Revert "syslog: Cache connections"

This reverts commit 95faba1.

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     docker:
-      - image: segment/golang:1.9
+      - image: segment/golang:latest
     working_directory: /go/src/github.com/segmentio/ecs-logs
     steps:
       - checkout

Dockerfile

@@ -1,6 +1,6 @@
 # We need a go compiler that's based on an image with libsystemd-dev installed,
 # segment/golang give us just that.
-FROM segment/golang:1.9
+FROM segment/golang:latest
 
 # Copy the ecs-logs sources so they can be built within the container.
 COPY . /go/src/github.com/segmentio/ecs-logs

lib/syslog/writer.go

@@ -11,7 +11,6 @@ import (
 	"os"
 	"strconv"
 	"strings"
-	"sync"
 	"text/template"
 	"time"
 
@@ -87,7 +86,7 @@ func DialWriter(config WriterConfig) (w lib.Writer, err error) {
 connect:
 	for _, n := range netopts {
 		for _, a := range addropts {
-			if backend, err = cachedDialWriter(n, a, config.TLS, config.SocksProxy); err == nil {
+			if backend, err = dialWriter(n, a, config.TLS, config.SocksProxy); err == nil {
 				break connect
 			}
 		}
@@ -99,7 +98,6 @@ connect:
 
 	w = newWriter(writerConfig{
 		backend:    backend,
-		config:     config,
 		template:   config.Template,
 		timeFormat: config.TimeFormat,
 		tag:        config.Tag,
@@ -109,7 +107,6 @@ connect:
 
 type writerConfig struct {
 	backend    io.Writer
-	config     WriterConfig
 	template   string
 	timeFormat string
 	tag        string
@@ -153,36 +150,20 @@ func newWriterTemplate(format string) *template.Template {
 
 type writer struct {
 	writerConfig
-	sync.Mutex
 	buf   bytes.Buffer
 	tpl   *template.Template
 	out   func(*writer, message) error
 	flush func() error
 }
 
-// For this backend, Close() will not actually close the socket. This is a
-// temporary hack to allow the connection to remain open for reuse between
-// multiple caller write() operations. It's not ever necessary to close the
-// socket during the normal operation of ecs-logs since we don't allow runtime
-// reconfiguration of destinations yet.  This is not ideal, but a more elegant
-// fix would involve updating the API and every destination and is significantly
-// more work than we can afford right now. --MSF 2017-10-02
 func (w *writer) Close() (err error) {
-	return
-}
-
-// This is the real close function.
-func (w *writer) reallyClose() (err error) {
 	if c, ok := w.backend.(io.Closer); ok {
 		err = c.Close()
-		writerCache.Delete(writerCacheKey(w.config.Network, w.config.Address, w.config.SocksProxy))
 	}
 	return
 }
 
 func (w *writer) WriteMessageBatch(batch lib.MessageBatch) (err error) {
-	w.Lock()
-	defer w.Unlock()
 	for _, msg := range batch {
 		if err = w.write(msg); err != nil {
 			return
@@ -192,8 +173,6 @@ func (w *writer) WriteMessageBatch(batch lib.MessageBatch) (err error) {
 }
 
 func (w *writer) WriteMessage(msg lib.Message) (err error) {
-	w.Lock()
-	defer w.Unlock()
 	if err = w.write(msg); err == nil {
 		err = w.flush()
 	}
@@ -226,11 +205,7 @@ func (w *writer) write(msg lib.Message) (err error) {
 	}
 
 	m.MSG = msg.Event.String()
-	err = w.out(w, m)
-	if err != nil {
-		w.reallyClose()
-	}
-	return
+	return w.out(w, m)
 }
 
 func (w *writer) directWrite(m message) (err error) {
@@ -269,34 +244,6 @@ func (c bufferedConn) Close() error                { return c.conn.Close() }
 func (c bufferedConn) Flush() error                { return c.buf.Flush() }
 func (c bufferedConn) Write(b []byte) (int, error) { return c.buf.Write(b) }
 
-var dialMutex = sync.Map{}
-var writerCache = sync.Map{}
-
-func writerCacheKey(network string, address string, socksProxy string) string {
-	// We don't currently include the TLS configuration in the cache key. For
-	// now, this is probably OK as the TLS configuration is unlikely to change.
-	return network + ";" + address + ";" + socksProxy
-}
-
-func cachedDialWriter(network string, address string, config *tls.Config, socksProxy string) (w io.Writer, err error) {
-	key := writerCacheKey(network, address, socksProxy)
-
-	res, _ := dialMutex.LoadOrStore(key, &sync.Mutex{})
-	mu := res.(*sync.Mutex)
-	mu.Lock()
-	defer mu.Unlock()
-
-	// Fast path: return if already in the cache
-	if w, ok := writerCache.Load(key); ok {
-		return w.(io.Writer), nil
-	}
-	w, err = dialWriter(network, address, config, socksProxy)
-	if err != nil {
-		writerCache.Store(key, w)
-	}
-	return w, err
-}
-
 func dialWriter(network string, address string, config *tls.Config, socksProxy string) (w io.Writer, err error) {
 	var conn, rawConn net.Conn
 	var dial func(string, string) (net.Conn, error)