[Mellanox] Check system eeprom existence in a retry manner (sonic-net#13884)

- Why I did it
On Mellanox platform, system EEPROM is a soft link provided by hw-management. There is chance that config-setup service accessing the EEPROM before hw-management creating it. It causes errors. The PR is aim to fix it.

- How I did it
Waiting EEPROM creation in platform API up to 10 seconds.

- How to verify it
Manual test

Author: Junchao-Mellanox

platform/mellanox/mlnx-platform-api/sonic_platform/eeprom.py

@@ -31,13 +31,13 @@
     raise ImportError (str(e) + "- required module not found")
 
 from .device_data import DeviceDataManager
-from .utils import default_return, is_host
+from .utils import default_return, is_host, wait_until
 
 logger = Logger()
 
 #
 # this is mlnx-specific
-# should this be moved to chass.py or here, which better?
+# should this be moved to chassis.py or here, which better?
 #
 EEPROM_SYMLINK = "/var/run/hw-management/eeprom/vpd_info"
 platform_name = DeviceDataManager.get_platform_name()
@@ -51,10 +51,12 @@
             os.makedirs(os.path.dirname(EEPROM_SYMLINK))
         subprocess.check_call(['/usr/bin/xxd', '-r', '-p', 'syseeprom.hex', EEPROM_SYMLINK], cwd=platform_path)
 
+WAIT_EEPROM_READY_SEC = 10
+
 
 class Eeprom(eeprom_tlvinfo.TlvInfoDecoder):
     def __init__(self):
-        if not os.path.exists(EEPROM_SYMLINK):
+        if not wait_until(predict=os.path.exists, timeout=WAIT_EEPROM_READY_SEC, path=EEPROM_SYMLINK):
             logger.log_error("Nowhere to read syseeprom from! No symlink found")
             raise RuntimeError("No syseeprom symlink found")
 

platform/mellanox/mlnx-platform-api/sonic_platform/utils.py

@@ -19,6 +19,7 @@
 import subprocess
 import json
 import sys
+import time
 import os
 from sonic_py_common import device_info
 from sonic_py_common.logger import Logger
@@ -266,3 +267,21 @@ def extract_RJ45_ports_index():
 
     return RJ45_port_index_list if bool(RJ45_port_index_list) else None
 
+
+def wait_until(predict, timeout, interval=1, *args, **kwargs):
+    """Wait until a condition become true
+
+    Args:
+        predict (object): a callable such as function, lambda
+        timeout (int): wait time in seconds
+        interval (int, optional): interval to check the predict. Defaults to 1.
+
+    Returns:
+        _type_: _description_
+    """
+    while timeout > 0:
+        if predict(*args, **kwargs):
+            return True
+        time.sleep(interval)
+        timeout -= interval
+    return False

platform/mellanox/mlnx-platform-api/tests/test_eeprom.py

@@ -49,6 +49,7 @@ def test_chassis_eeprom(self, mock_eeprom_info):
         assert chassis.get_serial() == 'MT2019X13878'
         assert chassis.get_system_eeprom_info() == mock_eeprom_info.return_value
 
+    @patch('sonic_platform.eeprom.wait_until', MagicMock(return_value=False))
     def test_eeprom_init(self):
         # Test symlink not exist, there is an exception
         with pytest.raises(RuntimeError):
@@ -83,7 +84,7 @@ def side_effect(key, field):
 
     @patch('os.path.exists', MagicMock(return_value=True))
     @patch('os.path.islink', MagicMock(return_value=True))
-    def test_get_system_eeprom_info_from_hardware(self):        
+    def test_get_system_eeprom_info_from_hardware(self):    
         eeprom = Eeprom()
         eeprom.p = os.path.join(test_path, 'mock_eeprom_data')
         eeprom._redis_hget = MagicMock()

platform/mellanox/mlnx-platform-api/tests/test_utils.py

@@ -18,6 +18,8 @@
 import os
 import pytest
 import sys
+import threading
+import time
 if sys.version_info.major == 3:
     from unittest import mock
 else:
@@ -125,3 +127,17 @@ def test_run_command(self):
     def test_extract_RJ45_ports_index(self):
         rj45_list = utils.extract_RJ45_ports_index()
         assert rj45_list is None
+
+    def test_wait_until(self):
+        values = []
+        assert utils.wait_until(lambda: len(values) == 0, timeout=1)
+        assert not utils.wait_until(lambda: len(values) > 0, timeout=1)
+
+        def thread_func(items):
+            time.sleep(3)
+            items.append(0)
+
+        t = threading.Thread(target=thread_func, args=(values, ))
+        t.start()
+        assert utils.wait_until(lambda: len(values) > 0, timeout=5)
+        t.join()