core (xmpp): avoid starting several clients at the same time:

a check is done to avoid running startConnection several times at once, which would lead
to the creation of several SatXMPPEntity instances at the same time, resulting in many
issues.

If startConnection is called while a previous one is not finished yet, a CancelError is
now raised.

sat/core/xmpp.py

@@ -56,8 +56,10 @@ NS_ROSTER_VER = "urn:xmpp:features:rosterver"
 ROSTER_VER_KEY = "@version@"
 
 
-class SatXMPPEntity(object):
+class SatXMPPEntity:
     """Common code for Client and Component"""
+    # profile is added there when startConnection begins and removed when it is finished
+    profiles_connecting = set()
 
     def __init__(self, host_app, profile, max_retries):
         factory = self.factory
@@ -154,6 +156,9 @@ class SatXMPPEntity(object):
         #        (e.g. adding subprotocols)
         #        but client should not be deleted except if session is finished
         #        (independently of connection/deconnection)
+        if profile in cls.profiles_connecting:
+            raise exceptions.CancelError(f"{profile} is already being connected")
+        cls.profiles_connecting.add(profile)
         try:
             port = int(
                 host.memory.getParamA(
@@ -169,9 +174,6 @@ class SatXMPPEntity(object):
         password = yield host.memory.asyncGetParamA(
             "Password", "Connection", profile_key=profile
         )
-        if profile in host.profiles:
-            raise exceptions.InternalError(
-                f"There is already a profile of name {profile} in host")
 
         entity_jid_s = yield host.memory.asyncGetParamA(
             "JabberID", "Connection", profile_key=profile)
@@ -195,6 +197,9 @@ class SatXMPPEntity(object):
                 resource=resource))
             entity_jid.resource = resource
 
+        if profile in host.profiles:
+            raise exceptions.InternalError(
+                f"There is already a profile of name {profile} in host")
         entity = host.profiles[profile] = cls(
             host, profile, entity_jid, password,
             host.memory.getParamA(C.FORCE_SERVER_PARAM, "Connection",
@@ -249,6 +254,8 @@ class SatXMPPEntity(object):
         )  # FIXME: we should have a timeout here, and a way to know if a plugin freeze
         # TODO: mesure launch time of each plugin
 
+        cls.profiles_connecting.remove(profile)
+
     def _disconnectionCb(self, __):
         self._connected_d = None
 
@@ -784,7 +791,11 @@ class SatXMPPClient(SatXMPPEntity, wokkel_client.XMPPClient):
     @classmethod
     @defer.inlineCallbacks
     def startConnection(cls, host, profile, max_retries):
-        yield super(SatXMPPClient, cls).startConnection(host, profile, max_retries)
+        try:
+            yield super(SatXMPPClient, cls).startConnection(host, profile, max_retries)
+        except exceptions.CancelError as e:
+            log.warning(f"startConnection cancelled: {e}")
+            return
         entity = host.profiles[profile]
         # we finally send our presence
         entity.presence.available()