circolog/cmd/circolog-tail/main.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"net/url"
	"os"
	"os/signal"
	"strconv"
	"time"

	"git.lattuga.net/boyska/circolog/formatter"
	"github.com/araddon/qlbridge/datasource"
	"github.com/araddon/qlbridge/expr"
	"github.com/araddon/qlbridge/value"
	"github.com/araddon/qlbridge/vm"
	"github.com/gorilla/websocket"
	"gopkg.in/mcuadros/go-syslog.v2/format"
	"gopkg.in/mgo.v2/bson"
)

// TODO: type ExpressionValue

func main() {
	addr := flag.String("addr", "localhost:9080", "http service address")
	querySocket := flag.String("socket", "", "Path to a unix domain socket for the HTTP server")
	backlogLimit := flag.Int("n", -1, "Limit the backlog length, defaults to no limit (-1)")
	filter := flag.String("where", "", "sql-like query to filter logs")
	flag.Parse()

	filterExpr, err := expr.ParseExpression(*filter)
	if err != nil {
		fmt.Fprintln(os.Stderr, "invalid filter:", err)
		os.Exit(2)
	}

	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt)
	var d *websocket.Dialer
	u := url.URL{Scheme: "ws",
		Host: *addr, // ignored in case of -socket; see the Dialer below
		Path: "/ws",
	}
	q := u.Query()
	q.Set("fmt", "bson")
	if *backlogLimit >= 0 {
		q.Set("l", strconv.Itoa(*backlogLimit))
	}
	u.RawQuery = q.Encode()
	if *querySocket != "" {
		d = &websocket.Dialer{
			NetDial: func(network, addr string) (net.Conn, error) {
				return net.Dial("unix", *querySocket)
			},
			HandshakeTimeout: 45 * time.Second, // same as DefaultDialer
		}

		log.Printf("connecting to %s", *querySocket)
	} else {
		d = websocket.DefaultDialer
		log.Printf("connecting to %s", *addr)
	}

	c, _, err := d.Dial(u.String(), nil)
	if err != nil {
		log.Fatal("dial:", err)
	}
	defer c.Close()
	log.Println("connected!", u.String())

	done := make(chan struct{})

	go func() {
		defer close(done)
		for {
			_, serialized, err := c.ReadMessage()
			if err != nil {
				log.Println("close:", err)
				return
			}
			var parsed format.LogParts
			if err := bson.Unmarshal(serialized, &parsed); err != nil {
				log.Println("invalid BSON", err)
				continue
			}
			context := datasource.NewContextSimpleNative(parsed)
			val, ok := vm.Eval(context, filterExpr)
			if !ok || val == nil { // errors when evaluating
				continue
			}
			if val.Type() != value.BoolType {
				fmt.Fprintln(os.Stderr, "WARNING: The expression doesn't return a boolean")
				continue
			}
			if val.Value().(bool) != true {
				continue
			}
			if err := formatter.WriteFormatted(os.Stdout, formatter.FormatSyslog, parsed); err != nil {
				log.Println("error printing", err)
			}
			fmt.Println()
		}
	}()

	for {
		select {
		case <-done:
			return
		case <-interrupt:
			log.Println("interrupt")

			// Cleanly close the connection by sending a close message and then waiting (with timeout) for the
			// server to close the connection.
			err := c.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
			if err != nil {
				log.Println("write close:", err)
				return
			}
			select {
			case <-done:
				log.Println("Successfully close")
			case <-time.After(1 * time.Second):
				log.Println("Forced close")
			}
			return
		}
	}

}