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A driver for DataStax Enterprise (DSE)
and Apache Cassandra 1.2+ clusters that works exclusively with the
Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol,
supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.
/*
* Copyright (C) 2012-2017 DataStax Inc.
*
* This software can be used solely with DataStax Enterprise. Please consult the license at
* http://www.datastax.com/terms/datastax-dse-driver-license-terms
*/
package com.datastax.driver.core;
import com.datastax.driver.core.policies.AddressTranslator;
import com.google.common.util.concurrent.ListenableFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Collections;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;
/**
* A Cassandra node.
*
* This class keeps the information the driver maintain on a given Cassandra node.
*/
public class Host {
private static final Logger logger = LoggerFactory.getLogger(Host.class);
static final Logger statesLogger = LoggerFactory.getLogger(Host.class.getName() + ".STATES");
// The address we'll use to connect to the node
private final InetSocketAddress address;
// The broadcast_address as known by Cassandra.
// We use that internally because
// that's the 'peer' in the 'System.peers' table and avoids querying the full peers table in
// ControlConnection.refreshNodeInfo.
private volatile InetAddress broadcastAddress;
// The listen_address as known by Cassandra.
// This is usually the same as broadcast_address unless
// specified otherwise in cassandra.yaml file.
private volatile InetAddress listenAddress;
private volatile UUID hostId;
private volatile UUID schemaVersion;
enum State {ADDED, DOWN, UP}
volatile State state;
/**
* Ensures state change notifications for that host are handled serially
*/
final ReentrantLock notificationsLock = new ReentrantLock(true);
final ConvictionPolicy convictionPolicy;
private final Cluster.Manager manager;
// Tracks later reconnection attempts to that host so we avoid adding multiple tasks.
final AtomicReference> reconnectionAttempt = new AtomicReference>();
final ExecutionInfo defaultExecutionInfo;
private volatile String datacenter;
private volatile String rack;
private volatile VersionNumber cassandraVersion;
private volatile Set tokens;
private volatile Set dseWorkloads = Collections.emptySet();
private volatile Boolean dseGraphEnabled;
private volatile VersionNumber dseVersion;
// ClusterMetadata keeps one Host object per inet address and we rely on this (more precisely,
// we rely on the fact that we can use Object equality as a valid equality), so don't use
// that constructor but ClusterMetadata.getHost instead.
Host(InetSocketAddress address, ConvictionPolicy.Factory convictionPolicyFactory, Cluster.Manager manager) {
if (address == null || convictionPolicyFactory == null)
throw new NullPointerException();
this.address = address;
this.convictionPolicy = convictionPolicyFactory.create(this, manager.reconnectionPolicy());
this.manager = manager;
this.defaultExecutionInfo = new ExecutionInfo(this);
this.state = State.ADDED;
}
void setLocationInfo(String datacenter, String rack) {
this.datacenter = datacenter;
this.rack = rack;
}
void setVersion(String cassandraVersion) {
VersionNumber versionNumber = null;
try {
if (cassandraVersion != null) {
versionNumber = VersionNumber.parse(cassandraVersion);
}
} catch (IllegalArgumentException e) {
logger.warn("Error parsing Cassandra version {}. This shouldn't have happened", cassandraVersion);
}
this.cassandraVersion = versionNumber;
}
void setBroadcastAddress(InetAddress broadcastAddress) {
this.broadcastAddress = broadcastAddress;
}
void setListenAddress(InetAddress listenAddress) {
this.listenAddress = listenAddress;
}
void setDseVersion(String dseVersion) {
VersionNumber versionNumber = null;
try {
if (dseVersion != null) {
versionNumber = VersionNumber.parse(dseVersion);
}
} catch (IllegalArgumentException e) {
logger.warn("Error parsing DSE version {}. This shouldn't have happened", dseVersion);
}
this.dseVersion = versionNumber;
}
void setDseWorkloads(Set dseWorkloads) {
this.dseWorkloads = Collections.unmodifiableSet(dseWorkloads);
}
void setDseGraphEnabled(boolean dseGraphEnabled) {
this.dseGraphEnabled = dseGraphEnabled;
}
void setHostId(UUID hostId) {
this.hostId = hostId;
}
void setSchemaVersion(UUID schemaVersion) {
this.schemaVersion = schemaVersion;
}
boolean supports(ProtocolVersion version) {
return getCassandraVersion() == null
|| version.minCassandraVersion().compareTo(getCassandraVersion().nextStable()) <= 0;
}
/**
* Returns the address that the driver will use to connect to the node.
*
* This is a shortcut for {@code getSocketAddress().getAddress()}.
*
* @return the address.
* @see #getSocketAddress()
*/
public InetAddress getAddress() {
return address.getAddress();
}
/**
* Returns the address and port that the driver will use to connect to the node.
*
* This is the node's broadcast RPC address, possibly translated if an {@link AddressTranslator} has been configured
* for this cluster.
*
* The broadcast RPC address is inferred from the following cassandra.yaml file settings:
*
* - {@code rpc_address}, {@code rpc_interface} or {@code broadcast_rpc_address}
* - {@code native_transport_port}
*
*
* @return the address and port.
* @see The cassandra.yaml configuration file
*/
public InetSocketAddress getSocketAddress() {
return address;
}
/**
* Returns the node broadcast address (that is, the IP by which it should be contacted by other peers in the
* cluster), if known.
*
* This corresponds to the {@code broadcast_address} cassandra.yaml file setting and
* is by default the same as {@link #getListenAddress()}, unless specified
* otherwise in cassandra.yaml.
* This is NOT the address clients should use to contact this node.
*
* This information is always available for peer hosts. For the control host, it's only available if CASSANDRA-9436
* is fixed on the server side (Cassandra versions >= 2.0.16, 2.1.6, 2.2.0 rc1). For older versions, note that if
* the driver loses the control connection and reconnects to a different control host, the old control host becomes
* a peer, and therefore its broadcast address is updated.
*
* @return the node broadcast address, if known. Otherwise {@code null}.
* @see The cassandra.yaml configuration file
*/
public InetAddress getBroadcastAddress() {
return broadcastAddress;
}
/**
* Returns the node listen address (that is, the IP the node uses to contact other peers in the cluster), if known.
*
* This corresponds to the {@code listen_address} cassandra.yaml file setting.
* This is NOT the address clients should use to contact this node.
*
* This information is available for the control host if CASSANDRA-9603 is fixed on the server side (Cassandra
* versions >= 2.0.17, 2.1.8, 2.2.0 rc2). It's currently not available for peer hosts. Note that the current driver
* code already tries to read a {@code listen_address} column in {@code system.peers}; when a future Cassandra
* version adds it, it will be picked by the driver without any further change needed.
*
* @return the node listen address, if known. Otherwise {@code null}.
* @see The cassandra.yaml configuration file
*/
public InetAddress getListenAddress() {
return listenAddress;
}
/**
* Returns the name of the datacenter this host is part of.
*
* The returned datacenter name is the one as known by Cassandra.
* It is also possible for this information to be unavailable. In that
* case this method returns {@code null}, and the caller should always be aware
* of this possibility.
*
* @return the Cassandra datacenter name or null if datacenter is unavailable.
*/
public String getDatacenter() {
return datacenter;
}
/**
* Returns the name of the rack this host is part of.
*
* The returned rack name is the one as known by Cassandra.
* It is also possible for this information to be unavailable. In that case
* this method returns {@code null}, and the caller should always be aware of this
* possibility.
*
* @return the Cassandra rack name or null if the rack is unavailable
*/
public String getRack() {
return rack;
}
/**
* The Cassandra version the host is running.
*
* It is also possible for this information to be unavailable. In that case
* this method returns {@code null}, and the caller should always be aware of this
* possibility.
*
* @return the Cassandra version the host is running.
*/
public VersionNumber getCassandraVersion() {
return cassandraVersion;
}
/**
* The DSE version the host is running.
*
* It is also possible for this information to be unavailable. In that case
* this method returns {@code null}, and the caller should always be aware of this
* possibility.
*
* @return the DSE version the host is running.
*/
public VersionNumber getDseVersion() {
return dseVersion;
}
/**
* The main DSE Workload the host is running.
*
* It is also possible for this information to be unavailable. In that case
* this method returns {@code null}, and the caller should always be aware of this
* possibility.
*
* @return the DSE workload the host is running.
* @deprecated This method returns only the first workload reported by the host;
* use {@link #getDseWorkloads()} instead.
*/
@Deprecated
public String getDseWorkload() {
return dseWorkloads.isEmpty() ? null : dseWorkloads.iterator().next();
}
/**
* The DSE Workloads the host is running.
*
* This is based on the "workload" or "workloads" columns in {@code system.local} and {@code system.peers}.
*
* Workload labels may vary depending on the DSE version in use;
* e.g. DSE 5.1 may report two distinct workloads: {@code Search} and
* {@code Analytics}, while DSE 5.0 would report a single
* {@code SearchAnalytics} workload instead.
* It is up to users to deal with such discrepancies;
* the driver simply returns the workload labels as reported by DSE, without
* any form of pre-processing.
*
* The returned set is immutable.
* It is also possible for this information to be unavailable. In that case
* this method returns an empty set, and the caller should always be aware of this
* possibility.
*
* @return the DSE workloads the host is running.
*/
public Set getDseWorkloads() {
return dseWorkloads;
}
/**
* Returns whether the host is running DSE Graph.
*
* This is based on the "graph" column in {@code system.local} and {@code system.peers}.
*
* @return whether the node is running DSE Graph.
* @deprecated As of DSE 5.1, users should determine whether
* this host has the graph workload enabled by inspecting the contents of
* {@link #getDseWorkloads()} instead. Note that this method will throw {@link UnsupportedOperationException} if the
* system tables do not contain a "graph" column.
*/
@Deprecated
public boolean isDseGraphEnabled() {
if (dseGraphEnabled == null) {
throw new UnsupportedOperationException("No 'graph' column in system tables. Try getDseWorkloads() instead.");
} else {
return dseGraphEnabled;
}
}
/**
* Return the host id value for the host.
*
* The host id is the main identifier used by Cassandra on the server for internal
* communication (gossip). It is referenced as the column {@code host_id} in the
* {@code system.local} or {@code system.peers} table.
*
* @return the node's host id value.
*/
public UUID getHostId() {
return hostId;
}
/**
* Return the current schema version for the host.
*
* Schema versions in Cassandra are used to ensure all the nodes agree on the current
* Cassandra schema when it is modified. For more information see {@link ExecutionInfo#isSchemaInAgreement()}
*
* @return the node's current schema version value.
*/
public UUID getSchemaVersion() {
return schemaVersion;
}
/**
* Returns the tokens that this host owns.
*
* @return the (immutable) set of tokens.
*/
public Set getTokens() {
return tokens;
}
void setTokens(Set tokens) {
this.tokens = tokens;
}
/**
* Returns whether the host is considered up by the driver.
*
* Please note that this is only the view of the driver and may not reflect
* reality. In particular a node can be down but the driver hasn't detected
* it yet, or it can have been restarted and the driver hasn't detected it
* yet (in particular, for hosts to which the driver does not connect (because
* the {@code LoadBalancingPolicy.distance} method says so), this information
* may be durably inaccurate). This information should thus only be
* considered as best effort and should not be relied upon too strongly.
*
* @return whether the node is considered up.
*/
public boolean isUp() {
return state == State.UP;
}
/**
* Returns a description of the host's state, as seen by the driver.
*
* This is exposed for debugging purposes only; the format of this string might
* change between driver versions, so clients should not make any assumptions
* about it.
*
* @return a description of the host's state.
*/
public String getState() {
return state.name();
}
/**
* Returns a {@code ListenableFuture} representing the completion of the reconnection
* attempts scheduled after a host is marked {@code DOWN}.
*
* If the caller cancels this future, the driver will not try to reconnect to
* this host until it receives an UP event for it. Note that this could mean never, if
* the node was marked down because of a driver-side error (e.g. read timeout) but no
* failure was detected by Cassandra. The caller might decide to trigger an explicit
* reconnection attempt at a later point with {@link #tryReconnectOnce()}.
*
* @return the future, or {@code null} if no reconnection attempt was in progress.
*/
public ListenableFuture getReconnectionAttemptFuture() {
return reconnectionAttempt.get();
}
/**
* Triggers an asynchronous reconnection attempt to this host.
*
* This method is intended for load balancing policies that mark hosts as {@link HostDistance#IGNORED IGNORED},
* but still need a way to periodically check these hosts' states (UP / DOWN).
*
* For a host that is at distance {@code IGNORED}, this method will try to reconnect exactly once: if
* reconnection succeeds, the host is marked {@code UP}; otherwise, no further attempts will be scheduled.
* It has no effect if the node is already {@code UP}, or if a reconnection attempt is already in progress.
*
* Note that if the host is not a distance {@code IGNORED}, this method will trigger a periodic
* reconnection attempt if the reconnection fails.
*/
public void tryReconnectOnce() {
this.manager.startSingleReconnectionAttempt(this);
}
@Override
public boolean equals(Object other) {
if (other instanceof Host) {
Host that = (Host) other;
return this.address.equals(that.address);
}
return false;
}
@Override
public int hashCode() {
return address.hashCode();
}
boolean wasJustAdded() {
return state == State.ADDED;
}
@Override
public String toString() {
return address.toString();
}
void setDown() {
state = State.DOWN;
}
void setUp() {
state = State.UP;
}
/**
* Interface for listeners that are interested in hosts added, up, down and
* removed events.
*
* It is possible for the same event to be fired multiple times,
* particularly for up or down events. Therefore, a listener should ignore
* the same event if it has already been notified of a node's state.
*/
public interface StateListener {
/**
* Called when a new node is added to the cluster.
*
* The newly added node should be considered up.
*
* @param host the host that has been newly added.
*/
void onAdd(Host host);
/**
* Called when a node is determined to be up.
*
* @param host the host that has been detected up.
*/
void onUp(Host host);
/**
* Called when a node is determined to be down.
*
* @param host the host that has been detected down.
*/
void onDown(Host host);
/**
* Called when a node is removed from the cluster.
*
* @param host the removed host.
*/
void onRemove(Host host);
/**
* Gets invoked when the tracker is registered with a cluster, or at cluster startup if the
* tracker was registered at initialization with
* {@link com.datastax.driver.core.Cluster.Initializer#register(LatencyTracker)}.
*
* @param cluster the cluster that this tracker is registered with.
*/
void onRegister(Cluster cluster);
/**
* Gets invoked when the tracker is unregistered from a cluster, or at cluster shutdown if
* the tracker was not unregistered.
*
* @param cluster the cluster that this tracker was registered with.
*/
void onUnregister(Cluster cluster);
}
/**
* A {@code StateListener} that tracks when it gets registered or unregistered with a cluster.
*
* This interface exists only for backward-compatibility reasons: starting with the 3.0 branch of the driver, its
* methods are on the parent interface directly.
*/
public interface LifecycleAwareStateListener extends StateListener {
/**
* Gets invoked when the listener is registered with a cluster, or at cluster startup if the
* listener was registered at initialization with
* {@link com.datastax.driver.core.Cluster#register(Host.StateListener)}.
*
* @param cluster the cluster that this listener is registered with.
*/
@Override
void onRegister(Cluster cluster);
/**
* Gets invoked when the listener is unregistered from a cluster, or at cluster shutdown if
* the listener was not unregistered.
*
* @param cluster the cluster that this listener was registered with.
*/
@Override
void onUnregister(Cluster cluster);
}
}