cLoadBalancer

cLoadBalancer properties

Component Family	Routing
Function	cLoadBalancer distributes the messages it received to multiple endpoints according to the load balancing policy.
Purpose	cLoadBalancer allows you to distribute messages among several endpoints using a variety of load balancing strategies.
Basic settings	Strategy	Select between Random, Round Robin, Sticky, Topic, Failover, and Custom. Each method is described below.
Random	The receiving endpoint is chosen randomly at each exchange.
Round Robin	Messages are distributed according to the round robin method which distributes the load evenly.
Sticky	Language	Select the language of the expression to use in the Expression field to distribute the messages.
	Expression	Type in the expression that will be used to calculate a correlation key that will determine the endpoint to choose.
Topic	Select this option to send all the messages to all the endpoints.
Failover	Basic mode	By default, the failover load balancing always sends the messages to the first endpoint. If the first endpoint fails, the messages are sent to subsequent endpoints.
	Specify exceptions	Specify the exceptions to which the failover should react to in the Exception table.
	Use with Round robin	Select this option to use failover with advanced options. From the Maximum failover attempt list, select the number of attempt to be proceed before giving up the transfer: –Attempt forever: always attempts to transfer the messages and always try to failover. –Never failover: gives up immediately the transfer of messages and never try to failover. –A number of attempts: attempts n number of time to transfer messages, specify that number in the Number of attempts field. Inherit error handler: Select true if you want Camel error handler to be used. If you select false, the load balancer will immediately failover when an exception is thrown. Use Round robin: Select true if you want to combine failover with round robin. Failover load balancing with round robin mode distributes the load evenly between the services, and it provides automatic failover.
Custom	Load balancer	Type in the name of your custom load balancer.
Usage	cLoadBalancer is used as a middle component in a Route.
Connections	Load Balance	Select this link to route messages to the next endpoint according to the selected load-balancing strategy.
	Route	Select this link to route all the messages from the sender to the next endpoint.
Limitation	n/a

Scenario: Distributing messages to receiver endpoints based on round robin

In this scenario, a cLoadBalancer component is used
to distribute four messages evenly to two receiving endpoints in accordance with the
round robin load balancing method.

Dropping and linking the components

This scenario requires one cFile component as the
message sender, one cLoadBalancer component to
distribute the messages to two different receivers in a load balancing manner, two
cJavaDSLProcessor components to define the URIs
of the receivers, two cMessagingEndpoint components
to retrieve the messages routed to the two receivers, and two cProcessor components to display the effect of round robin load
balancing.

From the Messaging folder of the
Palette, drop one cFile component and two cMessagingEndpoint components onto the workspace, and label
them according to their roles in the Route: Sender, Receiver_A, and
Receiver_B respectively.
From the Routing folder, drop a cLoadBalancer component onto the design
workspace, and label it Load_balancer.
From the Processor folder, drop two cJavaDSLProcessor components and two cProcessor components onto the design workspace,
and label them according to their roles in the Route: To_Receiver_A, To_Receiver_B, Monitor_A,
and Monitor_B respectively.
Link the cFile component to the cLoadBalancer component using a Row > Route
connection.
Link cLoadBalancer to each of the two cJavaDSLProcessor components using a Row > Load
Balance connection.
Link each of the two cMessagingEndpoint
components to the corresponding cProcessor
component using a Row > Route connection.

Configuring the components and connections

Double-click the cFile component to open
its Basic Settings view in the Component tab.
In the Path field, specify the file path
to message source.
From the Encoding list, select the
encoding type of your message files. Leave the other parameters as they
are.
Double-click the cLoadBalancer component
to open its Basic Settings view in the
Component tab, and select the load
balancing method you want to use from the Strategy list. In this scenario, we use the default
Round robin method.
Double-click the cJavaDSLProcessor
component labeled To_Receiver_A to open
its Basic Settings view in the Component tab, and enter URI of the first
receiver between the double quotation marks in the Code area, direct:a in this example.

Repeat this step to define the URI of the other receiver,
direct:b, in the cJavaDSLProcessor component labeled To_Receiver_B.
Double-click the cMessagingEndpoint
component labeled Receiver_A to open its
Basic Settings view in the Component tab, and enter URI of the first
receiver between the double quotation marks in the URI field, direct:a in this example.

Repeat this step to define the URI of the other receiver,
direct:b, in the cMessagingEndpoint component labeled Receiver_B.
Double-click the cProcessor component labeled Monitor_A to open its Basic Settings view in the Component tab, and customize the code in the Code area to display the file names of the
messages routed to Receiver_A on the
console:

System.out.println("Message on Receiver_A: "+ exchange.getIn().getHeader("CamelFileName"));

1
2

System.out.println("Message on Receiver_A: "+
exchange.getIn().getHeader("CamelFileName"));

Repeat this step to customize the code in the cProcessor component labeled
Monitor_B to display the file names of the messages routed to Receiver_B on the console.
Press Ctrl+S to save your Route.

Viewing the code and executing the Route

Click the Code tab at the bottom of the
design workspace to check the generated code:

As shown above, while messages are routed from the source endpoint
.to the destination endpoints, routing load balancing is
implemented according to the .roundRobin() method by
cLoadBalancer_1.
Press F6 to run your Route.

RESULT: Of the four messages from the sender, two are routed to Receiver_A and two are routed to Receiver_B in a round robin manner.

Document get from Talend https://help.talend.com

Thank you for watching.

Docs 5.x

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cLoadBalancer – Docs for ESB 5.x