add ability to log errors, warnings and fatals to slack

Author: mjarkk

.env.example

@@ -27,3 +27,8 @@ BACKUP_S3_ACCESS_KEY_ID=
 BACKUP_S3_SECRET_ACCESS_KEY=
 BACKUP_S3_BUCKET=rtcv-backups
 BACKUP_S3_USE_SSL=true
+
+# On errors, warnings and fatals, log them to a slack channel
+# The SLACK_ENVIRONMENT is added to the message to show from wich envourment the error came from
+SLACK_ENVIRONMENT=development
+SLACK_WEBHOOK_URL=

helpers/slack/slack.go

@@ -0,0 +1,79 @@
+package slack
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/apex/log"
+)
+
+// SetupLogHandler changes the log handler to send errors, fatals and warns to slack
+func SetupLogHandler(webhookURL string) {
+	messageEnv := os.Getenv("SLACK_ENVIRONMENT")
+	originalHandler := log.Log.(*log.Logger).Handler.HandleLog
+	var handler log.HandlerFunc = func(entry *log.Entry) error {
+		handleLogEntry(entry, webhookURL, messageEnv)
+		return originalHandler(entry)
+	}
+	log.SetHandler(handler)
+}
+
+func handleLogEntry(entry *log.Entry, webhookURL string, messageEnv string) {
+	// IMPORTANT:
+	// Do not send error, fatal or warn logs in this method as it will cause a n+1 loop
+
+	switch entry.Level {
+	case log.WarnLevel, log.FatalLevel, log.ErrorLevel:
+		// Continue
+	default:
+		return
+	}
+
+	text := fmt.Sprintf("*RTCV %s %s: %s*", messageEnv, entry.Level, strings.TrimSpace(entry.Message))
+
+	if len(entry.Fields) != 0 {
+		text += "\n\nFields:"
+		for key, value := range entry.Fields {
+			text += fmt.Sprintf("\n%s: %+v", key, value)
+		}
+	}
+
+	type m = map[string]any
+	body, err := json.Marshal(m{
+		"text": "",
+		"blocks": []m{{
+			"type": "section",
+			"text": m{"type": "mrkdwn", "text": text},
+		}},
+	})
+	if err != nil {
+		log.WithError(err).Info("Unable to marshal log entry meant for slack webhook")
+		return
+	}
+
+	req, err := http.NewRequest("POST", webhookURL, bytes.NewBuffer(body))
+	if err != nil {
+		log.WithError(err).Info("Unable create post request for slack webhook")
+		return
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		log.WithError(err).Info("Unable to post to slack webhook")
+		return
+	}
+
+	if resp.StatusCode >= 400 {
+		respBody, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			log.WithError(err).Info(fmt.Sprintf("slack webhook returned status code \"%s\" with a unreadable message", resp.Status))
+		} else {
+			log.Info(fmt.Sprintf("slack webhook returned status code \"%s\" with message: %s", resp.Status, string(respBody)))
+		}
+	}
+}

main.go

@@ -20,6 +20,7 @@ import (
 	"github.com/script-development/RT-CV/db/mongo/backup"
 	"github.com/script-development/RT-CV/helpers/random"
 	"github.com/script-development/RT-CV/helpers/requestLogger"
+	"github.com/script-development/RT-CV/helpers/slack"
 	"github.com/script-development/RT-CV/mock"
 	"github.com/script-development/RT-CV/models"
 	"github.com/script-development/RT-CV/models/matcher"
@@ -80,6 +81,11 @@ func main() {
 		log.Info("No .env file found")
 	}
 
+	slackWebHookURL := strings.TrimSpace(os.Getenv("SLACK_WEBHOOK_URL"))
+	if slackWebHookURL != "" {
+		slack.SetupLogHandler(slackWebHookURL)
+	}
+
 	// Initialize the database
 	var dbConn db.Connection
 	useTestingDB := strings.ToLower(os.Getenv("USE_TESTING_DB")) == "true"