Limit PFC WD Detection time to maximum value of 1000ms

[tirupatihemanth]

Fixing: sonic-net/sonic-buildimage#25033
Should be merged before: sonic-net/sonic-buildimage#25034

What I did
PFC WD Detection time is defined by the following calculation:

DEFAULT_POLL_INTERVAL * multiply

where:

multiply = max(1, (port_num-1)//DEFAULT_PORT_NUM+1)
port_num = len(list(self.config_db.get_table('PORT').keys()))
DEFAULT_POLL_INTERVAL = 200
DEFAULT_PORT_NUM = 32
There is an allowed range for this value which is between 100..3000 [ms].
For system with more than 448 ports, we will violate this range.

In addition, there is no meaning to have detection time of more than 1000[ms], hence, this change limit the maximum detection time for PFC WD to 1000[ms]

How I did it
Calculate PFC WD Detection time, if it become bigger than 1000[ms], set it to 1000[ms]

How to verify it
Run PFC WD Tests on several platforms

[mssonicbld]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

This PR updates SONiC’s PFC watchdog CLI behavior to cap the configured polling interval at 1000ms (including start_default computation and CLI validation), and extends unit tests to cover scaling behavior across different port counts.

Changes:

• Add MAX_POLL_INTERVAL_TIME = 1000 and use it for pfcwd interval Click validation.
• Cap the PFC_WD|GLOBAL|POLL_INTERVAL value produced by start_default to 1000ms.
• Add/extend unit tests and expected outputs for 32-port and 512-port scenarios.
• Update config pfcwd interval argument validation to a 1000ms max.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pfcwd/main.py	Introduces max poll-interval constant, caps start_default poll interval, updates Click range validation.
config/main.py	Narrows config pfcwd interval argument range to max 1000ms and documents sync expectations.
tests/pfcwd_test.py	Adds new tests to validate start_default behavior for 32-port and 512-port systems.
tests/pfcwd_input/pfcwd_test_vectors.py	Adds expected outputs corresponding to the new tests (including poll interval cap).

Comments suppressed due to low confidence (1)

pfcwd/main.py:430

• The PR title/description talk about capping detection time to 1000ms, but this change only caps the GLOBAL POLL_INTERVAL. detection_time/restoration_time still scale with multiply and can exceed 1000ms (and even 3000ms on large systems). If the intent is truly to cap detection/restoration times, apply the same cap there; otherwise update the PR title/description (and related comments/tests) to reflect that only the polling interval is capped.

        pfc_wd_poll_interval_time = DEFAULT_POLL_INTERVAL * multiply
        if pfc_wd_poll_interval_time > MAX_POLL_INTERVAL_TIME:
            pfc_wd_poll_interval_time = MAX_POLL_INTERVAL_TIME

        pfcwd_info = {
            'detection_time': DEFAULT_DETECTION_TIME * multiply,
            'restoration_time': DEFAULT_RESTORATION_TIME * multiply,
            'action': DEFAULT_ACTION,