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

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The Nats component supports 41 options, which are listed below.

Name Description Default Type

configuration (common)

To use a shared configuration.

NatsConfiguration

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

jetstreamEnabled (common)

Sets whether to enable JetStream support for this endpoint.

false

boolean

jetstreamName (common)

Sets the name of the JetStream stream to use.

String

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

ackPolicy (consumer)

Acknowledgement mode. none = Messages are acknowledged as soon as the server sends them (danger: messages that Camel failed to process is also ack). Clients do not need to ack. all = All messages with a sequence number less than the message acked are also acknowledged. E.g. reading a batch of messages 1..100. Ack on message 100 will acknowledge 1..99 as well. explicit (default) = Each message is acknowledged individually by Camel after the message has been processed, this ensures the message is only ack if success and nack if processing failed due to an exception during routing. Message can be acked out of sequence and create gaps of unacknowledged messages in the consumer.

Enum values:

  • None

  • All

  • Explicit

Explicit

AckPolicy

ackWait (consumer)

After a message is delivered to a consumer, the server waits 30 seconds (default) for an acknowledgement. If none arrives (timeout), the message becomes eligible for redelivery.

30000

long

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. 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

durableName (consumer)

Sets the name to assign to the JetStream durable consumer. Setting this value makes the consumer durable. The value is used to set the durable() field in the underlying NATS ConsumerConfiguration.Builder.

String

maxDeliver (consumer)

Maximum number of attempts to deliver a message from Nats to a consumer. Once MaxDeliver is reached, the NATS server stops attempting to deliver that specific message. The message is not deleted, it remains in the stream but is simply skipped. It is recommended to set this option to a sensible value in case a message is poison and can not successfully be processed and would always keep failing.

long

maxMessages (consumer)

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

String

nackWait (consumer)

For negative acknowledgements (NAK), redelivery is delayed by 5 seconds (default). Setting this to 0 or negative makes the redelivery immediately. Be careful as this can cause the consumer to keep re-processing the same message over and over again due to intermediate error that last a while.

5000

long

poolSize (consumer)

Consumer thread pool size (default is 10).

10

int

pullSubscription (consumer)

Sets the consumer subscription type for JetStream. Set to true to use a Pull Subscription (consumer explicitly requests messages). Set to false to use a Push Subscription (messages are automatically delivered).

true

boolean

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

consumerConfiguration (consumer (advanced))

Sets a custom ConsumerConfiguration object for the JetStream consumer. This is an advanced option typically used when you need to configure properties not exposed as simple Camel URI parameters. When set, this object will be used to build the final consumer subscription options.

ConsumerConfiguration

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

requestTimeout (producer)

Request timeout in milliseconds.

20000

long

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

connection (advanced)

Reference an already instantiated connection to Nats server.

Connection

headerFilterStrategy (advanced)

To use a custom header filter strategy.

HeaderFilterStrategy

jetstreamAsync (advanced)

Sets whether to operate JetStream requests asynchronously.

true

boolean

traceConnection (advanced)

Whether or not connection trace messages should be printed to standard out for fine grained debugging of connection issues.

false

boolean

credentialsFilePath (security)

If we use useCredentialsFile to true we’ll need to set the credentialsFilePath option. It can be loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems.

String

secure (security)

Set secure option indicating TLS is required.

false

boolean

sslContextParameters (security)

To configure security using SSLContextParameters.

SSLContextParameters

useGlobalSslContextParameters (security)

Enable usage of global SSL context parameters.

false

boolean

Endpoint Options

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 (common)

Required The name of topic we want to use.

String

Query Parameters (40 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

jetstreamEnabled (common)

Sets whether to enable JetStream support for this endpoint.

false

boolean

jetstreamName (common)

Sets the name of the JetStream stream to use.

String

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

ackPolicy (consumer)

Acknowledgement mode. none = Messages are acknowledged as soon as the server sends them (danger: messages that Camel failed to process is also ack). Clients do not need to ack. all = All messages with a sequence number less than the message acked are also acknowledged. E.g. reading a batch of messages 1..100. Ack on message 100 will acknowledge 1..99 as well. explicit (default) = Each message is acknowledged individually by Camel after the message has been processed, this ensures the message is only ack if success and nack if processing failed due to an exception during routing. Message can be acked out of sequence and create gaps of unacknowledged messages in the consumer.

Enum values:

  • None

  • All

  • Explicit

Explicit

AckPolicy

ackWait (consumer)

After a message is delivered to a consumer, the server waits 30 seconds (default) for an acknowledgement. If none arrives (timeout), the message becomes eligible for redelivery.

30000

long

durableName (consumer)

Sets the name to assign to the JetStream durable consumer. Setting this value makes the consumer durable. The value is used to set the durable() field in the underlying NATS ConsumerConfiguration.Builder.

String

maxDeliver (consumer)

Maximum number of attempts to deliver a message from Nats to a consumer. Once MaxDeliver is reached, the NATS server stops attempting to deliver that specific message. The message is not deleted, it remains in the stream but is simply skipped. It is recommended to set this option to a sensible value in case a message is poison and can not successfully be processed and would always keep failing.

long

maxMessages (consumer)

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

String

nackWait (consumer)

For negative acknowledgements (NAK), redelivery is delayed by 5 seconds (default). Setting this to 0 or negative makes the redelivery immediately. Be careful as this can cause the consumer to keep re-processing the same message over and over again due to intermediate error that last a while.

5000

long

poolSize (consumer)

Consumer thread pool size (default is 10).

10

int

pullSubscription (consumer)

Sets the consumer subscription type for JetStream. Set to true to use a Pull Subscription (consumer explicitly requests messages). Set to false to use a Push Subscription (messages are automatically delivered).

true

boolean

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

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. 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

consumerConfiguration (consumer (advanced))

Sets a custom ConsumerConfiguration object for the JetStream consumer. This is an advanced option typically used when you need to configure properties not exposed as simple Camel URI parameters. When set, this object will be used to build the final consumer subscription options.

ConsumerConfiguration

exceptionHandler (consumer (advanced))

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 (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

replySubject (producer)

the subject to which subscribers should send response.

String

requestTimeout (producer)

Request timeout in milliseconds.

20000

long

lazyStartProducer (producer (advanced))

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

connection (advanced)

Reference an already instantiated connection to Nats server.

Connection

headerFilterStrategy (advanced)

To use a custom header filter strategy.

HeaderFilterStrategy

jetstreamAsync (advanced)

Sets whether to operate JetStream requests asynchronously.

true

boolean

traceConnection (advanced)

Whether or not connection trace messages should be printed to standard out for fine grained debugging of connection issues.

false

boolean

credentialsFilePath (security)

If we use useCredentialsFile to true we’ll need to set the credentialsFilePath option. It can be loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems.

String

secure (security)

Set secure option indicating TLS is required.

false

boolean

sslContextParameters (security)

To configure security using SSLContextParameters.

SSLContextParameters

Message Headers

The Nats component supports 8 message header(s), which is/are listed below:

Name Description Default Type

CamelNatsMessageTimestamp (common)

Constant: NATS_MESSAGE_TIMESTAMP

The timestamp of a consumed message.

long

CamelNatsSID (common)

Constant: NATS_SID

The SID of a consumed message.

String

CamelNatsReplyTo (common)

Constant: NATS_REPLY_TO

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

String

CamelNatsSubject (common)

Constant: NATS_SUBJECT

The Subject of a consumed message.

String

CamelNatsQueueName (common)

Constant: NATS_QUEUE_NAME

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

String

CamelNatsStatusCode (consumer)

Constant: NATS_STATUS_CODE

Status message code.

int

CamelNatsStatusError (consumer)

Constant: NATS_STATUS_ERROR

Status message error message.

String

CamelNatsDeliveryCounter (consumer)

Constant: NATS_DELIVERY_COUNTER

Number of times this message has been delivered (1 = first, 1 then message has been redelivered).

long

Usage

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

Request/Reply support

The producer supports 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 42 options, which are listed below.

Name Description Default Type

camel.component.nats.ack-policy

Acknowledgement mode. none = Messages are acknowledged as soon as the server sends them (danger: messages that Camel failed to process is also ack). Clients do not need to ack. all = All messages with a sequence number less than the message acked are also acknowledged. E.g. reading a batch of messages 1..100. Ack on message 100 will acknowledge 1..99 as well. explicit (default) = Each message is acknowledged individually by Camel after the message has been processed, this ensures the message is only ack if success and nack if processing failed due to an exception during routing. Message can be acked out of sequence and create gaps of unacknowledged messages in the consumer.

explicit

AckPolicy

camel.component.nats.ack-wait

After a message is delivered to a consumer, the server waits 30 seconds (default) for an acknowledgement. If none arrives (timeout), the message becomes eligible for redelivery.

30000

Long

camel.component.nats.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.nats.bridge-error-handler

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. 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.configuration

To use a shared configuration. The option is a org.apache.camel.component.nats.NatsConfiguration type.

NatsConfiguration

camel.component.nats.connection

Reference an already instantiated connection to Nats server. The option is a io.nats.client.Connection type.

Connection

camel.component.nats.connection-timeout

Timeout for connection attempts. (in milliseconds).

2000

Integer

camel.component.nats.consumer-configuration

Sets a custom ConsumerConfiguration object for the JetStream consumer. This is an advanced option typically used when you need to configure properties not exposed as simple Camel URI parameters. When set, this object will be used to build the final consumer subscription options. The option is a io.nats.client.api.ConsumerConfiguration type.

ConsumerConfiguration

camel.component.nats.credentials-file-path

If we use useCredentialsFile to true we’ll need to set the credentialsFilePath option. It can be loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems.

String

camel.component.nats.durable-name

Sets the name to assign to the JetStream durable consumer. Setting this value makes the consumer durable. The value is used to set the durable() field in the underlying NATS ConsumerConfiguration.Builder.

String

camel.component.nats.enabled

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

Boolean

camel.component.nats.flush-connection

Define if we want to flush connection when stopping or not.

true

Boolean

camel.component.nats.flush-timeout

Set the flush timeout (in milliseconds).

1000

Integer

camel.component.nats.header-filter-strategy

To use a custom header filter strategy. The option is a org.apache.camel.spi.HeaderFilterStrategy type.

HeaderFilterStrategy

camel.component.nats.jetstream-async

Sets whether to operate JetStream requests asynchronously.

true

Boolean

camel.component.nats.jetstream-enabled

Sets whether to enable JetStream support for this endpoint.

false

Boolean

camel.component.nats.jetstream-name

Sets the name of the JetStream stream to use.

String

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.max-deliver

Maximum number of attempts to deliver a message from Nats to a consumer. Once MaxDeliver is reached, the NATS server stops attempting to deliver that specific message. The message is not deleted, it remains in the stream but is simply skipped. It is recommended to set this option to a sensible value in case a message is poison and can not successfully be processed and would always keep failing.

Long

camel.component.nats.max-messages

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

String

camel.component.nats.max-pings-out

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

2

Integer

camel.component.nats.max-reconnect-attempts

Max reconnection attempts.

60

Integer

camel.component.nats.nack-wait

For negative acknowledgements (NAK), redelivery is delayed by 5 seconds (default). Setting this to 0 or negative makes the redelivery immediately. Be careful as this can cause the consumer to keep re-processing the same message over and over again due to intermediate error that last a while.

5000

Long

camel.component.nats.no-echo

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

camel.component.nats.no-randomize-servers

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

false

Boolean

camel.component.nats.pedantic

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

false

Boolean

camel.component.nats.ping-interval

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

120000

Integer

camel.component.nats.pool-size

Consumer thread pool size (default is 10).

10

Integer

camel.component.nats.pull-subscription

Sets the consumer subscription type for JetStream. Set to true to use a Pull Subscription (consumer explicitly requests messages). Set to false to use a Push Subscription (messages are automatically delivered).

true

Boolean

camel.component.nats.queue-name

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

String

camel.component.nats.reconnect

Whether or not using reconnection feature.

true

Boolean

camel.component.nats.reconnect-time-wait

Waiting time before attempts reconnection (in milliseconds).

2000

Integer

camel.component.nats.reply-subject

the subject to which subscribers should send response.

String

camel.component.nats.reply-to-disabled

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

false

Boolean

camel.component.nats.request-cleanup-interval

Interval to clean up cancelled/timed out requests.

5000

Integer

camel.component.nats.request-timeout

Request timeout in milliseconds.

20000

Long

camel.component.nats.secure

Set secure option indicating TLS is required.

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.ssl-context-parameters

To configure security using SSLContextParameters. The option is a org.apache.camel.support.jsse.SSLContextParameters type.

SSLContextParameters

camel.component.nats.trace-connection

Whether or not connection trace messages should be printed to standard out for fine grained debugging of connection issues.

false

Boolean

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
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