[chassis][voq] Add test_voq_fabric_capacity.py (#15994)

Summary: Add test_voq_fabric_capacity.py to test fabric capacity monitoring and related CLI.

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -2355,6 +2355,12 @@ voq/test_fabric_reach.py:
       - "not any(i in platform for i in ['arista_7800', 'x86_64-nokia_ixr7250e'])"
       - "(asic_type in ['cisco-8000'])"
 
+voq/test_voq_fabric_capacity.py:
+  skip:
+    reason: "Skip test_voq_fabric_capacity on unsupported testbed."
+    conditions:
+      - "('t2' not in topo_name) or (asic_subtype not in ['broadcom-dnx']) or (asic_type in ['cisco-8000'])"
+
 voq/test_voq_fabric_isolation.py:
   skip:
     reason: "Skip test_voq_fabric_isolation on unsupported testbed."

tests/voq/test_voq_fabric_capacity.py

@@ -0,0 +1,138 @@
+import logging
+import pytest
+import random
+from tests.common.helpers.assertions import pytest_assert
+from tests.common.utilities import wait_until
+
+logger = logging.getLogger(__name__)
+
+# This test only runs on t2 systems.
+pytestmark = [
+    pytest.mark.topology('t2')
+]
+
+# This test checks the output of the "show fabric monitor capacity" command
+# on a linecard. It is designed to run on a modular chassis.
+
+
+def test_fabric_capacity(duthosts, enum_frontend_dut_hostname):
+    """Checks if the fabric capacity monitor works"""
+
+    # get a start state from system
+    # by running "show fabric monitor capcity" command
+    duthost = duthosts[enum_frontend_dut_hostname]
+    asic = 0
+    if duthost.is_multi_asic:
+        asic = random.randint(0, duthost.num_asics())
+    asicName = "asic{}".format(asic)
+    logger.info(asicName)
+
+    if duthost.is_multi_asic:
+        cmd = "show fabric monitor capacity -n asic{}".format(asic)
+    else:
+        cmd = "show fabric monitor capacity"
+    # The output of this show command is:
+    # # show fabric monitor capacity
+    # Monitored fabric capacity threshold:  100%
+    #
+    #   ASIC    Operating     Total #    %    Last Event    Last Time
+    #               Links    of Links
+    # ------  -----------  ----------  ---  ------------  -----------
+    #  asic0          112         112  100          None        Never
+    cmd_output = duthost.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+    operating_links = 0
+    for line in cmd_output:
+        if not line:
+            continue
+        token = line.split()
+        if token[0].startswith("asic"):
+            operating_links = int(token[1])
+
+    # get list of up/unisolated links by running "show fabric isolation" with Isolated=0
+    # example output:
+    # # show fabric isolation -n asic0
+    #
+    # asic0
+    #   Local Link    Auto Isolated    Manual Isolated    Isolated
+    # ------------  ---------------  -----------------  ----------
+    #           20                0                  0           0
+    #           21                0                  0           0
+    up_link_list = []
+    if duthost.is_multi_asic:
+        cmd = "show fabric isolation -n asic{}".format(asic)
+    else:
+        cmd = "show fabric isolation"
+
+    cmd_output = duthost.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+    for line in cmd_output:
+        if not line:
+            continue
+        token = line.split()
+        if not token[0].isdigit():
+            continue
+        localPort = token[0]
+        isolateSt = token[3]
+        if isolateSt == "0":
+            up_link_list.append(localPort)
+
+    if len(up_link_list) > 0:
+        shutlink = random.choice(up_link_list)
+    else:
+        return
+
+    # Start the test. Isolate a link and check if the capacity command get updated.
+    # Unisolate the link and check if the capacity command get updated.
+    if duthost.is_multi_asic:
+        asicName = "asic{}".format(asic)
+    else:
+        asicName = ""
+    try:
+        # isolate a link on the chip
+        cmd = "sudo config fabric port isolate {} {}".format(shutlink, asicName)
+        cmd_output = duthost.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+
+        # check the output of "show fabric monitor capcity" command
+        exp_links = operating_links - 1
+        pytest_assert(wait_until(180, 30, 0, check_operational_link,
+                                 duthost, asic, exp_links),
+                      "The number of opertional links should be {}".format(exp_links))
+
+        # unisolate the link so the capacity is back
+        cmd = "sudo config fabric port unisolate {} {}".format(shutlink, asicName)
+        cmd_output = duthost.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+
+        # check the output of "show fabric monitor capcity" command
+        exp_links = operating_links
+        pytest_assert(wait_until(180, 30, 0, check_operational_link,
+                                 duthost, asic, exp_links),
+                      "The number of opertional links should be {}".format(exp_links))
+    finally:
+        # clean up the test
+        cmd = "sudo config fabric port unisolate {} {}".format(shutlink, asicName)
+        cmd_output = duthost.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+
+
+def check_operational_link(host, asic, op_links):
+    if host.is_multi_asic:
+        cmd = "show fabric monitor capacity -n asic{}".format(asic)
+    else:
+        cmd = "show fabric monitor capacity"
+    # Example output is:
+    # # show fabric monitor capacity
+    #
+    #   ASIC    Operating     Total #    %    Last Event    Last Time
+    #               Links    of Links
+    # ------  -----------  ----------  ---  ------------  -----------
+    #  asic0          112         112  100          None        Never
+    cmd_output = host.shell(cmd, module_ignore_errors=True)["stdout"].split("\n")
+    operating_links = 0
+    for line in cmd_output:
+        if not line:
+            continue
+        token = line.split()
+        if token[0].startswith("asic"):
+            operating_links = int(token[1])
+    if operating_links == op_links:
+        return True
+    else:
+        return False