Add Heka log decoder for Keystone/Apache

Partially implements: blueprint heka
Change-Id: I562dddcfa75f3a814874f7735d735416d9aa7803

docker/heka/plugins/decoders/os_keystone_apache_log.lua

+-- Copyright 2015 Mirantis, Inc.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+local l      = require 'lpeg'
+l.locale(l)
+
+local common_log_format = require 'common_log_format'
+local patt = require 'os_patterns'
+local utils  = require 'os_utils'
+
+local msg = {
+    Timestamp   = nil,
+    Type        = 'log',
+    Hostname    = nil,
+    Payload     = nil,
+    Pid         = nil,
+    Fields      = nil,
+    Severity    = 6,
+}
+
+local severity_label = utils.severity_to_label_map[msg.Severity]
+
+local apache_log_pattern = read_config("apache_log_pattern") or error(
+    "apache_log_pattern configuration must be specificed")
+local apache_grammar = common_log_format.build_apache_grammar(apache_log_pattern)
+local request_grammar = l.Ct(patt.http_request)
+
+function process_message ()
+
+    -- logger is either "keystone-apache-public" or "keystone-apache-admin"
+    local logger = read_message("Logger")
+
+    local log = read_message("Payload")
+
+    local m
+
+    m = apache_grammar:match(log)
+    if m then
+        msg.Logger = 'openstack.keystone'
+        msg.Payload = log
+        msg.Timestamp = m.time
+
+        msg.Fields = {}
+        msg.Fields.http_status = m.status
+        msg.Fields.http_response_time = m.request_time.value / 1e6 -- us to sec
+        msg.Fields.programname = logger
+        msg.Fields.severity_label = severity_label
+
+        local request = m.request
+        m = request_grammar:match(request)
+        if m then
+            msg.Fields.http_method = m.http_method
+            msg.Fields.http_url = m.http_url
+            msg.Fields.http_version = m.http_version
+        end
+
+        return utils.safe_inject_message(msg)
+    end
+
+    return -1, string.format("Failed to parse %s log: %s", logger, string.sub(log, 1, 64))
+end