Unusually Large Counts of Requests to Web.xml Servlet 404 Error Page

[Josh Suarez]

Hello

Has anyone else run into this problem before?

I'm seeing a huge amount of requests (< 1000 requests per hour) for the servlet 404 error page by our app monitoring tool (AppDynamics).  The servlet 404 page is the one configured in the web.xml under 

  <error-page>

    <error-code>404</error-code>

    <location>/WEB-INF/jsp/errorpages/ErrorPage404.jsp</location>

  </error-page>

The strange thing is that our Hippo logs do not show these requests and our monitoring tool does not show any referrer in the HTTP header for these requests unlike other requests.

Our load balancer will not allow direct requests to this page either.  Instead our site uses a normal hst:Page configured in sitemap items for 404 not found responses.  So we should never see any requests for this default servlet 404 page defined in the web.xml.  This makes me wonder if internally there's a redirect happening in Hippo that would trigger a request to this web.xml 404 error page as seen by our monitoring tool but not by the hippo logs.  For instance, is it possible that once a user goes to our site's custom 404 hst:Page that internally Hippo sees the 404 response we're sending and internally triggers a second request to the web.xml's servlet 404 page as well?  This or some variation is one possibility I've come up with.

The second possibility is that these requests are for missing images.  I've noticed that any request for an image not found in the CMS does indeed return the web.xml's servlet 404 page.  I understand this is because images are served by a separate "binaries" servlet which is a different servlet that is used for normal hst requests to the site.  So I'm wondering if this huge amount of requests for the servlet 404 error page are just requests for images that are not found.

Unfortunately, our app monitoring tool does not provide any additional information to correlate either of these two possibilities.  In fact, the monitoring tool only tells us we have > 1K requests per hour for the servlet 404 error page but nothing more.

Has anyone else run into this problem before?  Do either of the two scenarios I've laid out sound plausible or is there another possibility I've overlooked?

We're using Hippo 7.9.7.

If any additional information is needed, such as an export of the sitemap or anything else, please let me know.

Thank you,

Josh

[Jasper Floor]

Hi,

I would expect the catalina access logs should tell you where these request are coming from, and otherwise your apache (or whatever webserver you are using) logs. 

If these are indeed missing images you should see that on your site I would expect. 

mvg,

Jasper

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[Bert Leunis]

Hi Josh,

On Wed, Nov 4, 2015 at 10:09 AM, Jasper Floor <j.f...@onehippo.com> wrote:

Hi,

I would expect the catalina access logs should tell you where these request are coming from, and otherwise your apache (or whatever webserver you are using) logs. 

Yes indeed, the 404 page in the web.xml is used by the container (Tomcat I presume), so you will not find anything about these requests in the Hippo logs. A bit more info about this can be found at [1].

Regards, Bert

[1] http://www.onehippo.org/library/concepts/error-pages-and-error-handling/1.-handling-error-codes-and-exceptions-by-the-web.xml.html
 

[Woonsan Ko]

Yes. The error-page in web.xml is by the servlet specification. So, whenever an application resulted in HttpServletResponse#sendError(404) or something equivalent, the servlet container such as Tomcat automatically forward to the configured error page. HST framework or component may invoke #sendError(404), but the forwarding will be handled by the servlet container in the end.

In this case, you should turn on tomcat access logging [1] which will show which resource access resulted in which status code. e.g, 200, 404, 500, ...

Regards,

Woonsan

[1] http://www.techstacks.com/howto/configure-access-logging-in-tomcat.html

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[Josh Suarez]

Wanted to post a follow up on this as we learned what the problem was and got it fixed two weeks back.

Our app team was unaware our ops team had setup a "health check" pinging tool in our data center which was hitting the root ("/") of our servers.

This was causing all the 404 errors!

Duh oh!

We had them change the ping to go to the right place ("/ping") and all is well now.

[Jeroen Reijn]

Ah good to hear it for solved! Thanks for reporting the cause. It might help others solve the same problem :-)

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