CometD makes overkill of requests

[bhorvat]

I keep seeing strange message in the log files of my webapp.

127.0.0.1 - - [15/Jan/2013:23:00:53 +0000] "POST /cometd/connect HTTP/1.1" 200 147

This message is keep appearing in there and for the last few days I have seen in more then 20000 times in one hour so it managed to put my CPU to 100 utilization. Does anyone have idea what this is about?

If I try to go to that address it throw a 400 Unknown Bayeux Transport Exception

[uklance]

Under the hood, tapestry-cometd is using the CometD integration in atmosphere [1], and an instance of
org.atmosphere.cometd.CometdServlet is created. Depending on what your servlet container supports, atmosphere will choose one of the following methods: WebSockets, Server Side Events (SSE), Long-Polling, HTTP Streaming (Forever frame) and JSONP. Based on your logging, I am guessing that Long-Polling has been chosen. Take a look at the supported servers table [2] to see what your servlet container supports.

Normally, the CometD servlet can be configured via init-params [3]. In tapestry-cometd, this can be configured in the AppModule [4]. I also have an outstanding issue in tapestry-cometd to support custom clientside configuration [5].

So, I suggest you pick a servlet container that supports your push method of choice and ask any further questions on the atmosphere mailing list. If you require custom client configuration [5] let me know and I can provide a fix and release a new version of tapestry-cometd.

[1] https://github.com/Atmosphere/atmosphere
[2] https://github.com/Atmosphere/atmosphere/wiki/Supported-WebServers-and-Browsers
[3] http://cometd.org/documentation/2.x/cometd-java/server/configuration
[4] https://github.com/uklance/tapestry-cometd/wiki/Configuring-the-CometD-Servlet
[5] #12

[bhorvat]

Ok I see what you mean and I will go to the atmosphere mailing list to check with them however if I try to go to that address it throw a 400 Unknown Bayeux Transport Exception. Could this indicate that something is not configured correctly?

In one of the examples above I found

  The org.cometd.server.CometdServlet must be defined and mapped in web.xml, or otherwise the server will not be able to interpret the Bayeux protocol.
  It is normally mapped on /cometd/*, but you can change the mapping url-pattern at your wish.

Does this mean that something should be configured in my app (or tapestry-cometd maybe)?

Thanks for fast reply

[uklance]

tapestry-cometd does a little trick so that you don't need to configure the CometDServlet in web.xml. A HTTPServletRequestFilter (managed by tapestry) is configured to handle any requests for "/cometd/*". The servlet has no idea that it was instantiated by tapestry and not directly through web.xml.

http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/services/HttpServletRequestFilter.html
https://github.com/uklance/tapestry-cometd/blob/master/src/main/java/org/lazan/t5/cometd/web/ServletHttpServletRequestFilter.java
https://github.com/uklance/tapestry-cometd/blob/master/src/main/java/org/lazan/t5/cometd/web/CometdHttpServletRequestFilter.java

[bhorvat]

I was expecting (hopping) for something like that. So if I receive an Unknown Bayeux Transport Exception would this indicated that Bayeux Transport is not correctly mapped to the url?

[uklance]

No, it means that you are hitting /cometd/* with an unexpected request. I'm guessing that atmosphere/cometd expects a POST request with some headers/parameters etc set. By hitting /cometd/ directly in your browser, you are sending an empty GET request which is unexpected.

[uklance]

http://www.checkupdown.com/status/E400.html

[bhorvat]

Ok I understand, then this has no barring on the overkill of the messages. Thanks, I have wrote on Atmosphere mailing lists and I am awaiting for their reply (I have also included the previous problem with the tomcat)

[bhorvat]

The problem seems to be passed on its own, so I am not really sure what was it about. However I did get one good idea that might have something to do with this so I am posting it here for future reference.

"please make sure there is no jetty-* class in the classpath as Atmosphere is detecting them and wrongly assume it is running on Jetty."

[uklance]

I'll have to check if tapestry-cometd has a jetty dependency. From memory it does and I may need to remove it.

[uklance]

BTW: I think it might be valid for atmosphere / cometd to send thousands of requests to achieve push. In cases where the browser (or server) don't support websockets etc it will revert to polling.