[jboss-jira] [JBoss JIRA] (JGRP-1416) NAKACK / NAKACK2: shorten scope of seqno_lock

NAKACK / NAKACK2: shorten scope of seqno_lock --------------------------------------------- Key: JGRP-1416 URL: https://issues.jboss.org/browse/JGRP-1416 Project: JGroups Issue Type: Enhancement Reporter: Bela Ban Assignee: Bela Ban Priority: Minor Fix For: 3.0.3, 3.1 The code in NAKACK/NAKACK2.send() acquires seqno_lock like this: {code:title=NAKACK.send()|borderStyle=solid} seqno_lock.lock(); try { try { // incrementing seqno and adding the msg to sent_msgs needs to be atomic msg_id=seqno +1; msg.putHeader(this.id, NakAckHeader.createMessageHeader(msg_id)); win.add(msg_id, msg); seqno=msg_id; } catch(Throwable t) { // throw exception } } finally { seqno_lock.unlock(); } {code} This slows concurrent sender threads down if add() takes a while. Method add() can take a while if we have many concurrent adds and removes. The reason we use seqno_lock is to prevent gaps in the sequence numbers, e.g. if we have an exception in add(). SOLUTION: - Assign a new msg_id by incrementing seqno *atomically* (seqno_lock is now de-scoped to only increment seqno, might replace this with an AtomicLong anyway) - In a loop: add the message (calling add()), until add() returns successfully, then break Example: {code} msg_id=seqno.incrementAndGet(); // uses an AtomicLong while(running) { // maybe bound with a counter try { msg.adddHeader(...); add(); break; } catch(Throwable t) { // log } } {code}