support syslog as a logging method

README.md

@@ -31,12 +31,17 @@ Imagine you want to take down the server `web01` for maintenance. Just SSH to it
 ### Configuration
 
 `hacheck` accepts a `-c` flag which should point to a YAML-formatted configuration file. Some notable properties of this file:
-* `cache_time`: The duration for which check results may be cached
-* `service_name_header`: If set, the name of a header which will be populated with the service name on HTTP checks
-* `log_path`: Either the string `"stdout"`, the string `"stderr"`, or a fully-qualified path to a file to write logs to. Uses a [WatchedFileHandler](http://docs.python.org/2/library/logging.handlers.html#watchedfilehandler) and ought to play nicely with logrotate
-* `mysql_username`: username to use when logging into mysql for checks
-* `mysql_password`: password to use when logging into mysql for checks
-* `rlimit_nofile`: set the NOFILE rlimit. If the string "max", will set the rlimit to the hard rlimit; otherwise, will be interpreted as an integer and set to that value.
+
+  * `cache_time`: The duration for which check results may be cached
+  * `service_name_header`: If set, the name of a header which will be populated with the service name on HTTP checks
+  * `log_path`: Either the string `"stdout"`, the string `"stderr"`, the string "syslog", or a fully-qualified path to a file to write logs to.
+    * If passed `syslog`, will write datagram messages to `/dev/log`. Can be passed `syslog,address,socktype` to write to other kinds of syslog. For example, `syslog,127.0.0.1:514,dgram` will write UDP to localhost:514; `syslog,/dev/log_stream,stream` will write stream (TCP) to `/dev/log`
+    * Files use a [WatchedFileHandler](http://docs.python.org/2/library/logging.handlers.html#watchedfilehandler) and ought to play nicely with logrotate
+  * `mysql_username`: username to use when logging into mysql for checks
+  * `mysql_password`: password to use when logging into mysql for checks
+  * `rlimit_nofile`: set the NOFILE rlimit. If the string "max", will set the rlimit to the hard rlimit; otherwise, will be interpreted as an integer and set to that value.
+
+The values in this configuration may contain shell variables, written as ${VARNAME}. These will be expanded at runtime.
 
 ### Monitoring
 

hacheck/config.py

@@ -1,4 +1,8 @@
 import yaml
+import os
+import re
+
+import six
 
 
 def max_or_int(some_str_value):
@@ -23,11 +27,25 @@ def max_or_int(some_str_value):
     config[key] = default
 
 
+def expand_shell_variables(key, value):
+    if not isinstance(value, six.string_types):
+        return value
+
+    def get_env(vmd):
+        variable = vmd.group(1)
+        if variable in os.environ:
+            return os.environ[variable]
+        else:
+            raise KeyError('${0} not in environment (from config {1}={2})'.format(variable, key, value))
+
+    return re.sub(r'\$\{([^}]+)\}', get_env, value)
+
+
 def load_from(path):
     with open(path, 'r') as f:
         c = yaml.safe_load(f)
         for key, value in c.items():
             if key in DEFAULTS:
                 constructor, default = DEFAULTS[key]
-                config[key] = constructor(value)
+                config[key] = constructor(expand_shell_variables(key, value))
     return config

hacheck/main.py

@@ -3,6 +3,7 @@
 import signal
 import time
 import sys
+import socket
 import resource
 
 import tornado.ioloop
@@ -42,7 +43,7 @@ def get_app():
         (r'/recent', handlers.ListRecentHandler),
         (r'/status/count', handlers.ServiceCountHandler),
         (r'/status', handlers.StatusHandler),
-   ], start_time=time.time(), log_function=log_request)
+    ], start_time=time.time(), log_function=log_request)
 
 
 def setrlimit_nofile(soft_target):
@@ -105,6 +106,34 @@ def main():
         handler = logging.StreamHandler(sys.stdout)
     elif log_path == 'stderr':
         handler = logging.StreamHandler(sys.stderr)
+    elif log_path.startswith('syslog'):
+        socktype = socket.SOCK_DGRAM
+        if log_path == 'syslog':
+            address = '/dev/log'
+        else:
+            syslog_address_parts = log_path.split(',')
+            if len(syslog_address_parts) == 3:
+                _, syslog_address, socktype = syslog_address_parts
+                socktypes = {
+                    'stream': socket.SOCK_STREAM,
+                    'dgram': socket.SOCK_DGRAM
+                }
+                if socktype not in socktypes:
+                    raise ValueError('Unrecognized socket type {0}'.format(socktype))
+                socktype = socktypes[socktype]
+            elif len(syslog_address_parts) == 2:
+                _, syslog_address = syslog_address_parts
+            else:
+                raise ValueError('Unrecognized syslog address format {0}'.format(log_path))
+            if ':' in syslog_address:
+                host, port = syslog_address.split(':')
+                port = int(port)
+                address = (host, port)
+            else:
+                address = syslog_address
+        handler = logging.handlers.SysLogHandler(
+            address, facility=logging.handlers.SysLogHandler.LOG_DAEMON, socktype=socktype
+        )
     else:
         handler = logging.handlers.WatchedFileHandler(log_path)
     fmt = logging.Formatter(logging.BASIC_FORMAT, None)