Add support for dynamic DNS resolution in host addresses

config-sample.py

@@ -60,6 +60,23 @@ unnamed   = Host(ipv4='127.0.0.1', ipv6='::1')
 v6only    = Host(ipv6='2001:0DB8::beef')
 
 
+# Dynamic DNS resolution for the hosts (discouraged but for truly dynamic DNS)
+from picomon.dyndns import DynDNS4, DynDNS6
+
+dynamic   = Host(ipv4=DynDNS4('example.com'), ipv6=DynDNS6('example.com'),
+                 name='example.com')
+
+# Shorthands for dynamic hosts
+from picomon.dyndns import DynHost, DynHost4, DynHost6
+
+dynamic2  = DynHost(dns='example.com')
+dynamic3  = DynHost('example.com')
+dynv4only = DynHost4(dns='example.com')
+dynv6only = DynHost6(dns='example.com')
+
+partdyn   = DynHost(dns='example.com', ipv6='::1')
+
+
 # Checks
 ########
 

picomon/checks.py

@@ -110,7 +110,7 @@ class Check(object):
                             lambda s: "'" + s.replace("'", "'\"'\"'") + "'",
                             command))
         try:
-            p = Popen(command, stdout=PIPE, stderr=PIPE)
+            p = Popen(map(str, command), stdout=PIPE, stderr=PIPE)
         except OSError as e:
             self.errmsg = 'Check not available: ' + e.strerror
             return False

picomon/dyndns.py

+import socket
+from .checks import Host
+
+
+class DynDNS(object):
+    """
+    mimicks a str() but resolves a host to an IP
+
+    >>> x=DynDNS('localhost')
+    >>> print(x)
+    127.0.0.1
+    >>> print(x.replace('.', ' '))
+    127 0 0 1
+    >>> x == 'localhost'
+    True
+    >>> x == '127.0.0.1'
+    True
+    """
+
+    def __init__(self, host, family=0):
+        self._host = host
+        self._family = family
+
+    def __str__(self):
+        """ pick up the first matching address """
+        return socket.getaddrinfo(self._host, None, self._family)[0][4][0]
+
+    def __repr__(self):
+        return str(self)
+
+    def __eq__(self, other):
+        """ consider equality if host or string representation match """
+        if isinstance(other, type(self)) and self._host == other._host:
+            return True
+
+        other_str = str(other)
+        return self._host == other_str or str(self) == other_str
+
+    def __getattr__(self, attr):
+        return getattr(str(self), attr)
+
+
+class DynDNS4(DynDNS):
+    def __init__(self, host):
+        DynDNS.__init__(self, host, socket.AF_INET)
+
+
+class DynDNS6(DynDNS):
+    def __init__(self, host):
+        DynDNS.__init__(self, host, socket.AF_INET6)
+
+
+class DynHost(Host):
+    def __init__(self, dns, ipv4=None, ipv6=None, name=None):
+        Host.__init__(self, ipv4=ipv4 or DynDNS4(dns),
+                      ipv6=ipv6 or DynDNS6(dns), name=name or dns)
+
+
+class DynHost4(Host):
+    def __init__(self, dns, name=None):
+        Host.__init__(self, ipv4=DynDNS4(dns), name=name or dns)
+
+
+class DynHost6(Host):
+    def __init__(self, dns):
+        Host.__init__(self, ipv6=DynDNS6(dns), name=name or dns)