topic StrongUuidGenerator not thread safe in Alfresco Archive https://connect.hyland.com/t5/alfresco-archive/stronguuidgenerator-not-thread-safe/m-p/112041#M78823 <HTML><HEAD></HEAD><BODY><SPAN>Activiti's StrongUuidGenerator uses fasterxml's TimeBasedGenerator to generate unique ids. Today, during performance testing, I encountered a lot of collisions. Diving in the sources I found that TimeBasedGenerator is, contrary to what the documentation suggests, not thread safe.</SPAN><BR /><BR /><SPAN>This can be easily demonstrated using the following test, which will find a collision even with just 2 threads:</SPAN><BR /><PRE class="language-none line-numbers"><CODE><BR />final TimeBasedGenerator timeBasedGenerator = Generators.timeBasedGenerator(EthernetAddress.fromInterface());<BR />final Set&lt;UUID&gt; ids = new HashSet&lt;UUID&gt;();<BR /><BR />Runnable r = new Runnable() {<BR />&nbsp;&nbsp;&nbsp;public void run() {<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (int i = 0; i &lt; 10000; i++) {<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;UUID id = timeBasedGenerator.generate();<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;synchronized (ids) {<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (!ids.add(id)) {<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw new RuntimeException("Id not unique: " + id);<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR />&nbsp;&nbsp;&nbsp;}<BR />};<BR /><BR />ExecutorService executorService = Executors.newFixedThreadPool(5);<BR />for (int i = 0; i &lt; 2; i++) {<BR />&nbsp;&nbsp;&nbsp;executorService.execute(r);<BR />}<BR />executorService.shutdown();<BR /><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN></CODE></PRE><SPAN>Synchronizing on timeBasedGenerator resolves this.</SPAN><BR /><BR /><SPAN>The root problem is in TimeBasedGenerator, where _uuidBytes is shared between calls to generate().</SPAN><BR /><BR /><SPAN>Edit: I may be using an old version of JUG…</SPAN></BODY></HTML> Mon, 14 May 2012 14:58:42 GMT marcus1 2012-05-14T14:58:42Z StrongUuidGenerator not thread safe https://connect.hyland.com/t5/alfresco-archive/stronguuidgenerator-not-thread-safe/m-p/112041#M78823 Activiti's StrongUuidGenerator uses fasterxml's TimeBasedGenerator to generate unique ids. Today, during performance testing, I encountered a lot of collisions. Diving in the sources I found that TimeBasedGenerator is, contrary to what the documentation suggests, not thread safe.This can be easily d Mon, 14 May 2012 14:58:42 GMT https://connect.hyland.com/t5/alfresco-archive/stronguuidgenerator-not-thread-safe/m-p/112041#M78823 marcus1 2012-05-14T14:58:42Z Re: StrongUuidGenerator not thread safe https://connect.hyland.com/t5/alfresco-archive/stronguuidgenerator-not-thread-safe/m-p/112042#M78824 <HTML><HEAD></HEAD><BODY><SPAN>Okay, I was indeed using an old version of JUG: 3.1.0. With 3.1.3 it's working fine. Oops, my mistake <img id="smileyhappy" class="emoticon emoticon-smileyhappy" src="https://connect.hyland.com/i/smilies/16x16_smiley-happy.png" alt="Smiley Happy" title="Smiley Happy" /></SPAN></BODY></HTML> Tue, 15 May 2012 08:12:19 GMT https://connect.hyland.com/t5/alfresco-archive/stronguuidgenerator-not-thread-safe/m-p/112042#M78824 marcus1 2012-05-15T08:12:19Z