This design is intended to address the following issues:
KNOX-179@jira: Simple way to introduce new servlet filters into the chains
KNOX-103@jira: Support multiple <pattern> children in <resource> for gateway.xml
KNOX-177@jira: Simplify service deployment contributor implementation
Each of these issues stem This issue stems from what is currently expected of a ServiceDeploymentContributor
in its contributeService
method.
Basically each service deployment contributor is expected to build its own filter chain.
This is currently done by making calls to Deploymentcontext.contributeFilter
.
While this provides a great deal of flexibility for each service to define a custom chain we have found that this isn't commonly necessary.
Furthermore it makes if very difficult if not impossible to introduce new provider/filters in a chain without impacting all services.
This design will provide an abstraction to the service deployment contributors that can create either a default or specifically configured chain of providers/filters.
The goal is to support a pattern in service deployment contributors that looks like this:
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public void contributeService( DeploymentContext context, Service service ) throws Exception { String chain = null; // Default if null, otherwise specific chain name defined in topoloy.xml Map<String,Map<String,String>>List<ServiceParamDescriptor> params = null; // Default if null, otherwise map of per provider role map of name/value pairs. ResourceDescriptor resource = context.addResource() resource.role( "WEBHDFS" ); resource.pattern( "webhdfs/v1/?**" ); resource.pattern( "webhdfs/v1/**?**" ); context.contributeChain( service, resource, chain, params ); } | ||||||||
Code Block | xml | xml | ||||||
title | Sample Topology Descriptor |
The over all context into which the method above fits into the deployment infrastructure is shown in the sequence diagram below.
PlantUML |
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@startuml
title Contribute Chain
hide footbox
autonumber
participant "Deployment\nFactory\n(df)" as df
participant "Deployment\nContext\n(dc)" as dc
participant "Service\nDeployment\nContributor\n(sdc)" as sdc
participant "Provider\nDeployment\nContributor\n(pdc)" as pdc
activate df
create dc
df -> dc: new
df -> sdc: contributeService(dc)
activate sdc
sdc -> dc: contributeChain()
activate dc
dc -> pdc: contributeFilter()
deactivate dc
sdc --> df
deactivate sdc
deactivate df
@endup
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The method below shows a more complete example of a contributeService method as it might be implemented for WebHDFS.
<topology>
<gateway>
<provider/>
<chain name="">
<provider role="" name="">
<param name="" value=""/>
</provider>
<provider/>
</chain>
</gateway>
</topology>
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public void contributeService( DeploymentContext context, Service service ) throws Exception {
UrlRewriteRulesDescriptor serviceRules = loadRulesFromClassPath();
UrlRewriteRulesDescriptor clusterRules = context.getDescriptor( "rewrite" );
clusterRules.addRules( serviceRules );
ResourceDescriptor resource;
List<ServiceParamDescriptor> params;
resource = context.getGatewayDescriptor().addResource();
resource.role( "WEBHDFS" );
resource.pattern( "webhdfs/v1/?**" );
resource.pattern( "webhdfs/v1/**?**" );
params = new ArrayList<ServiceParamDescriptor>();
params.add( resource.createParam().role( "rewrite", "request.url", "/webhdfs/namenode/inbound/path" );
params.add( resource.createParam().role( "rewrite", "response.headers", "/webhdfs/namenode/outbound/headers" );
context.contributeChain( service, resource, params );
resource = context.getGatewayDescriptor().addResource();
resource.role( "WEBHDFS" );
resource.pattern( "webhdfs/data/v1/**?**" );
params = new ArrayList<ServiceParamDescriptor>();
params.add( resource.createParam().role( "rewrite", "request.url", "/webhdfs/datanode/inbound/path" );
context.contributeChain( service, resource, params );
}
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This is a sketch of how topology files would need to be extended to support the external chain definitions.
See table below for details on the new elements introduced.
Note: I don't really like the names for provider-ref and chain-ref but I can't come up with anything better.
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<topology>
<gateway>
<provider>
<role>...</role>
<name>...</name>
<param><name>...</name><value>...</value></param>
</provider>
<chain>
<name>...</name>
<provider-ref>
<role>...</role>
<name>...</name>
<param><name>...</name><value>...</value></param>
</provider-ref>
<provider-ref>...</provider-ref>
</chain>
<chain>...</chain>
</gateway>
<service>
<role>...</role>
<url>...</url>
<chain-ref>
<name>...</name>
<param><role></role><name></name><value></value></param>
</chain-ref>
<param><name></name><value></value></param>
</service>
</topology>
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Details on the new elements within the topology are described below.
Path | Description |
---|---|
topology/gateway/chain | This defines a new chain structure and configuration for use by services. There will be a "built-in" chain named "default". |
topology/gateway/chain/name | Specifies the name of the chain so that it can be referenced by services. |
topology/gateway/chain/provider-ref | References a configured or default provider. May repeat. |
topology/gateway/chain/provider-ref/role | A required role of a provider to be included in the chain. |
topology/gateway/chain/provider-ref/name | An optional name of a specific provider for the given role. |
topology/gateway/chain/provider-ref/param | Optional config parameters to augment the provider's configuration. |
topology/service/chain-ref | Selects a specific chain to use for the service. May repeat. |
topology/service/chain-ref/name | Specifies the name of the chain to use for the service. Default is "default" |
topology/service/chain-ref/param | Optional parameters to augment the chain and provider configuration. |
topology/service/chain-ref/param/role | A role name to disambiguate which provider the param is intended. |
topology/service/param | Configuration parameters used by the service. May repeat. |
This shows the new method contributeChain()
that would be added to the DeploymentContext interface.
The existing contributeFilter method would be deprecated.
This is actually a point worth further discussion.
Is there a use case where a service might want to define a chain this way?
Code Block | ||||||||
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public interface DeploymentContext {
...
@Deprecated
void contributeFilter(
Service service,
ResourceDescriptor resource,
String role,
String name,
List<FilterParamDescriptor> params );
void contributeChain(
Service service,
ResourceDescriptor resource,
List<ServiceParamDescriptor> params );
...
}
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This shows the relevant portions of the existing, unmodified ServiceDeploymentContributor interface.
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public interface ServiceDeploymentContributor {
...
// Called per service based on the service's role.
void contributeService( DeploymentContext context, Service service ) throws Exception;
...
}
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This shows the relevant portions of the existing, unmodified ProviderDeploymentContributor interface.
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public interface ProviderDeploymentContributor {
... | ||||||||
public interface DeploymentContext {
GatewayConfig getGatewayConfig();
Topology getTopology();
WebArchive getWebArchive();
WebAppDescriptor getWebAppDescriptor();
GatewayDescriptor getGatewayDescriptor();
void contributeChain(
Service service,
ResourceDescriptor resource,
String chainName,
Map<String,List<FilterParamDescriptor>> params );
void addDescriptor( String name, Object descriptor );
<T> T getDescriptor( String name );
}
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Code Block | java | java | ||||||
title | ServiceDeploymentContributor | |||||||
public interface ServiceDeploymentContributor {
// The role of this service deployment contributor. e.g. WEBHDFS
String getRole();
// The name of this service deployment contributor. Not used yet.
String getName();
// Called after provider initializeContribution methods and in arbitrary order relative to other service contributors.
void initializeContribution( DeploymentContext context );
// Called per service based on the service's role.
// Returns a list of resources it added to the descriptor.
void contributeService( DeploymentContext context, Service service ) throws Exception;
// Called after all contributors and before provider finalizeContribution methods.
void finalizeContribution( DeploymentContext context );
}
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Code Block | ||||||||
java | java | |||||||
title | ProviderDeploymentContributor | public interface ProviderDeploymentContributor { // The role this provider supports (e.g. authentication) String getRole(); // In the topology the provider will have an optional name element. If it is present // then the framework will look for the the provider deployment contributor with the correct // role and name. String getName(); // All provider initializeContribution methods are called first in arbitrary order. void initializeContribution( DeploymentContext context ); // Called for each provider in the topology based on the role and optionally name. void contributeProvider( DeploymentContext context, Provider provider ); // This will be called indirectly by a ServiceDeploymentContributor when it needs a filterasks // contributed for this providers role. A ServiceDeploymentContributor may request a specific chain to //be providercontributed by role and name otherwise the default provider for the role will be usedvia DeploymentContext.contributeChain. void contributeFilter( DeploymentContext context, Provider provider, Service service, ResourceDescriptor resource, List<FilterParamDescriptor> params ); // All provider finalizeContribution methods are called last in arbitrary order. void finalizeContribution( DeploymentContext context ); | ||||||
PlantUML | ||||||||
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Filter -> Chain: Text ... } |