Persister

Overview

In DIGIT, the Persister Service is used to store data in the database by listening to messages from Kafka topics.

It needs a configuration file (in YAML) to understand:

• Which Kafka topic to listen to

• What data to extract from the Kafka message

• Where and how to insert/update this data in the database

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Configure Persister

1

Add YAML Config in MDMS/Config Repo

• Go to your MDMS or the config GitHub repo.

• Use the right branch based on your environment: example: dev, uat, prod, master

• Add a new file named like this: egov-persister/persister-pgr.yml. This file tells the persister how to save PGR complaints.

Sample Persister Configuration (For PGR)

persister:
  moduleName: PGR

  kafkaTopics:
    - topic: save-pgr-request
      configKey: PGR_SAVE
    - topic: update-pgr-request
      configKey: PGR_UPDATE

  PGR_SAVE:
    - query: INSERT INTO eg_pgr_service (id, tenantid, servicecode, description, status, createdby, createdtime, lastmodifiedby, lastmodifiedtime)
             VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
      basePath: $.service
      jsonMaps:
        - jsonPath: $.service.id
        - jsonPath: $.service.tenantId
        - jsonPath: $.service.serviceCode
        - jsonPath: $.service.description
        - jsonPath: $.service.applicationStatus
        - jsonPath: $.service.auditDetails.createdBy
        - jsonPath: $.service.auditDetails.createdTime
        - jsonPath: $.service.auditDetails.lastModifiedBy
        - jsonPath: $.service.auditDetails.lastModifiedTime

  PGR_UPDATE:
    - query: UPDATE eg_pgr_service SET status = ?, lastmodifiedby = ?, lastmodifiedtime = ? WHERE id = ?
      basePath: $.service
      jsonMaps:
        - jsonPath: $.service.applicationStatus
        - jsonPath: $.service.auditDetails.lastModifiedBy
        - jsonPath: $.service.auditDetails.lastModifiedTime
        - jsonPath: $.service.id

How to read this sample persister configuration:

Term	What it means
moduleName	Logical name (here, PGR)
topic	Kafka topic (like save-pgr-request) that triggers DB action
basePath	Root path in JSON (e.g., $.service) from which data is picked
jsonPath	Specific path in the request JSON to map to a DB column
query	SQL query to insert/update data in the database

2

Restart Persister Service

• After saving the configuration, run this to reload the updated configuration. Command to run the configuration: kubectl rollout restart deployment <persister-deployment-name> -n <namespace>

• The service will not read the new configuration file until it's restarted.

3

Validate Configuration

Once the service is restarted:

• Submit a PGR complaint (via API or UI)

• Check:

  • A message is published on Kafka (e.g., save-pgr-request)

  • The data is stored in the DB (check table eg_pgr_service)

• If nothing happens:

  • Check that the topic name matches in both the application and the persister YAML

  • Look for logs in the persister pod for errors

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Reference

• Persister Config Samples on GitHub

• DIGIT Dev Docs → MDMS & Persister

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Summary

• The Persister config ensures that the complaint data is saved automatically when it is created or updated.

• It works behind the scenes, triggered by Kafka.

• You configure it using a simple YAML file to define what to save and where.

• Restart the service after adding or editing the config.