Enable Session Affinity

11.1.1 Enable Session Affinity

When you enable session affinity, all the requests for a unique transaction or session are routed to the same endpoint or replica of the participant service that served the first request.

Use the instructions provided in this section to enable session affinity or sticky sessions if you have deployed the participant service or transaction coordinator within an Istio service mesh. If you are using load balancers, such as Nginx or HAProxy, refer to the load balancer documentation to configure session affinity or sticky sessions.

The steps provided in this section are specific to enabling session affinity for a participant service. You can enable session affinity for the transaction coordinator in a similar manner.

Before you begin, complete the following tasks:

Ensure that you have deployed the transaction coordinator and participant services within an Istio service mesh.
Identify if you need to enable session affinity for your participant service or for the transaction coordinator. See About Session Affinity.

To enable session affinity for a participant service:

Enable session affinity for the MicroTx transaction coordinator. In the values.yaml file of the MicroTx transaction coordinator, add the following line of code. This file is available in the installation_directory/otmm-RELEASE/otmm/helmcharts folder. See Configure the values.yaml File.
```
tmmConfiguration:
    sessionAffinity: true
```
Enable session affinity for transaction participant services and the transaction initiator service. In the values.yaml file, which is located in the Helm Chart of the service, add the following line of code.
```
sessionAffinity: true
```
Note:

If your application uses the Saga transaction protocol, you must set the sessionAffinity property to true in all the participant services and the transaction initiator service. In case of XA transaction protocol, you can set the sessionAffinity property to true in one or more participant services.

Parent topic: About Session Affinity