Google PubSub Lite

URI Format

The Google PubSub Component uses the following URI format:

google-pubsub-lite://project-id:location:destinationName?[options]

Destination Name can be either a topic or a subscription 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 Google PubSub Lite component supports 9 options, which are listed below.

Name	Description	Default	Type
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
consumerBytesOutstanding (consumer (advanced))	The number of quota bytes that may be outstanding to the client. Must be greater than the allowed size of the largest message (1 MiB).	10485760	long
consumerMessagesOutstanding (consumer (advanced))	The number of messages that may be outstanding to the client. Must be 0.	1000	long
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
publisherCacheSize (producer (advanced))	Maximum number of producers to cache. This could be increased if you have producers for lots of different topics.	100	int
publisherCacheTimeout (producer (advanced))	How many milliseconds should each producer stay alive in the cache.	180000	int
publisherTerminationTimeout (producer (advanced))	How many milliseconds should a producer be allowed to terminate.	60000	int
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
serviceAccountKey (security)	The Service account key that can be used as credentials for the PubSub Lite publisher/subscriber. 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

Name

Description

Default

Type

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

consumerBytesOutstanding (consumer (advanced))

The number of quota bytes that may be outstanding to the client. Must be greater than the allowed size of the largest message (1 MiB).

10485760

long

consumerMessagesOutstanding (consumer (advanced))

The number of messages that may be outstanding to the client. Must be 0.

1000

long

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

publisherCacheSize (producer (advanced))

Maximum number of producers to cache. This could be increased if you have producers for lots of different topics.

100

int

publisherCacheTimeout (producer (advanced))

How many milliseconds should each producer stay alive in the cache.

180000

int

publisherTerminationTimeout (producer (advanced))

How many milliseconds should a producer be allowed to terminate.

60000

int

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

serviceAccountKey (security)

The Service account key that can be used as credentials for the PubSub Lite publisher/subscriber. 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

Endpoint Options

The Google PubSub Lite endpoint is configured using URI syntax:

google-pubsub-lite:projectId:location:destinationName

With the following path and query parameters:

Path Parameters (3 parameters)

Name	Description	Type
projectId (common)	Required The Google Cloud PubSub Lite Project Id.	Long
location (common)	Required The Google Cloud PubSub Lite location.	String
destinationName (common)	Required The Destination Name. For the consumer this will be the subscription name, while for the producer this will be the topic name.	String

Name

Description

Default

Type

projectId (common)

Required The Google Cloud PubSub Lite Project Id.

Long

location (common)

Required The Google Cloud PubSub Lite location.

String

destinationName (common)

Required The Destination Name. For the consumer this will be the subscription name, while for the producer this will be the topic name.

String

Query Parameters (12 parameters)

Name	Description	Default	Type
loggerId (common)	Logger ID to use when a match to the parent route required.		String
ackMode (consumer)	AUTO = exchange gets ack’ed/nack’ed on completion. NONE = downstream process has to ack/nack explicitly. Enum values: AUTO NONE	AUTO	AckMode
concurrentConsumers (consumer)	The number of parallel streams consuming from the subscription.	1	Integer
maxAckExtensionPeriod (consumer)	Set the maximum period a message ack deadline will be extended. Value in seconds.	3600	int
maxMessagesPerPoll (consumer)	The max number of messages to receive from the server in a single API call.	1	Integer
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
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
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
pubsubEndpoint (producer (advanced))	Pub/Sub endpoint to use. Required when using message ordering, and ensures that messages are received in order even when multiple publishers are used.		String
serializer (producer (advanced))	Autowired A custom GooglePubsubLiteSerializer to use for serializing message payloads in the producer.		GooglePubsubSerializer
serviceAccountKey (security)	The Service account key that can be used as credentials for the PubSub publisher/subscriber. 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

Name

Description

Default

Type

loggerId (common)

Logger ID to use when a match to the parent route required.

String

ackMode (consumer)

AUTO = exchange gets ack’ed/nack’ed on completion. NONE = downstream process has to ack/nack explicitly.

Enum values:

AUTO
NONE

AUTO

AckMode

concurrentConsumers (consumer)

The number of parallel streams consuming from the subscription.

1

Integer

maxAckExtensionPeriod (consumer)

Set the maximum period a message ack deadline will be extended. Value in seconds.

3600

int

maxMessagesPerPoll (consumer)

The max number of messages to receive from the server in a single API call.

1

Integer

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

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

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

pubsubEndpoint (producer (advanced))

Pub/Sub endpoint to use. Required when using message ordering, and ensures that messages are received in order even when multiple publishers are used.

String

serializer (producer (advanced))

Autowired A custom GooglePubsubLiteSerializer to use for serializing message payloads in the producer.

GooglePubsubSerializer

serviceAccountKey (security)

The Service account key that can be used as credentials for the PubSub publisher/subscriber. 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

Message Headers

The Google PubSub Lite component supports 5 message header(s), which is/are listed below:

Name Description Default Type

Name	Description	Type
CamelGooglePubsubMessageId (common) Constant: `MESSAGE_ID`	The ID of the message, assigned by the server when the message is published.	String
CamelGooglePubsubMsgAckId (consumer) Constant: `ACK_ID`	The ID used to acknowledge the received message.	String
CamelGooglePubsubPublishTime (consumer) Constant: `PUBLISH_TIME`	The time at which the message was published.	Timestamp
CamelGooglePubsubAttributes (common) Constant: `ATTRIBUTES`	The attributes of the message.	Map
CamelGooglePubsubOrderingKey (producer) Constant: `ORDERING_KEY`	If non-empty, identifies related messages for which publish order should be respected.	String

CamelGooglePubsubMessageId (common)

Constant: MESSAGE_ID

The ID of the message, assigned by the server when the message is published.

String

CamelGooglePubsubMsgAckId (consumer)

Constant: ACK_ID

The ID used to acknowledge the received message.

String

CamelGooglePubsubPublishTime (consumer)

Constant: PUBLISH_TIME

The time at which the message was published.

Timestamp

CamelGooglePubsubAttributes (common)

Constant: ATTRIBUTES

The attributes of the message.

Map

CamelGooglePubsubOrderingKey (producer)

Constant: ORDERING_KEY

If non-empty, identifies related messages for which publish order should be respected.

String

Producer Endpoints

Google PubSub Lite expects the payload to be byte[] array, Producer endpoints will send:

String body as byte[] encoded as UTF-8
byte[] body as is
Everything else will be serialised into byte[] array

A Map set as message header GooglePubsubConstants.ATTRIBUTES will be sent as PubSub attributes.

When producing messages set the message header GooglePubsubConstants.ORDERING_KEY . This will be set as the PubSub Lite orderingKey for the message. More information in Using ordering keys.

Consumer Endpoints

Google PubSub Lite will redeliver the message if it has not been acknowledged within the time period set as a configuration option on the subscription.

The component will acknowledge the message once exchange processing has been completed.

Message Body

The consumer endpoint returns the content of the message as byte[] - exactly as the underlying system sends it. It is up for the route to convert/unmarshall the contents.

Examples

You’ll need to provide a connectionFactory to the ActiveMQ Component, to have the following examples working.

Producer Example

 from("timer://scheduler?fixedRate=true&period=5s")
            .setBody(simple("Hello World ${date:now:HH:mm:ss.SSS}"))
            .to("google-pubsub-lite:123456789012:europe-west3-a:my-topic-lite")
            .log("Message sent: ${body}");

Consumer Example

from("google-pubsub-lite:123456789012:europe-west3-a:my-subscription-lite")
            .log("Message received: ${body}");

Spring Boot Auto-Configuration

When using google-pubsub-lite 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-google-pubsub-lite-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 10 options, which are listed below.

Name	Description	Default	Type
camel.component.google-pubsub-lite.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.google-pubsub-lite.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.google-pubsub-lite.consumer-bytes-outstanding	The number of quota bytes that may be outstanding to the client. Must be greater than the allowed size of the largest message (1 MiB).	10485760	Long
camel.component.google-pubsub-lite.consumer-messages-outstanding	The number of messages that may be outstanding to the client. Must be 0.	1000	Long
camel.component.google-pubsub-lite.enabled	Whether to enable auto configuration of the google-pubsub-lite component. This is enabled by default.		Boolean
camel.component.google-pubsub-lite.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.google-pubsub-lite.publisher-cache-size	Maximum number of producers to cache. This could be increased if you have producers for lots of different topics.	100	Integer
camel.component.google-pubsub-lite.publisher-cache-timeout	How many milliseconds should each producer stay alive in the cache.	180000	Integer
camel.component.google-pubsub-lite.publisher-termination-timeout	How many milliseconds should a producer be allowed to terminate.	60000	Integer
camel.component.google-pubsub-lite.service-account-key	The Service account key that can be used as credentials for the PubSub Lite publisher/subscriber. 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

Name

Description

Default

Type

camel.component.google-pubsub-lite.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.google-pubsub-lite.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.google-pubsub-lite.consumer-bytes-outstanding

The number of quota bytes that may be outstanding to the client. Must be greater than the allowed size of the largest message (1 MiB).

10485760

Long

camel.component.google-pubsub-lite.consumer-messages-outstanding

The number of messages that may be outstanding to the client. Must be 0.

1000

Long

camel.component.google-pubsub-lite.enabled

Whether to enable auto configuration of the google-pubsub-lite component. This is enabled by default.

Boolean

camel.component.google-pubsub-lite.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.google-pubsub-lite.publisher-cache-size

Maximum number of producers to cache. This could be increased if you have producers for lots of different topics.

100

Integer

camel.component.google-pubsub-lite.publisher-cache-timeout

How many milliseconds should each producer stay alive in the cache.

180000

Integer

camel.component.google-pubsub-lite.publisher-termination-timeout

How many milliseconds should a producer be allowed to terminate.

60000

Integer

camel.component.google-pubsub-lite.service-account-key

The Service account key that can be used as credentials for the PubSub Lite publisher/subscriber. 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