled.")
+
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	clientConfig := &client.Config{
+		Host:    *metricatorHost,
+		Timeout: *metricatorTimeout,
+	}
+
+	clnt := client.NewClient(clientConfig, logger)
+
+	var data interface{}
+
+	switch {
+	case *appsList:
+		data = clnt.GetAppsList()
+	case *metricsList:
+		data = clnt.GetMetricsList(*application)
+	case *metric != "":
+		data = clnt.GetMetric(*application, *metric)
+	}
+
+	switch *output {
+	case "json":
+		dataAsBytes, err := json.Marshal(data)
+		if err != nil {
+			logger.Infoln("Failed to marshal data from Metricator:", err.Error())
+
+			os.Exit(2)
+		}
+
+		fmt.Println(string(dataAsBytes))
+	case "plain-by-lines":
+		// For plain mode if we request metric - we should just print it and exit.
+		if *metric != "" {
+			fmt.Println(data)
+			os.Exit(0)
+		}
+
+		dataToPrint := []string{}
+
+		switch {
+		case *appsList:
+			appsListData, ok := data.(schema.AppsList)
+			if !ok {
+				logger.Infoln("Failed to cast parsed data into schema.AppsList!")
+
+				os.Exit(3)
+			}
+
+			for _, app := range appsListData {
+				dataToPrint = append(dataToPrint, app)
+			}
+		case *metric != "":
+			metricData, ok := data.(string)
+			if !ok {
+				logger.Infoln("Failed to cast parsed data into string!")
+
+				os.Exit(3)
+			}
+
+			dataToPrint = append(dataToPrint, metricData)
+		case *metricsList:
+			metricsData, ok := data.(schema.Metrics)
+			if !ok {
+				logger.Infoln("Failed to cast parsed data into schema.Metrics!")
+
+				os.Exit(3)
+			}
+
+			for _, metric := range metricsData {
+				dataToPrint = append(dataToPrint, metric.Name)
+			}
+		}
+
+		for _, line := range dataToPrint {
+			fmt.Println(line)
+		}
+	}
+}

cmd/metricatord/main.go

@@ -29,8 +29,7 @@ func main() {
 	// Parse configuration.
 	flag.Parse()
 
-	err := config.Parse()
+	if err := config.Parse(); err != nil {
-	if err != nil {
 		log.Fatalln("Failed to parse configuration:", err.Error())
 	}
 

docs/CLIENT.md

@@ -0,0 +1,53 @@
+# Metricator Client
+
+Metricator client was created to help with Metricator daemon communication. It is able to produce different output based on selected format.
+
+## Parameters
+
+| Parameter | Type | Description |
+| --------- | ---- | ----------- |
+| `-application` | string | Name of application to query. |
+| `-apps-list` | bool | Request type: applications list. |
+| `-config` | string | Path to configuration file. **MANDATORY** |
+| `-metric` | string | Request type: single metric. Name of metric to request. |
+| `-metricator-host` | URL | URL to Metricator daemon. (e.g. `http://127.0.0.1:34421`). **MANDATORY** |
+| `-metricator-timeout` | integer | Timeout in seconds for Metricator Client's HTTP requests. By default - 5 seconds. |
+| `-metrics-list` | bool | Request type: list of metrics. **Requires `-application` parameter to be filled.** |
+| `-output` | string | Type of output to produce (see below). |
+
+## Request types
+
+One of following parameters should be defined:
+
+* `-apps-list` to get listing of applications that is registered at Metricator daemon.
+* `-metrics-list` with `-application` parameters to get list of metrics for application which Metricator know.
+* `-metric` with name of metric and `-application` (with a name of application) parameters to get specific metric for application which Metricator know.
+
+See Examples section below.
+
+## Outputs
+
+Currently Metricator client is able to produce JSON and "Plain By Line" outputs. Their meanings:
+
+* When `-output=json` is specified (or `-output` wasn't specified at all) Metricator Client will just dump response from Metricator Daemon.
+* When `-output=plain-by-line` is specified Metricator Client will transform received data into line-by-line output, e.g. every application name on separate line, every metric name on separate line, etc.
+
+## Examples
+
+* Get list of applications registered at Metricator daemon line-by-line (for later use with metrics autodiscovery helper):
+
+```shell
+metricator-client -config=./metricator.yaml -metricator-host http://127.0.0.1:34421 -output plain-by-line -apps-list
+```
+
+* Get list of metrics for application `test` in JSON format:
+
+```shell
+metricator-client -config ./metricator.yaml -metricator-host http://127.0.0.1:34421 -application test -metrics-list
+```
+
+* Get specific metric for application `test`:
+
+```shell
+metricator-client -config ./metricator.yaml -metricator-host http://127.0.0.1:34421 -application test -metric mymegametric
+```

docs/INDEX.md

@@ -31,3 +31,4 @@ dnsdist_frontend_responses/frontend:127.0.0.1:53/proto:UDP/thread:0
 * [Installation](INSTALL.md)
 * [Configuration](CONFIGURE.md)
 * [API](API.md)
+* [Client](CLIENT.md)

internal/application/application.go

@@ -28,16 +28,18 @@ type Application struct {
 
 // NewApplication creates new application.
 func NewApplication(ctx context.Context, name string, config *Config, logger *logger.Logger) *Application {
-	a := &Application{
+	// Some variables are initialized in initialize() function.
+	// nolint:exhaustruct
+	app := &Application{
 		config:   config,
 		ctx:      ctx,
 		doneChan: make(chan struct{}),
 		logger:   logger,
 		name:     name,
 	}
-	a.initialize()
+	app.initialize()
 
-	return a
+	return app
 }
 
 // GetDoneChan returns a channel which should be used to block execution until

internal/application/config.go

@@ -11,5 +11,6 @@ type Config struct {
 	Endpoint string `yaml:"endpoint"`
 	// TimeBetweenRequests is a minimal amount of time which should pass
 	// between requests.
+	// nolint:tagliatelle
 	TimeBetweenRequests time.Duration `yaml:"time_between_requests"`
 }

internal/application/fetcher.go

@@ -1,7 +1,6 @@
 package application
 
 import (
-	"io/ioutil"
 	"net/http"
 	"time"
 )
@@ -11,6 +10,9 @@ func (a *Application) fetch() {
 	// Do not do anything if fetching is running.
 	// ToDo: maybe another approach?
 	a.fetchIsRunningMutex.RLock()
+	// This is an optimization to avoid excessive waiting when using Lock().
+	// Most of time application will wait between fetches.
+	// nolint:ifshort
 	isFetching := a.fetchIsRunning
 	a.fetchIsRunningMutex.RUnlock()
 
@@ -44,15 +46,13 @@ func (a *Application) fetch() {
 
 	defer resp.Body.Close()
 
-	body, err := ioutil.ReadAll(resp.Body)
+	data, err := a.parse(resp.Body)
 	if err != nil {
-		a.logger.Infoln("Failed to read response body for", a.name, "metrics:", err.Error())
+		a.logger.Infoln("Failed to parse response body for", a.name, "metrics:", err.Error())
 
 		return
 	}
 
-	data := a.parse(string(body))
-
 	a.storage.Put(data)
 
 	a.fetchIsRunningMutex.Lock()
@@ -64,7 +64,7 @@ func (a *Application) fetch() {
 func (a *Application) startFetcher() {
 	fetchTicker := time.NewTicker(a.config.TimeBetweenRequests)
 
-	// nolint:exhaustivestruct
+	// nolint:exhaustruct
 	a.httpClient = &http.Client{
 		Timeout: time.Second * 5,
 	}

internal/application/parser.go

@@ -1,19 +1,27 @@
 package application
 
 import (
+	"bufio"
+	"fmt"
+	"io"
 	"strings"
 
-	"go.dev.pztrn.name/metricator/internal/models"
+	"go.dev.pztrn.name/metricator/pkg/schema"
 )
 
-// Parses passed body and returns a map suitable for pushing into storage.
+// Parses io.Reader passed and returns a map suitable for pushing into storage.
-func (a *Application) parse(body string) map[string]models.Metric {
+func (a *Application) parse(r io.Reader) (map[string]schema.Metric, error) {
-	data := make(map[string]models.Metric)
+	data := make(map[string]schema.Metric)
 
-	// ToDo: switch to bytes buffer and maybe do not read body in caller?
+	scanner := bufio.NewScanner(r)
-	splittedBody := strings.Split(body, "\n")
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		// Skip empty lines.
+		if line == "" {
+			continue
+		}
 
-	for _, line := range splittedBody {
 		// Prometheus line contains metric name and metric parameters defined
 		// in "{}".
 		var (
@@ -21,11 +29,6 @@ func (a *Application) parse(body string) map[string]models.Metric {
 			params []string
 		)
 
-		// Skip empty lines.
-		if line == "" {
-			continue
-		}
-
 		a.logger.Debugln("Analyzing line:", line)
 
 		name = a.getMetricName(line)
@@ -35,7 +38,7 @@ func (a *Application) parse(body string) map[string]models.Metric {
 		if !found {
 			a.logger.Debugln("Metric wasn't yet created, creating new structure")
 
-			metric = models.NewMetric(name, "", "", nil)
+			metric = schema.NewMetric(name, "", "", nil)
 		}
 
 		a.logger.Debugf("Got metric to use: %+v\n", metric)
@@ -80,19 +83,22 @@ func (a *Application) parse(body string) map[string]models.Metric {
 			newMetric.Params = params
 
 			metric = newMetric
-			data[metric.Name] = metric
 		}
 
 		metric.Value = a.getMetricValue(line)
 
 		a.logger.Debugf("Got metric: %+v\n", metric)
 
-		data[name] = metric
+		data[metric.Name] = metric
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("wasn't able to scan input: %w", err)
 	}
 
 	a.logger.Debugf("Data parsed: %+v\n", data)
 
-	return data
+	return data, nil
 }
 
 // Gets metric description from passed line.
@@ -137,8 +143,8 @@ func (a *Application) getParametersForPrometheusMetric(line string) []string {
 		paramNameFinished, paramValueStarted, paramValueFinished bool
 	)
 
-	for _, r := range valuesString {
+	for _, runeChar := range valuesString {
-		if paramValueFinished && string(r) == "," {
+		if paramValueFinished && string(runeChar) == "," {
 			params = append(params, paramName+":"+paramValue)
 			paramName, paramValue = "", ""
 			paramNameFinished, paramValueStarted, paramValueFinished = false, false, false
@@ -150,8 +156,8 @@ func (a *Application) getParametersForPrometheusMetric(line string) []string {
 		// "deeply nested"? I think not. So:
 		// nolint:nestif
 		if !paramNameFinished {
-			if string(r) != "=" {
+			if string(runeChar) != "=" {
-				paramName += string(r)
+				paramName += string(runeChar)
 
 				continue
 			} else {
@@ -160,19 +166,19 @@ func (a *Application) getParametersForPrometheusMetric(line string) []string {
 				continue
 			}
 		} else {
-			if string(r) == "\"" && !paramValueStarted {
+			if string(runeChar) == "\"" && !paramValueStarted {
 				paramValueStarted = true
 
 				continue
 			}
 
-			if paramValueStarted && string(r) != "\"" {
+			if paramValueStarted && string(runeChar) != "\"" {
-				paramValue += string(r)
+				paramValue += string(runeChar)
 
 				continue
 			}
 
-			if paramValueStarted && string(r) == "\"" {
+			if paramValueStarted && string(runeChar) == "\"" {
 				paramValueFinished = true
 
 				continue

internal/common/version_info.go

@@ -1,5 +1,6 @@
 package common
 
+// nolint:gochecknoglobals
 var (
 	Branch     string
 	Build      string

internal/configuration/config.go

@@ -21,16 +21,18 @@ var (
 
 // Config is an application's configuration.
 type Config struct {
-	configPath string
 	// Applications describes configuration for remote application's endpoints.
 	// Key is an application's name.
 	Applications map[string]*application.Config `yaml:"applications"`
 	// Logger is a logging configuration.
 	Logger     *logger.Config `yaml:"logger"`
+	configPath string
 }
 
 // NewConfig returns new configuration.
 func NewConfig() *Config {
+	// Fields are initialized when parsing YAML file.
+	// nolint:exhaustruct
 	c := &Config{}
 	c.initialize()
 

internal/httpserver/handler.go

@@ -13,6 +13,7 @@ import (
 	"go.dev.pztrn.name/metricator/internal/models"
 )
 
+// nolint:gochecknoglobals
 var (
 	errInvalidAPIVersion  = errors.New("invalid API version")
 	errInvalidApplication = errors.New("invalid application")
@@ -47,14 +48,14 @@ func (h *handler) getAppsList() ([]byte, error) {
 
 // Gets request information from URL. Returns a structure with filled request
 // info and error if it occurs.
-func (h *handler) getRequestInfo(r *http.Request) (*models.RequestInfo, error) {
+func (h *handler) getRequestInfo(req *http.Request) (*models.RequestInfo, error) {
 	// Request isn't for API or isn't versioned.
-	if !strings.HasPrefix(r.URL.Path, "/api/v") {
+	if !strings.HasPrefix(req.URL.Path, "/api/v") {
 		return nil, errInvalidPath
 	}
 
 	// Note: first element will always be empty!
-	pathSplitted := strings.Split(r.URL.Path, "/")
+	pathSplitted := strings.Split(req.URL.Path, "/")
 
 	// Request is for API but not enough items in URL was passed.
 	if len(pathSplitted) < 4 {
@@ -118,20 +119,20 @@ func (h *handler) register(appName string, hndl common.HTTPHandlerFunc) {
 }
 
 // ServeHTTP handles every HTTP request.
-func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+func (h *handler) ServeHTTP(writer http.ResponseWriter, req *http.Request) {
 	startTime := time.Now()
 
 	defer func() {
 		requestDuration := time.Since(startTime)
 
-		log.Printf("[HTTP Request] from %s to %s, duration %.4fs\n", r.RemoteAddr, r.URL.Path, requestDuration.Seconds())
+		log.Printf("[HTTP Request] from %s to %s, duration %.4fs\n", req.RemoteAddr, req.URL.Path, requestDuration.Seconds())
 	}()
 
 	// Validate request and extract needed info.
-	rInfo, err := h.getRequestInfo(r)
+	rInfo, err := h.getRequestInfo(req)
 	if err != nil {
-		w.WriteHeader(http.StatusBadRequest)
+		writer.WriteHeader(http.StatusBadRequest)
-		_, _ = w.Write([]byte("400 bad request - " + err.Error()))
+		_, _ = writer.Write([]byte("400 bad request - " + err.Error()))
 
 		return
 	}
@@ -143,14 +144,14 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case "apps_list":
 		appsList, err := h.getAppsList()
 		if err != nil {
-			w.WriteHeader(http.StatusBadRequest)
+			writer.WriteHeader(http.StatusBadRequest)
-			_, _ = w.Write([]byte("400 bad request - " + err.Error()))
+			_, _ = writer.Write([]byte("400 bad request - " + err.Error()))
 
 			return
 		}
 
-		w.WriteHeader(http.StatusOK)
+		writer.WriteHeader(http.StatusOK)
-		_, _ = w.Write(appsList)
+		_, _ = writer.Write(appsList)
 
 		return
 	case "info":
@@ -166,17 +167,18 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			Version:    common.Version,
 		}
 
+		// nolint:errchkjson
 		infoBytes, _ := json.Marshal(infoData)
 
-		w.WriteHeader(http.StatusOK)
+		writer.WriteHeader(http.StatusOK)
-		_, _ = w.Write(infoBytes)
+		_, _ = writer.Write(infoBytes)
 
 		return
 	case "metrics":
 		handler, found := h.handlers[rInfo.Application]
 		if !found {
-			w.WriteHeader(http.StatusBadRequest)
+			writer.WriteHeader(http.StatusBadRequest)
-			_, _ = w.Write([]byte("400 bad request - " + errInvalidApplication.Error()))
+			_, _ = writer.Write([]byte("400 bad request - " + errInvalidApplication.Error()))
 
 			return
 		}
@@ -184,16 +186,16 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		// Get data from handler.
 		data := handler(rInfo)
 		if data == "" {
-			w.WriteHeader(http.StatusBadRequest)
+			writer.WriteHeader(http.StatusBadRequest)
-			_, _ = w.Write([]byte("400 bad request - " + errNoData.Error()))
+			_, _ = writer.Write([]byte("400 bad request - " + errNoData.Error()))
 		}
 
-		w.WriteHeader(http.StatusOK)
+		writer.WriteHeader(http.StatusOK)
-		_, _ = w.Write([]byte(data))
+		_, _ = writer.Write([]byte(data))
 
 		return
 	}
 
-	w.WriteHeader(http.StatusBadRequest)
+	writer.WriteHeader(http.StatusBadRequest)
-	_, _ = w.Write([]byte("400 bad request - " + errInvalidPath.Error()))
+	_, _ = writer.Write([]byte("400 bad request - " + errInvalidPath.Error()))
 }

internal/httpserver/httpserver.go

@@ -25,15 +25,16 @@ type HTTPServer struct {
 // NewHTTPServer creates HTTP server and executes preliminary initialization
 // (HTTP server structure initialized but it doesn't start).
 func NewHTTPServer(ctx context.Context, cfg *configuration.Config, logger *logger.Logger) (*HTTPServer, chan struct{}) {
-	h := &HTTPServer{
+	// nolint:exhaustruct
+	httpServer := &HTTPServer{
 		config:   cfg,
 		ctx:      ctx,
 		doneChan: make(chan struct{}),
 		logger:   logger,
 	}
-	h.initialize()
+	httpServer.initialize()
 
-	return h, h.doneChan
+	return httpServer, httpServer.doneChan
 }
 
 // Returns request's context based on main context of application.
@@ -50,7 +51,7 @@ func (h *HTTPServer) initialize() {
 		handlers: make(map[string]common.HTTPHandlerFunc),
 	}
 	// We do not need to specify all possible parameters for HTTP server, so:
-	// nolint:exhaustivestruct
+	// nolint:exhaustruct
 	h.server = &http.Server{
 		// ToDo: make it all configurable.
 		Addr:           ":34421",

internal/logger/logger.go

@@ -9,6 +9,10 @@ type Logger struct {
 
 // NewLogger creates new logging wrapper and returns it to caller.
 func NewLogger(config *Config) *Logger {
+	if config == nil {
+		config = &Config{Debug: false}
+	}
+
 	l := &Logger{config: config}
 
 	return l

internal/storage/generic.go

@@ -1,19 +1,19 @@
 package storage
 
-import "go.dev.pztrn.name/metricator/internal/models"
+import "go.dev.pztrn.name/metricator/pkg/schema"
 
 // GenericStorage describes interface every other storage should embed
 // and conform to as it contains essential things like context handling.
 type GenericStorage interface {
 	// Get returns data from storage by key.
-	Get(string) (models.Metric, error)
+	Get(string) (schema.Metric, error)
 	// GetAsSlice returns all data from storage as slice.
-	GetAsSlice() []models.Metric
+	GetAsSlice() []schema.Metric
 	// GetDoneChan returns a channel which should be used to block execution
 	// until storage's routines are completed.
 	GetDoneChan() chan struct{}
 	// Put puts passed data into storage.
-	Put(map[string]models.Metric)
+	Put(map[string]schema.Metric)
 	// Start starts asynchronous things if needed.
 	Start()
 }

internal/storage/memory/memory.go

@@ -6,7 +6,7 @@ import (
 	"sync"
 
 	"go.dev.pztrn.name/metricator/internal/logger"
-	"go.dev.pztrn.name/metricator/internal/models"
+	"go.dev.pztrn.name/metricator/pkg/schema"
 )
 
 // ErrMetricNotFound appears if requested metric wasn't found in storage.
@@ -14,29 +14,31 @@ var ErrMetricNotFound = errors.New("metric not found")
 
 // Storage is an in-memory storage.
 type Storage struct {
+	dataMutex sync.RWMutex
 	ctx       context.Context
 	doneChan  chan struct{}
 	logger    *logger.Logger
-	data      map[string]models.Metric
+	data      map[string]schema.Metric
 	name      string
-	dataMutex sync.RWMutex
 }
 
 // NewStorage creates new in-memory storage to use.
 func NewStorage(ctx context.Context, name string, logger *logger.Logger) (*Storage, chan struct{}) {
-	s := &Storage{
+	// nolint:exhaustruct
+	storage := &Storage{
 		ctx:      ctx,
 		doneChan: make(chan struct{}),
 		logger:   logger,
 		name:     name,
+		data:     make(map[string]schema.Metric),
 	}
-	s.initialize()
+	storage.initialize()
 
-	return s, s.doneChan
+	return storage, storage.doneChan
 }
 
 // Get returns data from storage by key.
-func (s *Storage) Get(key string) (models.Metric, error) {
+func (s *Storage) Get(key string) (schema.Metric, error) {
 	s.logger.Debugln("Retrieving data for", key, "key from storage...")
 
 	s.dataMutex.RLock()
@@ -46,7 +48,7 @@ func (s *Storage) Get(key string) (models.Metric, error) {
 	if !found {
 		s.logger.Infoln("Key", key, "not found in storage!")
 
-		return models.NewMetric("", "", "", nil), ErrMetricNotFound
+		return schema.NewMetric("", "", "", nil), ErrMetricNotFound
 	}
 
 	s.logger.Debugf("Key %s found: %+v\n", key, data)
@@ -55,10 +57,10 @@ func (s *Storage) Get(key string) (models.Metric, error) {
 }
 
 // GetAsSlice returns all data from storage as slice.
-func (s *Storage) GetAsSlice() []models.Metric {
+func (s *Storage) GetAsSlice() []schema.Metric {
 	s.logger.Debugln("Returning all stored metrics as slice...")
 
-	metrics := make([]models.Metric, 0, len(s.data))
+	metrics := make([]schema.Metric, 0, len(s.data))
 
 	for _, metric := range s.data {
 		metrics = append(metrics, metric)
@@ -75,11 +77,11 @@ func (s *Storage) GetDoneChan() chan struct{} {
 
 // Initializes internal things.
 func (s *Storage) initialize() {
-	s.data = make(map[string]models.Metric)
+	s.data = make(map[string]schema.Metric)
 }
 
 // Put puts passed data into storage.
-func (s *Storage) Put(data map[string]models.Metric) {
+func (s *Storage) Put(data map[string]schema.Metric) {
 	s.dataMutex.Lock()
 	defer s.dataMutex.Unlock()
 

pkg/client/client.go

@@ -0,0 +1,147 @@
+package client
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"time"
+
+	"go.dev.pztrn.name/metricator/internal/logger"
+	"go.dev.pztrn.name/metricator/pkg/schema"
+)
+
+// Client is a Metricator client that is ready to be used in other applications
+// or libraries.
+type Client struct {
+	config *Config
+	logger *logger.Logger
+
+	httpClient *http.Client
+}
+
+// NewClient creates new Metricator client.
+func NewClient(config *Config, logger *logger.Logger) *Client {
+	// nolint:exhaustruct
+	client := &Client{
+		config: config,
+		logger: logger,
+	}
+	client.initialize()
+
+	return client
+}
+
+// Executes request and parses it's contents.
+func (c *Client) executeAndParse(req *http.Request, dest interface{}) error {
+	c.logger.Debugf("Executing HTTP request to %s%s", c.config.Host, req.URL.RequestURI())
+
+	ctx, cancelFunc := context.WithTimeout(context.Background(), time.Second*time.Duration(c.config.Timeout))
+	defer cancelFunc()
+
+	req = req.WithContext(ctx)
+
+	response, err := c.httpClient.Do(req)
+	if err != nil {
+		c.logger.Infoln("Failed to execute request to Metricator:", err.Error())
+
+		return fmt.Errorf("metricator client: %w", err)
+	}
+
+	defer response.Body.Close()
+
+	respData, err := ioutil.ReadAll(response.Body)
+	if err != nil {
+		c.logger.Infoln("Failed to read response body:", err.Error())
+
+		return fmt.Errorf("metricator client: %w", err)
+	}
+
+	err = json.Unmarshal(respData, dest)
+	if err != nil {
+		c.logger.Infoln("Failed to parse response:", err.Error())
+
+		return fmt.Errorf("metricator client: %w", err)
+	}
+
+	return nil
+}
+
+// GetAppsList returns a slice with applications that was registered at Metricator.
+func (c *Client) GetAppsList() schema.AppsList {
+	address := fmt.Sprintf("%s/api/v1/apps_list", c.config.Host)
+
+	// Request's context sets in c.executeAndParse, so:
+	// nolint:noctx
+	req, err := http.NewRequest("GET", address, nil)
+	if err != nil {
+		c.logger.Infoln("Failed to create HTTP request:", err.Error())
+
+		return nil
+	}
+
+	appsList := make(schema.AppsList, 0)
+
+	err = c.executeAndParse(req, &appsList)
+	if err != nil {
+		return nil
+	}
+
+	return appsList
+}
+
+// GetMetric returns value for metric.
+func (c *Client) GetMetric(appName, metricName string) interface{} {
+	address := fmt.Sprintf("%s/api/v1/metrics/%s/%s", c.config.Host, appName, metricName)
+
+	// Request's context sets in c.executeAndParse, so:
+	// nolint:noctx
+	req, err := http.NewRequest("GET", address, nil)
+	if err != nil {
+		c.logger.Infoln("Failed to create HTTP request:", err.Error())
+
+		return ""
+	}
+
+	var data interface{}
+
+	err = c.executeAndParse(req, &data)
+	if err != nil {
+		return ""
+	}
+
+	return data
+}
+
+// GetMetricsList returns a slice with metrics names for passed application.
+func (c *Client) GetMetricsList(appName string) schema.Metrics {
+	address := fmt.Sprintf("%s/api/v1/metrics/%s", c.config.Host, appName)
+
+	// Request's context sets in c.executeAndParse, so:
+	// nolint:noctx
+	req, err := http.NewRequest("GET", address, nil)
+	if err != nil {
+		c.logger.Infoln("Failed to create HTTP request:", err.Error())
+
+		return nil
+	}
+
+	data := make(schema.Metrics, 0)
+
+	err = c.executeAndParse(req, &data)
+	if err != nil {
+		return nil
+	}
+
+	return data
+}
+
+// Initializes internal states and storages.
+func (c *Client) initialize() {
+	// We do not need to set everything for client actually, so:
+	// nolint:exhaustruct
+	c.httpClient = &http.Client{
+		Timeout: time.Second * time.Duration(c.config.Timeout),
+	}
+}

pkg/client/config.go

@@ -0,0 +1,9 @@
+package client
+
+// Config is a Metricator client configuration.
+type Config struct {
+	// Host is a host where Metricator is available for requests.
+	Host string
+	// Timeout specifies HTTP client timeout.
+	Timeout int
+}

pkg/schema/apps_list.go

@@ -0,0 +1,9 @@
+package schema
+
+// AppsList represents applications list structure from Metricator's API.
+type AppsList []string
+
+// IsEmpty returns true if returned applications list is empty.
+func (a AppsList) IsEmpty() bool {
+	return len(a) == 0
+}

pkg/schema/metric.go

@@ -1,6 +1,6 @@
-package models
+package schema
 
-// Metric is a generic metric structure.
+// Metric is a generic metric structure. Used in HTTP responses and data storage.
 type Metric struct {
 	// BaseName is a metric's base name, used for constructing name.
 	BaseName string
@@ -18,7 +18,7 @@ type Metric struct {
 
 // NewMetric creates new structure for storing single metric data.
 func NewMetric(name, mType, description string, params []string) Metric {
-	m := Metric{
+	metric := Metric{
 		BaseName:    name,
 		Name:        name,
 		Description: description,
@@ -27,7 +27,7 @@ func NewMetric(name, mType, description string, params []string) Metric {
 		Value:       "",
 	}
 
-	return m
+	return metric
 }
 
 // GetValue returns metric's value.

pkg/schema/metrics.go

@@ -0,0 +1,9 @@
+package schema
+
+// Metrics is a metrics collection response.
+type Metrics []*Metric
+
+// IsEmpty returns true if returned applications list is empty.
+func (m Metrics) IsEmpty() bool {
+	return len(m) == 0
+}

scripts/build.sh

@@ -2,7 +2,13 @@
 
 # Metricator build script.
 
+GO=${GO:=$(which go)}
+
+if [ -d .git ]; then
     source ./scripts/shell_helpers/get_git_data.sh
+else
+    source ./scripts/shell_helpers/get_release_data.sh
+fi
 
 WHATTOBUILD=$1
 
@@ -13,5 +19,7 @@ LINKERFLAGS="\
 -X go.dev.pztrn.name/metricator/internal/common.Version=${VERSION}"
 
 
+echo "Using $(go version) at ${GO}"
+
 cd cmd/${WHATTOBUILD}
-go build -tags netgo -ldflags "${LINKERFLAGS} -w -extldflags '-static'" -o ../../._bin/${WHATTOBUILD}
+${GO} build -tags netgo -ldflags "${LINKERFLAGS} -w -extldflags '-static'" -o ../../._bin/${WHATTOBUILD}

scripts/shell_helpers/get_git_data.sh

@@ -1,7 +1,6 @@
 # Gets git data.
 # Should be sourced where neccessary.
-
 export BRANCHNAME=${BRANCHNAME:=$(git branch --no-color --show-current)}
 export BUILDID=${BUILDID:=$(git rev-list HEAD --count)}
 export COMMITHASH=${COMMITHASH:=$(git rev-parse --verify HEAD)}
-export VERSION=${VERSION:="0.1.0-dev"}
+export VERSION=${VERSION:=$(cat VERSION)}

scripts/shell_helpers/get_release_data.sh

@@ -0,0 +1,6 @@
+# Overrides some variables for release.
+
+export VERSION=$(cat VERSION)
+export BRANCHNAME="release/${VERSION}"
+export COMMITHASH="none"
+export BUILDID="0"

scripts/show_git_data.sh

@@ -1,7 +1,11 @@
 #!/usr/bin/env bash
 
 # Showing git data in console.
+if [ -d .git ]; then
     source ./scripts/shell_helpers/get_git_data.sh
+else
+    source ./scripts/shell_helpers/get_release_data.sh
+fi
 
 echo "* Branch: ${BRANCHNAME}"
 echo "* Build ID: ${BUILDID}"