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Chapter 229. Netty4 Component
Available as of Camel version 2.14
The netty4 component in Camel is a socket communication component, based on the Netty project version 4.
Netty is a NIO client server framework which enables quick and easy development of netwServerInitializerFactoryork applications such as protocol servers and clients.
Netty greatly simplifies and streamlines network programming such as TCP and UDP socket server.
This camel component supports both producer and consumer endpoints.
The Netty component has several options and allows fine-grained control of a number of TCP/UDP communication parameters (buffer sizes, keepAlives, tcpNoDelay etc) and facilitates both In-Only and In-Out communication on a Camel route.
Maven users will need to add the following dependency to their pom.xml for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-netty4</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>229.1. URI format
The URI scheme for a netty component is as follows
netty4:tcp://localhost:99999[?options] netty4:udp://remotehost:99999/[?options]
This component supports producer and consumer endpoints for both TCP and UDP.
You can append query options to the URI in the following format, ?option=value&option=value&…
229.2. Options
The Netty4 component supports 5 options which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| maximumPoolSize (advanced) | The thread pool size for the EventExecutorGroup if its in use. The default value is 16. | 16 | int |
| configuration (advanced) | To use the NettyConfiguration as configuration when creating endpoints. | NettyConfiguration | |
| executorService (advanced) | To use the given EventExecutorGroup | EventExecutorGroup | |
| useGlobalSslContext Parameters (security) | Enable usage of global SSL context parameters. | false | boolean |
| resolveProperty Placeholders (advanced) | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | boolean |
The Netty4 endpoint is configured using URI syntax:
netty4:protocol:host:port
with the following path and query parameters:
229.2.1. Path Parameters (3 parameters):
| Name | Description | Default | Type |
|---|---|---|---|
| protocol | Required The protocol to use which can be tcp or udp. | String | |
| host | Required The hostname. For the consumer the hostname is localhost or 0.0.0.0 For the producer the hostname is the remote host to connect to | String | |
| port | Required The host port number | int |
229.2.2. Query Parameters (72 parameters):
| Name | Description | Default | Type |
|---|---|---|---|
| disconnect (common) | Whether or not to disconnect(close) from Netty Channel right after use. Can be used for both consumer and producer. | false | boolean |
| keepAlive (common) | Setting to ensure socket is not closed due to inactivity | true | boolean |
| reuseAddress (common) | Setting to facilitate socket multiplexing | true | boolean |
| reuseChannel (common) | This option allows producers and consumers (in client mode) to reuse the same Netty Channel for the lifecycle of processing the Exchange. This is useful if you need to call a server multiple times in a Camel route and want to use the same network connection. When using this the channel is not returned to the connection pool until the Exchange is done; or disconnected if the disconnect option is set to true. The reused Channel is stored on the Exchange as an exchange property with the key link NettyConstantsNETTY_CHANNEL which allows you to obtain the channel during routing and use it as well. | false | boolean |
| sync (common) | Setting to set endpoint as one-way or request-response | true | boolean |
| tcpNoDelay (common) | Setting to improve TCP protocol performance | true | boolean |
| bridgeErrorHandler (consumer) | Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. | false | boolean |
| broadcast (consumer) | Setting to choose Multicast over UDP | false | boolean |
| clientMode (consumer) | If the clientMode is true, netty consumer will connect the address as a TCP client. | false | boolean |
| reconnect (consumer) | Used only in clientMode in consumer, the consumer will attempt to reconnect on disconnection if this is enabled | true | boolean |
| reconnectInterval (consumer) | Used if reconnect and clientMode is enabled. The interval in milli seconds to attempt reconnection | 10000 | int |
| backlog (consumer) | Allows to configure a backlog for netty consumer (server). Note the backlog is just a best effort depending on the OS. Setting this option to a value such as 200, 500 or 1000, tells the TCP stack how long the accept queue can be If this option is not configured, then the backlog depends on OS setting. | int | |
| bossCount (consumer) | When netty works on nio mode, it uses default bossCount parameter from Netty, which is 1. User can use this operation to override the default bossCount from Netty | 1 | int |
| bossGroup (consumer) | Set the BossGroup which could be used for handling the new connection of the server side across the NettyEndpoint | EventLoopGroup | |
| disconnectOnNoReply (consumer) | If sync is enabled then this option dictates NettyConsumer if it should disconnect where there is no reply to send back. | true | boolean |
| exceptionHandler (consumer) | To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this options is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored. | ExceptionHandler | |
| exchangePattern (consumer) | Sets the exchange pattern when the consumer creates an exchange. | ExchangePattern | |
| nettyServerBootstrapFactory (consumer) | To use a custom NettyServerBootstrapFactory | NettyServerBootstrap Factory | |
| networkInterface (consumer) | When using UDP then this option can be used to specify a network interface by its name, such as eth0 to join a multicast group. | String | |
| noReplyLogLevel (consumer) | If sync is enabled this option dictates NettyConsumer which logging level to use when logging a there is no reply to send back. | WARN | LoggingLevel |
| serverClosedChannel ExceptionCaughtLogLevel (consumer) | If the server (NettyConsumer) catches an java.nio.channels.ClosedChannelException then its logged using this logging level. This is used to avoid logging the closed channel exceptions, as clients can disconnect abruptly and then cause a flood of closed exceptions in the Netty server. | DEBUG | LoggingLevel |
| serverExceptionCaughtLog Level (consumer) | If the server (NettyConsumer) catches an exception then its logged using this logging level. | WARN | LoggingLevel |
| serverInitializerFactory (consumer) | To use a custom ServerInitializerFactory | ServerInitializer Factory | |
| usingExecutorService (consumer) | Whether to use ordered thread pool, to ensure events are processed orderly on the same channel. | true | boolean |
| connectTimeout (producer) | Time to wait for a socket connection to be available. Value is in millis. | 10000 | int |
| requestTimeout (producer) | Allows to use a timeout for the Netty producer when calling a remote server. By default no timeout is in use. The value is in milli seconds, so eg 30000 is 30 seconds. The requestTimeout is using Netty’s ReadTimeoutHandler to trigger the timeout. | long | |
| clientInitializerFactory (producer) | To use a custom ClientInitializerFactory | ClientInitializer Factory | |
| correlationManager (producer) | To use a custom correlation manager to manage how request and reply messages are mapped when using request/reply with the netty producer. This should only be used if you have a way to map requests together with replies such as if there is correlation ids in both the request and reply messages. This can be used if you want to multiplex concurrent messages on the same channel (aka connection) in netty. When doing this you must have a way to correlate the request and reply messages so you can store the right reply on the inflight Camel Exchange before its continued routed. We recommend extending the TimeoutCorrelationManagerSupport when you build custom correlation managers. This provides support for timeout and other complexities you otherwise would need to implement as well. See also the producerPoolEnabled option for more details. | NettyCamelState CorrelationManager | |
| lazyChannelCreation (producer) | Channels can be lazily created to avoid exceptions, if the remote server is not up and running when the Camel producer is started. | true | boolean |
| producerPoolEnabled (producer) | Whether producer pool is enabled or not. Important: If you turn this off then a single shared connection is used for the producer, also if you are doing request/reply. That means there is a potential issue with interleaved responses if replies comes back out-of-order. Therefore you need to have a correlation id in both the request and reply messages so you can properly correlate the replies to the Camel callback that is responsible for continue processing the message in Camel. To do this you need to implement NettyCamelStateCorrelationManager as correlation manager and configure it via the correlationManager option. See also the correlationManager option for more details. | true | boolean |
| producerPoolMaxActive (producer) | Sets the cap on the number of objects that can be allocated by the pool (checked out to clients, or idle awaiting checkout) at a given time. Use a negative value for no limit. | -1 | int |
| producerPoolMaxIdle (producer) | Sets the cap on the number of idle instances in the pool. | 100 | int |
| producerPoolMinEvictable Idle (producer) | Sets the minimum amount of time (value in millis) an object may sit idle in the pool before it is eligible for eviction by the idle object evictor. | 300000 | long |
| producerPoolMinIdle (producer) | Sets the minimum number of instances allowed in the producer pool before the evictor thread (if active) spawns new objects. | int | |
| udpConnectionlessSending (producer) | This option supports connection less udp sending which is a real fire and forget. A connected udp send receive the PortUnreachableException if no one is listen on the receiving port. | false | boolean |
| useByteBuf (producer) | If the useByteBuf is true, netty producer will turn the message body into ByteBuf before sending it out. | false | boolean |
| allowSerializedHeaders (advanced) | Only used for TCP when transferExchange is true. When set to true, serializable objects in headers and properties will be added to the exchange. Otherwise Camel will exclude any non-serializable objects and log it at WARN level. | false | boolean |
| bootstrapConfiguration (advanced) | To use a custom configured NettyServerBootstrapConfiguration for configuring this endpoint. | NettyServerBootstrap Configuration | |
| channelGroup (advanced) | To use a explicit ChannelGroup. | ChannelGroup | |
| nativeTransport (advanced) | Whether to use native transport instead of NIO. Native transport takes advantage of the host operating system and is only supported on some platforms. You need to add the netty JAR for the host operating system you are using. See more details at: http://netty.io/wiki/native-transports.html | false | boolean |
| options (advanced) | Allows to configure additional netty options using option. as prefix. For example option.child.keepAlive=false to set the netty option child.keepAlive=false. See the Netty documentation for possible options that can be used. | Map | |
| receiveBufferSize (advanced) | The TCP/UDP buffer sizes to be used during inbound communication. Size is bytes. | 65536 | int |
| receiveBufferSizePredictor (advanced) | Configures the buffer size predictor. See details at Jetty documentation and this mail thread. | int | |
| sendBufferSize (advanced) | The TCP/UDP buffer sizes to be used during outbound communication. Size is bytes. | 65536 | int |
| synchronous (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean |
| transferExchange (advanced) | Only used for TCP. You can transfer the exchange over the wire instead of just the body. The following fields are transferred: In body, Out body, fault body, In headers, Out headers, fault headers, exchange properties, exchange exception. This requires that the objects are serializable. Camel will exclude any non-serializable objects and log it at WARN level. | false | boolean |
| udpByteArrayCodec (advanced) | For UDP only. If enabled the using byte array codec instead of Java serialization protocol. | false | boolean |
| workerCount (advanced) | When netty works on nio mode, it uses default workerCount parameter from Netty, which is cpu_core_threads2. User can use this operation to override the default workerCount from Netty | int | |
| workerGroup (advanced) | To use a explicit EventLoopGroup as the boss thread pool. For example to share a thread pool with multiple consumers or producers. By default each consumer or producer has their own worker pool with 2 x cpu count core threads. | EventLoopGroup | |
| allowDefaultCodec (codec) | The netty component installs a default codec if both, encoder/deocder is null and textline is false. Setting allowDefaultCodec to false prevents the netty component from installing a default codec as the first element in the filter chain. | true | boolean |
| autoAppendDelimiter (codec) | Whether or not to auto append missing end delimiter when sending using the textline codec. | true | boolean |
| decoder (codec) | Deprecated A custom ChannelHandler class that can be used to perform special marshalling of inbound payloads. | ChannelHandler | |
| decoderMaxLineLength (codec) | The max line length to use for the textline codec. | 1024 | int |
| decoders (codec) | A list of decoders to be used. You can use a String which have values separated by comma, and have the values be looked up in the Registry. Just remember to prefix the value with so Camel knows it should lookup. | String | |
| delimiter (codec) | The delimiter to use for the textline codec. Possible values are LINE and NULL. | LINE | TextLineDelimiter |
| encoder (codec) | Deprecated A custom ChannelHandler class that can be used to perform special marshalling of outbound payloads. | ChannelHandler | |
| encoders (codec) | A list of encoders to be used. You can use a String which have values separated by comma, and have the values be looked up in the Registry. Just remember to prefix the value with so Camel knows it should lookup. | String | |
| encoding (codec) | The encoding (a charset name) to use for the textline codec. If not provided, Camel will use the JVM default Charset. | String | |
| textline (codec) | Only used for TCP. If no codec is specified, you can use this flag to indicate a text line based codec; if not specified or the value is false, then Object Serialization is assumed over TCP. | false | boolean |
| enabledProtocols (security) | Which protocols to enable when using SSL | TLSv1,TLSv1.1,TLSv1.2 | String |
| keyStoreFile (security) | Client side certificate keystore to be used for encryption | File | |
| keyStoreFormat (security) | Keystore format to be used for payload encryption. Defaults to JKS if not set | String | |
| keyStoreResource (security) | Client side certificate keystore to be used for encryption. Is loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems. | String | |
| needClientAuth (security) | Configures whether the server needs client authentication when using SSL. | false | boolean |
| passphrase (security) | Password setting to use in order to encrypt/decrypt payloads sent using SSH | String | |
| securityProvider (security) | Security provider to be used for payload encryption. Defaults to SunX509 if not set. | String | |
| ssl (security) | Setting to specify whether SSL encryption is applied to this endpoint | false | boolean |
| sslClientCertHeaders (security) | When enabled and in SSL mode, then the Netty consumer will enrich the Camel Message with headers having information about the client certificate such as subject name, issuer name, serial number, and the valid date range. | false | boolean |
| sslContextParameters (security) | To configure security using SSLContextParameters | SSLContextParameters | |
| sslHandler (security) | Reference to a class that could be used to return an SSL Handler | SslHandler | |
| trustStoreFile (security) | Server side certificate keystore to be used for encryption | File | |
| trustStoreResource (security) | Server side certificate keystore to be used for encryption. Is loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems. | String |
229.3. Registry based Options
Codec Handlers and SSL Keystores can be enlisted in the Registry, such as in the Spring XML file. The values that could be passed in, are the following:
| Name | Description |
|---|---|
|
| password setting to use in order to encrypt/decrypt payloads sent using SSH |
|
| keystore format to be used for payload encryption. Defaults to "JKS" if not set |
|
| Security provider to be used for payload encryption. Defaults to "SunX509" if not set. |
|
| deprecated: Client side certificate keystore to be used for encryption |
|
| deprecated: Server side certificate keystore to be used for encryption |
|
|
Camel 2.11.1: Client side certificate keystore to be used for encryption. Is loaded by default from classpath, but you can prefix with |
|
|
Camel 2.11.1: Server side certificate keystore to be used for encryption. Is loaded by default from classpath, but you can prefix with |
|
| Reference to a class that could be used to return an SSL Handler |
|
|
A custom |
|
| A list of encoders to be used. You can use a String which have values separated by comma, and have the values be looked up in the Registry. Just remember to prefix the value with # so Camel knows it should lookup. |
|
|
A custom |
|
| A list of decoders to be used. You can use a String which have values separated by comma, and have the values be looked up in the Registry. Just remember to prefix the value with # so Camel knows it should lookup. |
Read below about using non shareable encoders/decoders.
229.4. Sending Messages to/from a Netty endpoint
229.4.1. Netty Producer
In Producer mode, the component provides the ability to send payloads to a socket endpoint using either TCP or UDP protocols (with optional SSL support).
The producer mode supports both one-way and request-response based operations.
229.4.2. Netty Consumer
In Consumer mode, the component provides the ability to:
- listen on a specified socket using either TCP or UDP protocols (with optional SSL support),
- receive requests on the socket using text/xml, binary and serialized object based payloads and
- send them along on a route as message exchanges.
The consumer mode supports both one-way and request-response based operations.
229.5. Examples
229.5.1. A UDP Netty endpoint using Request-Reply and serialized object payload
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("netty4:udp://localhost:5155?sync=true")
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
Poetry poetry = (Poetry) exchange.getIn().getBody();
poetry.setPoet("Dr. Sarojini Naidu");
exchange.getOut().setBody(poetry);
}
}
}
};229.5.2. A TCP based Netty consumer endpoint using One-way communication
RouteBuilder builder = new RouteBuilder() {
public void configure() {
from("netty4:tcp://localhost:5150")
.to("mock:result");
}
};229.5.3. An SSL/TCP based Netty consumer endpoint using Request-Reply communication
Using the JSSE Configuration Utility
As of Camel 2.9, the Netty component supports SSL/TLS configuration through the Camel JSSE Configuration Utility. This utility greatly decreases the amount of component specific code you need to write and is configurable at the endpoint and component levels. The following examples demonstrate how to use the utility with the Netty component.
Programmatic configuration of the component
KeyStoreParameters ksp = new KeyStoreParameters();
ksp.setResource("/users/home/server/keystore.jks");
ksp.setPassword("keystorePassword");
KeyManagersParameters kmp = new KeyManagersParameters();
kmp.setKeyStore(ksp);
kmp.setKeyPassword("keyPassword");
SSLContextParameters scp = new SSLContextParameters();
scp.setKeyManagers(kmp);
NettyComponent nettyComponent = getContext().getComponent("netty4", NettyComponent.class);
nettyComponent.setSslContextParameters(scp);Spring DSL based configuration of endpoint
...
<camel:sslContextParameters
id="sslContextParameters">
<camel:keyManagers
keyPassword="keyPassword">
<camel:keyStore
resource="/users/home/server/keystore.jks"
password="keystorePassword"/>
</camel:keyManagers>
</camel:sslContextParameters>...
...
<to uri="netty4:tcp://localhost:5150?sync=true&ssl=true&sslContextParameters=#sslContextParameters"/>
...[[Netty4-UsingBasicSSL/TLSconfigurationontheJettyComponent]] Using Basic SSL/TLS configuration on the Jetty Component
JndiRegistry registry = new JndiRegistry(createJndiContext());
registry.bind("password", "changeit");
registry.bind("ksf", new File("src/test/resources/keystore.jks"));
registry.bind("tsf", new File("src/test/resources/keystore.jks"));
context.createRegistry(registry);
context.addRoutes(new RouteBuilder() {
public void configure() {
String netty_ssl_endpoint =
"netty4:tcp://localhost:5150?sync=true&ssl=true&passphrase=#password"
+ "&keyStoreFile=#ksf&trustStoreFile=#tsf";
String return_string =
"When You Go Home, Tell Them Of Us And Say,"
+ "For Your Tomorrow, We Gave Our Today.";
from(netty_ssl_endpoint)
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getOut().setBody(return_string);
}
}
}
});Getting access to SSLSession and the client certificate
You can get access to the javax.net.ssl.SSLSession if you eg need to get details about the client certificate. When ssl=true then the Netty4 component will store the SSLSession as a header on the Camel Message as shown below:
SSLSession session = exchange.getIn().getHeader(NettyConstants.NETTY_SSL_SESSION, SSLSession.class); // get the first certificate which is client certificate javax.security.cert.X509Certificate cert = session.getPeerCertificateChain()[0]; Principal principal = cert.getSubjectDN();
Remember to set needClientAuth=true to authenticate the client, otherwise SSLSession cannot access information about the client certificate, and you may get an exception javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated. You may also get this exception if the client certificate is expired or not valid etc.
The option sslClientCertHeaders can be set to true which then enriches the Camel Message with headers having details about the client certificate. For example the subject name is readily available in the header CamelNettySSLClientCertSubjectName.
229.5.4. Using Multiple Codecs
In certain cases it may be necessary to add chains of encoders and decoders to the netty pipeline. To add multpile codecs to a camel netty endpoint the 'encoders' and 'decoders' uri parameters should be used. Like the 'encoder' and 'decoder' parameters they are used to supply references (to lists of ChannelUpstreamHandlers and ChannelDownstreamHandlers) that should be added to the pipeline. Note that if encoders is specified then the encoder param will be ignored, similarly for decoders and the decoder param.
Read further above about using non shareable encoders/decoders.
The lists of codecs need to be added to the Camel’s registry so they can be resolved when the endpoint is created.
ChannelHandlerFactory lengthDecoder = ChannelHandlerFactories.newLengthFieldBasedFrameDecoder(1048576, 0, 4, 0, 4);
StringDecoder stringDecoder = new StringDecoder();
registry.bind("length-decoder", lengthDecoder);
registry.bind("string-decoder", stringDecoder);
LengthFieldPrepender lengthEncoder = new LengthFieldPrepender(4);
StringEncoder stringEncoder = new StringEncoder();
registry.bind("length-encoder", lengthEncoder);
registry.bind("string-encoder", stringEncoder);
List<ChannelHandler> decoders = new ArrayList<ChannelHandler>();
decoders.add(lengthDecoder);
decoders.add(stringDecoder);
List<ChannelHandler> encoders = new ArrayList<ChannelHandler>();
encoders.add(lengthEncoder);
encoders.add(stringEncoder);
registry.bind("encoders", encoders);
registry.bind("decoders", decoders);Spring’s native collections support can be used to specify the codec lists in an application context
<util:list id="decoders" list-class="java.util.LinkedList">
<bean class="org.apache.camel.component.netty4.ChannelHandlerFactories" factory-method="newLengthFieldBasedFrameDecoder">
<constructor-arg value="1048576"/>
<constructor-arg value="0"/>
<constructor-arg value="4"/>
<constructor-arg value="0"/>
<constructor-arg value="4"/>
</bean>
<bean class="io.netty.handler.codec.string.StringDecoder"/>
</util:list>
<util:list id="encoders" list-class="java.util.LinkedList">
<bean class="io.netty.handler.codec.LengthFieldPrepender">
<constructor-arg value="4"/>
</bean>
<bean class="io.netty.handler.codec.string.StringEncoder"/>
</util:list>
<bean id="length-encoder" class="io.netty.handler.codec.LengthFieldPrepender">
<constructor-arg value="4"/>
</bean>
<bean id="string-encoder" class="io.netty.handler.codec.string.StringEncoder"/>
<bean id="length-decoder" class="org.apache.camel.component.netty4.ChannelHandlerFactories" factory-method="newLengthFieldBasedFrameDecoder">
<constructor-arg value="1048576"/>
<constructor-arg value="0"/>
<constructor-arg value="4"/>
<constructor-arg value="0"/>
<constructor-arg value="4"/>
</bean>
<bean id="string-decoder" class="io.netty.handler.codec.string.StringDecoder"/>The bean names can then be used in netty endpoint definitions either as a comma separated list or contained in a List e.g.
from("direct:multiple-codec").to("netty4:tcp://localhost:{{port}}?encoders=#encoders&sync=false");
from("netty4:tcp://localhost:{{port}}?decoders=#length-decoder,#string-decoder&sync=false").to("mock:multiple-codec");or via XML.
<camelContext id="multiple-netty-codecs-context" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:multiple-codec"/>
<to uri="netty4:tcp://localhost:5150?encoders=#encoders&sync=false"/>
</route>
<route>
<from uri="netty4:tcp://localhost:5150?decoders=#length-decoder,#string-decoder&sync=false"/>
<to uri="mock:multiple-codec"/>
</route>
</camelContext>229.6. Closing Channel When Complete
When acting as a server you sometimes want to close the channel when, for example, a client conversion is finished.
You can do this by simply setting the endpoint option disconnect=true.
However you can also instruct Camel on a per message basis as follows.
To instruct Camel to close the channel, you should add a header with the key CamelNettyCloseChannelWhenComplete set to a boolean true value.
For instance, the example below will close the channel after it has written the bye message back to the client:
from("netty4:tcp://localhost:8080").process(new Processor() {
public void process(Exchange exchange) throws Exception {
String body = exchange.getIn().getBody(String.class);
exchange.getOut().setBody("Bye " + body);
// some condition which determines if we should close
if (close) {
exchange.getOut().setHeader(NettyConstants.NETTY_CLOSE_CHANNEL_WHEN_COMPLETE, true);
}
}
});Adding custom channel pipeline factories to gain complete control over a
229.7. Custom pipeline
Custom channel pipelines provide complete control to the user over the handler/interceptor chain by inserting custom handler(s), encoder(s) & decoders without having to specify them in the Netty Endpoint URL in a very simple way.
In order to add a custom pipeline, a custom channel pipeline factory must be created and registered with the context via the context registry (JNDIRegistry, or the camel-spring ApplicationContextRegistry etc).
A custom pipeline factory must be constructed as follows
-
A Producer linked channel pipeline factory must extend the abstract class
ClientPipelineFactory. -
A Consumer linked channel pipeline factory must extend the abstract class
ServerInitializerFactory. -
The classes should override the initChannel() method in order to insert custom handler(s), encoder(s) and decoder(s). Not overriding the
initChannel()method creates a pipeline with no handlers, encoders or decoders wired to the pipeline.
The example below shows how ServerInitializerFactory factory may be created
229.7.1. Using custom pipeline factory
public class SampleServerInitializerFactory extends ServerInitializerFactory {
private int maxLineSize = 1024;
protected void initChannel(Channel ch) throws Exception {
ChannelPipeline channelPipeline = ch.pipeline();
channelPipeline.addLast("encoder-SD", new StringEncoder(CharsetUtil.UTF_8));
channelPipeline.addLast("decoder-DELIM", new DelimiterBasedFrameDecoder(maxLineSize, true, Delimiters.lineDelimiter()));
channelPipeline.addLast("decoder-SD", new StringDecoder(CharsetUtil.UTF_8));
// here we add the default Camel ServerChannelHandler for the consumer, to allow Camel to route the message etc.
channelPipeline.addLast("handler", new ServerChannelHandler(consumer));
}
}The custom channel pipeline factory can then be added to the registry and instantiated/utilized on a camel route in the following way
Registry registry = camelContext.getRegistry();
ServerInitializerFactory factory = new TestServerInitializerFactory();
registry.bind("spf", factory);
context.addRoutes(new RouteBuilder() {
public void configure() {
String netty_ssl_endpoint =
"netty4:tcp://localhost:5150?serverInitializerFactory=#spf"
String return_string =
"When You Go Home, Tell Them Of Us And Say,"
+ "For Your Tomorrow, We Gave Our Today.";
from(netty_ssl_endpoint)
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
exchange.getOut().setBody(return_string);
}
}
}
});229.8. Reusing Netty boss and worker thread pools
Netty has two kind of thread pools: boss and worker. By default each Netty consumer and producer has their private thread pools. If you want to reuse these thread pools among multiple consumers or producers then the thread pools must be created and enlisted in the Registry.
For example using Spring XML we can create a shared worker thread pool using the NettyWorkerPoolBuilder with 2 worker threads as shown below:
<!-- use the worker pool builder to help create the shared thread pool -->
<bean id="poolBuilder" class="org.apache.camel.component.netty.NettyWorkerPoolBuilder">
<property name="workerCount" value="2"/>
</bean>
<!-- the shared worker thread pool -->
<bean id="sharedPool" class="org.jboss.netty.channel.socket.nio.WorkerPool"
factory-bean="poolBuilder" factory-method="build" destroy-method="shutdown">
</bean>
For boss thread pool there is a org.apache.camel.component.netty4.NettyServerBossPoolBuilder builder for Netty consumers, and a org.apache.camel.component.netty4.NettyClientBossPoolBuilder for the Netty producers.
Then in the Camel routes we can refer to this worker pools by configuring the workerPool option in the URI as shown below:
<route> <from uri="netty4:tcp://localhost:5021?textline=true&sync=true&workerPool=#sharedPool&usingExecutorService=false"/> <to uri="log:result"/> ... </route>
And if we have another route we can refer to the shared worker pool:
<route> <from uri="netty4:tcp://localhost:5022?textline=true&sync=true&workerPool=#sharedPool&usingExecutorService=false"/> <to uri="log:result"/> ... </route>
and so forth.
229.9. Multiplexing concurrent messages over a single connection with request/reply
When using Netty for request/reply messaging via the netty producer then by default each message is sent via a non-shared connection (pooled). This ensures that replies are automatic being able to map to the correct request thread for further routing in Camel. In other words correlation between request/reply messages happens out-of-the-box because the replies comes back on the same connection that was used for sending the request; and this connection is not shared with others. When the response comes back, the connection is returned back to the connection pool, where it can be reused by others.
However if you want to multiplex concurrent request/responses on a single shared connection, then you need to turn off the connection pooling by setting producerPoolEnabled=false. Now this means there is a potential issue with interleaved responses if replies comes back out-of-order. Therefore you need to have a correlation id in both the request and reply messages so you can properly correlate the replies to the Camel callback that is responsible for continue processing the message in Camel. To do this you need to implement NettyCamelStateCorrelationManager as correlation manager and configure it via the correlationManager=#myManager option.
We recommend extending the TimeoutCorrelationManagerSupport when you build custom correlation managers. This provides support for timeout and other complexities you otherwise would need to implement as well.
