7.3.30. request_cancel

7.3.30.1. Summary

Note

This command is an experimental feature.

New in version 4.0.9.

request_cancel command cancels a running request.

There are some limitations:

• Request ID must be managed by user. (You need to assign unique key for each request.)
• Cancel request may be ignored. (You can send request_cancel command multiple times for the same request ID.)
• Only multithreading type Groonga server is supported. (You can use with groonga command based server but can't use with groonga-httpd.)

See Request ID about request ID.

If request is canceled, the canceled request has -5 (GRN_INTERRUPTED_FUNCTION_CALL) as Return code.

7.3.30.2. Syntax

request_cancel command takes only one parameter.

The required parameter is only id:

request_cancel id

7.3.30.3. Usage

Here is an example of request_cancel command:

$ curl 'http://localhost:10041/d/select?table=LargeTable&filter=true&request_id=unique-id-1' &
# The above "select" takes a long time...
# Point: "request_id=unique-id-1"
$ curl 'http://localhost:10041/d/request_cancel?id=unique-id-1'
[[...], {"id": "unique-id-1", "canceled": true}]
# Point: "id=unique-id-1"

Assume that the first select command takes a long time. unique-id-1 request ID is assigned to the select command by request_id=unique-id-1 parameter.

The second request_cancel command passes id=unique-id-1 parameter. unique-id-1 is the same request ID passed in select command.

The select command may not be canceled immediately. And the cancel request may be ignored.

You can send cancel request for the same request ID multiple times. If the target request is canceled or finished, "canceled" value is changed to false from true:

$ curl 'http://localhost:10041/d/request_cancel?id=unique-id-1'
[[...], {"id": "unique-id-1", "canceled": true}]
# "select" is still running... ("canceled" is "true")
$ curl 'http://localhost:10041/d/request_cancel?id=unique-id-1'
[[...], {"id": "unique-id-1", "canceled": true}]
# "select" is still running... ("canceled" is "true")
$ curl 'http://localhost:10041/d/request_cancel?id=unique-id-1'
[[...], {"id": "unique-id-1", "canceled": false}]
# "select" is canceled or finished. ("canceled" is "false")

If the select command is canceled, response of the select command has -5 (GRN_INTERRUPTED_FUNCTION_CALL) as Return code:

$ curl 'http://localhost:10041/d/select?table=LargeTable&filter=true&request_id=unique-id-1' &
[[-5, ...], ...]

7.3.30.4. Parameters

This section describes parameters of request_cancel.

7.3.30.4.1. Required parameter

There is required parameter, id.

7.3.30.4.1.1. id

Specifies the ID for the target request.

7.3.30.5. Return value

request_cancel command returns the result of the cancel request:

[
  HEADER,
  {
    "id":       ID,
    "canceled": CANCEL_REQUEST_IS_ACCEPTED_OR_NOT
  }
]

HEADER

See Output format about HEADER.

ID

The ID of the target request.

CANCEL_REQUEST_IS_ACCEPTED_OR_NOT

If the cancel request is accepted, this is true, otherwise this is false.

Note that "cancel request is accepted" doesn't means that "the target request is canceled". It just means "cancel request is notified to the target request but the cancel request may be ignored by the target request".

If request assigned with the request ID doesn't exist, this is false.

7.3.30.6. See also

• Request ID