Shuttind down an embedded server does not clean up properly.

[Dawid Weiss <da...@cs.put.poznan.pl>]

Hi there,

Is there any special way to 'clean up' after an Embedded server is 
started? Because at the moment it simply doesn't work properly -- when 
shutting down an instance of Embedded (.stop()) and starting a new 
instance of Embedded (.start()) for a short period of time (one or two 
seconds) the requests are served with the old mapper. This causes HTTP 
400 (No Host matches server name...). In StandardEngineValve we have:

     public final void invoke(Request request, Response response)
         throws IOException, ServletException {

         // Select the Host to be used for this Request
         Host host = request.getHost();
         if (host == null) {
             response.sendError
                 (HttpServletResponse.SC_BAD_REQUEST,
                  sm.getString("standardEngine.noHost",
                               request.getServerName()));

host is null because in Mapper:

         if (mappingData.host == null) {
             Host[] hosts = this.hosts;

the hosts variable correctly indicates there is a 'localhost' 
initialized and ready, but in a later check the list of contexts is 
empty (!) and the method returns immediately without further 
initializations.

I'm guessing the problem is in static collections somewhere (Registry?) 
being shared by different engines and reusing the stopped instance's 
list of contexts, but I just can't figure out how to cleanup properly on 
shutdown. Is there any (undocumented :) requirement to spawn Engine 
instances in separate class loaders? It seems perfectly justified and 
reasonable to shutdown one embedded Engine and spawn another one bound 
to the same host/port combination from within the same class loader, so 
to me the current behavior appears to be a bug.

I realize the question goes quite deep in Tomcat internals, so if 
developers mailing list is more adequate, let me know and I'll repost it 
over there.

Thanks,
Dawid






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Re: Shuttind down an embedded server does not clean up properly.

[Dawid Weiss <da...@cs.put.poznan.pl>]

Ok, it took me a while, but I eventually got it working -- maybe it'll 
help someone.

Indeed the problem is related to a left-over stale connector. If you 
have a keep alive TCP connection then even shutting down the entire 
engine leaves the connection open and active. I suppose this should be 
taken into account in connector shutdown methods -- the master thread 
should wait for all slaves to finish (by join()-ing them?). Setting a 
volatile termination flag doesn't work for keepalive connections.

My workaround to this problem was to set the connector to no-keepalive 
mode (it is perfectly fine in my application). So:

connector.setAttribute("maxKeepAliveRequests", "" + 1);

Dawid


Dawid Weiss wrote:
> 
> Hi there,
> 
> Is there any special way to 'clean up' after an Embedded server is 
> started? Because at the moment it simply doesn't work properly -- when 
> shutting down an instance of Embedded (.stop()) and starting a new 
> instance of Embedded (.start()) for a short period of time (one or two 
> seconds) the requests are served with the old mapper. This causes HTTP 
> 400 (No Host matches server name...). In StandardEngineValve we have:
> 
>     public final void invoke(Request request, Response response)
>         throws IOException, ServletException {
> 
>         // Select the Host to be used for this Request
>         Host host = request.getHost();
>         if (host == null) {
>             response.sendError
>                 (HttpServletResponse.SC_BAD_REQUEST,
>                  sm.getString("standardEngine.noHost",
>                               request.getServerName()));
> 
> host is null because in Mapper:
> 
>         if (mappingData.host == null) {
>             Host[] hosts = this.hosts;
> 
> the hosts variable correctly indicates there is a 'localhost' 
> initialized and ready, but in a later check the list of contexts is 
> empty (!) and the method returns immediately without further 
> initializations.
> 
> I'm guessing the problem is in static collections somewhere (Registry?) 
> being shared by different engines and reusing the stopped instance's 
> list of contexts, but I just can't figure out how to cleanup properly on 
> shutdown. Is there any (undocumented :) requirement to spawn Engine 
> instances in separate class loaders? It seems perfectly justified and 
> reasonable to shutdown one embedded Engine and spawn another one bound 
> to the same host/port combination from within the same class loader, so 
> to me the current behavior appears to be a bug.
> 
> I realize the question goes quite deep in Tomcat internals, so if 
> developers mailing list is more adequate, let me know and I'll repost it 
> over there.
> 
> Thanks,
> Dawid
> 
> 
> 
> 
> 
> 

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