The very basic metricator-client and package.

Package can be used in external things if needed.

pkg/client/client.go

@@ -0,0 +1,146 @@
+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 {
+	c := &Client{
+		config: config,
+		logger: logger,
+	}
+	c.initialize()
+
+	return c
+}
+
+// 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:exhaustivestruct
+	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

@@ -0,0 +1,41 @@
+package schema
+
+// 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
+	// Name is a metric name.
+	Name string
+	// Description is a metric description from HELP line.
+	Description string
+	// Type is a metric type from TYPE line.
+	Type string
+	// Value is a metric value.
+	Value string
+	// Params is an additional params which are placed inside "{}".
+	Params []string
+}
+
+// NewMetric creates new structure for storing single metric data.
+func NewMetric(name, mType, description string, params []string) Metric {
+	m := Metric{
+		BaseName:    name,
+		Name:        name,
+		Description: description,
+		Type:        mType,
+		Params:      params,
+		Value:       "",
+	}
+
+	return m
+}
+
+// GetValue returns metric's value.
+func (m *Metric) GetValue() string {
+	return m.Value
+}
+
+// SetValue sets value for metric.
+func (m *Metric) SetValue(value string) {
+	m.Value = 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
+}