I just realized that the "copy on deploy" mechanism might not be a good
idea for config from gateway-core/site.xml. The issue is that any
changes to gateway-core/site.xml won't be detected even after a gateway
restart. With that in mind the right thing to do here is probably the
ServletContext attribute mechanism I described below.
On 8/13/13 3:00 PM, Kevin Minder wrote:
Hi Dilli,
The existing model for configuration of a filter relies upon the
deployment step to copy any config required by a filter out of either
global or topology config into filter init params at deployment time.
The "hook" point for this is in the API
gateway-spi/src/main/java/org/apache/hadoop/gateway/deploy/ProviderDeploymentContributor.java
specifically the method contributeFilter().
This method ends up being called whenever a
ServiceDeploymentContributor adds a filter via
DeploymentContext.contributeFilter.
So take a look at TempletetonDeploymentContributor.contributeService
it calls DeploymentContext.contributeFilter
this indirectly ends up calling
DispatchDeploymentContributor.contributeFilter
In this method you can interogate the DeploymentContext where you can
find both the global config gateway-core/site.xml) via
getGatewayConfig and the topology config (e.g. sample.xml) via
getTopology().
From that filter init params could be added like this.
@Override
public void contributeFilter( DeploymentContext context, Provider
provider, Service service, ResourceDescriptor resource,
List<FilterParamDescriptor> params ) {
FilterDescriptor filter = resource.addFilter().name( getName()
).role( getRole() ).impl( HttpClientDispatch.class );
if( context.getGatewayConfig().isHadoopKerberosSecured() ) {
filter.param().name("kerberos").value("true");
}
}
I don't currently see a way to access GatewayConfig at request
processing time. It looks like it would be fairly easy to add as a
ServletContext attribute. This would be done in
GatewayServer.internalDeploy where the WebAppContext.setAttribute() is
setup. It could then be read by each filter in Filter.init() via
FilterConfig.getServletContext().getAttribute();
Kevin.
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