Merge pull request #7 from hellofresh/feature/checkers

Added rabbit, redis and pg checkers implementations

.gitignore

@@ -0,0 +1 @@
+vendor/

Makefile

@@ -1,10 +1,9 @@
 all: lint test
-.PHONY: all
 
 lint:
-	go vet .
-.PHONY: lint
+	@go vet ./...
 
 test:
-	go test -v -cover .
-.PHONY: test
+	@go test -v -cover ./...
+
+.PHONY: all test lint

README.md

@@ -1,11 +1,18 @@
 # health-go
 
-* Exposes an HTTP handler that retrieves health status of the application.
+* Exposes an HTTP handler that retrieves health status of the application
+* Implements some generic checkers for the following services:
+  * RabbitMQ
+  * PostgreSQL
+  * Redis
+  * HTTP
+
+## Usage
 
-### Usage
 The library exports `Handler` and `HandlerFunc` functions which are fully compatible with `net/http`.
 
-#### Handler
+### Handler
+
 ```go
 package main
 
@@ -38,7 +45,7 @@ func main() {
 }
 ```
 
-#### HandlerFunc
+### HandlerFunc
 ```go
 package main
 
@@ -73,8 +80,10 @@ func main() {
 }
 ```
 
-### API Documentation
-#### `GET /status`
+## API Documentation
+
+### `GET /status`
+
 Get the health of the application.
 - Method: `GET`
 - Endpoint: `/status`

checks/http/check.go

@@ -0,0 +1,65 @@
+package http
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"time"
+)
+
+// Config is the HTTP checker configuration settings container.
+type Config struct {
+	// URL is the remote service health check URL.
+	URL string
+	// RequestTimeout is the duration that health check will try to consume published test message.
+	// If not set - 5 seconds
+	RequestTimeout time.Duration
+	// LogFunc is the callback function for errors logging during check.
+	// If not set logging is skipped.
+	LogFunc func(err error, details string, extra ...interface{})
+}
+
+// New creates new HTTP service health check that verifies the following:
+// - connection establishing
+// - getting response status from defined URL
+// - verifying that status code is less than 500
+func New(config Config) func() error {
+	return func() error {
+		if config.LogFunc == nil {
+			config.LogFunc = func(err error, details string, extra ...interface{}) {}
+		}
+
+		if config.RequestTimeout == 0 {
+			config.RequestTimeout = time.Second * 5
+		}
+
+		req, err := http.NewRequest(http.MethodGet, config.URL, nil)
+		if err != nil {
+			config.LogFunc(err, "Creating the request for the health check failed")
+			return err
+		}
+
+		ctx, cancel := context.WithCancel(context.TODO())
+
+		// Inform remote service to close the connection after the transaction is complete
+		req.Header.Set("Connection", "close")
+		req = req.WithContext(ctx)
+
+		time.AfterFunc(config.RequestTimeout, func() {
+			cancel()
+		})
+
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			config.LogFunc(err, "Making the request for the health check failed")
+			return err
+		}
+		defer res.Body.Close()
+
+		if res.StatusCode >= http.StatusInternalServerError {
+			return errors.New("remote service is not available at the moment")
+		}
+
+		return nil
+	}
+}

checks/postgres/check.go

@@ -0,0 +1,123 @@
+package postgres
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"strings"
+
+	_ "github.com/lib/pq"
+)
+
+// Config is the PostgreSQL checker configuration settings container.
+type Config struct {
+	// DSN is the PostgreSQL instance connection DSN. Required.
+	DSN string
+	// Table is the table name used for testing, must already exist in the DB and has insert/select/delete
+	// privileges for the connection user. Required.
+	Table string
+	// IDColumn is the primary column for the table used for testing. Required.
+	IDColumn string
+	// InsertColumnsFunc is the callback function that returns map[<column>]<value> for testing insert operation.
+	// Required.
+	InsertColumnsFunc func() map[string]interface{}
+	// LogFunc is the callback function for errors logging during check.
+	// If not set logging is skipped.
+	LogFunc func(err error, details string, extra ...interface{})
+}
+
+// New creates new PostgreSQL health check that verifies the following:
+// - connection establishing
+// - inserting a row into defined table
+// - selecting inserted row
+// - deleting inserted row
+func New(config Config) func() error {
+	return func() error {
+		if config.LogFunc == nil {
+			config.LogFunc = func(err error, details string, extra ...interface{}) {}
+		}
+
+		db, err := sql.Open("postgres", config.DSN)
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during connect")
+			return err
+		}
+
+		defer func() {
+			if err = db.Close(); err != nil {
+				config.LogFunc(err, "PostgreSQL health check failed during connection closing")
+			}
+		}()
+
+		columns := config.InsertColumnsFunc()
+		columnNames := []string{}
+		columnPlaceholders := []string{}
+		columnValues := []interface{}{}
+		i := 1
+		for column, value := range columns {
+			columnNames = append(columnNames, column)
+			columnPlaceholders = append(columnPlaceholders, fmt.Sprintf("$%d", i))
+			columnValues = append(columnValues, value)
+
+			i++
+		}
+
+		insertQuery := fmt.Sprintf(
+			"INSERT INTO %s (%s) VALUES (%s) RETURNING %s",
+			config.Table,
+			strings.Join(columnNames, ", "),
+			strings.Join(columnPlaceholders, ", "),
+			config.IDColumn,
+		)
+
+		var idValue interface{}
+		err = db.QueryRow(insertQuery, columnValues...).Scan(&idValue)
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during insert and scan")
+			return err
+		}
+
+		selectQuery := fmt.Sprintf(
+			"SELECT %s FROM %s WHERE %s = $1",
+			strings.Join(columnNames, ", "),
+			config.Table,
+			config.IDColumn,
+		)
+		selectRows, err := db.Query(selectQuery, idValue)
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during select")
+			return err
+		}
+		if !selectRows.Next() {
+			config.LogFunc(err, "PostgreSQL health check failed during checking select result rows")
+			return errors.New("looks like select result has 0 rows")
+		}
+		err = selectRows.Close()
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during closing select result")
+			return err
+		}
+
+		deleteQuery := fmt.Sprintf(
+			"DELETE FROM %s WHERE %s = $1",
+			config.Table,
+			config.IDColumn,
+		)
+		deleteResult, err := db.Exec(deleteQuery, idValue)
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during delete")
+			return err
+		}
+		deleted, err := deleteResult.RowsAffected()
+		if err != nil {
+			config.LogFunc(err, "PostgreSQL health check failed during extracting delete result")
+			return err
+		}
+		if deleted < 1 {
+			config.LogFunc(err, "PostgreSQL health check failed during checking delete result")
+			return errors.New("looks like delete removed 0 rows")
+		}
+
+		return nil
+	}
+}

checks/postgres/check_test.go

@@ -0,0 +1,33 @@
+package postgres
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+const pgDSNEnv = "HEALTH_GO_PG_DSN"
+
+func TestNew(t *testing.T) {
+	if os.Getenv(pgDSNEnv) == "" {
+		t.SkipNow()
+	}
+
+	check := New(Config{
+		DSN:      os.Getenv(pgDSNEnv),
+		Table:    "client",
+		IDColumn: "id",
+		InsertColumnsFunc: func() map[string]interface{} {
+			return map[string]interface{}{
+				"id":           time.Now().Format(time.RFC3339Nano),
+				"secret":       time.Now().Format(time.RFC3339Nano),
+				"extra":        time.Now().Format(time.RFC3339Nano),
+				"redirect_uri": "http://localhost",
+			}
+		},
+	})
+
+	if err := check(); err != nil {
+		t.Fatalf("PostgreSQL check failed: %s", err.Error())
+	}
+}