[OMCSession*] simplify code for timeout loops

Author: syntron

OMPython/OMCSession.py

@@ -727,17 +727,13 @@ def sendExpression(self, command: str, parsed: bool = True) -> Any:
 
         logger.debug("sendExpression(%r, parsed=%r)", command, parsed)
 
-        MAX_RETRIES = 50
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self.omc_process._timeout_loop(timestep=0.05)
+        while next(loop):
             try:
                 self.omc_zmq.send_string(str(command), flags=zmq.NOBLOCK)
                 break
             except zmq.error.Again:
                 pass
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.omc_process.get_log()}")
             raise OMCSessionException(f"No connection with OMC (timeout={self._timeout}).")
@@ -912,6 +908,31 @@ def __del__(self):
             finally:
                 self._omc_process = None
 
+    def _timeout_loop(
+            self,
+            timeout: Optional[float] = None,
+            timestep: float = 0.1,
+    ):
+        """
+        Helper (using yield) for while loops to check OMC startup / response. The loop is executed as long as True is
+        returned, i.e. the first False will stop the while loop.
+        """
+
+        if timeout is None:
+            timeout = self._timeout
+        if timeout <= 0:
+            raise OMCSessionException(f"Invalid timeout: {timeout}")
+
+        timer = 0
+        yield True
+        while True:
+            timer += timestep
+            if timer > timeout:
+                break
+            time.sleep(timestep)
+            yield True
+        yield False
+
     def get_port(self) -> Optional[str]:
         """
         Get the port to connect to the OMC process.
@@ -1033,11 +1054,8 @@ def _omc_port_get(self) -> str:
         port = None
 
         # See if the omc server is running
-        MAX_RETRIES = 80
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self._timeout_loop(timestep=0.1)
+        while next(loop):
             omc_portfile_path = self._get_portfile_path()
             if omc_portfile_path is not None and omc_portfile_path.is_file():
                 # Read the port file
@@ -1046,7 +1064,6 @@ def _omc_port_get(self) -> str:
                 break
             if port is not None:
                 break
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.get_log()}")
             raise OMCSessionException(f"OMC Server did not start (timeout={self._timeout}).")
@@ -1131,11 +1148,8 @@ def _docker_process_get(self, docker_cid: str) -> Optional[DockerPopen]:
             raise NotImplementedError("Docker not supported on win32!")
 
         docker_process = None
-        MAX_RETRIES = 40
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self._timeout_loop(timestep=0.2)
+        while next(loop):
             docker_top = subprocess.check_output(["docker", "top", docker_cid]).decode().strip()
             docker_process = None
             for line in docker_top.split("\n"):
@@ -1148,7 +1162,6 @@ def _docker_process_get(self, docker_cid: str) -> Optional[DockerPopen]:
                                                   "is this a docker instance spawned without --pid=host?") from ex
             if docker_process is not None:
                 break
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.get_log()}")
             raise OMCSessionException(f"Docker based OMC Server did not start (timeout={self._timeout}).")
@@ -1173,11 +1186,8 @@ def _omc_port_get(self) -> str:
             raise OMCSessionException(f"Invalid docker container ID: {self._docker_container_id}")
 
         # See if the omc server is running
-        MAX_RETRIES = 80
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self._timeout_loop(timestep=0.1)
+        while next(loop):
             omc_portfile_path = self._get_portfile_path()
             if omc_portfile_path is not None:
                 try:
@@ -1190,7 +1200,6 @@ def _omc_port_get(self) -> str:
                     pass
             if port is not None:
                 break
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.get_log()}")
             raise OMCSessionException(f"Docker based OMC Server did not start (timeout={self._timeout}).")
@@ -1361,19 +1370,15 @@ def _docker_omc_start(self) -> Tuple[subprocess.Popen, DockerPopen, str]:
             raise OMCSessionException(f"Invalid content for docker container ID file path: {docker_cid_file}")
 
         docker_cid = None
-        MAX_RETRIES = 40
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self._timeout_loop(timestep=0.1)
+        while next(loop):
             try:
                 with open(file=docker_cid_file, mode="r", encoding="utf-8") as fh:
                     docker_cid = fh.read().strip()
             except IOError:
                 pass
             if docker_cid is not None:
                 break
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.get_log()}")
             raise OMCSessionException(f"Docker did not start (timeout={self._timeout} might be too short "
@@ -1538,11 +1543,8 @@ def _omc_port_get(self) -> str:
         port = None
 
         # See if the omc server is running
-        MAX_RETRIES = 80
-        attempts = 0
-        while attempts < MAX_RETRIES:
-            attempts += 1
-
+        loop = self._timeout_loop(timestep=0.1)
+        while next(loop):
             try:
                 omc_portfile_path = self._get_portfile_path()
                 if omc_portfile_path is not None:
@@ -1555,7 +1557,6 @@ def _omc_port_get(self) -> str:
                 pass
             if port is not None:
                 break
-            time.sleep(self._timeout / MAX_RETRIES)
         else:
             logger.error(f"Docker did not start. Log-file says:\n{self.get_log()}")
             raise OMCSessionException(f"WSL based OMC Server did not start (timeout={self._timeout}).")