Wait for process completion for sflow script

[weiguo-nvidia]

Description of PR

Summary: Wait for process completion for sflow script
Fixes #
Sflow reboot testcase pytest sflow/test_sflow.py::TestReboot might fail due to sflow packets are not received in active collector
When open the /tmp/collector0 and /tmp/collector1 files, we can see sflow packets recorded by sflow tool

{"datagramSourceIP":"20.1.1.1","datagramSize":"448","unixSecondsUTC":"1732083938","localtime":"2024-11-20T06:25:38+0000","datagramVersion":"5","agentSubId":"100000","agent":"20.1.1.1","packetSequenceNo":"8","sysUpTime":"50697","samplesInPacket":"3","samples":[{"sampleType_tag":"0:2","sampleType":"COUNTERSSAMPLE","sampleSequenceNo":"1","sourceId":"0:205","elements":[{"counterBlock_tag":"0:1005","ifName":"Ethernet204"},{"counterBlock_tag":"0:1","ifIndex":"205","networkType":"6","ifSpeed":"200000000000","ifDirection":"0","ifStatus":"0","ifInOctets":"0","ifInUcastPkts":"0","ifInMulticastPkts":"4294967295","ifInBroadcastPkts":"4294967295","ifInDiscards":"0","ifInErrors":"0","ifInUnknownProtos":"4294967295","ifOutOctets":"0","ifOutUcastPkts":"0","ifOutMulticastPkts":"4294967295","ifOutBroadcastPkts":"4294967295","ifOutDiscards":"0","ifOutErrors":"0","ifPromiscuousMode":"0"}]},{"sampleType_tag":"0:2","sampleType":"COUNTERSSAMPLE","sampleSequenceNo":"1","sourceId":"0:81","elements":[{"counterBlock_tag":"0:1005","ifName":"Ethernet80"},{"counterBlock_tag":"0:1","ifIndex":"81","networkType":"6","ifSpeed":"200000000000","ifDirection":"0","ifStatus":"3","ifInOctets":"0","ifInUcastPkts":"0","ifInMulticastPkts":"4294967295","ifInBroadcastPkts":"4294967295","ifInDiscards":"0","ifInErrors":"0","ifInUnknownProtos":"4294967295","ifOutOctets":"0","ifOutUcastPkts":"0","ifOutMulticastPkts":"4294967295","ifOutBroadcastPkts":"4294967295","ifOutDiscards":"0","ifOutErrors":"0","ifPromiscuousMode":"0"}]},{"sampleType_tag":"0:2","sampleType":"COUNTERSSAMPLE","sampleSequenceNo":"1","sourceId":"0:25","elements":[{"counterBlock_tag":"0:1005","ifName":"Ethernet24"},{"counterBlock_tag":"0:1","ifIndex":"25","networkType":"6","ifSpeed":"200000000000","ifDirection":"0","ifStatus":"3","ifInOctets":"0","ifInUcastPkts":"0","ifInMulticastPkts":"4294967295","ifInBroadcastPkts":"4294967295","ifInDiscards":"0","ifInErrors":"0","ifInUnknownProtos":"4294967295","ifOutOctets":"0","ifOutUcastPkts":"0","ifOutMulticastPkts":"4294967295","ifOutBroadcastPkts":"4294967295","ifOutDiscards":"0","ifOutErrors":"0","ifPromiscuousMode":"0"}]}]}

Run the ansible/roles/test/files/ptftests/py3/sflow_test.py, get info

collector0 Sampled Packets : Total flow samples -> 800 Total counter samples -> 47

While the test logged:

06:19:28.572  root      : INFO    : collector0 Sampled Packets : Total flow samples -> 0 Total counter samples -> 0

This is very likely due to incorrect process termination in the test:

        outfile = '/tmp/%s' % collector
        with open(outfile, 'w') as f:
            process = subprocess.Popen(['/usr/local/bin/sflowtool', '-j', '-p'] + sflow_port,
                                       stdout=f,
                                       stderr=subprocess.STDOUT,
                                       shell=False
                                       )

            ....

            # Wait for event to be set from Main Thread or to pass out by timeout
            event_is_set = event.wait(timeout=timeout)
            logging.info("{}; Event set: {}".format(
                threading.current_thread().getName(), event_is_set))

        process.terminate()
        f.close()
        with open(outfile, 'r') as sflow_data:
            ...

        logging.info("%s Sampled Packets : Total flow samples -> %s Total counter samples -> %s" %
                     (collector, flow_count, counter_count))
        return (port_sample)

The process.terminate() is sending SIGTERM to sflow but there is a missing process.wait() to wait for process to exit. So, likelly the file content was buffered and not fully written by the time we open the file for reading

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

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Supported testbed topology if it's a new test case?

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