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Unified Java client for ClickHouse
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package com.clickhouse.client;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.util.Locale;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import com.clickhouse.client.ClickHouseNode.Status;
import com.clickhouse.data.ClickHouseChecker;
import com.clickhouse.data.ClickHouseDataStreamFactory;
import com.clickhouse.data.ClickHouseUtils;
/**
* Load balancing policy. In general, a policy is responsible for 3 things: 1)
* get node from a managed list; 2) managing node's status; and 3) optionally
* schedule background tasks like node discovery and health check.
*/
public abstract class ClickHouseLoadBalancingPolicy implements Serializable {
static class DefaultPolicy extends ClickHouseLoadBalancingPolicy {
@Override
protected ScheduledExecutorService getScheduler() {
return null;
}
}
static class FirstAlivePolicy extends ClickHouseLoadBalancingPolicy {
@Override
protected ClickHouseNode get(ClickHouseNodes manager, ClickHouseNodeSelector t) {
boolean noSelector = t == null || t == ClickHouseNodeSelector.EMPTY;
ClickHouseNode node = null;
for (ClickHouseNode n : manager.nodes) {
if (noSelector || t.match(n)) {
node = n;
}
if (node != null && !manager.faultyNodes.contains(node)) {
break;
}
}
if (node == null) {
throw new IllegalArgumentException(ClickHouseUtils.format(ERROR_NO_SUITABLE_NODE, manager, t));
}
return node;
}
@Override
protected void update(ClickHouseNodes manager, ClickHouseNode node, Status status) {
if (status != Status.HEALTHY && status != Status.FAULTY) {
super.update(manager, node, status);
return;
}
if (status == Status.HEALTHY) {
manager.faultyNodes.remove(node);
} else if (!manager.faultyNodes.contains(node)) {
manager.faultyNodes.add(node);
manager.scheduleHealthCheck();
}
}
}
static class RandomPolicy extends ClickHouseLoadBalancingPolicy {
private final Random rand;
protected RandomPolicy() {
this.rand = new Random(System.currentTimeMillis()); // NOSONAR
}
@Override
protected ClickHouseNode get(ClickHouseNodes manager, ClickHouseNodeSelector t) {
int size = manager.nodes.size();
manager.index.set(size < 1 ? 0 : rand.nextInt(size));
return super.get(manager, t);
}
}
static class RoundRobinPolicy extends ClickHouseLoadBalancingPolicy {
@Override
protected ClickHouseNode get(ClickHouseNodes manager, ClickHouseNodeSelector t) {
boolean noSelector = t == null || t == ClickHouseNodeSelector.EMPTY;
int idx = manager.index.getAndUpdate(v -> v + 1 >= manager.nodes.size() ? 0 : v + 1);
int i = 0;
ClickHouseNode node = null;
for (ClickHouseNode n : manager.nodes) {
if (noSelector || t.match(n)) {
node = n;
}
if (i++ >= idx && node != null) {
break;
}
}
if (node == null) {
throw new IllegalArgumentException(ClickHouseUtils.format(ERROR_NO_SUITABLE_NODE, manager, t));
}
return node;
}
}
private static final long serialVersionUID = 1481796695764210324L;
private static final Map policies = new ConcurrentHashMap<>();
static final ClickHouseLoadBalancingPolicy DEFAULT = new DefaultPolicy();
static final String ERROR_NO_SUITABLE_NODE = "%s does not contain suitable node for %s";
public static final String QUERY_GET_ALL_NODES = "select cluster, host_address, host_name, "
+ "replica_num, shard_num, shard_weight from system.clusters where is_local=1";
public static final String QUERY_GET_CLUSTER_NODES = "select cluster, host_address, host_name, "
+ "replica_num, shard_num, shard_weight from system.clusters where is_local=1 and cluster=:cluster";
public static final String QUERY_GET_OTHER_NODES = "select distinct cluster, :host, replica_num, shard_num, shard_weight "
+ "from system.clusters where is_local=0 and cluster in :cluster "
+ "order by estimated_recovery_time asc, shard_weight desc, shard_num asc, (errors_count + slowdowns_count) desc";
/**
* Similar as the default policy, which always picks the first healthy node.
* Besides, it provides scheduler for node discovery and health check.
*/
public static final String FIRST_ALIVE = "firstAlive";
/**
* Policy to pick a healthy node randomly from the list.
*/
public static final String RANDOM = "random";
/**
* Policy to pick healthy node one after another based their order in the list.
*/
public static final String ROUND_ROBIN = "roundRobin";
/**
* Creates policy.
*
* @param name policy name or a full qualified class name
* @return non-null policy
* @throw IllegalArgumentException when failed to create policy
*/
static ClickHouseLoadBalancingPolicy create(String name) {
ClickHouseLoadBalancingPolicy policy;
if (FIRST_ALIVE.equalsIgnoreCase(name)) {
policy = new FirstAlivePolicy();
} else if (RANDOM.equalsIgnoreCase(name)) {
policy = new RandomPolicy();
} else if (ROUND_ROBIN.equalsIgnoreCase(name)) {
policy = new RoundRobinPolicy();
} else {
try {
Class clazz = ClickHouseLoadBalancingPolicy.class.getClassLoader().loadClass(name);
if (!ClickHouseLoadBalancingPolicy.class.isAssignableFrom(clazz)) {
throw new IllegalArgumentException(
ClickHouseUtils.format("Unsupported policy: class [%s] must extend [%s]", name,
ClickHouseLoadBalancingPolicy.class.getName()));
}
policy = (ClickHouseLoadBalancingPolicy) clazz.getDeclaredConstructor().newInstance();
} catch (ClassNotFoundException e) {
throw new IllegalArgumentException("Unknown policy: " + name, e);
} catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException
| SecurityException e) {
throw new IllegalArgumentException("Failed to instantiate policy: " + name, e);
}
}
return policy;
}
/**
* Gets or creates singleton load balancing policy.
*
* @param name policy name, one of {@link #FIRST_ALIVE},{@link #RANDOM} and
* {@link #ROUND_ROBIN}, or a fully qualified class name
* @return non-null load balancing policy
*/
public static ClickHouseLoadBalancingPolicy of(String name) {
return ClickHouseChecker.isNullOrEmpty(name) ? DEFAULT
: policies.computeIfAbsent(name.toLowerCase(Locale.ROOT), k -> create(name));
}
/**
* Gets a SQL query for finding all local nodes regardless which cluster it
* belongs to. Defaults to {@link #QUERY_GET_ALL_NODES}.
*
* @return non-null SQL query
*/
protected String getQueryForAllLocalNodes() {
return QUERY_GET_ALL_NODES;
}
/**
* Gets a parameterized SQL query for finding all local nodes of a specific
* cluster. Defaults to {@link #QUERY_GET_CLUSTER_NODES}.
*
* @return non-null SQL query
*/
protected String getQueryForClusterLocalNodes() {
return QUERY_GET_CLUSTER_NODES;
}
/**
* Gets a parameterized SQL query for finding all non-local nodes in one or many
* clusters. Defaults to {@link #QUERY_GET_OTHER_NODES}.
*
* @return non-null SQL query
*/
protected String getQueryForNonLocalNodes() {
return QUERY_GET_OTHER_NODES;
}
/**
* Gets next node available in the list.
*
* @param manager managed nodes
* @return next node
*/
protected final ClickHouseNode get(ClickHouseNodes manager) {
return get(manager, manager.getNodeSelector());
}
/**
* Gets next node available in the list according to the given node selector.
*
* @param manager managed nodes
* @param t node selector
* @return next node
* @throws IllegalArgumentException when no node available to use
*/
protected ClickHouseNode get(ClickHouseNodes manager, ClickHouseNodeSelector t) {
boolean noSelector = t == null || t == ClickHouseNodeSelector.EMPTY;
int idx = manager.index.get();
int i = 0;
ClickHouseNode node = null;
for (ClickHouseNode n : manager.nodes) {
if (noSelector || t.match(n)) {
node = n;
}
if (i++ >= idx && node != null) {
break;
}
}
if (node == null) {
for (ClickHouseNode n : manager.faultyNodes) {
ClickHouseNode probed = n.probe();
if (noSelector || t.match(probed)) {
node = probed;
}
if (i++ >= idx && node != null) {
break;
}
}
}
if (node == null) {
throw new IllegalArgumentException(ClickHouseUtils.format(ERROR_NO_SUITABLE_NODE, manager, t));
}
return node;
}
/**
* Sugguests a new node as replacement of the given one in order to recover from
* the failure, which is usually a connection error.
*
* @param manager non-null manager for finding suitable node
* @param server non-null server to replace
* @param failure non-null recoverable exception
* @return new server, or the exact same server from input when running out of
* options
*/
protected ClickHouseNode suggest(ClickHouseNodes manager, ClickHouseNode server, Throwable failure) {
if (manager == null || server == null || !(failure instanceof ClickHouseException)) {
return server;
}
ClickHouseException exp = (ClickHouseException) failure;
// only connection errors at this point
if (exp.getErrorCode() == ClickHouseException.ERROR_NETWORK
|| ClickHouseException.isConnectTimedOut(exp.getCause())) {
ClickHouseNodeSelector selector = manager.getNodeSelector();
for (ClickHouseNode node : manager.nodes) {
if (selector.match(node) && !node.isSameEndpoint(server)) {
return node;
}
}
}
return server;
}
/**
* Updates node status to one of {@link ClickHouseNode.Status}.
*
* @param manager non-null node manager
* @param node non-null node to update
* @param status non-null status of the node
*/
protected void update(ClickHouseNodes manager, ClickHouseNode node, Status status) {
switch (status) {
case MANAGED:
node.setManager(manager);
if (!manager.nodes.contains(node) && !manager.faultyNodes.contains(node)) {
if (node.getProtocol() == ClickHouseProtocol.ANY) {
manager.faultyNodes.add(node);
} else {
manager.nodes.add(node);
}
}
break;
case HEALTHY:
manager.faultyNodes.remove(node);
if (!manager.nodes.contains(node)) {
manager.nodes.add(node);
}
break;
case FAULTY:
manager.nodes.remove(node);
if (!manager.faultyNodes.contains(node)) {
manager.faultyNodes.add(node);
// in case scheduled check was stopped(e.g. aborted or no faulty node)
manager.scheduleHealthCheck();
}
break;
case STANDALONE:
boolean removed = manager.nodes.remove(node);
removed = manager.faultyNodes.remove(node) || removed;
if (removed) {
node.setManager(null);
}
break;
default:
break;
}
}
/**
* Gets scheduled executor service for auto discovery and health check.
*
* @return scheduled executor service, null will turn off auto discovery and
* health check
*/
protected ScheduledExecutorService getScheduler() {
return ClickHouseDataStreamFactory.getInstance().getScheduler();
}
/**
* Schedules the {@code task} to run only when {@code current} run has been
* completed/cancelled or does not exist.
*
* @param current current task, which could be null or in running status
* @param task scheduled task to run
* @param interval interval between each run
* @return future object representing the scheduled task, could be null when no
* scheduler available({@link #getScheduler()} returns null)
*/
protected ScheduledFuture schedule(ScheduledFuture current, Runnable task, long interval) {
ScheduledExecutorService scheduler = getScheduler();
if (scheduler == null || task == null || (current != null && !current.isDone() && !current.isCancelled())) {
return null;
}
return interval < 1L ? scheduler.schedule(task, 0L, TimeUnit.MILLISECONDS)
: scheduler.scheduleAtFixedRate(task, 0L, interval, TimeUnit.MILLISECONDS);
}
@Override
public String toString() {
return new StringBuilder(110).append("ClickHouseLoadBalancingPolicy [name=").append(getClass().getSimpleName())
.append(", scheduler=").append(getScheduler() != null).append("]@").append(hashCode()).toString();
}
}