Configuring a log facility using filters

Using a LuaFilter ) allows you to implement your own log facility. The LuaFilter might be used to create the log line which shall be logged, while the LoggerFilter defines when and to which file to write the log data.

Example:

 <filter>
 <filter-name>LuaDataCollector</filter-name>
 <filter-class>ch::nevis::isiweb4::filter::lua::LuaFilter</filter-class>
 <init-param>
  <param-name>Script OutputHeaderFunctionName </param-name>
  <param-value> createLogData</param-value>
 </init-param>
 <init-param>
  <param-name>Script</param-name>
  <param-value>
local timer = nevis.sys.timer.new()
responseProcessed = false

-- escapes non-printable / non 7-bit ASCII characters and double quotes
function escapeNonePrintableChars (c)
 local c_byte = c:byte()
 -- non printable
 if c_byte > 127 then
  return "0x" .. string.format("%X", c_byte)
 elseif c_byte < 32 then
  return "0x" .. string.format("%X", c_byte)
 elseif c_byte == 34 then
  return "\\\""
 end
 -- no change
 return nil
end

function createLogData (request, response)

 local frame = {}
 -- timestamp:
 local reqTime = timer:getTime()
 local timeInMs = timer:getTime()
 local timeMsPart = timeInMs%1000
 local timeInS = (timeInMs - timeMsPart)/1000
 local timeFormat = os.date("%Y-%m-%dT%H:%M:%S", timeInS).."."..timeMsPart
 table.insert(frame, "{ \"timestamp\":\"" .. timeFormat .. "\", ")

 -- userAgent:
 local userAgent = request:getHeader("User-Agent")
 if userAgent == nil then
  userAgent = "null"
 else
  local escapedUserAgent = string.gsub(userAgent, "(.)", escapeNonePrintableChars)
  userAgent = "\"" .. escapedUserAgent .. "\""
 end
 table.insert(frame, "\"userAgent\":" .. userAgent .. ", ")

 -- address:
 local address = request:getEnv("AD_REMOTE_ADDR")
 table.insert(frame, "\"address\":\"" .. address .. "\", ")

 -- HTTP method:
 local method = request:getEnv("REQUEST_METHOD")
 if method == nil then
  method = "null"
 else
  method = "\"" .. method .. "\""
 end
 table.insert(frame, "\"method\":" .. method .. ", ")

 --reqPath:
 local path = request:getUri()
 path = string.gsub(path, "(.)", escapeNonePrintableChars)
 table.insert(frame, "\"reqPath\":\"" .. path .. "\", ")

 -- client id:
 local clID = request:getEnv("bcx.servlet.session.HttpSessionId")
 if clID == nil then
  clID = "null"
 else
  clID = "\"" .. clID .. "\""
 end
 table.insert(frame, "\"clID\":" .. clID .. ", ")

 -- transaction id:
 local trID = request:getEnv("UNIQUE_ID")
 if trID == nil then
  trID = "null"
 else
  trID = "\"" .. trID .. "\""
 end
 table.insert(frame, "\"trID\":" .. trID .. " }")

 local logLine = table.concat(frame)
 -- store the data within the "LOGLINE" variable:
 request:setEnv("LOGLINE", logLine)
end
  </param-value>
 </init-param>
 </filter>

 <filter>
 <filter-name>Logger</filter-name>
 <filter-class>ch::nevis::isiweb4::filter::audit::LoggerFilter</filter-class>
 <init-param>
  <param-name>FileName</param-name>
  <param-value>/var/opt/nevisproxy/default/logs/custom.log</param-value>
 </init-param>
 <init-param>
  <param-name>RotationPolicy</param-name>
  <param-value>size:52428803:5</param-value>
 </init-param>
 <init-param>
  <param-name>LogLine</param-name>
  <param-value>ENV:LOGLINE;</param-value>
 </init-param>
 </filter>

 <filter-mapping>
 <filter-name>Logger</filter-name>
 <url-pattern>/app/*</url-pattern>
 </filter-mapping>

 <filter-mapping>
 <filter-name>LuaDataCollector</filter-name>
 <url-pattern>/app/*</url-pattern>
 </filter-mapping>

Always ensure to properly encode the data to be logged according to the format definition you use.

This example can be found in examples/monitoring/data_collection.example on the installed nevisProxy package