fineract-doc/src/docs/en/chapters/architecture/idempotency.adoc - fineract - Git at Google

 = Idempotency

 Idempotency is the way to make sure your specific action is only executed once.
 For example, if you have a button that is supposed to send a repayment, you don’t want to repayment twice if the user clicks the button twice. Idempotency is a way to make sure that the action is only executed once.

 There are two ways to use idempotency:

   * HTTP Request with idempotency key header
   * Batch request with batch item header

 == How it works

 The `idempotency key` with `action name` and `entity name` is unique, and identify a specific command in the system.
 If no idempotency key is assigned to the request, the system will generate one for you.

 1. User send a request
 2. The system checks there are already executed commands with the same `idempotency key` and `action name` and `entity name`
 3. The action based on the result of the check
   * If the request is completed the system return with the already generated result
   * If not completed, return HTTP 409 response
   * If the request is not completed, we process the requests and store the results in the database


 == Idempotency in HTTP requests

 To achieve idempotency in HTTP requests, you can use the HTTP header from `fineract.idempotency-key-header-name` configuration variables (default `Idemptency-Key`). This header is a unique identifier for the request. If you send the same request twice, the second request will be ignored and the response from the first request will be returned.

 == Idempotency in Batch requests

 In batch requests, you can set the idempotency key for every batch item, in the batch item `header` fields. The header key is from `fineract.idempotency-key-header-name` configuration variables (default `Idemptency-Key`).

 == Result of the request

 * When the request is already executed and completed, the system will return a `x-served-from-cache` header with the value `true` in the response and return the original request body.
 * When the request is already executed but still not completed, the system will return to HTTP 409 error code
 * When the request is not executed, the system runs it normally and stores the result in the date
	= Idempotency

	Idempotency is the way to make sure your specific action is only executed once.
	For example, if you have a button that is supposed to send a repayment, you don’t want to repayment twice if the user clicks the button twice. Idempotency is a way to make sure that the action is only executed once.

	There are two ways to use idempotency:

	* HTTP Request with idempotency key header
	* Batch request with batch item header

	== How it works

	The `idempotency key` with `action name` and `entity name` is unique, and identify a specific command in the system.
	If no idempotency key is assigned to the request, the system will generate one for you.

	1. User send a request
	2. The system checks there are already executed commands with the same `idempotency key` and `action name` and `entity name`
	3. The action based on the result of the check
	* If the request is completed the system return with the already generated result
	* If not completed, return HTTP 409 response
	* If the request is not completed, we process the requests and store the results in the database


	== Idempotency in HTTP requests

	To achieve idempotency in HTTP requests, you can use the HTTP header from `fineract.idempotency-key-header-name` configuration variables (default `Idemptency-Key`). This header is a unique identifier for the request. If you send the same request twice, the second request will be ignored and the response from the first request will be returned.

	== Idempotency in Batch requests

	In batch requests, you can set the idempotency key for every batch item, in the batch item `header` fields. The header key is from `fineract.idempotency-key-header-name` configuration variables (default `Idemptency-Key`).

	== Result of the request

	* When the request is already executed and completed, the system will return a `x-served-from-cache` header with the value `true` in the response and return the original request body.
	* When the request is already executed but still not completed, the system will return to HTTP 409 error code
	* When the request is not executed, the system runs it normally and stores the result in the date