better session handeling

* improved session handeling

Due to the with statement in the session creation process, every requests to the api created a new session. This patch decreases the enormous TCP overhead, by creating a single global session to reuse.

ejabberdrpc.py

@@ -20,7 +20,10 @@ class EjabberdMetrics:
             self.url = url
             self._cmd = self._rpc
         else:
+            import requests
+
             self._url = url
+            self.session = requests.Session()
             self._cmd = self._rest
 
     @property
@@ -43,15 +46,19 @@ class EjabberdMetrics:
 
         return None
 
-    def _rest(self, command: str, data):
-        import requests
+    def _rest(self, command: str, data) -> dict:
+        # add authentication header to the session obj
+        if self.session.auth is None:
+            self.session.auth = self._auth
 
-        with requests.Session() as s:
-            r = s.post(f'{self._url}/{command}', auth=self._auth, json=data)
+        # post
+        r = self.session.post('/'.join([self._url, command]), json=data)
 
-            if r.status_code == 200:
-                return r.json()
-            return{}
+        # proceed if response is ok
+        if r.ok:
+            return r.json()
+
+        return {}
 
     def _rpc(self, command: str, data):
         from xmlrpc import client