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Elasticsearch subproject :client:sniffer
/*
* 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.client.sniff;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Class responsible for sniffing nodes from some source (default is elasticsearch itself) and setting them to a provided instance of
* {@link RestClient}. Must be created via {@link SnifferBuilder}, which allows to set all of the different options or rely on defaults.
* A background task fetches the nodes through the {@link HostsSniffer} and sets them to the {@link RestClient} instance.
* It is possible to perform sniffing on failure by creating a {@link SniffOnFailureListener} and providing it as an argument to
* {@link RestClientBuilder#setFailureListener(RestClient.FailureListener)}. The Sniffer implementation needs to be lazily set to the
* previously created SniffOnFailureListener through {@link SniffOnFailureListener#setSniffer(Sniffer)}.
*/
public class Sniffer implements Closeable {
private static final Log logger = LogFactory.getLog(Sniffer.class);
private final Task task;
Sniffer(RestClient restClient, HostsSniffer hostsSniffer, long sniffInterval, long sniffAfterFailureDelay) {
this.task = new Task(hostsSniffer, restClient, sniffInterval, sniffAfterFailureDelay);
}
/**
* Triggers a new sniffing round and explicitly takes out the failed host provided as argument
*/
public void sniffOnFailure(HttpHost failedHost) {
this.task.sniffOnFailure(failedHost);
}
@Override
public void close() throws IOException {
task.shutdown();
}
private static class Task implements Runnable {
private final HostsSniffer hostsSniffer;
private final RestClient restClient;
private final long sniffIntervalMillis;
private final long sniffAfterFailureDelayMillis;
private final ScheduledExecutorService scheduledExecutorService;
private final AtomicBoolean running = new AtomicBoolean(false);
private ScheduledFuture scheduledFuture;
private Task(HostsSniffer hostsSniffer, RestClient restClient, long sniffIntervalMillis, long sniffAfterFailureDelayMillis) {
this.hostsSniffer = hostsSniffer;
this.restClient = restClient;
this.sniffIntervalMillis = sniffIntervalMillis;
this.sniffAfterFailureDelayMillis = sniffAfterFailureDelayMillis;
this.scheduledExecutorService = Executors.newScheduledThreadPool(1);
scheduleNextRun(0);
}
synchronized void scheduleNextRun(long delayMillis) {
if (scheduledExecutorService.isShutdown() == false) {
try {
if (scheduledFuture != null) {
//regardless of when the next sniff is scheduled, cancel it and schedule a new one with updated delay
this.scheduledFuture.cancel(false);
}
logger.debug("scheduling next sniff in " + delayMillis + " ms");
this.scheduledFuture = this.scheduledExecutorService.schedule(this, delayMillis, TimeUnit.MILLISECONDS);
} catch(Exception e) {
logger.error("error while scheduling next sniffer task", e);
}
}
}
@Override
public void run() {
sniff(null, sniffIntervalMillis);
}
void sniffOnFailure(HttpHost failedHost) {
sniff(failedHost, sniffAfterFailureDelayMillis);
}
void sniff(HttpHost excludeHost, long nextSniffDelayMillis) {
if (running.compareAndSet(false, true)) {
try {
List sniffedHosts = hostsSniffer.sniffHosts();
logger.debug("sniffed hosts: " + sniffedHosts);
if (excludeHost != null) {
sniffedHosts.remove(excludeHost);
}
if (sniffedHosts.isEmpty()) {
logger.warn("no hosts to set, hosts will be updated at the next sniffing round");
} else {
this.restClient.setHosts(sniffedHosts.toArray(new HttpHost[sniffedHosts.size()]));
}
} catch (Exception e) {
logger.error("error while sniffing nodes", e);
} finally {
scheduleNextRun(nextSniffDelayMillis);
running.set(false);
}
}
}
synchronized void shutdown() {
scheduledExecutorService.shutdown();
try {
if (scheduledExecutorService.awaitTermination(1000, TimeUnit.MILLISECONDS)) {
return;
}
scheduledExecutorService.shutdownNow();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
/**
* Returns a new {@link SnifferBuilder} to help with {@link Sniffer} creation.
*
* @param restClient the client that gets its hosts set (via {@link RestClient#setHosts(HttpHost...)}) once they are fetched
* @return a new instance of {@link SnifferBuilder}
*/
public static SnifferBuilder builder(RestClient restClient) {
return new SnifferBuilder(restClient);
}
}