Nats

Since Camel 2.17

Both producer and consumer are supported

NATS is a fast and reliable messaging platform.

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

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

URI format

nats:topic[?options]

Where topic is the topic name

Options

The Nats component supports 6 options, which are listed below.

Name Description Default Type

servers (common)

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

verbose (common)

Whether or not running in verbose mode

false

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

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

basicPropertyBinding (advanced)

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

boolean

useGlobalSslContextParameters (security)

Enable usage of global SSL context parameters.

false

boolean

The Nats endpoint is configured using URI syntax:

nats:topic

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

topic

Required The name of topic we want to use

String

Query Parameters (28 parameters):

Name Description Default Type

connectionTimeout (common)

Timeout for connection attempts. (in milliseconds)

2000

int

flushConnection (common)

Define if we want to flush connection when stopping or not

true

boolean

flushTimeout (common)

Set the flush timeout (in milliseconds)

1000

int

maxPingsOut (common)

maximum number of pings have not received a response allowed by the client

2

int

maxReconnectAttempts (common)

Max reconnection attempts

60

int

noEcho (common)

Turn off echo. If supported by the gnatsd version you are connecting to this flag will prevent the server from echoing messages back to the connection if it has subscriptions on the subject being published to.

false

boolean

noRandomizeServers (common)

Whether or not randomizing the order of servers for the connection attempts

false

boolean

pedantic (common)

Whether or not running in pedantic mode (this affects performance)

false

boolean

pingInterval (common)

Ping interval to be aware if connection is still alive (in milliseconds)

120000

int

reconnect (common)

Whether or not using reconnection feature

true

boolean

reconnectTimeWait (common)

Waiting time before attempts reconnection (in milliseconds)

2000

int

requestCleanupInterval (common)

Interval to clean up cancelled/timed out requests.

5000

int

servers (common)

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

verbose (common)

Whether or not running in verbose mode

false

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

maxMessages (consumer)

Stop receiving messages from a topic we are subscribing to after maxMessages

String

poolSize (consumer)

Consumer thread pool size (default is 10)

10

int

queueName (consumer)

The Queue name if we are using nats for a queue configuration

String

replyToDisabled (consumer)

Can be used to turn off sending back reply message in the consumer.

false

boolean

exceptionHandler (consumer)

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option 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. The value can be one of: InOnly, InOut, InOptionalOut

ExchangePattern

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

replySubject (producer)

the subject to which subscribers should send response

String

basicPropertyBinding (advanced)

Whether the endpoint should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

boolean

connection (advanced)

Reference an already instantiated connection to Nats server

Connection

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

secure (security)

Set secure option indicating TLS is required

false

boolean

sslContextParameters (security)

To configure security using SSLContextParameters

SSLContextParameters

Configuring servers

You configure the NATS servers on either the component or the endpoint.

For example to configure this once on the component you can do:

NatsComponent nats = context.getComponent("nats", NatsComponent.class);
nats.setServers("someserver:4222,someotherserver:42222");

Notice how you can specify multiple servers separated by comma.

Or you can specify the servers in the endpoint URI

from("direct:send").to("nats:test?servers=localhost:4222");

The endpoint configuration will override any server configuration on the component level.

Configuring username and password or token

You can specify username and password for the servers in the server URLs, where its username:password@url, or token@url etc:

NatsComponent nats = context.getComponent("nats", NatsComponent.class);
nats.setServers("scott:tiger@someserver:4222,superman:123@someotherserver:42222");

If you are using Camel Main or Spring Boot you can configure the server urls in the application.properties file

camel.component.nats.servers=scott:tiger@someserver:4222,superman:123@someotherserver:42222

Headers

Name Type Description

CamelNatsSID

String

The SID of a consumed message.

CamelNatsReplyTo

String

The ReplyTo of a consumed message (may be null).

CamelNatsSubject

String

The Subject of a consumed message.

CamelNatsQueueName

String

The Queue name of a consumed message (may be null).

CamelNatsMessageTimestamp

long

The timestamp of a consumed message.

Request/Reply support

The producer only supports publishing (sending) messages. The producer does not support request/reply where it can wait for an expected reply message.

The consumer will when routing the message is complete, send back the message as reply-message if required.

Examples

Producer example:

from("direct:send")
  .to("nats:mytopic");

In case of using Authorization you can directly specify your credentials in the server URL

from("direct:send")
  .to("nats:mytopic?servers=username:password@localhost:4222");

or your token

from("direct:send")
  .to("nats:mytopic?servers=token@localhost:4222);

Consumer example:

from("nats:mytopic?maxMessages=5&queueName=myqueue")
  .to("mock:result");

Spring Boot Auto-Configuration

When using nats with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

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

The component supports 7 options, which are listed below.

Name Description Default Type

camel.component.nats.bridge-error-handler

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

camel.component.nats.enabled

Whether to enable auto configuration of the nats component. This is enabled by default.

Boolean

camel.component.nats.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean

camel.component.nats.servers

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

camel.component.nats.use-global-ssl-context-parameters

Enable usage of global SSL context parameters.

false

Boolean

camel.component.nats.verbose

Whether or not running in verbose mode

false

Boolean

camel.component.nats.basic-property-binding

Deprecated Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

Boolean