August 15, 2023

cLoadBalancer – Docs for ESB 6.x

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cLoadBalancer

Distributes the messages it received to multiple endpoints according to the load
balancing policy.

cLoadBalancer Standard properties

These properties are used to configure cLoadBalancer running in the Standard Job framework.

The Standard
cLoadBalancer component belongs to the Routing family.

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 from None, Bean, Constant, CorrelationID, EL,
Groovy, Header, JavaScript,
JoSQL, JSonPath, JXPath,
MVEL, OGNL, PHP, Property, Python, Ruby, Simple, SpEL,
SQL, XPath, and XQuery.

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

Usage rule

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

This scenario applies only to a Talend solution with ESB.

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.

use_case_cloadbalancer_1.png

  1. From the Connectivity 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.
  2. From the Routing folder, drop a cLoadBalancer component onto the design
    workspace, and label it Load_balancer.
  3. From the Core folder, drop two cJavaDSLProcessor components onto the design
    workspace, and label them according to their roles in the Route: To_Receiver_A and To_Receiver_B respectively.
  4. From the Custom folder, drop two
    cProcessor components onto the design
    workspace, and label them according to their roles in the Route: Monitor_A, and Monitor_B respectively.
  5. Link the cFile component to the cLoadBalancer component using a Row > Route
    connection.
  6. Link cLoadBalancer to each of the two
    cJavaDSLProcessor components using a
    Row > Load
    Balance     connection.
  7. Link each of the two cMessagingEndpoint
    components to the corresponding cProcessor
    component using a Row > Route connection.

Configuring the components and connections

  1. Double-click the cFile component to open
    its Basic Settings view in the Component tab.

    use_case_cloadbalancer_2.png

  2. In the Path field, specify the file path
    to message source.
  3. From the Encoding list, select the
    encoding type of your message files. Leave the other parameters as they
    are.
  4. 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.

    use_case_cloadbalancer_6.png

  5. 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.

    use_case_cloadbalancer_3.png

    Repeat this step to define the URI of the other receiver,
    direct:b, in the cJavaDSLProcessor component labeled To_Receiver_B.
  6. 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.

    use_case_cloadbalancer_4.png

    Repeat this step to define the URI of the other receiver,
    direct:b, in the cMessagingEndpoint component labeled Receiver_B.
  7. 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:

    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.
  8. Press Ctrl+S to save your Route.

Viewing the code and executing the Route

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

    use_case_cloadbalancer_7.png

    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.
  2. 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.
    use_case_cloadbalancer_5.png

Document get from Talend https://help.talend.com
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Docs 6.x
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