Configuring a log facility using filters

Using a LuaFilter and a LoggerFilter allows you to implement your own log facility, see chapters LuaFilter and LoggerFilter. 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