Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF 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.apache.nifi.distributed.cache.client; import java.io.ByteArrayOutputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.concurrent.BlockingQueue; import java.util.concurrent.LinkedBlockingQueue; import java.util.concurrent.TimeUnit; import org.apache.commons.io.IOUtils; import org.apache.nifi.annotation.documentation.CapabilityDescription; import org.apache.nifi.annotation.documentation.SeeAlso; import org.apache.nifi.annotation.documentation.Tags; import org.apache.nifi.annotation.lifecycle.OnEnabled; import org.apache.nifi.components.PropertyDescriptor; import org.apache.nifi.controller.AbstractControllerService; import org.apache.nifi.controller.ConfigurationContext; import org.apache.nifi.distributed.cache.protocol.ProtocolHandshake; import org.apache.nifi.distributed.cache.protocol.exception.HandshakeException; import org.apache.nifi.processor.util.StandardValidators; import org.apache.nifi.remote.StandardVersionNegotiator; import org.apache.nifi.remote.VersionNegotiator; import org.apache.nifi.ssl.SSLContextService; import org.apache.nifi.ssl.SSLContextService.ClientAuth; import org.slf4j.Logger; import org.slf4j.LoggerFactory; @Tags({ "distributed", "cache", "state", "map", "cluster" }) @SeeAlso(classNames = { "org.apache.nifi.distributed.cache.server.map.DistributedMapCacheServer", "org.apache.nifi.ssl.StandardSSLContextService" }) @CapabilityDescription("Provides the ability to communicate with a DistributedMapCacheServer. This can be used in order to share a Map " + "between nodes in a NiFi cluster") public class DistributedMapCacheClientService extends AbstractControllerService implements AtomicDistributedMapCacheClient { private static final Logger logger = LoggerFactory.getLogger(DistributedMapCacheClientService.class); public static final PropertyDescriptor HOSTNAME = new PropertyDescriptor.Builder().name("Server Hostname") .description("The name of the server that is running the DistributedMapCacheServer service") .required(true).addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build(); public static final PropertyDescriptor PORT = new PropertyDescriptor.Builder().name("Server Port").description( "The port on the remote server that is to be used when communicating with the DistributedMapCacheServer service") .required(true).addValidator(StandardValidators.PORT_VALIDATOR).defaultValue("4557").build(); public static final PropertyDescriptor SSL_CONTEXT_SERVICE = new PropertyDescriptor.Builder() .name("SSL Context Service") .description("If specified, indicates the SSL Context Service that is used to communicate with the " + "remote server. If not specified, communications will not be encrypted") .required(false).identifiesControllerService(SSLContextService.class).build(); public static final PropertyDescriptor COMMUNICATIONS_TIMEOUT = new PropertyDescriptor.Builder() .name("Communications Timeout") .description( "Specifies how long to wait when communicating with the remote server before determining that " + "there is a communications failure if data cannot be sent or received") .required(true).addValidator(StandardValidators.TIME_PERIOD_VALIDATOR).defaultValue("30 secs").build(); private final BlockingQueue<CommsSession> queue = new LinkedBlockingQueue<>(); private volatile ConfigurationContext configContext; private volatile boolean closed = false; @Override protected List<PropertyDescriptor> getSupportedPropertyDescriptors() { final List<PropertyDescriptor> descriptors = new ArrayList<>(); descriptors.add(HOSTNAME); descriptors.add(PORT); descriptors.add(SSL_CONTEXT_SERVICE); descriptors.add(COMMUNICATIONS_TIMEOUT); return descriptors; } @OnEnabled public void cacheConfig(final ConfigurationContext context) { this.configContext = context; } @Override public <K, V> boolean putIfAbsent(final K key, final V value, final Serializer<K> keySerializer, final Serializer<V> valueSerializer) throws IOException { return withCommsSession(new CommsAction<Boolean>() { @Override public Boolean execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("putIfAbsent"); serialize(key, keySerializer, dos); serialize(value, valueSerializer, dos); dos.flush(); final DataInputStream dis = new DataInputStream(session.getInputStream()); return dis.readBoolean(); } }); } @Override public <K, V> void put(final K key, final V value, final Serializer<K> keySerializer, final Serializer<V> valueSerializer) throws IOException { withCommsSession(new CommsAction<Object>() { @Override public Object execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("put"); serialize(key, keySerializer, dos); serialize(value, valueSerializer, dos); dos.flush(); final DataInputStream dis = new DataInputStream(session.getInputStream()); final boolean success = dis.readBoolean(); if (!success) { throw new IOException( "Expected to receive confirmation of 'put' request but received unexpected response"); } return null; } }); } @Override public <K> boolean containsKey(final K key, final Serializer<K> keySerializer) throws IOException { return withCommsSession(new CommsAction<Boolean>() { @Override public Boolean execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("containsKey"); serialize(key, keySerializer, dos); dos.flush(); final DataInputStream dis = new DataInputStream(session.getInputStream()); return dis.readBoolean(); } }); } @Override public <K, V> V getAndPutIfAbsent(final K key, final V value, final Serializer<K> keySerializer, final Serializer<V> valueSerializer, final Deserializer<V> valueDeserializer) throws IOException { return withCommsSession(new CommsAction<V>() { @Override public V execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("getAndPutIfAbsent"); serialize(key, keySerializer, dos); serialize(value, valueSerializer, dos); dos.flush(); // read response final DataInputStream dis = new DataInputStream(session.getInputStream()); final byte[] responseBuffer = readLengthDelimitedResponse(dis); return valueDeserializer.deserialize(responseBuffer); } }); } @Override public <K, V> V get(final K key, final Serializer<K> keySerializer, final Deserializer<V> valueDeserializer) throws IOException { return withCommsSession(new CommsAction<V>() { @Override public V execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("get"); serialize(key, keySerializer, dos); dos.flush(); // read response final DataInputStream dis = new DataInputStream(session.getInputStream()); final byte[] responseBuffer = readLengthDelimitedResponse(dis); return valueDeserializer.deserialize(responseBuffer); } }); } @Override public <K> boolean remove(final K key, final Serializer<K> serializer) throws IOException { return withCommsSession(new CommsAction<Boolean>() { @Override public Boolean execute(final CommsSession session) throws IOException { final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("remove"); serialize(key, serializer, dos); dos.flush(); // read response final DataInputStream dis = new DataInputStream(session.getInputStream()); return dis.readBoolean(); } }); } @Override public <K, V> CacheEntry<K, V> fetch(final K key, final Serializer<K> keySerializer, final Deserializer<V> valueDeserializer) throws IOException { return withCommsSession(session -> { validateProtocolVersion(session, 2); final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("fetch"); serialize(key, keySerializer, dos); dos.flush(); // read response final DataInputStream dis = new DataInputStream(session.getInputStream()); final long revision = dis.readLong(); final byte[] responseBuffer = readLengthDelimitedResponse(dis); if (revision < 0) { // This indicates that key was not found. return null; } final StandardCacheEntry<K, V> standardCacheEntry = new StandardCacheEntry<>(key, valueDeserializer.deserialize(responseBuffer), revision); return standardCacheEntry; }); } private void validateProtocolVersion(final CommsSession session, final int requiredProtocolVersion) { if (session.getProtocolVersion() < requiredProtocolVersion) { throw new UnsupportedOperationException( "Remote cache server doesn't support protocol version " + requiredProtocolVersion); } } @Override public <K, V> boolean replace(final K key, final V value, final Serializer<K> keySerializer, final Serializer<V> valueSerializer, final long revision) throws IOException { return withCommsSession(session -> { validateProtocolVersion(session, 2); final DataOutputStream dos = new DataOutputStream(session.getOutputStream()); dos.writeUTF("replace"); serialize(key, keySerializer, dos); dos.writeLong(revision); serialize(value, valueSerializer, dos); dos.flush(); // read response final DataInputStream dis = new DataInputStream(session.getInputStream()); return dis.readBoolean(); }); } private byte[] readLengthDelimitedResponse(final DataInputStream dis) throws IOException { final int responseLength = dis.readInt(); final byte[] responseBuffer = new byte[responseLength]; dis.readFully(responseBuffer); return responseBuffer; } public CommsSession createCommsSession(final ConfigurationContext context) throws IOException { final String hostname = context.getProperty(HOSTNAME).getValue(); final int port = context.getProperty(PORT).asInteger(); final long timeoutMillis = context.getProperty(COMMUNICATIONS_TIMEOUT).asTimePeriod(TimeUnit.MILLISECONDS); final SSLContextService sslContextService = context.getProperty(SSL_CONTEXT_SERVICE) .asControllerService(SSLContextService.class); final CommsSession commsSession; if (sslContextService == null) { commsSession = new StandardCommsSession(hostname, port); } else { commsSession = new SSLCommsSession(sslContextService.createSSLContext(ClientAuth.REQUIRED), hostname, port); } commsSession.setTimeout(timeoutMillis, TimeUnit.MILLISECONDS); return commsSession; } private CommsSession leaseCommsSession() throws IOException { CommsSession session = queue.poll(); if (session != null && !session.isClosed()) { return session; } session = createCommsSession(configContext); final VersionNegotiator versionNegotiator = new StandardVersionNegotiator(2, 1); try { ProtocolHandshake.initiateHandshake(session.getInputStream(), session.getOutputStream(), versionNegotiator); session.setProtocolVersion(versionNegotiator.getVersion()); } catch (final HandshakeException e) { try { session.close(); } catch (final IOException ioe) { } throw new IOException(e); } return session; } @Override public void close() throws IOException { this.closed = true; CommsSession commsSession; while ((commsSession = queue.poll()) != null) { try (final DataOutputStream dos = new DataOutputStream(commsSession.getOutputStream())) { dos.writeUTF("close"); dos.flush(); commsSession.close(); } catch (final IOException e) { } } if (logger.isDebugEnabled() && getIdentifier() != null) { logger.debug("Closed {}", new Object[] { getIdentifier() }); } } @Override protected void finalize() throws Throwable { if (!closed) { close(); } logger.debug("Finalize called"); } private <T> void serialize(final T value, final Serializer<T> serializer, final DataOutputStream dos) throws IOException { final ByteArrayOutputStream baos = new ByteArrayOutputStream(); serializer.serialize(value, baos); dos.writeInt(baos.size()); baos.writeTo(dos); } private <T> T withCommsSession(final CommsAction<T> action) throws IOException { if (closed) { throw new IllegalStateException("Client is closed"); } boolean tryToRequeue = true; final CommsSession session = leaseCommsSession(); try { return action.execute(session); } catch (final IOException ioe) { tryToRequeue = false; throw ioe; } finally { if (tryToRequeue == true && this.closed == false) { queue.offer(session); } else { IOUtils.closeQuietly(session); } } } private static interface CommsAction<T> { T execute(CommsSession commsSession) throws IOException; } }