simplelog/relp_handler.go

package simplelog

import (
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"log/slog"
	"net"
	"net/url"
	"os"
	"os"
	"path/filepath"
	"strconv"
	"time"

	"github.com/google/uuid"
)

func getEnvAsInt(name string, defaultVal int) int {
	valStr := os.Getenv(name)
	if val, err := strconv.Atoi(valStr); err == nil {
		return val
	}
	return defaultVal
}

func getEnvAsDuration(name string, defaultVal time.Duration) time.Duration {
	valStr := os.Getenv(name)
	if val, err := time.ParseDuration(valStr); err == nil {
		return val
	}
	return defaultVal
}

var (
	cacheDir, _       = os.UserCacheDir()
	diskBufferLimit   = getEnvAsInt("LOGGER_DISK_BUFFER_LIMIT", 100)
	diskWriteInterval = getEnvAsDuration("LOGGER_DISK_WRITE_INTERVAL", time.Second)
	relpDebug         = os.Getenv("RELP_DEBUG") != ""
)

type RELPHandler struct {
	relpServerURL string
	conn          net.Conn
	ch            chan Event
	done          chan struct{}
	failedCh      chan Event
	timer         *time.Timer
}

func NewRELPHandler(relpURL string) (*RELPHandler, error) {
	parsedURL, err := url.Parse(relpURL)
	if err != nil {
		return nil, fmt.Errorf("Error parsing RELP URL: %v", err)
	}
	if parsedURL.Scheme != "tcp" {
		return nil, fmt.Errorf("RELP URL must have the tcp scheme, got %s", parsedURL.Scheme)
	}
	if err := os.MkdirAll(filepath.Join(cacheDir, "simplelog"), 0755); err != nil {
		return nil, fmt.Errorf("Failed to create cache directory: %v", err)
	}
	r := &RELPHandler{
		relpServerURL: parsedURL.Host,
		ch:            make(chan Event, diskBufferLimit),
		done:          make(chan struct{}),
		failedCh:      make(chan Event, diskBufferLimit),
		timer:         time.NewTimer(diskWriteInterval),
	}
	if relpDebug {
		log.Printf("Created new RELP handler for server at %s", r.relpServerURL)
	}
	return r, nil
}

func (r *RELPHandler) connectToRELPServer() (net.Conn, error) {
	parsedURL, err := url.Parse(r.relpServerURL)
	if err != nil {
		return nil, fmt.Errorf("Error parsing RELP URL: %v", err)
	}
	if parsedURL.Scheme != "tcp" {
		return nil, fmt.Errorf("RELP URL must have the tcp scheme, got %s", parsedURL.Scheme)
	}
	host, port, err := net.SplitHostPort(parsedURL.Host)
	if err != nil {
		return nil, fmt.Errorf("Error splitting host and port: %v", err)
	}
	conn, err := net.Dial("tcp", net.JoinHostPort(host, port))
	if err != nil {
		if relpDebug {
			log.Printf("Failed to connect to RELP server at %s: %v", net.JoinHostPort(host, port), err)
		}
		return nil, err
	}
	if relpDebug {
		log.Printf("Successfully connected to RELP server at %s", net.JoinHostPort(host, port))
	}
	return conn, nil
}

func (r *RELPHandler) Startup() error {
	var err error
	r.conn, err = r.connectToRELPServer()
	if err != nil {
		if relpDebug {
			log.Printf("Failed to establish TCP connection to RELP server: %v", err)
		}
		return fmt.Errorf("Failed to establish TCP connection to RELP server: %v", err)
	}
	if relpDebug {
		log.Printf("Successfully connected to RELP server at %s", r.relpServerURL)
	}
	go r.receiveEventsFromChannel()
	go r.processFailedEvents()
	go r.watchDirectoryForFailedEventFiles()
	return nil
}

func (r *RELPHandler) Enabled(ctx context.Context, level slog.Level) bool {
	return true
}

func (r *RELPHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	return r
}

func (r *RELPHandler) WithGroup(name string) slog.Handler {
	return r
}

func (r *RELPHandler) Handle(ctx context.Context, record slog.Record) error {
	attrs := make(map[string]interface{})
	record.Attrs(func(attr slog.Attr) bool {
		attrs[attr.Key] = attr.Value
		return true
	})
	jsonData, err := json.Marshal(attrs)
	if err != nil {
		return fmt.Errorf("error marshaling attributes: %v", err)
	}
	event := NewEvent(record.Level.String(), record.Message, jsonData)
	select {
	case r.ch <- event:
		return nil // Successfully sent event to channel
	default:
		return fmt.Errorf("failed to log event: channel is full")
	}
}

func (r *RELPHandler) receiveEventsFromChannel() {
	for {
		select {
		case event := <-r.ch:
			if err := r.sendEventToRELPServer(event); err != nil {
				r.failedCh <- event
			}
		case <-r.done:
			return
		}
	}
}

func (r *RELPHandler) processFailedEvents() {
	for {
		select {
		case event := <-r.failedCh:
			if err := r.sendEventToRELPServer(event); err != nil {
				// If still failing, write to disk
				r.writeFailedToDisk(event)
			}
		case <-r.timer.C:
			// Flush all events in failedCh to disk
			for len(r.failedCh) > 0 {
				event := <-r.failedCh
				r.writeFailedToDisk(event)
			}
		case <-r.done:
			return
		}
	}
}

func (r *RELPHandler) sendEventToRELPServer(event Event) error {
	jsonData, err := json.Marshal(event)
	if err != nil {
		return fmt.Errorf("error marshaling event: %v", err)
	}
	_, err = r.conn.Write(jsonData)
	if err != nil {
		return err
	}
	// Implement TCP read for the acknowledgment with a timeout
	r.conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	ack := make([]byte, 256)
	n, err := r.conn.Read(ack)
	if err != nil {
		return err
	}
	if string(ack[:n]) != "ACK" {
		return fmt.Errorf("expected ACK from server, got %s", string(ack[:n]))
	}
	if relpDebug {
		log.Printf("Received ACK from RELP server for event %s", event.ID)
	}
	return nil
}

func (r *RELPHandler) watchDirectoryForFailedEventFiles() {
	for {
		select {
		case <-r.done:
			return
		default:
			if r.isConnected() {
				if relpDebug {
					log.Printf("Reconnected to RELP server at %s", r.relpServerURL)
				}
				files, err := ioutil.ReadDir(cacheDir)
				if err != nil {
					log.Printf("Error reading cache directory: %v", err)
					continue
				}
				for _, file := range files {
					filePath := filepath.Join(cacheDir, file.Name())
					data, err := ioutil.ReadFile(filePath)
					if err != nil {
						log.Printf("Error reading event cache file %s: %v", file.Name(), err)
						continue
					}
					var event Event
					if err := json.Unmarshal(data, &event); err != nil {
						log.Printf("Error unmarshalling event from file %s: %v", file.Name(), err)
						continue
					}
					r.ch <- event
					os.Remove(filePath) // Remove file after processing
				}
			}
			time.Sleep(10 * time.Second) // Check disk every 10 seconds
		}
	}
}

func (r *RELPHandler) isConnected() bool {
	_, err := r.conn.Write([]byte{})
	return err == nil
}

func (r *RELPHandler) Shutdown() error {
	close(r.done)
	if r.conn != nil {
		if err := r.conn.Close(); err != nil {
			return fmt.Errorf("error closing TCP connection: %v", err)
		}
	}
	return nil
}

func (r *RELPHandler) writeFailedToDisk(event Event) {
	fileName := filepath.Join(cacheDir, "simplelog", uuid.New().String()+".logevent")
	data, _ := json.Marshal(event)
	ioutil.WriteFile(fileName, data, 0600)
}