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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.documentapi;
import com.yahoo.document.Document;
import com.yahoo.document.DocumentId;
import com.yahoo.documentapi.messagebus.protocol.*;
import com.yahoo.messagebus.Message;
import com.yahoo.vdslib.SearchResult;
import com.yahoo.vdslib.DocumentSummary;
import com.yahoo.document.BucketId;
import java.util.List;
/**
* A data handler is a class that handles responses from a visitor.
* Different clients might want different interfaces.
* Some might want a callback interface, some might want a polling interface.
* Some want good control of acking, while others just want something simple.
* <p>
* Use a data handler that fits your needs to be able to use visiting easily.
*
* @author Håkon Humberset
*/
public abstract class VisitorDataHandler {
protected VisitorControlSession session;
/** Creates a new visitor data handler. */
public VisitorDataHandler() {
}
/**
* Called before the visitor starts. Override this method if you need
* to reset local data. Remember to call the superclass' method as well.
*/
public void reset() {
session = null;
}
/**
* Sets which session this visitor data handler belongs to. This is done by
* the session itself and should not be called manually. The session is
* needed for ack to work.
*
* @param session the session currently using this data handler
*/
public void setSession(VisitorControlSession session) {
this.session = session;
}
/**
* Returns the next response of this session. This method returns
* immediately.
*
* @return the next response, or null if no response is ready at this time
* @throws UnsupportedOperationException if data handler does not support
* the operation
*/
public VisitorResponse getNext() {
throw new UnsupportedOperationException("This datahandler doesn't support polling");
}
/**
* Returns the next response of this session. This will block until a
* response is ready or the given timeout is reached.
*
* @param timeoutMilliseconds the max time to wait for a response. If the
* number is 0, this will block without any
* timeout limit
* @return the next response, or null if no response becomes ready before
* the timeout expires
* @throws InterruptedException if this thread is interrupted while waiting
* @throws UnsupportedOperationException if data handler does not support
* the operation
*/
public VisitorResponse getNext(int timeoutMilliseconds) throws InterruptedException {
throw new UnsupportedOperationException("This datahandler doesn't support polling");
}
/**
* Called when visiting is done, to notify clients waiting on getNext().
*/
public void onDone() {}
/**
* Called when a data message is received.
*
* IMPORTANT:
* May be called concurrently from multiple threads. Any internal state
* mutations MUST be done in a thread-safe manner.
*
* @param m The message received
* @param token A token to reply with when finished processing the message.
*/
public abstract void onMessage(Message m, AckToken token);
/**
* Function used to ack data. You need to ack data periodically, as storage
* will halt visiting when it has too much client requests pending.
*
* @param token The token to ack. Gotten from an earlier callback.
*/
public void ack(AckToken token) {
session.ack(token);
}
}
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