Bugfix: Stop the integration and error out when web server port is already...

Author: diningPhilosopher64

jupyter_matlab_proxy/app.py

@@ -407,6 +407,8 @@ def main():
 
     logger = mwi_logger.get(init=True)
 
+    app = create_app()
+
     logger.info("Starting MATLAB proxy-app")
     logger.info(
         f" with base_url: {os.environ[mwi_env.get_env_name_base_url()]} and "
@@ -417,8 +419,6 @@ def main():
             f"\n The webdesktop can be accessed on http://localhost:{os.environ[mwi_env.get_env_name_app_port()]}{os.environ[mwi_env.get_env_name_base_url()]}/index.html"
         )
 
-    app = create_app()
-
     loop = asyncio.get_event_loop()
 
     # Override default loggers

jupyter_matlab_proxy/settings.py

@@ -120,7 +120,9 @@ def get(dev=False):
             ],
             "create_xvfb_cmd": create_xvfb_cmd,
             "base_url": os.environ[mwi_env.get_env_name_base_url()],
-            "app_port": os.environ[mwi_env.get_env_name_app_port()],
+            "app_port": mwi_validators.validate_app_port_is_free(
+                os.environ[mwi_env.get_env_name_app_port()]
+            ),
             "host_interface": os.environ.get(mwi_env.get_env_name_app_host()),
             "mwapikey": str(uuid.uuid4()),
             "matlab_protocol": "https",

jupyter_matlab_proxy/util/mwi_validators.py

@@ -10,6 +10,11 @@
 
 Exceptions are thrown to signal failure.
 """
+from . import mwi_logger
+from jupyter_matlab_proxy import mwi_environment_variables as mwi_env
+import sys
+
+logger = mwi_logger.get()
 
 
 def validate_mlm_license_file(nlm_conn_str):
@@ -20,11 +25,8 @@ def validate_mlm_license_file(nlm_conn_str):
     """
     import re
     import os
-    from . import mwi_logger
     from .mwi_exceptions import NetworkLicensingError
 
-    logger = mwi_logger.get()
-
     if nlm_conn_str is None:
         return None
 
@@ -59,3 +61,34 @@ def validate_mlm_license_file(nlm_conn_str):
 
     # Validation passed
     return nlm_conn_str
+
+
+def validate_app_port_is_free(port):
+    """Validates and returns port if its free else will error out and exit.
+
+    Args:
+        port (str|int): Port number either as a string or an integer.
+
+    Raises:
+        e: socket.error
+
+    Returns:
+        Boolean: True if provided port is occupied else False.
+    """
+    import socket, errno
+
+    try:
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.bind(("", int(port)))
+        s.close()
+
+        # Was able to allocate port. Validation passed.
+        return port
+    except socket.error as e:
+        if e.errno == errno.EADDRINUSE:
+            logger.error(
+                f"The port {port} is not available. Please set another value for the environment variable {mwi_env.get_env_name_app_port()}"
+            )
+            sys.exit(1)
+        else:
+            raise e

tests/util/test_mwi_validators.py

@@ -2,7 +2,7 @@
 """Tests for functions in jupyter_matlab_proxy/util/mwi_validators.py
 """
 
-import pytest, os, tempfile
+import pytest, os, tempfile, socket
 from jupyter_matlab_proxy.util import mwi_validators
 from jupyter_matlab_proxy import mwi_environment_variables as mwi_env
 from jupyter_matlab_proxy.util.mwi_exceptions import NetworkLicensingError
@@ -50,3 +50,23 @@ def test_get_with_environment_variables(monkeypatch):
         assert conn_str == str(path)
     finally:
         os.remove(path)
+
+
+def test_validate_app_port_is_free_false():
+    """Test to validate if supplied app port is free"""
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.bind(("", 0))
+    port = s.getsockname()[1]
+    with pytest.raises(SystemExit) as e:
+        mwi_validators.validate_app_port_is_free(port)
+    assert e.value.code == 1
+    s.close()
+
+
+def test_validate_app_port_is_free_true():
+    """Test to validate if supplied app port is free"""
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    s.bind(("", 0))
+    port = s.getsockname()[1]
+    s.close()
+    assert mwi_validators.validate_app_port_is_free(port) == port