loki/pkg/logcli/query/tail.go

package query

import (
	"log"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/fatih/color"
	"github.com/gorilla/websocket"

	"github.com/grafana/loki/pkg/logcli/client"
	"github.com/grafana/loki/pkg/logcli/output"
	"github.com/grafana/loki/pkg/loghttp"
	"github.com/grafana/loki/pkg/util/unmarshal"
)

// TailQuery connects to the Loki websocket endpoint and tails logs
func (q *Query) TailQuery(delayFor time.Duration, c client.Client, out output.LogOutput) {
	conn, err := c.LiveTailQueryConn(q.QueryString, delayFor, q.Limit, q.Start, q.Quiet)
	if err != nil {
		log.Fatalf("Tailing logs failed: %+v", err)
	}

	go func() {
		stopChan := make(chan os.Signal, 1)
		signal.Notify(stopChan, os.Interrupt, syscall.SIGTERM)
		<-stopChan
		if err := conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")); err != nil {
			log.Println("Error closing websocket:", err)
		}
		os.Exit(0)
	}()

	tailResponse := new(loghttp.TailResponse)

	if len(q.IgnoreLabelsKey) > 0 && !q.Quiet {
		log.Println("Ignoring labels key:", color.RedString(strings.Join(q.IgnoreLabelsKey, ",")))
	}

	if len(q.ShowLabelsKey) > 0 && !q.Quiet {
		log.Println("Print only labels key:", color.RedString(strings.Join(q.ShowLabelsKey, ",")))
	}

	for {
		err := unmarshal.ReadTailResponseJSON(tailResponse, conn)
		if err != nil {
			log.Println("Error reading stream:", err)
			return
		}

		labels := loghttp.LabelSet{}
		for _, stream := range tailResponse.Streams {
			if !q.NoLabels {
				if len(q.IgnoreLabelsKey) > 0 || len(q.ShowLabelsKey) > 0 {

					ls := stream.Labels

					if len(q.ShowLabelsKey) > 0 {
						ls = matchLabels(true, ls, q.ShowLabelsKey)
					}

					if len(q.IgnoreLabelsKey) > 0 {
						ls = matchLabels(false, ls, q.ShowLabelsKey)
					}

					labels = ls

				} else {
					labels = stream.Labels
				}
			}

			for _, entry := range stream.Entries {
				out.FormatAndPrintln(entry.Timestamp, labels, 0, entry.Line)
			}

		}
		if len(tailResponse.DroppedStreams) != 0 {
			log.Println("Server dropped following entries due to slow client")
			for _, d := range tailResponse.DroppedStreams {
				log.Println(d.Timestamp, d.Labels)
			}
		}
	}
}