The gtask component contributes to the Camel Components for Google App Engine (GAE). It supports asynchronous message
processing on GAE by using the task queueing service
as message queue. For adding messages to a queue it uses the task queue API. For receiving
messages from a queue it installs an HTTP callback handler. The handler is called by an HTTP
POST callback (a web hook) initiated by the
task queueing service. Whenever a new task is added to a queue a callback will be sent. The
gtask component abstracts from these details and supports endpoint URIs
that make message queueing on GAE as easy as message queueing with JMS or SEDA.
| Name | Default Value | Context | Description |
|---|---|---|---|
workerRoot
|
worker
|
Producer | The servlet mapping for callback handlers. By default, this component requires a
callback servlet mapping of /worker/*. If another servlet mapping is
used e.g. /myworker/* it must be set as option on the producer side:
to("gtask:myqueue?workerRoot=myworker"). |
inboundBindingRef
|
reference to GTaskBinding
|
Consumer | Reference to an InboundBinding<GTaskEndpoint, HttpServletRequest,
HttpServletResponse> in the Registry for
customizing the binding of an Exchange to the Servlet API. The
referenced binding is used as post-processor to
org.apache.camel.component.http.HttpBinding. |
outboundBindingRef
|
reference to GTaskBinding
|
Producer | Reference to an OutboundBinding<GTaskEndpoint, TaskOptions, void>
in the Registry for customizing the binding of an
Exchange to the task queueing service. |
On the consumer-side, all options of the Servlet component are supported.
On the consumer-side all headers of the Servlet component component are supported plus the following.
| Name | Type | Context | Description |
|---|---|---|---|
GTaskBinding.GTASK_QUEUE_NAME
|
String
|
Consumer | Name of the task queue. |
GTaskBinding.GTASK_TASK_NAME
|
String
|
Consumer | Name of the task (generated value). |
GTaskBinding.GTASK_RETRY_COUNT
|
int
|
Consumer | Number of callback retries. |
On the producer side the in message body is converted to a
byte[] and is POSTed to the callback handler as content-type
application/octet-stream.
Setting up tasks queues is an administrative task on Google App Engine. Only one queue is
pre-configured and can be referenced by name out-of-the-box: the default
queue. This queue will be used in the following examples. Please note that when using task
queues on the local development server, tasks must be executed manually from the developer console.
... .to(gtask:default) // add message to default queue from(gtask:default) // receive message from default queue (via a web hook) ...
This example requires the following servlet mapping.
![[Note]](imagesdb/note.gif) | web.xml |
|---|---|
...
<servlet>
<servlet-name>CamelServlet</servlet-name>
<servlet-class>org.apache.camel.component.servlet.CamelHttpTransportServlet</servlet-class>
...
</servlet>
...
<servlet-mapping>
<servlet-name>CamelServlet</servlet-name>
<url-pattern>/worker/*</url-pattern>
</servlet-mapping>
... |
Maven users will need to add the following dependency to their pom.xml.
| pom.xml |
|---|---|
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-gae</artifactId>
<version>${camel-version}</version>
</dependency> |
where ${camel-version} must be replaced by the actual version of
Fuse Mediation Router (2.1.0 or higher).
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