Vincenzo Lombardo created NIFI-16457:
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Summary: Add C2 CLEAR CONNECTION operation to MiNiFi
Key: NIFI-16457
URL: https://issues.apache.org/jira/browse/NIFI-16457
Project: Apache NiFi
Issue Type: New Feature
Components: MiNiFi
Reporter: Vincenzo Lombardo
h3. Problem
The C2 protocol defines {{OperationType.CLEAR}} with {{OperandType.CONNECTION}}
as its only supported operand ({{c2-protocol-api}}), but MiNiFi Java does not
register any {{C2OperationHandler}} for it. As a result:
* a C2 server has no way to empty a connection queue on an agent (the
equivalent of "Empty Queue" on the NiFi canvas), for example to recover an
agent blocked by back pressure or by FlowFiles that cannot be processed
* an operation CLEAR / CONNECTION sent to an agent is never acknowledged
The only current workaround is pushing a new flow configuration or accessing
the host directly.
h3. Proposed change
Implement the operation with the same structure used for processor START/STOP -
(NIFI-15017):
* {{ConnectionQueueStrategy}} interface and {{ClearConnectionOperationHandler}}
in {{c2-client-service}}; the handler reads the {{connectionId}} argument and
returns NOT_APPLIED when it is missing
* {{DefaultConnectionQueueStrategy}} in {{minifi-framework-core}}: looks up the
connection through {{FlowManager}} and calls
{{FlowFileQueue.dropFlowFiles(...)}}, the same mechanism
{{DefaultUpdateConfigurationStrategy}} already uses to empty queues removed by
a flow update
* the drop request is asynchronous, so the strategy waits for its completion up
to a timeout (30 seconds):
** FULLY_APPLIED when the drop request completes
** PARTIALLY_APPLIED when it is still running after the timeout
** NOT_APPLIED when the connection does not exist or the drop request fails
* register the handler in {{C2NifiClientService}}, so CLEAR / CONNECTION is
advertised in the agent's supported operations
Example operation:
{code:json}
{
"identifier": "op-1",
"operation": "CLEAR",
"operand": "CONNECTION",
"args": { "connectionId": "<connection instance identifier>" }
}
{code}
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