Issue 1415 (#1416)

* Don't rely on localhost being resolvable.  #1415

* Fixups.  #1415

pscheduler-server/pscheduler-server/api-server/pschedulerapiserver/admin.py

@@ -22,8 +22,8 @@
 
 @application.route("/", methods=['GET'])
 def root():
-    return ok_json("This is the pScheduler API server on %s (%s)."
-                   % (server_hostname(), pscheduler.api_local_host_name()),
+    return ok_json('This is the pScheduler API server'
+                   f' on {server_hostname()} ({socket.gethostname()})',
                    sanitize=False)
 
 

python-pscheduler/pscheduler/pscheduler/api.py

@@ -4,7 +4,10 @@
 
 import multiprocessing
 import multiprocessing.dummy
+import netaddr
+import netifaces
 import os
+import re
 import socket
 import threading
 import urllib
@@ -23,9 +26,53 @@ def api_local_host():
     "Return a hostname and, optionally, a port that should point to the server on this host."
     return os.environ.get("PSCHEDULER_LOCALHOST", api_local_host_name())
 
+
 def api_local_host_name():
-    "Return the local system's hostname"
-    return socket.gethostname()
+    """
+    Return a host name or IP suitable for reaching the local system
+    """
+
+    # Try the system's hostname.  This shoud cover most cases.
+
+    hostname = socket.gethostname()
+    try:
+        socket.gethostbyname(hostname)
+        # Local host name resolves.  Use that.
+        return hostname
+    except socket.gaierror:
+        # Local host name didn't resolve.  Do what's next.
+        pass
+
+    # Enumerate the interface addresses on the system and pick the
+    # first one, preferring loopbacks and IPv6.  This is based loosely
+    # on the code in pScheduler's LocalIPList class and is duplicated
+    # here so it can be used elsewhere without the rest of the
+    # pScehduler library.
+
+    if_regex = r'%.*$'
+
+    addresses = []
+
+    # Netifaces returns a very deep structure.
+    for ifhash in [ netifaces.ifaddresses(iface)
+                    for iface in netifaces.interfaces() ]:
+        for afamily in ifhash:
+            for iface in ifhash[afamily]:
+                address = re.sub(if_regex, '', iface["addr"])
+                try:
+                    addresses.append(netaddr.IPAddress(address))
+                except netaddr.core.AddrFormatError:
+                    # Don't care about things that don't look like IPS.
+                    pass
+
+    addresses = sorted(addresses,
+                       key=lambda v: [v.is_loopback(), v.version, v.sort_key()],
+                       reverse=True)
+    try:
+        return str(addresses[0])
+    except IndexError:
+        raise RuntimeError('No interfaces found on this system')
+
 
 def __host_per_rfc_2732(host):
     "Format a host name or IP for a URL according to RFC 2732"

python-pscheduler/pscheduler/tests/api_test.py

@@ -3,6 +3,7 @@
 test for the api module.
 """
 
+import socket
 import unittest
 
 from pscheduler.api import *
@@ -15,6 +16,15 @@ class TestApi(PschedTestBase):
     Api tests.
     """
 
+
+    def test_local_host(self):
+        self.assertTrue(api_local_host_name() in [
+            socket.gethostname(),
+            '::1',
+            '127.0.0.1'
+            ])
+
+
     def test_api(self):
         """taken from api.__main__"""