Merge pull request #4 from micw/resolve-host-if-address-not-set

Resolve host if address not set

core/base/libs/socrate/socrate/system.py

@@ -1,5 +1,6 @@
 import socket
 import tenacity
+from os import environ
 
 
 @tenacity.retry(stop=tenacity.stop_after_attempt(100),
@@ -18,3 +19,14 @@ def resolve_address(address):
     hostname, *rest = address.rsplit(":", 1)
     ip_address = resolve_hostname(hostname)
     return ip_address + "".join(":" + port for port in rest)
+
+
+def get_host_address_from_environment(name, default):
+    """ This function looks up an envionment variable ``{{ name }}_ADDRESS``.
+    If it's defined, it is returned unmodified. If it's undefined, an environment
+    variable ``HOST_{{ name }}`` is looked up and resolved to an ip address.
+    If this is also not defined, the default is resolved to an ip address.
+    """
+    if "{}_ADDRESS".format(name) in environ:
+        return environ.get("{}_ADDRESS".format(name))
+    return resolve_address(environ.get("HOST_{}".format(name), default))

core/base/libs/socrate/test.py

@@ -1,5 +1,6 @@
 import unittest
 import io
+import os
 
 from socrate import conf, system
 
@@ -78,3 +79,30 @@ class TestSystem(unittest.TestCase):
             system.resolve_address("1.2.3.4.xip.io:80"),
             "1.2.3.4:80"
         )
+
+    def test_get_host_address_from_environment(self):
+        if "TEST_ADDRESS" in os.environ:
+            del os.environ["TEST_ADDRESS"]
+        if "HOST_TEST" in os.environ:
+            del os.environ["HOST_TEST"]
+        # if nothing is set, the default must be resolved
+        self.assertEqual(
+            system.get_host_address_from_environment("TEST", "1.2.3.4.xip.io:80"),
+            "1.2.3.4:80"
+        )
+        # if HOST is set, the HOST must be resolved
+        os.environ['HOST_TEST']="1.2.3.5.xip.io:80"
+        self.assertEqual(
+            system.get_host_address_from_environment("TEST", "1.2.3.4.xip.io:80"),
+            "1.2.3.5:80"
+        )
+        # if ADDRESS is set, the ADDRESS must be returned unresolved
+        os.environ['TEST_ADDRESS']="1.2.3.6.xip.io:80"
+        self.assertEqual(
+            system.get_host_address_from_environment("TEST", "1.2.3.4.xip.io:80"),
+            "1.2.3.6.xip.io:80"
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()