Add MemoryStatsCfg class to manage memory statistics configuration

Signed-off-by: Arham-Nasir <arqamnasir719@gmail.com>

scripts/hostcfgd

@@ -1694,64 +1694,68 @@ class FipsCfg(object):
         syslog.syslog(syslog.LOG_INFO, f'FipsCfg: update the FIPS enforce option {self.enforce}.')
         loader.set_fips(image, self.enforce)
 
-class Memory_StatisticsCfg(object):
-    def __init__(self, CfgDb):
-        self.config_db = CfgDb
-        self.memory_statistics_defaults= {
-            "enabled": "false",
-            "retention_time": "15",
-            "sampling_interval": "5"
-        }
+class MemoryStatsCfg(object):
+    """
+    Memory Stats Config Daemon
+    Handles changes in MEMORY_STATS table.
+    1) Handle enabling or disabling the feature
+    2) Handle change of retention period
+    3) Handle change of sampling interval
+    """
+    def __init__(self):
+        self.cache = {}
 
-    def load(self, memory_statistics_table):
-        """
-        Set the MEMORY_STATISTICS table in CFG DB to memory_statistics_defaults if not set by the user
+    def load(self, memory_stats_config: dict):
+        """Memory stats configuration
+        Force load memory statistics configuration.
+        Args:
+            memory_stats_config: Configured memory statistics settings.
         """
-        syslog.syslog(syslog.LOG_INFO, "Memory_StatisticsCfg init ...")
-        memory_statistics_conf = memory_statistics_table.get("config", {})
-        for row in self.memory_statistics_defaults:
-            value = self.memory_statistics_defaults.get(row)
-            if not memory_statistics_conf.get(row):
-                self.config_db.mod_entry("MEMORY_STATISTICS", "config", {row: value})
-
-    def memory_statistics_update(self, key, data):
-        syslog.syslog(syslog.LOG_INFO, "Memory_Statistics global configuration update")
-        if key == "config":
-            # Admin mode
-            memory_statistics_enabled = self.memory_statistics_defaults["enabled"]
-            if data.get("enabled") is not None:
-                memory_statistics_enabled = data.get("enabled")
-            if memory_statistics_enabled.lower() == "true":
-                enabled = True
-            else:
-                enabled = False
-            if enabled:
-                run_cmd(["sonic-memory_statistics-conifg", "--enable"])
-            else:
-                run_cmd(["sonic-memory_statistics-config", "--disable"])
-
-            # Memory configuration
-            retention_time = self.memory_statistics_defaults["retention_time"]
-            if data.get("retention_time") is not None:
-                retention_time = data.get("retention_time")
-            run_cmd(["sonic-memory_statistics-config", "--retention_time", retention_time])
-
-            # Sampling interval
-            sampling_interval = self.memory_statistics_defaults["sampling_interval"]
-            if data.get("sampling_interval") is not None:
-                sampling_interval = data.get("sampling_interval")
-            run_cmd(["sonic-memory_statistics-config", "--sampling_interval", sampling_interval])
-
-    def run_cmd(cmd):
+        syslog.syslog(syslog.LOG_INFO, 'MemoryStatsCfg: load initial')
+
+        if not memory_stats_config:
+            memory_stats_config = {}
+
+        # Force load memory statistics settings.
+        enable_data = memory_stats_config.get("enable", {})
+        retention_data = memory_stats_config.get("retention", {})
+        sampling_data = memory_stats_config.get("sampling", {})
+
+        self.memory_stats_message("enable", enable_data)
+        self.memory_stats_message("retention", retention_data)
+        self.memory_stats_message("sampling", sampling_data)
+
+    def memory_stats_message(self, key, data):
         """
-        Execute a shell command and return the output
+        Apply memory stats settings handler.
+        Args:
+            key: DB table's key that was triggered change.
+            data: Read table data.
         """
-        import subprocess
+        if type(data) != dict:
+            # Nothing to handle
+            return
+
+        update_required = False
+        # Check with cache
+        for k, v in data.items():
+            if v != self.cache.get(k):
+                update_required = True
+                break
+
+        if not update_required:
+            return
+
         try:
-            output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
-            syslog.syslog(syslog.LOG_INFO, output.decode('utf-8'))
-        except subprocess.CalledProcessError as e:
-            syslog.syslog(syslog.LOG_ERR, e.output.decode('utf-8'))
+            # Signal the memory stats daemon to reload configuration
+            run_cmd(["systemctl", "reload", "memory-stats-daemon"], True, True)
+        except Exception:
+            syslog.syslog(syslog.LOG_ERR, 'MemoryStatsCfg: Failed to reload memory-stats-daemon')
+            return
+
+        # Update cache
+        for k, v in data.items():
+            self.cache[k] = v
 
 class HostConfigDaemon:
     def __init__(self):