/** Java client configuration. */
public class GridClientConfiguration {
/** Default client protocol. */
public static final GridClientProtocol DFLT_CLIENT_PROTOCOL = GridClientProtocol.TCP;
/** Default topology refresh frequency is 2 sec. */
public static final int DFLT_TOP_REFRESH_FREQ = 2000;
/** Default maximum time connection can be idle. */
public static final long DFLT_MAX_CONN_IDLE_TIME = 30000;
/** Default ping interval in milliseconds. */
public static final long DFLT_PING_INTERVAL = 5000;
/** Default ping timeout in milliseconds. */
public static final long DFLT_PING_TIMEOUT = 7000;
/** Default connect timeout in milliseconds. */
public static final int DFLT_CONNECT_TIMEOUT = 10000;
/** Default flag setting for TCP_NODELAY option. */
public static final boolean DFLT_TCP_NODELAY = true;
/** List of servers to connect to. */
private Collection<String> srvs = Collections.emptySet();
/** List of routers to connect to. */
private Collection<String> routers = Collections.emptySet();
/** Client protocol. */
private GridClientProtocol proto = DFLT_CLIENT_PROTOCOL;
/** Socket connect timeout. */
private int connectTimeout = DFLT_CONNECT_TIMEOUT;
/** TCP_NODELAY flag. */
private boolean tcpNoDelay = DFLT_TCP_NODELAY;
/** SSL context factory */
private GridSslContextFactory sslCtxFactory;
/** Flag indicating whether metrics cache is enabled. */
private boolean enableMetricsCache = true;
/** Flag indicating whether attributes cache is enabled. */
private boolean enableAttrsCache = true;
/** Flag indicating whether metrics should be automatically fetched. */
private boolean autoFetchMetrics = true;
/** Flag indicating whether attributes should be automatically fetched. */
private boolean autoFetchAttrs = true;
/** Topology refresh frequency. */
private long topRefreshFreq = DFLT_TOP_REFRESH_FREQ;
/** Max time of connection idleness. */
private long maxConnIdleTime = DFLT_MAX_CONN_IDLE_TIME;
/** Ping interval. */
private long pingInterval = DFLT_PING_INTERVAL;
/** Ping timeout. */
private long pingTimeout = DFLT_PING_TIMEOUT;
/** Default balancer. */
private GridClientLoadBalancer balancer = new GridClientRandomBalancer();
/** Collection of data configurations. */
private Map<String, GridClientDataConfiguration> dataCfgs = Collections.emptyMap();
/** Credentials. */
private SecurityCredentialsProvider credProvider;
/** Executor. */
private ExecutorService executor;
/** Marshaller. */
private GridClientMarshaller marshaller =
new GridClientOptimizedMarshaller(U.allPluginProviders());
/** Daemon flag. */
private boolean daemon;
/** Creates default configuration. */
public GridClientConfiguration() {
// No-op.
}
/**
* Copy constructor.
*
* @param cfg Configuration to be copied.
*/
public GridClientConfiguration(GridClientConfiguration cfg) {
// Preserve alphabetical order for maintenance;
autoFetchAttrs = cfg.isAutoFetchAttributes();
autoFetchMetrics = cfg.isAutoFetchMetrics();
balancer = cfg.getBalancer();
connectTimeout = cfg.getConnectTimeout();
credProvider = cfg.getSecurityCredentialsProvider();
enableAttrsCache = cfg.isEnableAttributesCache();
enableMetricsCache = cfg.isEnableMetricsCache();
executor = cfg.getExecutorService();
marshaller = cfg.getMarshaller();
maxConnIdleTime = cfg.getMaxConnectionIdleTime();
pingInterval = cfg.getPingInterval();
pingTimeout = cfg.getPingTimeout();
proto = cfg.getProtocol();
routers = cfg.getRouters();
srvs = cfg.getServers();
sslCtxFactory = cfg.getSslContextFactory();
tcpNoDelay = cfg.isTcpNoDelay();
topRefreshFreq = cfg.getTopologyRefreshFrequency();
daemon = cfg.isDaemon();
marshaller = cfg.getMarshaller();
setDataConfigurations(cfg.getDataConfigurations());
}
/**
* Creates properties-based configuration based on passed in properties.
*
* @param in Client configuration in properties format.
* @throws GridClientException If parsing configuration failed.
*/
public GridClientConfiguration(Properties in) throws GridClientException {
this("ignite.client", in);
}
/**
* Creates properties-based configuration.
*
* @param prefix Prefix for the client properties.
* @param in Properties map to load configuration from.
* @throws GridClientException If parsing configuration failed.
*/
public GridClientConfiguration(String prefix, Properties in) throws GridClientException {
load(prefix, in);
}
/**
* Collection of {@code 'host:port'} pairs representing remote grid servers used to establish
* initial connection to the grid. Once connection is established, Ignite will get a full view on
* grid topology and will be able to connect to any available remote node.
*
* <p>Note that only these addresses are used to perform topology updates in background and to
* detect Grid connectivity status.
*
* @return Collection of {@code 'host:port'} pairs representing remote grid servers.
* @see GridClient#connected()
*/
public Collection<String> getServers() {
return Collections.unmodifiableCollection(srvs);
}
/**
* Collection of {@code 'host:port'} pairs representing grid routers used to establish connection
* to the grid.
*
* <p>Addresses here could be owned by Routers as well as by individual Grid nodes. No additional
* connections will be made even if other Grid nodes are available.
*
* <p>This configuration mode is designated for cases when some Grid nodes are unavailable (due to
* security restrictions for example). So only few nodes acting as routers or dedicated router
* components used to access entire Grid.
*
* <p>This configuration parameter will not be used and direct connections to all grid nodes will
* be established if {@link #getServers()} return non-empty collection value.
*
* <p>Note that only these addresses are used to perform topology updates in background and to
* detect Grid connectivity status.
*
* @return Collection of {@code 'host:port'} pairs representing routers.
* @see GridClient#connected()
*/
public Collection<String> getRouters() {
return routers;
}
/**
* Sets list of servers this client should connect to.
*
* @param srvs List of servers.
*/
public void setServers(Collection<String> srvs) {
this.srvs = srvs != null ? srvs : Collections.<String>emptySet();
}
/**
* Sets list of routers this client should connect to.
*
* @param routers List of routers.
*/
public void setRouters(Collection<String> routers) {
this.routers = routers != null ? routers : Collections.<String>emptySet();
}
/**
* Gets protocol for communication between client and remote grid. Default is defined by {@link
* #DFLT_CLIENT_PROTOCOL} constant.
*
* @return Protocol for communication between client and remote grid.
*/
public GridClientProtocol getProtocol() {
return proto;
}
/**
* Sets protocol type that should be used in communication. Protocol type cannot be changed after
* client is created.
*
* @param proto Protocol type.
* @see GridClientProtocol
*/
public void setProtocol(GridClientProtocol proto) {
this.proto = proto;
}
/**
* Gets timeout for socket connect operation in milliseconds. If {@code 0} - then wait infinitely.
* Default is defined by {@link #DFLT_CONNECT_TIMEOUT} constant.
*
* @return Connect timeout in milliseconds.
*/
public int getConnectTimeout() {
return connectTimeout;
}
/**
* Gets flag indicating whether {@code TCP_NODELAY} flag should be enabled for outgoing
* connections. This flag reduces communication latency and in the majority of cases should be set
* to true. For more information, see {@link Socket#setTcpNoDelay(boolean)}
*
* <p>If not set, default value is {@link #DFLT_TCP_NODELAY}
*
* @return If {@code TCP_NODELAY} should be set on underlying sockets.
*/
public boolean isTcpNoDelay() {
return tcpNoDelay;
}
/**
* Sets whether {@code TCP_NODELAY} flag should be set on underlying socket connections.
*
* @param tcpNoDelay {@code True} if flag should be set.
*/
public void setTcpNoDelay(boolean tcpNoDelay) {
this.tcpNoDelay = tcpNoDelay;
}
/**
* Sets timeout for socket connect operation.
*
* @param connectTimeout Connect timeout in milliseconds.
*/
public void setConnectTimeout(int connectTimeout) {
this.connectTimeout = connectTimeout;
}
/**
* Gets a factory that should be used for SSL context creation. If it returns {@code null} then
* SSL is considered disabled.
*
* @return Factory instance.
* @see GridSslContextFactory
*/
public GridSslContextFactory getSslContextFactory() {
return sslCtxFactory;
}
/**
* Sets SSL context factory that will be used for creation of secure connections.
*
* @param sslCtxFactory Context factory.
*/
public void setSslContextFactory(GridSslContextFactory sslCtxFactory) {
this.sslCtxFactory = sslCtxFactory;
}
/**
* Default balancer to be used for computational client. It can be overridden for different
* compute instances. By default {@link GridClientRandomBalancer} is used.
*
* @return Default balancer to be used for computational client.
*/
public GridClientLoadBalancer getBalancer() {
return balancer;
}
/**
* Sets default compute balancer.
*
* @param balancer Balancer to use.
*/
public void setBalancer(GridClientLoadBalancer balancer) {
this.balancer = balancer;
}
/**
* Gets client credentials provider to authenticate with.
*
* @return Credentials provider.
*/
public SecurityCredentialsProvider getSecurityCredentialsProvider() {
return credProvider;
}
/**
* Sets client credentials provider used in authentication process.
*
* @param credProvider Client credentials provider.
*/
public void setSecurityCredentialsProvider(SecurityCredentialsProvider credProvider) {
this.credProvider = credProvider;
}
/**
* Gets a collection of data configurations specified by user.
*
* @return Collection of data configurations (possibly empty).
*/
public Collection<GridClientDataConfiguration> getDataConfigurations() {
return dataCfgs.values();
}
/**
* Sets data configurations.
*
* @param dataCfgs Data configurations.
*/
public void setDataConfigurations(Collection<? extends GridClientDataConfiguration> dataCfgs) {
this.dataCfgs = U.newHashMap(dataCfgs.size());
for (GridClientDataConfiguration dataCfg : dataCfgs)
this.dataCfgs.put(dataCfg.getName(), new GridClientDataConfiguration(dataCfg));
}
/**
* Gets data configuration for a cache with specified name.
*
* @param name Name of grid cache.
* @return Configuration or {@code null} if there is not configuration for specified name.
*/
public GridClientDataConfiguration getDataConfiguration(@Nullable String name) {
return dataCfgs.get(name);
}
/**
* Sets flag indicating whether node and cache metrics should be cached by client.
*
* @param enableMetricsCache {@code True} if cache should be enabled.
*/
public void setEnableMetricsCache(boolean enableMetricsCache) {
this.enableMetricsCache = enableMetricsCache;
}
/**
* Enables client to cache per-node and per-cache metrics internally. In memory sensitive
* environments, such as mobile platforms, caching metrics may be expensive and, hence, this
* parameter should be set to {@code false}.
*
* <p>Note that topology is refreshed automatically every {@link #getTopologyRefreshFrequency()}
* interval, and if {@link #isAutoFetchMetrics()} enabled then metrics will be updated with that
* frequency.
*
* <p>By default this value is {@code true} which means that metrics will be cached on the client
* side.
*
* @return {@code True} if metrics cache is enabled, {@code false} otherwise.
*/
public boolean isEnableMetricsCache() {
return enableMetricsCache;
}
/**
* Sets flag indicating whether node attributes should be cached by client.
*
* @param enableAttrsCache {@code True} if cache should be enabled.
*/
public void setEnableAttributesCache(boolean enableAttrsCache) {
this.enableAttrsCache = enableAttrsCache;
}
/**
* Enables client to cache per-node attributes internally. In memory sensitive environments, such
* as mobile platforms, caching node attributes may be expensive and, hence, this parameter should
* be set to {@code false}.
*
* <p>Note that node attributes are static and, if cached, there is no need to refresh them again.
* If {@link #isAutoFetchAttributes()} is enabled then attributes will be cached during client
* initialization.
*
* <p>By default this value is {@code true} which means that node attributes will be cached on the
* client side.
*
* @return {@code True} if attributes cache is enabled, {@code false} otherwise.
*/
public boolean isEnableAttributesCache() {
return enableAttrsCache;
}
/**
* Sets flag indicating whether node metrics should be fetched by client automatically.
*
* @param autoFetchMetrics {@code True} if metrics should be fetched.
*/
public void setAutoFetchMetrics(boolean autoFetchMetrics) {
this.autoFetchMetrics = autoFetchMetrics;
}
/**
* Allows client to fetch node metrics automatically with background topology refresh.
*
* <p>Note that this parameter will only affect auto-fetching of node metrics. Cache metrics still
* need to be fetched explicitly via {@link GridClientData#metrics()} or {@link
* GridClientData#metricsAsync()} methods.
*
* <p>By default this value is {@code true} which means that metrics will be fetched
* automatically.
*
* @return {@code true} if client should fetch metrics on topology refresh, {@code false}
* otherwise.
*/
public boolean isAutoFetchMetrics() {
return autoFetchMetrics;
}
/**
* Sets flag indicating whether node attributes should be fetched by client automatically.
*
* @param autoFetchAttrs {@code True} if attributes should be fetched.
*/
public void setAutoFetchAttributes(boolean autoFetchAttrs) {
this.autoFetchAttrs = autoFetchAttrs;
}
/**
* Allows client to fetch node attributes automatically with background topology refresh.
*
* <p>By default this value is {@code true} which means that attributes will be fetched
* automatically.
*
* @return {@code True} if client should fetch attributes once on topology refresh, {@code false}
* otherwise.
*/
public boolean isAutoFetchAttributes() {
return autoFetchAttrs;
}
/**
* Gets topology refresh frequency. Default is defined by {@link #DFLT_TOP_REFRESH_FREQ} constant.
*
* @return Topology refresh frequency.
*/
public long getTopologyRefreshFrequency() {
return topRefreshFreq;
}
/**
* Sets topology refresh frequency. If topology cache is enabled, grid topology will be refreshed
* every {@code topRefreshFreq} milliseconds.
*
* @param topRefreshFreq Topology refresh frequency in milliseconds.
*/
public void setTopologyRefreshFrequency(long topRefreshFreq) {
this.topRefreshFreq = topRefreshFreq;
}
/**
* Gets maximum amount of time that client connection can be idle before it is closed. Default is
* defined by {@link #DFLT_MAX_CONN_IDLE_TIME} constant.
*
* @return Maximum idle time in milliseconds.
*/
public long getMaxConnectionIdleTime() {
return maxConnIdleTime;
}
/**
* Sets maximum time in milliseconds which connection can be idle before it is closed by client.
*
* @param maxConnIdleTime Maximum time of connection idleness in milliseconds.
*/
public void setMaxConnectionIdleTime(long maxConnIdleTime) {
this.maxConnIdleTime = maxConnIdleTime;
}
/**
* Gets time interval in milliseconds between ping requests. Default is defined by {@link
* #DFLT_PING_INTERVAL} constant.
*
* <p>Ping requests used by {@link GridClientProtocol#TCP} protocol to detect network failures and
* half-opened sockets.
*
* @return Ping interval.
*/
public long getPingInterval() {
return pingInterval;
}
/**
* Sets ping interval in milliseconds.
*
* @param pingInterval Ping interval in milliseconds.
*/
public void setPingInterval(long pingInterval) {
this.pingInterval = pingInterval;
}
/**
* Gets ping timeout. Default is defined by {@link #DFLT_PING_TIMEOUT} constant.
*
* <p>Ping requests used by {@link GridClientProtocol#TCP} protocol to detect network failures and
* half-opened sockets. If no response received in period equal to this timeout than connection
* considered broken and closed.
*
* @return Ping timeout.
*/
public long getPingTimeout() {
return pingTimeout;
}
/**
* Sets ping timeout in milliseconds.
*
* @param pingTimeout Ping interval in milliseconds.
*/
public void setPingTimeout(long pingTimeout) {
this.pingTimeout = pingTimeout;
}
/**
* Gets {@link ExecutorService} where client could run asynchronous operations.
*
* <p>When using {@link GridClientProtocol#TCP} this executor should be able to serve at least
* {@code Runtime.getRuntime().availableProcessors()} parallel tasks.
*
* <p>Note that this executor will be automatically shut down when client get closed.
*
* @return {@link ExecutorService} instance to use.
*/
public ExecutorService getExecutorService() {
return executor;
}
/**
* Sets executor service.
*
* @param executor Executor service to use in client.
*/
public void setExecutorService(ExecutorService executor) {
this.executor = executor;
}
/**
* Gets the marshaller, that is used to communicate between client and server.
*
* <p>Options, that can be used out-of-the-box:
*
* <ul>
* <li>{@link GridClientOptimizedMarshaller} (default) - Ignite's optimized marshaller.
* <li>{@code GridClientPortableMarshaller} - Marshaller that supports portable objects.
* <li>{@link org.apache.ignite.internal.client.marshaller.jdk.GridClientJdkMarshaller} - JDK
* marshaller (not recommended).
* </ul>
*
* @return A marshaller to use.
*/
public GridClientMarshaller getMarshaller() {
return marshaller;
}
/**
* Sets the marshaller to use for communication.
*
* @param marshaller A marshaller to use.
*/
public void setMarshaller(GridClientMarshaller marshaller) {
this.marshaller = marshaller;
}
/**
* Load client configuration from the properties map.
*
* @param prefix Prefix for the client properties.
* @param in Properties map to load configuration from.
* @throws GridClientException If parsing configuration failed.
*/
public void load(String prefix, Properties in) throws GridClientException {
while (prefix.endsWith(".")) prefix = prefix.substring(0, prefix.length() - 1);
if (!prefix.isEmpty()) prefix += ".";
String balancer = in.getProperty(prefix + "balancer");
String connectTimeout = in.getProperty(prefix + "connectTimeout");
String cred = in.getProperty(prefix + "credentials");
String autoFetchMetrics = in.getProperty(prefix + "autoFetchMetrics");
String autoFetchAttrs = in.getProperty(prefix + "autoFetchAttributes");
String maxConnIdleTime = in.getProperty(prefix + "idleTimeout");
String proto = in.getProperty(prefix + "protocol");
String srvrs = in.getProperty(prefix + "servers");
String tcpNoDelay = in.getProperty(prefix + "tcp.noDelay");
String topRefreshFreq = in.getProperty(prefix + "topology.refresh");
String sslEnabled = in.getProperty(prefix + "ssl.enabled");
String sslProto = in.getProperty(prefix + "ssl.protocol", "TLS");
String sslKeyAlg = in.getProperty(prefix + "ssl.key.algorithm", "SunX509");
String keyStorePath = in.getProperty(prefix + "ssl.keystore.location");
String keyStorePwd = in.getProperty(prefix + "ssl.keystore.password");
String keyStoreType = in.getProperty(prefix + "ssl.keystore.type");
String trustStorePath = in.getProperty(prefix + "ssl.truststore.location");
String trustStorePwd = in.getProperty(prefix + "ssl.truststore.password");
String trustStoreType = in.getProperty(prefix + "ssl.truststore.type");
String dataCfgs = in.getProperty(prefix + "data.configurations");
setBalancer(resolveBalancer(balancer));
if (!F.isEmpty(connectTimeout)) setConnectTimeout(Integer.parseInt(connectTimeout));
if (!F.isEmpty(cred)) {
int idx = cred.indexOf(':');
if (idx >= 0 && idx < cred.length() - 1) {
setSecurityCredentialsProvider(
new SecurityCredentialsBasicProvider(
new SecurityCredentials(cred.substring(0, idx), cred.substring(idx + 1))));
} else {
setSecurityCredentialsProvider(
new SecurityCredentialsBasicProvider(new SecurityCredentials(null, null, cred)));
}
}
if (!F.isEmpty(autoFetchMetrics)) setAutoFetchMetrics(Boolean.parseBoolean(autoFetchMetrics));
if (!F.isEmpty(autoFetchAttrs)) setAutoFetchAttributes(Boolean.parseBoolean(autoFetchAttrs));
if (!F.isEmpty(maxConnIdleTime)) setMaxConnectionIdleTime(Integer.parseInt(maxConnIdleTime));
if (!F.isEmpty(proto)) setProtocol(GridClientProtocol.valueOf(proto));
if (!F.isEmpty(srvrs)) setServers(Arrays.asList(srvrs.replaceAll("\\s+", "").split(",")));
if (!F.isEmpty(tcpNoDelay)) setTcpNoDelay(Boolean.parseBoolean(tcpNoDelay));
if (!F.isEmpty(topRefreshFreq)) setTopologyRefreshFrequency(Long.parseLong(topRefreshFreq));
//
// SSL configuration section
//
if (!F.isEmpty(sslEnabled) && Boolean.parseBoolean(sslEnabled)) {
GridSslBasicContextFactory factory = new GridSslBasicContextFactory();
factory.setProtocol(F.isEmpty(sslProto) ? "TLS" : sslProto);
factory.setKeyAlgorithm(F.isEmpty(sslKeyAlg) ? "SunX509" : sslKeyAlg);
if (F.isEmpty(keyStorePath))
throw new IllegalArgumentException("SSL key store location is not specified.");
factory.setKeyStoreFilePath(keyStorePath);
if (keyStorePwd != null) factory.setKeyStorePassword(keyStorePwd.toCharArray());
factory.setKeyStoreType(F.isEmpty(keyStoreType) ? "jks" : keyStoreType);
if (F.isEmpty(trustStorePath))
factory.setTrustManagers(GridSslBasicContextFactory.getDisabledTrustManager());
else {
factory.setTrustStoreFilePath(trustStorePath);
if (trustStorePwd != null) factory.setTrustStorePassword(trustStorePwd.toCharArray());
factory.setTrustStoreType(F.isEmpty(trustStoreType) ? "jks" : trustStoreType);
}
setSslContextFactory(factory);
}
//
// Data configuration section
//
if (!F.isEmpty(dataCfgs)) {
String[] names = dataCfgs.replaceAll("\\s+", "").split(",");
Collection<GridClientDataConfiguration> list = new ArrayList<>();
for (String cfgName : names) {
if (F.isEmpty(cfgName)) continue;
String name = in.getProperty(prefix + "data." + cfgName + ".name");
String bal = in.getProperty(prefix + "data." + cfgName + ".balancer");
String aff = in.getProperty(prefix + "data." + cfgName + ".affinity");
GridClientDataConfiguration dataCfg = new GridClientDataConfiguration();
dataCfg.setName(F.isEmpty(name) ? null : name);
dataCfg.setBalancer(resolveBalancer(bal));
dataCfg.setAffinity(resolveAffinity(aff));
list.add(dataCfg);
}
setDataConfigurations(list);
}
}
/**
* Resolve load balancer from string definition.
*
* @param balancer Load balancer string definition.
* @return Resolved load balancer.
* @throws GridClientException If loading failed.
*/
private static GridClientLoadBalancer resolveBalancer(String balancer)
throws GridClientException {
if (F.isEmpty(balancer) || "random".equals(balancer)) return new GridClientRandomBalancer();
if ("roundrobin".equals(balancer)) return new GridClientRoundRobinBalancer();
return newInstance(GridClientLoadBalancer.class, balancer);
}
/**
* Resolve data affinity from string definition.
*
* @param affinity Data affinity string definition.
* @return Resolved data affinity.
* @throws GridClientException If loading failed.
*/
private static GridClientDataAffinity resolveAffinity(String affinity)
throws GridClientException {
if (F.isEmpty(affinity)) return null;
if ("partitioned".equals(affinity)) return new GridClientPartitionAffinity();
return newInstance(GridClientDataAffinity.class, affinity);
}
/**
* Constructs new instance of the specified class.
*
* @param exp Expected class for the new instance.
* @param clsName Class name to create new instance for.
* @param <T> Expected class type for the new instance.
* @return New instance of specified class.
* @throws GridClientException If loading failed.
*/
private static <T> T newInstance(Class<T> exp, String clsName) throws GridClientException {
Object obj;
try {
obj = Class.forName(clsName).newInstance();
}
// Catch all for convenience.
catch (Exception e) {
throw new GridClientException("Failed to create class instance: " + clsName, e);
}
return exp.cast(obj);
}
/**
* Set the daemon flag value. Communication threads will be created as daemons if this flag is
* set.
*
* @param daemon Daemon flag.
*/
public void setDaemon(boolean daemon) {
this.daemon = daemon;
}
/**
* Get the daemon flag.
*
* @return Daemon flag.
*/
public boolean isDaemon() {
return daemon;
}
}
/**
* Sets list of servers this client should connect to.
*
* @param srvs List of servers.
*/
public void setServers(Collection<String> srvs) {
this.srvs = srvs != null ? srvs : Collections.<String>emptySet();
}
/**
* Sets list of routers this client should connect to.
*
* @param routers List of routers.
*/
public void setRouters(Collection<String> routers) {
this.routers = routers != null ? routers : Collections.<String>emptySet();
}
/**
* Collection of {@code 'host:port'} pairs representing remote grid servers used to establish
* initial connection to the grid. Once connection is established, Ignite will get a full view on
* grid topology and will be able to connect to any available remote node.
*
* <p>Note that only these addresses are used to perform topology updates in background and to
* detect Grid connectivity status.
*
* @return Collection of {@code 'host:port'} pairs representing remote grid servers.
* @see GridClient#connected()
*/
public Collection<String> getServers() {
return Collections.unmodifiableCollection(srvs);
}