Add apachelog.resolve.Resolver for reverse-DNS.

diff --git a/apachelog/resolve.py b/apachelog/resolve.py
new file mode 100644 (file)
index 0000000..db17f6b
--- /dev/null
+++ b/apachelog/resolve.py
@@ -0,0 +1,73 @@
+import re as _re
+import socket as _socket
+
+
+class Resolver (object):
+    """A simple reverse-DNS resolver.
+
+    Maintains a class-level cache of resolved IPs to avoid repeated
+    lookups on the same IP address.
+
+    >>> r = Resolver()
+    >>> r.resolve('198.41.0.4')
+    'a.root-servers.net'
+    >>> r.IP
+    {'198.41.0.4': ('a.root-servers.net', [], ['198.41.0.4'])}
+
+    If you want to give shorter names to various DNS names, you can
+    add an entry to the class-level ``REGEXPS``.  The entry should use
+    your name as the key, and a list of matching regexps as the value.
+    You need to enable this enhanced resolution using the ``smart``
+    argument.
+
+    >>> r.resolve('66.249.68.33')
+    'crawl-66-249-68-33.googlebot.com'
+    >>> r = Resolver(smart=True)
+    >>> r.resolve('66.249.68.34')
+    'googlebot'
+    """
+    IP = {}
+
+    REGEXPS = {
+        'feedburner': [_re.compile('.*rate-limited-proxy-.*.google.com.*')],
+        }
+    for bot in [
+        'googlebot',
+        'yandex',
+        'baiduspider',
+        'msnbot',
+        ]:
+        REGEXPS[bot] = [_re.compile('.*{}.*'.format(bot))]
+
+    def __init__(self, smart=False):
+        self._smart = smart
+
+    def resolve(self, ip):
+        if ip not in self.IP:
+            try:
+                self.IP[ip] = _socket.gethostbyaddr(ip)
+            except _socket.herror as e:
+                self.IP[ip] = (ip, [], [ip])
+            except _socket.gaierror as e:
+                self.IP[ip] = (ip, [], [ip])
+            else:
+                if self._smart:
+                    self._smart_resolve(ip)
+        return self.IP[ip][0]
+
+    def _smart_resolve(self, ip):
+        x = self.IP[ip]
+        if self._smart:
+            for name,regexps in self.REGEXPS.items():
+                for regexp in regexps:
+                    if regexp.match(self.IP[ip][0]):
+                        self.IP[ip] = (name, x[1], x[2])
+
+    def ips(self, name):
+        "Return a set of IP addresses used by a smart-resolved name."
+        ips = set()
+        for ip,values in self.IP.items():
+            if values[0] == name:
+                for x in values[2]:
+                    ips.add(x)
+        return ips