Add Heka log decoder for RabbitMQ

In the future the Heka Lua sandboxes will be moved out of Kolla, and
installed in the Heka container using a deb or rpm package.

Partially implements: blueprint heka
Change-Id: I1aa27048d22f1a5ed385180696d320af9a961389

docker/heka/plugins/decoders/os_rabbitmq_log.lua

+-- Copyright 2015-2016 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 dt     = require "date_time"
+local l      = require 'lpeg'
+l.locale(l)
+
+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    = nil,
+}
+
+-- RabbitMQ message logs are formatted like this:
+--   =ERROR REPORT==== 2-Jan-2015::09:17:22 ===
+--   Blabla
+--   Blabla
+--
+local message   = l.Cg(patt.Message / utils.chomp, "Message")
+-- The token before 'REPORT' isn't standardized so it can be a valid severity
+-- level as 'INFO' or 'ERROR' but also 'CRASH' or 'SUPERVISOR'.
+local severity  = l.Cg(l.R"AZ"^1, "SeverityLabel")
+local day = l.R"13" * l.R"09" + l.R"19"
+local datetime = l.Cg(day, "day") * patt.dash * dt.date_mabbr * patt.dash * dt.date_fullyear *
+                 "::" * dt.rfc3339_partial_time
+local timestamp = l.Cg(l.Ct(datetime)/ dt.time_to_ns, "Timestamp")
+
+local grammar = l.Ct("=" * severity * " REPORT==== " * timestamp * " ===" * l.P'\n' * message)
+
+function process_message ()
+    local log = read_message("Payload")
+
+    local m = grammar:match(log)
+    if not m then
+        return -1
+    end
+
+    msg.Timestamp = m.Timestamp
+    msg.Payload = m.Message
+    if utils.label_to_severity_map[m.SeverityLabel] then
+        msg.Severity = utils.label_to_severity_map[m.SeverityLabel]
+    elseif m.SeverityLabel == 'CRASH' then
+        msg.Severity = 2 -- CRITICAL
+    else
+        msg.Severity = 5 -- NOTICE
+    end
+
+    msg.Fields = {}
+    msg.Fields.severity_label = utils.severity_to_label_map[msg.Severity]
+    msg.Fields.programname = 'rabbitmq'
+
+    return utils.safe_inject_message(msg)
+end