Netty

Netty Component

Available as of Camel 2.3

The netty component in Apache Camel is a socket communication component, based on the JBoss Netty community offering (available under an Apache 2.0 license). Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. Netty greatly simplifies and streamlines network programming such as TCP and UDP socket server.

This Apache 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 Apache Camel route.

URI format

The URI scheme for a netty component is as follows

netty:tcp://localhost:99999[?options]
netty: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&...

Dependencies

Maven users need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-netty</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

Options

Table 65 list the Netty uri options:

Table 65. URI options

NameDefaultDescription
keepAlive true Setting to ensure socket is not closed due to inactivity
tcpNoDelay true Setting to improve TCP protocol performance
backlog If not set, depends on OS setting

Camel 2.9.6/2.10.4/2.11: Enables you to configure a backlog for netty consumer (server). The backlog is just a best effort, depending on the OS.

Setting this option to a value, such as 200, 500 or 1000, informs the TCP stack how long the "accept" queue can be.

broadcast false Setting to choose Multicast over UDP
connectTimeout 10000 Time to wait for a socket connection to be available. Value is in millis.
reuseAddress true Setting to facilitate socket multiplexing
sync true Setting to set endpoint as one-way or request-response
synchronous false

Camel 2.10: Specifies whether Asynchronous Routing Engine is not in use.

false then the Asynchronous Routing Engine is used, true to force synchronous processing.

ssl false Setting to specify whether SSL encryption is applied to this endpoint
sslClientCertHeaders false Camel 2.12: When enabled and in SSL mode, the Netty consumer enrichs the Camel Message with headers having information about the client certificate—such as subject name, issuer name, serial number, and the valid date range.
sendBufferSize 65536 bytes The TCP/UDP buffer sizes to be used during outbound communication. Size is bytes.
receiveBufferSize 65536 bytes The TCP/UDP buffer sizes to be used during inbound communication. Size is bytes.
option.XXX null

Camel 2.11/2.10.4: Allows configuring 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 other options.

corePoolSize 10

Specifies the number of allocated threads at component startup. Defaults to 10.

Note: This option is removed from Camel 2.9.2 onwards, as we rely on Netty's default settings.

maxPoolSize 100

Specifies the maximum number of threads that may be allocated to this endpoint. Defaults to 100.

Note: This option is removed from Camel 2.9.2 onwards. As we rely on Nettys default settings.

disconnect false

Specifies whether to disconnect (close) from Netty Channel right after use.

Can be used for both consumer and producer.

lazyChannelCreation true Channels can be lazily created to avoid exceptions, if the remote server is not up and running when the Camel producer is started.
transferExchange false

Only used for TCP. You can transfer the exchange over the wire instead of just the body.

These fields are transferred:

  • In body

  • Out body

  • fault body

  • In headers

  • Out headers

  • fault headers

  • exchange properties

  • exchange exception

This feature requires that the objects be serializable. Camel excludes any non-serializable object and logs it at WARN level.

disconnectOnNoReply true If sync is enabled, this option dictates whether NettyConsumer should disconnect when there is no reply.
noReplyLogLevel WARN

If sync is enabled, this option dictates which logging level NettyConsumer should use for logging when there is no reply.

Values are: FATAL, ERROR, INFO, DEBUG, OFF.

serverExceptionCaughtLogLevel WARN Camel 2.11.1: When the server (NettyConsumer) catches an exception, it is logged using this logging level.
serverClosedChannelExceptionCaughtLogLevel DEBUG

Camel 2.11.1: When the server (NettyConsumer) catches an java.nio.channels.ClosedChannelException, it is logged using this logging level.

This is used to avoid logging the closed channel exceptions, as clients can disconnect abruptly, then cause a flood of closed exceptions in the Netty server.

allowDefaultCodec true

Camel 2.4: The netty component installs a default codec if encoder/decoder 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.

textline false

Camel 2.4: 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.

delimiter LINE

Camel 2.4: pecifies the delimiter to use for the textline codec.

Possible values are LINE and NULL.

decoderMaxLineLength 1024 Camel 2.4: Specifies the max line length to use for the textline codec.
autoAppendDelimiter true Camel 2.4: Specifies whether to auto append a missing end delimiter when sending using the textline codec.
encoding null

Camel 2.4: The encoding (a charset name) to use for the textline codec.

If not provided, Camel will use the JVM default Charset.

workerCount null

Camel 2.9: When netty works in nio mode, it uses default workerCount parameter from Netty, which is cpu_core_threads*2.

You can use this operation to override Netty's default workerCount.

sslContextParameters null

Camel 2.9: Specifies the SSL configuration using an org.apache.camel.util.jsse.SSLContextParameters instance.

See Using the JSSE Configuration Utility.

receiveBufferSizePredictor null

Camel 2.9: Configures the buffer size predictor.

See details at Jetty documentation and this mail thread.

requestTimeout 0

Camel 2.11.1: Allows using a timeout, in milliseconds, for the Netty producer when calling a remote server.

By default (0), no timeout is used.

needClientAuth false Camel 2.11: Configures whether the server needs client authentication when using SSL.
orderedThreadPoolExecutor true

Camel 2.10.2: Specifies whether to use ordered thread pool to ensure events are processed orderly on the same channel.

For more details, see the netty javadoc.

maximumPoolSize 16 Camel 2.10.2: Specifies the core pool size for the ordered thread pool, when it is used.
producerPoolEnabled true

Camel 2.10.4/Camel 2.11: Producer only. Enables/disables the producer pool.

Important: Do not turn this off, as pooling is needed for handling concurrency and reliable request/reply messaging.

producerPoolMaxActive -1

Camel 2.10.3: Producer only. 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.

producerPoolMinIdle 0 Camel 2.10.3: Producer only. Sets the minimum number of instances allowed in the producer pool before the evictor thread (if active) spawns new objects.
producerPoolMaxIdle 100 Camel 2.10.3: Producer only. Sets the cap on the number of "idle" instances in the pool.
producerPoolMinEvictableIdle 30000 Camel 2.10.3: Producer only. Sets the minimum amount of time (in milliseconds) an object may sit idle in the pool before it is eligible for eviction by the idle object evictor.
bootstrapConfiguration null

Camel 2.12: Consumer only. Allows configuring the Netty ServerBootstrap options using a Netty Server Bootstrap Configuration instance.

Use this option to reuse the same configuration for multiple consumers and align their configuration more easily.

bossPoll null

Camel 2.12: Specifies to use an explicit org.jboss.netty.channel.socket.nio.BossPool as the boss thread pool.

By default, each consumer has their own boss pool with one core thread.

You can use this option, for example, to share a thread pool with multiple consumers.

workerPool null

Camel 2.12: Specifies to use an explicit org.jboss.netty.channel.socket.nio.WorkerPool as the worker thread pool.

By default, each consumer has their own worker pool with 2 x cpu count core threads.

You can use this option, for example, to share a thread pool with multiple consumers.

networkInterface null Camel 2.12: Consumer only. When using UDP, this option can be used to specify a network interface by its name, such as eth0 to join a multicast group.

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:

Table 66. Registry-based options

Name Description
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 org.jboss.netty.channel.ChannelDownStreamHandler.
encorders 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 org.jboss.netty.channel.ChannelUpStreamHandler.
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.

Using nonshareable encoders or decoders

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

[Note]Note

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

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.

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.

A UDP Netty endpoint using Request-Reply and serialized object payload

RouteBuilder builder = new RouteBuilder() {
  public void configure() {
    from("netty: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);
         }
       }
    }
};

A TCP based Netty consumer endpoint using One-way communication

RouteBuilder builder = new RouteBuilder() {
  public void configure() {
       from("netty:tcp://localhost:5150")
           .to("mock:result"); 
  }
};

An SSL/TCP based Netty consumer endpoint using Request-Reply communication

[Note]Note

As of Camel 2.9, the Netty component supports SSL/TLS configuration through the Using the 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.

  • 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 = 
             "netty: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);                           
              }
           }
      }
    });

  • 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("netty", NettyComponent.class);
    nettyComponent.setSslContextParameters(scp);

  • Spring DSL-based configuration of the 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="netty:tcp://localhost:5150?sync=true&ssl=true&sslContextParameters=#sslContextParameters"/>
    ...

Getting access to SSLSession and the client certificate

Available as of Camel 2.12

You can get access to the javax.net.ssl.SSLSession if you eg need to get details about the client certificate. When ssl=true, the Netty component stores 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.

[Note]Note

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.

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 Apache 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.

The lists of codecs need to be added to the Apache 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<ChannelUpstreamHandler> decoders = new ArrayList<ChannelUpstreamHandler>();
decoders.add(lengthDecoder);
decoders.add(stringDecoder);

List<ChannelDownstreamHandler> encoders = new ArrayList<ChannelDownstreamHandler>();
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.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder">
            <constructor-arg value="1048576"/>
            <constructor-arg value="0"/>
            <constructor-arg value="4"/>
            <constructor-arg value="0"/>
            <constructor-arg value="4"/>
        </bean>
        <bean class="org.jboss.netty.handler.codec.string.StringDecoder"/>
    </util:list>

    <util:list id="encoders" list-class="java.util.LinkedList">
        <bean class="org.jboss.netty.handler.codec.frame.LengthFieldPrepender">
            <constructor-arg value="4"/>
        </bean>
        <bean class="org.jboss.netty.handler.codec.string.StringEncoder"/>
    </util:list>

    <bean id="length-encoder" class="org.jboss.netty.handler.codec.frame.LengthFieldPrepender">
        <constructor-arg value="4"/>
    </bean>
    <bean id="string-encoder" class="org.jboss.netty.handler.codec.string.StringEncoder"/>

    <bean id="length-decoder" class="org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder">
        <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="org.jboss.netty.handler.codec.string.StringDecoder"/>

</beans>

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("netty:tcp://localhost:{{port}}?encoders=#encoders&sync=false");
                
         from("netty:tcp://localhost:{{port}}?decoders=#length-decoder,#string-decoder&sync=false").to("mock:multiple-codec");
      }
    };
  }
}

or via Spring:

<camelContext id="multiple-netty-codecs-context" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:multiple-codec"/>
        <to uri="netty:tcp://localhost:5150?encoders=#encoders&ync=false"/>
    </route>
    <route>
        <from uri="netty:tcp://localhost:5150?decoders=#length-decoder,#string-decoder&ync=false"/>
        <to uri="mock:multiple-codec"/>
    </route>
</camelContext>

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 Apache Camel on a per message basis as follows. To instruct Apache 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("netty: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 created pipeline

Available as of Apache Camel 2.5

Custom channel pipelines provide complete control to the user over the handler/interceptor chain by inserting custom handler(s), encoder(s) and 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 through the context registry (JNDIRegistry,or the 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, ServerPipelineFactory.

  • The classes can optionally override the getPipeline() method in order to insert custom handler(s), encoder(s) and decoder(s). Not overriding the getPipeline() method creates a pipeline with no handlers, encoders or decoders wired to the pipeline.

The example below shows how ServerChannel Pipeline factory may be created

public class SampleServerChannelPipelineFactory extends ServerPipelineFactory {
    private int maxLineSize = 1024;

    public ChannelPipeline getPipeline() throws Exception {
      
        ChannelPipeline channelPipeline = Channels.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));

        return channelPipeline;
   }
}

The custom channel pipeline factory can then be added to the registry and instantiated/utilized on a camel route as follows:

Registry registry = camelContext.getRegistry();
serverPipelineFactory = new TestServerChannelPipelineFactory();
registry.bind("spf", serverPipelineFactory);
context.addRoutes(new RouteBuilder() {
    public void configure() {
        String netty_ssl_endpoint =
          "netty:tcp://localhost:5150?serverPipelineFactory=#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);
            }
          }
    }
});

Reusing Netty boss and worker thread pools

Available as of Camel 2.12

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 create 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>
[Note]Note

For boss thread pool there is a org.apache.camel.component.netty.NettyServerBossPoolBuilder builder for Netty consumers, and a org.apache.camel.component.netty.NettyClientBossPoolBuilder for the Netty produces.

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="netty:tcp://localhost:5021?textline=true&ync=true&orkerPool=#sharedPool&rderedThreadPoolExecutor=false"/>
      <to uri="log:result"/>
      ...
    </route>

And if we have another route we can refer to the shared worker pool:

    <route>
      <from uri="netty:tcp://localhost:5022?textline=true&ync=true&orkerPool=#sharedPool&rderedThreadPoolExecutor=false"/>
      <to uri="log:result"/>
      ...
    </route>

... and so forth.

See also