Netty Component

Available as of Camel 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 network 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:

URI format

The URI scheme for a netty component is as follows

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&...

Options

Name

Default Value

Description

keepAlive

true

Setting to ensure socket is not closed due to inactivity

tcpNoDelay

true

Setting to improve TCP protocol performance

backlog

 

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.

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

By default, the Asynchronous Routing Engine is used. Set to true to force processing synchronously.

ssl

false

Setting to specify whether SSL encryption is applied to this endpoint

sslClientCertHeaders

false

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.

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

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.

corePoolSize

10

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 Nettys default settings.

maxPoolSize

100

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

Whether or not 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. 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.

allowSerializedHeaders
false
Camel 2.18 Only used for TCP when transferExchange is true. Serializable objects in In/Out headers and exchange properties are transfered.

disconnectOnNoReply

true

If sync is enabled then this option dictates NettyConsumer if it should disconnect where there is no reply to send back.

noReplyLogLevel

WARN

If sync is enabled this option dictates NettyConsumer which logging level to use when logging a there is no reply to send back. Values are: FATAL, ERROR, INFO, DEBUG, OFF.

serverExceptionCaughtLogLevel

WARN

If the server (NettyConsumer) catches an exception then its logged using this logging level.

serverClosedChannelExceptionCaughtLogLevel

DEBUG

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 flod of closed exceptions in the Netty server.

allowDefaultCodec

true

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.

textline

false

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

The delimiter to use for the textline codec. Possible values are LINE and NULL.

decoderMaxLineLength

1024

The max line length to use for the textline codec.

autoAppendDelimiter

true

Whether or not to auto append missing end delimiter when sending using the textline codec.

encoding

null

The encoding (a charset name) to use for the textline codec. If not provided, Camel will use the JVM default Charset.

workerCount

null

 When netty works on nio mode, it uses default workerCount parameter from Netty, which is cpu_core_threads*2. User can use this operation to override the default workerCount from Netty.

sslContextParameters

null

 SSL configuration using an org.apache.camel.util.jsse.SSLContextParameters instance. See Using the JSSE Configuration Utility.

receiveBufferSizePredictor

null

Configures the buffer size predictor. See details at Jetty documentation and this mail thread.

requestTimeout

0

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. Camel 2.16, 2.15.3 you can also override this setting by setting the CamelNettyRequestTimeout header.

needClientAuth

false

 Configures whether the server needs client authentication when using SSL.

usingExecutorService

true

Whether to use executorService to handle the message inside the camel route, the executorService can be set from NettyComponent.

maximumPoolSize

16

The core pool size for the ordered thread pool, if its in use. NOTE: you can just setup this on the NettyComponent level since Camel 2.15, 2.14.1.

producerPoolEnabled

true

Producer only. Whether producer pool is enabled or not. Important: Do not turn this off, as the pooling is needed for handling concurrency and reliable request/reply.

producerPoolMaxActive

-1

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

Producer only. Sets the minimum number of instances allowed in the producer pool before the evictor thread (if active) spawns new objects.

producerPoolMaxIdle

100

Producer only. Sets the cap on the number of "idle" instances in the pool.

producerPoolMinEvictableIdle

300000

Producer only. 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.

bootstrapConfiguration

null

Consumer only. Allows to configure the Netty ServerBootstrap options using a org.apache.camel.component.netty4.NettyServerBootstrapConfiguration instance. This can be used to reuse the same configuration for multiple consumers, to align their configuration more easily.

bossGroup

null

To use a explicit io.netty.channel.EventLoopGroup as the boss thread pool. For example to share a thread pool with multiple consumers. By default each consumer has their own boss pool with 1 core thread.

workerGroup

null

To use a explicit io.netty.channel.EventLoopGroup as the worker 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.

channelGroupnullCamel 2.17 To use a explicit io.netty.channel.group.ChannelGroup for example to broadact a message to multiple channels.
networkInterface

null

Consumer only. 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.

clientInitializerFactorynullCamel 2.15: To use a custom client initializer factory to control the pipelines in the channel. See further below for more details.
serverInitializerFactorynullCamel 2.15: To use a custom server initializer factory to control the pipelines in the channel. See further below for more details.

clientPipelineFactory

nullDeprecated: Use clientInitializerFactory instead.

serverPipelineFactory

nullDeprecated: Use serverInitializerFactory instead.

udpConnectionlessSending

false

Camel 2.15: Producer only.  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.

clientModefalseCamel 2.15: Consumer only. If the clientMode is true, netty consumer will connect the address as a TCP client.
reconnecttrueCamel 2.16: Consumer only. Used only in clientMode in consumer, the consumer will attempt to reconnect on disconnection automatically.
reconnectInterval10000Camel 2.16: Consumer only. Used if reconnect and clientMode is enabled. The interval in milli seconds to attempt reconnection.

useByteBuf

falseCamel 2.16: Producer only. If the useByteBuf is true, netty producer will turn the message body into ByteBuf before sending it out.

udpByteArrayCodec

falseCamel 2.16: When using UDP protocol then turning this option to true sends the data as a byte array instead of the default object serialization codec.
reuseChannelfalseCamel 2.17: Producer only. This option allows producers to reuse the same Netty Channel for the lifecycle of processing the Exchange. This is useable 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 NettyConstants#NETTY_CHANNEL which allows you to obtain the channel during routing and use it as well.
nativeTransportfalseCamel 2.18: 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

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

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.

Important: Read below about using non shareable encoders/decoders.

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.

Sending Messages to/from a Netty endpoint

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.

Usage Samples

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

A TCP based Netty consumer endpoint using One-way communication

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
Spring DSL based configuration of endpoint
Using Basic SSL/TLS configuration on the Jetty Component
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 then the Netty4 component will store the SSLSession as a header on the Camel Message as shown below:

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.

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.

Spring's native collections support can be used to specify the codec lists in an application context

The bean names can then be used in netty endpoint definitions either as a comma separated list or contained in a List e.g.

or via spring.

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:

Adding custom channel pipeline factories to gain complete control over a created 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

Using custom pipeline factory

The custom channel pipeline factory can then be added to the registry and instantiated/utilized on a camel route in the following way

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:

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 produces.

Then in the Camel routes we can refer to this worker pools by configuring the workerPool option in the URI as shown below:

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

... and so forth.

See Also


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