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Elasticsearch subproject :server
/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.transport;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.tasks.Task;
import org.elasticsearch.threadpool.ThreadPool;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.function.Function;
/**
* TransportActionProxy allows an arbitrary action to be executed on a defined target node while the initial request is sent to a second
* node that acts as a request proxy to the target node. This is useful if a node is not directly connected to a target node but is
* connected to an intermediate node that establishes a transitive connection.
*/
public final class TransportActionProxy {
private TransportActionProxy() {} // no instance
private static class ProxyRequestHandler implements TransportRequestHandler {
private final TransportService service;
private final String action;
private final Function> responseFunction;
ProxyRequestHandler(TransportService service, String action, Function> responseFunction) {
this.service = service;
this.action = action;
this.responseFunction = responseFunction;
}
@Override
public void messageReceived(T request, TransportChannel channel, Task task) throws Exception {
DiscoveryNode targetNode = request.targetNode;
TransportRequest wrappedRequest = request.wrapped;
service.sendRequest(targetNode, action, wrappedRequest,
new ProxyResponseHandler<>(channel, responseFunction.apply(wrappedRequest)));
}
}
private static class ProxyResponseHandler implements TransportResponseHandler {
private final Writeable.Reader reader;
private final TransportChannel channel;
ProxyResponseHandler(TransportChannel channel, Writeable.Reader reader) {
this.reader = reader;
this.channel = channel;
}
@Override
public T read(StreamInput in) throws IOException {
return reader.read(in);
}
@Override
public void handleResponse(T response) {
try {
channel.sendResponse(response);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
@Override
public void handleException(TransportException exp) {
try {
channel.sendResponse(exp);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
@Override
public String executor() {
return ThreadPool.Names.SAME;
}
}
static class ProxyRequest extends TransportRequest {
final T wrapped;
final DiscoveryNode targetNode;
ProxyRequest(T wrapped, DiscoveryNode targetNode) {
this.wrapped = wrapped;
this.targetNode = targetNode;
}
ProxyRequest(StreamInput in, Writeable.Reader reader) throws IOException {
super(in);
targetNode = new DiscoveryNode(in);
wrapped = reader.read(in);
}
@Override
public void readFrom(StreamInput in) throws IOException {
throw new UnsupportedOperationException("usage of Streamable is to be replaced by Writeable");
}
@Override
public void writeTo(StreamOutput out) throws IOException {
super.writeTo(out);
targetNode.writeTo(out);
wrapped.writeTo(out);
}
}
/**
* Registers a proxy request handler that allows to forward requests for the given action to another node. To be used when the
* response type changes based on the upcoming request (quite rare)
*/
public static void registerProxyActionWithDynamicResponseType(TransportService service, String action,
Function> responseFunction) {
RequestHandlerRegistry requestHandler = service.getRequestHandler(action);
service.registerRequestHandler(getProxyAction(action), ThreadPool.Names.SAME, true, false,
in -> new ProxyRequest<>(in, requestHandler::newRequest), new ProxyRequestHandler<>(service, action, responseFunction));
}
/**
* Registers a proxy request handler that allows to forward requests for the given action to another node. To be used when the
* response type is always the same (most of the cases).
*/
public static void registerProxyAction(TransportService service, String action,
Writeable.Reader reader) {
RequestHandlerRegistry requestHandler = service.getRequestHandler(action);
service.registerRequestHandler(getProxyAction(action), ThreadPool.Names.SAME, true, false,
in -> new ProxyRequest<>(in, requestHandler::newRequest), new ProxyRequestHandler<>(service, action, request -> reader));
}
private static final String PROXY_ACTION_PREFIX = "internal:transport/proxy/";
/**
* Returns the corresponding proxy action for the given action
*/
public static String getProxyAction(String action) {
return PROXY_ACTION_PREFIX + action;
}
/**
* Wraps the actual request in a proxy request object that encodes the target node.
*/
public static TransportRequest wrapRequest(DiscoveryNode node, TransportRequest request) {
return new ProxyRequest<>(request, node);
}
/**
* Unwraps a proxy request and returns the original request
*/
public static TransportRequest unwrapRequest(TransportRequest request) {
if (request instanceof ProxyRequest) {
return ((ProxyRequest)request).wrapped;
}
return request;
}
/**
* Unwraps a proxy action and returns the underlying action
*/
public static String unwrapAction(String action) {
assert isProxyAction(action) : "Attempted to unwrap non-proxy action: " + action;
return action.substring(PROXY_ACTION_PREFIX.length());
}
/**
* Returns true
iff the given action is a proxy action
*/
public static boolean isProxyAction(String action) {
return action.startsWith(PROXY_ACTION_PREFIX);
}
/**
* Returns true
iff the given request is a proxy request
*/
public static boolean isProxyRequest(TransportRequest request) {
return request instanceof ProxyRequest;
}
}