We have an issue with GWT RPC calls and IE6 (yeah!). The thing is that sometimes client-server communication is too slow (takes about 15 seconds). Usually it happens after cash clear on IE and invoking RPC for the first time (other iterations with server are really fast). Since we have it embedded into another program, cash is cleared every time you close the window. So, such “delays” are quite annoying. With Firefox and even IE 8 it is OK. Server side is really simple and does not take much time.
To investigate it I installed LightweightMetrics tool and got following information:
<event event="rpc0" time="12636ms" start="16:31:38.800" end="16:31:51.436" module="app" service___response="Service.getDisplay">
<event event="requestSerialized" time="1ms" start="16:31:38.800" end="16:31:38.801" module="app" service___response=""/>
<event event="requestSent" time="1ms" start="16:31:38.801" end="16:31:38.802" module="app" service___response=""/>
<event event="responseReceived" time="12420ms" start="16:31:38.802" end="16:31:51.222" module="app" service___response=""/>
<event event="responseDeserialized" time="0ms" start="16:31:51.222" end="16:31:51.222" module="app" service___response=""/>
<event event="callback" time="214ms" start="16:31:51.222" end="16:31:51.436" module="app" service___response=""/>
</event>
As you can see the most time consuming event is responseReceived event. From application logs I can see that server-side code is invoked at 16:31:51.000. That means that to serve request and send response back it takes about 222 ms. (this diagram is also helpful http://google-web-toolkit.googlecode.com/svn/wiki/LightweightMetricsDesign-rpc.png).
Based on above-mentioned I can assume, that request “walks” somewhere for about 12.5 secs. My question is – where does it walk and how to speed up the whole process?
BTW: Both client and server are deployed on localhost. If using gwt.HTML + servlets, then seems that there is no such issue.
Seems, that problems is now solved, thanks to this question. I changed registry to have 10 concurrent connections and it works perfectly.