聊聊jest的NodeChecker

摘要： 序 本文主要研究一下jest的NodeChecker NodeChecker jest-common-6.3.1-sources.jar!/io/searchbox/client/config/discovery/NodeChecker.java public class No...

序

本文主要研究一下jest的NodeChecker

NodeChecker

jest-common-6.3.1-sources.jar!/io/searchbox/client/config/discovery/NodeChecker.java

public class NodeChecker extends AbstractScheduledService {

private final static Logger log = LoggerFactory.getLogger(NodeChecker.class);
private final static String PUBLISH_ADDRESS_KEY = "http_address";
private final static String PUBLISH_ADDRESS_KEY_V5 = "publish_address"; // The one that under "http" node
private final static Pattern INETSOCKETADDRESS_PATTERN = Pattern.compile("(?:inet\\[)?(?:(?:[^:]+)?\\/)?([^:]+):(\\d+)\\]?");

private final NodesInfo action;

protected JestClient client;
protected Scheduler scheduler;
protected String defaultScheme;
protected Set<String> bootstrapServerList;
protected Set<String> discoveredServerList;

public NodeChecker(JestClient jestClient, ClientConfig clientConfig) {
action = new NodesInfo.Builder()
.withHttp()
.addNode(clientConfig.getDiscoveryFilter())
.build();
this.client = jestClient;
this.defaultScheme = clientConfig.getDefaultSchemeForDiscoveredNodes();
this.scheduler = Scheduler.newFixedDelaySchedule(
0l,
clientConfig.getDiscoveryFrequency(),
clientConfig.getDiscoveryFrequencyTimeUnit()
);
this.bootstrapServerList = ImmutableSet.copyOf(clientConfig.getServerList());
this.discoveredServerList = new LinkedHashSet<String>();
}

@Override
protected void runOneIteration() throws Exception {
JestResult result;
try {
result = client.execute(action);
} catch (CouldNotConnectException cnce) {
// Can't connect to this node, remove it from the list
log.error("Connect exception executing NodesInfo!", cnce);
removeNodeAndUpdateServers(cnce.getHost());
return;
// do not elevate the exception since that will stop the scheduled calls.
// throw new RuntimeException("Error executing NodesInfo!", e);
} catch (Exception e) {
log.error("Error executing NodesInfo!", e);
client.setServers(bootstrapServerList);
return;
// do not elevate the exception since that will stop the scheduled calls.
// throw new RuntimeException("Error executing NodesInfo!", e);
}

if (result.isSucceeded()) {
LinkedHashSet<String> httpHosts = new LinkedHashSet<String>();

JsonObject jsonMap = result.getJsonObject();
JsonObject nodes = (JsonObject) jsonMap.get("nodes");
if (nodes != null) {
for (Entry<String, JsonElement> entry : nodes.entrySet()) {

JsonObject host = entry.getValue().getAsJsonObject();
JsonElement addressElement = null;
if (host.has("version")) {
int majorVersion = Integer.parseInt(Splitter.on('.').splitToList(host.get("version").getAsString()).get(0));

if (majorVersion >= 5) {
JsonObject http = host.getAsJsonObject("http");
if (http != null && http.has(PUBLISH_ADDRESS_KEY_V5))
addressElement = http.get(PUBLISH_ADDRESS_KEY_V5);
}
}

if (addressElement == null) {
// get as a JsonElement first as some nodes in the cluster may not have an http_address
if (host.has(PUBLISH_ADDRESS_KEY)) addressElement = host.get(PUBLISH_ADDRESS_KEY);
}

if (addressElement != null && !addressElement.isJsonNull()) {
String httpAddress = getHttpAddress(addressElement.getAsString());
if(httpAddress != null) httpHosts.add(httpAddress);
}
}
}
if (log.isDebugEnabled()) {
log.debug("Discovered {} HTTP hosts: {}", httpHosts.size(), Joiner.on(',').join(httpHosts));
}
discoveredServerList = httpHosts;
client.setServers(discoveredServerList);
} else {
log.warn("NodesInfo request resulted in error: {}", result.getErrorMessage());
client.setServers(bootstrapServerList);
}
}

protected void removeNodeAndUpdateServers(final String hostToRemove) {
log.warn("Removing host {}", hostToRemove);
discoveredServerList.remove(hostToRemove);
if (log.isInfoEnabled()) {
log.info("Discovered server pool is now: {}", Joiner.on(',').join(discoveredServerList));
}
if (!discoveredServerList.isEmpty()) {
client.setServers(discoveredServerList);
} else {
client.setServers(bootstrapServerList);
}
}

@Override
protected Scheduler scheduler() {
return scheduler;
}

@Override
protected ScheduledExecutorService executor() {
final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(
new ThreadFactoryBuilder()
.setDaemon(true)
.setNameFormat(serviceName())
.build());
// Add a listener to shutdown the executor after the service is stopped.This ensures that the
// JVM shutdown will not be prevented from exiting after this service has stopped or failed.
// Technically this listener is added after start() was called so it is a little gross, but it
// is called within doStart() so we know that the service cannot terminate or fail concurrently
// with adding this listener so it is impossible to miss an event that we are interested in.
addListener(new Listener() {
@Override public void terminated(State from) {
executor.shutdown();
}
@Override public void failed(State from, Throwable failure) {
executor.shutdown();
}}, MoreExecutors.directExecutor());
return executor;
}

/**
* Converts the Elasticsearch reported publish address in the format "inet[<hostname>:<port>]" or
* "inet[<hostname>/<hostaddress>:<port>]" to a normalized http address in the form "http://host:port".
*/
protected String getHttpAddress(String httpAddress) {
Matcher resolvedMatcher = INETSOCKETADDRESS_PATTERN.matcher(httpAddress);
if (resolvedMatcher.matches()) {
return defaultScheme + resolvedMatcher.group(1) + ":" + resolvedMatcher.group(2);
}

return null;
}

}

• NodeChecker繼承了AbstractScheduledService，它的構造器根據clientConfig的discoveryFrequency及discoveryFrequencyTimeUnit新建了fixedDelayScheduler來執行node checker；它實現了runOneIteration方法，該方法主要是傳送NodesInfo請求(GET /_nodes/_all/http )
• 如果請求丟擲CouldNotConnectException則呼叫removeNodeAndUpdateServers方法移除該host；如果丟擲其他的Exception則將client的servers重置為bootstrapServerList
• 如果請求成功則解析body，如果nodes下面有version且大於等於5則取http節點下面的PUBLISH_ADDRESS_KEY_V5(publish_address )屬性值新增到discoveredServerList；舊版本的則從nodes下面的PUBLISH_ADDRESS_KEY(http_address )屬性值新增到discoveredServerList

NodesInfo返回例項

{
"_nodes" : {
"total" : 1,
"successful" : 1,
"failed" : 0
},
"cluster_name" : "docker-cluster",
"nodes" : {
"RmyGhZEbTjC7JCQFVS3HWQ" : {
"name" : "RmyGhZE",
"transport_address" : "172.17.0.2:9300",
"host" : "172.17.0.2",
"ip" : "172.17.0.2",
"version" : "6.6.2",
"build_flavor" : "oss",
"build_type" : "tar",
"build_hash" : "3bd3e59",
"roles" : [
"master",
"data",
"ingest"
],
"http" : {
"bound_address" : [
"0.0.0.0:9200"
],
"publish_address" : "192.168.99.100:9200",
"max_content_length_in_bytes" : 104857600
}
}
}
}

• 如果是5版本及以上的則在nodes下面有http屬性，裡頭有publish_address屬性用於返回該node的publish address

JestHttpClient

jest-6.3.1-sources.jar!/io/searchbox/client/http/JestHttpClient.java

public class JestHttpClient extends AbstractJestClient {
//......

@Override
public <T extends JestResult> T execute(Action<T> clientRequest) throws IOException {
return execute(clientRequest, null);
}

public <T extends JestResult> T execute(Action<T> clientRequest, RequestConfig requestConfig) throws IOException {
HttpUriRequest request = prepareRequest(clientRequest, requestConfig);
CloseableHttpResponse response = null;
try {
response = executeRequest(request);
return deserializeResponse(response, request, clientRequest);
} catch (HttpHostConnectException ex) {
throw new CouldNotConnectException(ex.getHost().toURI(), ex);
} finally {
if (response != null) {
try {
response.close();
} catch (IOException ex) {
log.error("Exception occurred while closing response stream.", ex);
}
}
}
}

@Override
public <T extends JestResult> void executeAsync(final Action<T> clientRequest, final JestResultHandler<? super T> resultHandler) {
executeAsync(clientRequest, resultHandler, null);
}

public <T extends JestResult> void executeAsync(final Action<T> clientRequest, final JestResultHandler<? super T> resultHandler, final RequestConfig requestConfig) {
synchronized (this) {
if (!asyncClient.isRunning()) {
asyncClient.start();
}
}

HttpUriRequest request = prepareRequest(clientRequest, requestConfig);
executeAsyncRequest(clientRequest, resultHandler, request);
}

protected <T extends JestResult> HttpUriRequest prepareRequest(final Action<T> clientRequest, final RequestConfig requestConfig) {
String elasticSearchRestUrl = getRequestURL(getNextServer(), clientRequest.getURI(elasticsearchVersion));
HttpUriRequest request = constructHttpMethod(clientRequest.getRestMethodName(), elasticSearchRestUrl, clientRequest.getData(gson), requestConfig);

log.debug("Request method={} url={}", clientRequest.getRestMethodName(), elasticSearchRestUrl);

// add headers added to action
for (Entry<String, Object> header : clientRequest.getHeaders().entrySet()) {
request.addHeader(header.getKey(), header.getValue().toString());
}

return request;
}

protected String getNextServer() {
return serverPoolReference.get().getNextServer();
}

//......
}

• JestHttpClient繼承了AbstractJestClient，它的execute及executeAsync方法都呼叫了prepareRequest來構造HttpUriRequest；該方法會先呼叫getNextServer方法來獲取要請求的elasticSearchServer的地址；而getNextServer方法則是呼叫的serverPoolReference.get().getNextServer()

AbstractJestClient

jest-common-6.3.1-sources.jar!/io/searchbox/client/AbstractJestClient.java

public abstract class AbstractJestClient implements JestClient {

private final AtomicReference<ServerPool> serverPoolReference =
new AtomicReference<ServerPool>(new ServerPool(ImmutableSet.<String>of()));

//......

public void setServers(Set<String> servers) {
if (servers.equals(serverPoolReference.get().getServers())) {
if (log.isDebugEnabled()) {
log.debug("Server pool already contains same list of servers: {}",
Joiner.on(',').join(scrubServerURIs(servers)));
}
return;
}
if (log.isInfoEnabled()) {
log.info("Setting server pool to a list of {} servers: [{}]",
servers.size(), Joiner.on(',').join(scrubServerURIs(servers)));
}
serverPoolReference.set(new ServerPool(servers));

if (servers.isEmpty()) {
log.warn("No servers are currently available to connect.");
}
}

//......
}

• AbstractJestClient有一個serverPoolReference屬性，它是AtomicReference，其泛型為ServerPool；setServers方法則是建立新的ServerPool，然後更新serverPoolReference

ServerPool

jest-common-6.3.1-sources.jar!/io/searchbox/client/AbstractJestClient.java

private static final class ServerPool {
private final List<String> serversRing;
private final AtomicInteger nextServerIndex = new AtomicInteger(0);

public ServerPool(final Set<String> servers) {
this.serversRing = ImmutableList.copyOf(servers);
}

public Set<String> getServers() {
return ImmutableSet.copyOf(serversRing);
}

public String getNextServer() {
if (serversRing.size() > 0) {
try {
return serversRing.get(nextServerIndex.getAndIncrement() % serversRing.size());
} catch (IndexOutOfBoundsException outOfBoundsException) {
// In the very rare case where nextServerIndex overflowed, this will end up with a negative number,
// resulting in an IndexOutOfBoundsException.
// We should then start back at the beginning of the server list.
// Note that this might happen on several threads at once, in which the reset might happen a few times
log.info("Resetting next server index");
nextServerIndex.set(0);
return serversRing.get(nextServerIndex.getAndIncrement() % serversRing.size());
}
}
else {
throw new NoServerConfiguredException("No Server is assigned to client to connect");
}
}

public int getSize() {
return serversRing.size();
}
}

• ServerPool有個AtomicInteger型別的nextServerIndex，getNextServer方法則是通過nextServerIndex.getAndIncrement() % serversRing.size()來確定取的serversRing這個List的index，其實現的是Round Robin策略；極端情況下出現IndexOutOfBoundsException的話，則會重置nextServerIndex為0，然後繼續按Round Robin策略取下一個server

小結

GET /_nodes/_all/http

doc

• NodeChecker