FRAG2: message corruption when thread pools are disabled -------------------------------------------------------- Key: JGRP-1973 URL: https://issues.jboss.org/browse/JGRP-1973 Project: JGroups Issue Type: Bug Affects Versions: 3.6.6 Reporter: Bela Ban Assignee: Bela Ban Fix For: 3.6.7 When disabling the thread pools (regular, OOB) and using {{UDP}}, fragments of a message get corrupted as a single buffer ({{UDP.receive_buf}}) is reused. * If we send a message of 1000 bytes, and {{FRAG2.frag_size}} is set to 600, then {{FRAG2}} sends 2 fragments: f1 (offset=0, length=600) and f2 (offset=600, length=400). * f1 is received and placed into {{receive_buf}}, then sent up the stack *without copying* as the {{DirectExecutor}} thread pool doesn't copy the data * f1 is received by {{FRAG2}} and added to the fragments list at index 0. The buffer of the message points to {{receive_buf}} * f2 is received and *overwrites* f1 in {{receive_buf}} ! * f2 is received by {{FRAG2}} and added to the fragments list at index 1. The buffer of the message points to {{receive_buf}} * {{FRAG2}} now creates a new message whose buffer is {{receive_buf}}[0-600] and {{receive_buf}}[600-1000]. * The problem here is that {{receive_buf}} contains only f2, which overwrote f1, so the resulting message will be incorrect ! This probably affects {{FRAG}}, too. Not too critical, as thread pools are enabled by default, and disabling them might even be removed in the future. SOLUTION: remove the check for DirectExecutor and copy the data if {{copy_buffer}} is true {code:title=Bar.java|borderStyle=solid} if(!copy_buffer || pool instanceof DirectExecutor) pool.execute(new MyHandler(sender, data, offset, length)); // we don't make a copy if we execute on this thread else { byte[] tmp=new byte[length]; System.arraycopy(data, offset, tmp, 0, length); pool.execute(new MyHandler(sender, tmp, 0, tmp.length)); } {code}