make startup faster in case of errors

When the io of one SECoP module fails, it takes ages to startup
because each parameter poll takes the time to wait for a timeout.
After the first communication error on an io, no more startup polls
are tried on the modules using this io.

Change-Id: I0d250953dfe91a7d68d2d2b108395cc25d471afe
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/28588
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/io.py

@@ -71,14 +71,6 @@ class HasIO(Module):
         elif not io:
             raise ConfigError("Module %s needs a value for either 'uri' or 'io'" % name)
 
-    def initModule(self):
-        try:
-            self.io.read_is_connected()
-        except (CommunicationFailedError, AttributeError):
-            # AttributeError: read_is_connected is not required for an io object
-            pass
-        super().initModule()
-
     def communicate(self, *args):
         return self.io.communicate(*args)
 
@@ -118,6 +110,7 @@ class IOBase(Communicator):
     _conn = None
     _last_error = None
     _lock = None
+    _last_connect_attempt = 0
 
     def earlyInit(self):
         super().earlyInit()
@@ -169,6 +162,17 @@ class IOBase(Communicator):
             return False
         return self.read_is_connected()
 
+    def check_connection(self):
+        """called before communicate"""
+        if not self.is_connected:
+            now = time.time()
+            if now >= self._last_connect_attempt + self.pollinterval:
+                # we do not try to reconnect more often than pollinterval
+                _last_connect_attempt = now
+                if self.read_is_connected():
+                    return
+            raise SilentError('disconnected') from None
+
     def registerReconnectCallback(self, name, func):
         """register reconnect callback
 
@@ -250,11 +254,7 @@ class StringIO(IOBase):
         wait_before is respected for end_of_lines within a command.
         """
         command = command.encode(self.encoding)
-        if not self.is_connected:
-            # do not try to reconnect here
-            # read_is_connected is doing this when called by its poller
-            self.read_is_connected()  # try to reconnect
-            raise SilentError('disconnected') from None
+        self.check_connection()
         try:
             with self._lock:
                 # read garbage and wait before send
@@ -359,11 +359,7 @@ class BytesIO(IOBase):
     @Command((BLOBType(), IntRange(0)), result=BLOBType())
     def communicate(self, request, replylen):  # pylint: disable=arguments-differ
         """send a request and receive (at least) <replylen> bytes as reply"""
-        if not self.is_connected:
-            # do not try to reconnect here
-            # read_is_connected is doing this when called by its poller
-            self.read_is_connected()  # try to reconnect
-            raise SilentError('disconnected') from None
+        self.check_connection()
         try:
             with self._lock:
                 # read garbage and wait before send

secop/modules.py

@@ -30,7 +30,7 @@ from functools import wraps
 
 from secop.datatypes import ArrayOf, BoolType, EnumType, FloatRange, \
     IntRange, StatusType, StringType, TextType, TupleOf, DiscouragedConversion
-from secop.errors import BadValueError, ConfigError, \
+from secop.errors import BadValueError, CommunicationFailedError, ConfigError, \
     ProgrammingError, SECoPError, secop_error
 from secop.lib import formatException, mkthread, UniqueObject, generalConfig
 from secop.lib.enum import Enum
@@ -620,7 +620,7 @@ class Module(HasAccessibles):
             self.pollInfo.interval = fast_interval if flag else self.pollinterval
             self.pollInfo.trigger()
 
-    def callPollFunc(self, rfunc):
+    def callPollFunc(self, rfunc, raise_com_failed=False):
         """call read method with proper error handling"""
         try:
             rfunc()
@@ -637,6 +637,8 @@ class Module(HasAccessibles):
                 else:
                     # uncatched error: this is more serious
                     self.log.error('%s: %s', name, formatException())
+            if raise_com_failed and isinstance(e, CommunicationFailedError):
+                raise
 
     def __pollThread(self, modules, started_callback):
         """poll thread body
@@ -661,7 +663,7 @@ class Module(HasAccessibles):
                 trg.set()
             self.registerReconnectCallback('trigger_polls', trigger_all)
 
-        # collect and call all read functions a first time
+        # collect all read functions
         for mobj in modules:
             pinfo = mobj.pollInfo = PollInfo(mobj.pollinterval, self.triggerPoll)
             # trigger a poll interval change when self.pollinterval changes.
@@ -672,7 +674,16 @@ class Module(HasAccessibles):
                 rfunc = getattr(mobj, 'read_' + pname)
                 if rfunc.poll:
                     pinfo.polled_parameters.append((mobj, rfunc, pobj))
-                    mobj.callPollFunc(rfunc)
+        # call all read functions a first time
+        try:
+            for m in modules:
+                for mobj, rfunc, _ in m.pollInfo.polled_parameters:
+                    mobj.callPollFunc(rfunc, raise_com_failed=True)
+        except CommunicationFailedError as e:
+            # when communication failed, probably all parameters and may be more modules are affected.
+            # as this would take a lot of time (summed up timeouts), we do not continue
+            # trying and let the server accept connections, further polls might success later
+            self.log.error('communication failure on startup: %s', e)
         started_callback()
         to_poll = ()
         while True: