Added option to not flush stream buffers on every message send

README.md

@@ -94,6 +94,9 @@ messageSender.setDefaultSeverity(Severity.INFORMATIONAL);
 messageSender.setSyslogServerHostname("127.0.0.1");
 messageSender.setSyslogServerPort(1234);
 messageSender.setMessageFormat(MessageFormat.RFC_3164); // optional, default is RFC 3164
+// onSend is the default value, other value is onClose which has higher throughput but
+// risks dataloss if the syslog server address dynamically changes 
+messageSender.setSocketFlush(TcpSyslogMessageSender.SocketFlush.onSend); 
 messageSender.setSsl(false);
 
 // send a Syslog message
@@ -119,6 +122,9 @@ messageSender.setDefaultSeverity(Severity.INFORMATIONAL);
 messageSender.setSyslogServerHostname("127.0.0.1");
 messageSender.setSyslogServerPort(1234);
 messageSender.setMessageFormat(MessageFormat.RFC_3164); // optional, default is RFC 3164
+// onSend is the default value, other value is onClose which has higher throughput but
+// risks dataloss if the syslog server address dynamically changes 
+messageSender.setSocketFlush(TcpSyslogMessageSender.SocketFlush.onSend); 
 messageSender.setSsl(true);
 
 // send a Syslog message
@@ -145,6 +151,9 @@ messageSender.setSyslogServerHostname("127.0.0.1");
 // syslog-tls usually uses port 6514 as per https://tools.ietf.org/html/rfc5425#page-11
 messageSender.setSyslogServerPort(6514);
 messageSender.setMessageFormat(MessageFormat.RFC_5425);
+// onSend is the default value, other value is onClose which has higher throughput but
+// risks dataloss if the syslog server address dynamically changes 
+messageSender.setSocketFlush(TcpSyslogMessageSender.SocketFlush.onSend); 
 messageSender.setSsl(true);
 
 // send a Syslog message

src/main/java/com/cloudbees/syslog/sender/TcpSyslogMessageSender.java

@@ -47,8 +47,14 @@
  */
 @ThreadSafe
 public class TcpSyslogMessageSender extends AbstractSyslogMessageSender implements Closeable  {
+    public enum SocketFlush {
+        onSend, // default,
+        onClose // higher throughput, but at a risk of data-loss if the syslog server address dynamically changes
+    };
+
     public final static int SETTING_SOCKET_CONNECT_TIMEOUT_IN_MILLIS_DEFAULT_VALUE = 500;
     public final static int SETTING_MAX_RETRY = 2;
+    public final static SocketFlush DEFAULT_SOCKET_FLUSH = SocketFlush.onSend;
 
     /**
      * {@link java.net.InetAddress InetAddress} of the remote Syslog Server.
@@ -74,6 +80,9 @@ public class TcpSyslogMessageSender extends AbstractSyslogMessageSender implemen
      * Number of retries to send a message before throwing an exception.
      */
     private int maxRetryCount = SETTING_MAX_RETRY;
+
+    private SocketFlush socketFlush = DEFAULT_SOCKET_FLUSH;
+
     /**
      * Number of exceptions trying to send message.
      */
@@ -97,7 +106,9 @@ public synchronized void sendMessage(@Nonnull SyslogMessage message) throws IOEx
                     ensureSyslogServerConnection();
                     message.toSyslogMessage(messageFormat, writer);
                     writer.write(postfix);
-                    writer.flush();
+                    if (socketFlush == SocketFlush.onSend) {
+                        writer.flush();
+                    }
                     return;
                 } catch (IOException e) {
                     lastException = e;
@@ -265,6 +276,14 @@ public synchronized void setPostfix(String postfix) {
         this.postfix = postfix;
     }
 
+    public SocketFlush getSocketFlush() {
+        return socketFlush;
+    }
+
+    public void setSocketFlush(SocketFlush socketFlush) {
+        this.socketFlush = socketFlush;
+    }
+
     @Override
     public String toString() {
         return getClass().getName() + "{" +
@@ -282,11 +301,17 @@ public String toString() {
                 ", sendDurationInNanosCounter=" + sendDurationInNanosCounter +
                 ", sendErrorCounter=" + sendErrorCounter +
                 ", trySendErrorCounter=" + trySendErrorCounter +
+                ", socketFlush=" + socketFlush +
                 '}';
     }
 
     @Override
     public void close() throws IOException {
-        this.socket.close();
+        if ((socketFlush == SocketFlush.onClose) && (writer != null)) {
+            // close will flush first, so if an exception ocurrs, data will still be passed to socket
+            writer.close();
+        }
+        socket.close();
+
     }
 }

src/test/java/com/cloudbees/syslog/sender/TcpSyslogMessageSenderLoadTest.java

@@ -45,6 +45,7 @@ public static void main(String[] args) throws Exception {
         // messageSender.setSyslogServerHostname("127.0.0.1");
         messageSender.setSyslogServerPort(46022);
         messageSender.setSsl(true);
+        messageSender.setSocketFlush(TcpSyslogMessageSender.SocketFlush.onSend);
 
         final AtomicInteger count = new AtomicInteger();