Chapter 230. 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>

230.1. 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&…​

230.2. Options

The Netty4 component supports 5 options which are listed below.

NameDescriptionDefaultType

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:

230.2.1. Path Parameters (3 parameters):

NameDescriptionDefaultType

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

230.2.2. Query Parameters (72 parameters):

NameDescriptionDefaultType

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

230.3. 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:

NameDescription

passphrase

password setting to use in order to encrypt/decrypt payloads sent using SSH

keyStoreFormat

keystore format to be used for payload encryption. Defaults to "JKS" if not set

securityProvider

Security provider to be used for payload encryption. Defaults to "SunX509" if not set.

keyStoreFile

deprecated: Client side certificate keystore to be used for encryption

trustStoreFile

deprecated: Server side certificate keystore to be used for encryption

keyStoreResource

Camel 2.11.1: 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.

trustStoreResource

Camel 2.11.1: 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.

sslHandler

Reference to a class that could be used to return an SSL Handler

encoder

A custom ChannelHandler class that can be used to perform special marshalling of outbound payloads. Must override io.netty.channel.ChannelInboundHandlerAdapter.

encoders

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.

decoder

A custom ChannelHandler class that can be used to perform special marshalling of inbound payloads. Must override io.netty.channel.ChannelOutboundHandlerAdapter.

decoders

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.

Note

Read below about using non shareable encoders/decoders.

230.3.1. Using non shareable encoders or decoders

If your encoders or decoders is not shareable (eg they have the @Shareable class annotation), then your encoder/decoder must implement the org.apache.camel.component.netty.ChannelHandlerFactory interface, and return a new instance in the newChannelHandler method. This is to ensure the encoder/decoder can safely be used. If this is not the case, then the Netty component will log a WARN when
an endpoint is created.

The Netty component offers a org.apache.camel.component.netty.ChannelHandlerFactories factory class, that has a number of commonly used methods.

230.4. Sending Messages to/from a Netty endpoint

230.4.1. 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.

230.4.2. 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.

230.5. Examples

230.5.1. 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);
         }
       }
    }
};

230.5.2. 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");
  }
};

230.5.3. 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.

Tip

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.

230.5.4. 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.

Note

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&amp;sync=false"/>
    </route>
    <route>
        <from uri="netty4:tcp://localhost:5150?decoders=#length-decoder,#string-decoder&amp;sync=false"/>
        <to uri="mock:multiple-codec"/>
    </route>
</camelContext>

230.6. 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

230.7. 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

230.7.1. 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);
          }
       }
  }
});

230.8. 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>
Tip

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&amp;sync=true&amp;workerPool=#sharedPool&amp;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&amp;sync=true&amp;workerPool=#sharedPool&amp;usingExecutorService=false"/>
  <to uri="log:result"/>
  ...
</route>

and so forth.

230.9. 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.

Note

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.

230.10. See Also