Independent Study Spring 2018/Logging

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Logging capability in Expertiza

Useful links

Github Pull Request

ELK configurations


Logging feature has been added to Expertiza through a custom logging module written uniquely to serve several purposes such as:

Message Format

All the messages are logged in either of the below formats:

TST=[2018-03-10 00:50:18 -0500] SVT=[<log_level>] PNM=[<program_name>] OIP=[<origin_ip>] RID=[<request_id>] CTR=[<controller_name>] UID=[<user_id>] MSG=[Message]


TST=[2018-03-10 00:50:18 -0500] SVT=[<log_level>] PNM=[<program_name>] OIP=[] RID=[] CTR=[<controller_name>] UID=[<user_id>] MSG=[[origin_ip] [request_id] Message]

Above variation is because when certain messages are logged, ExpertizaLogger is unaware of origin_ip and request_ip and thus it is appended to the message instead of their respective placeholders.

Meaning of each placeholder

SVT - It denotes the severity level of the log. For eg, if the logging is done by calling, the severity level is "INFO".

PNM - It's the program name and is same as provided by default Rails logger.

OIP - It denotes the IP address of the system from where the request has been made.

RID - It's the ID of the request. All subsequent calls made by the client till the actual response is returned will have same request ID. For eg, when a page is first requested, all smaller page template fetched, all method flow will have same request ID. This field can be used to understand how a certain request was served.

CTR - It is the controller name from where the logging happened.

UID - It is the unity id/user id of the user making requests. This field could also be used in identifying the cause of an error.

Message - It is the actual message logged.

Log files

For different log levels, log messages are written in different files named expertiza_<log_level>.log

Currently, expertiza provides the capability of writing logs into 5 different custom log files.

For eg,

Apart from above files, <environment>.log file is used for logging messages which could not be logged by ExpertizaLogger, like, page load messages or certain load time exceptions.

Since Rails logger provides writing into a specific log file, to restrict least file switch, ExpertizaLogger holds different log level loggers in separate instance variables. A new logger instance is created and assigned whenever Rails removes the link to manage memory consumption.



This class provides the logger needed for logging messages for different log levels. It provides 5 different static methods namely info, warn, error, fatal and debug which could be called as follows: message

where message could be an instance of LoggerMessage or a string.

Custom LoggerMessage

A LoggerMessage instance could be created as follows:<controller_name>, <user_id>, <message>, <request object>)

Fourth parameter i.e <request object> is an optional parameter.

Whenever a request is made, the request object is injected into the controller and is available in the controller as "request". Similarly, <controller_name> is available in "controller_name" inside controller. For other trigger points, file name could be passed as a string.

Since the request object holds the <origin_ip> and <request_id>, it is used to capture and log both into the log message.


It captures the message and determines if the message is an instance of LoggerMessage or not. Based on that, it creates a message by populating message placeholders as below:

   if msg.is_a?(LoggerMessage)
     "TST=[#{ts}] SVT=[#{s}] PNM=[#{pg}] OIP=[#{msg.oip}] RID=[#{msg.req_id}] CTR=[#{msg.generator}] UID=[#{msg.unity_id}] MSG=[#{filter(msg.message)}]\n"
     "TST=[#{ts}] SVT=[#{s}] PNM=[#{pg}] OIP=[] RID=[] CTR=[] UID=[] MSG=[#{filter(msg)}]\n"

All the exceptions are preprocessed to remove newline characters so that it could fit in a single line as a message.

All the messages that are not logged by ExpertizaLogger, there is a separate logger definition provided in config/environments/<environment>.rb as:

 config.log_formatter = proc do |s, ts, pg, msg|
   if msg.is_a?(LoggerMessage)
     "TST=[#{ts}] SVT=[#{s}] PNM=[#{pg}] OIP=[#{msg.oip}] RID=[#{msg.req_id}] CTR=[#{msg.generator}] UID=[#{msg.unity_id}] MSG=[#{filter(msg.message)}]\n"
     "TST=[#{ts}] SVT=[#{s}] PNM=[#{pg}] OIP=[] RID=[] CTR=[] UID=[] MSG=[#{filter(msg)}]\n"

Environment config

config.log_tags = [ :remote_ip, :uuid ]

These config.log_tags entries make sure that <origin_ip> and <request_id> are prepended to messages. These are for messages which are not logged by ExpertizaLogger but by the Rails default logger. These messages go in <environment>.log file.


The request object is not available beyond the controllers. Hence, <origin_ip> and <request_id> remains uncaptured if messages are logged from somewhere other than controllers.

Visualization through ELK stack


Filebeat (filebeat.yml)


- type: log

 # Change to true to enable this prospector configuration.
 enabled: true
 # Paths that should be crawled and fetched. Glob based paths.
   - <path to log files>*.log


 # The Logstash hosts
 hosts: ["<ip>:<5044:port of logstash>"]

Filebeat sends all log files to logstash.

Logstash (expertiza-logstash.conf)

  input { 
       beats {
           port => "5044"
  filter {
   grok {
   	match => { "message" => "TST=\[%{DATA:timestamp}\] SVT=\[%{DATA:sev}\] PNM=\[%{DATA:pgnm}\] OIP=\[%{DATA:originip}\] RID=\[%{DATA:requestid}\] CTR=\[%{DATA:generatedby}\] UID=\[% 
  {DATA:unityid}\] MSG=\[%{GREEDYDATA:message}\]" }
   	overwrite => [ "message", "timestamp" ]
 	date {
   	match => ["timestamp", "ISO8601"]
   output {
     elasticsearch {
       hosts => [ "localhost:9200" ]

Logstash reads each line from the log file and parses it based on the template provided in grok match above. It then sends each message entry into Elastic search.

Kibana (config/kibana.yml)

   elasticsearch.url: "http://localhost:9200"

Kibana picks each entry from Elastic search and provides into the web interface.


ELK stack could be set up to visualize and analyze the messages from the log files.

Once ELK is installed, below commands could be used to run each server:

Clear Elastic search cache

curl -X DELETE 'http://localhost:9200/_all'


sudo rm data/registry

sudo ./filebeat -e -c filebeat.yml -d "publish"


bin/logstash -f expertiza-logstash.conf --config.reload.automatic



Kibana Interface

Success message in Kibana

Kibana success msg.png

Exception in kibana

Kibana exception.png

Tracing error in kibana

Kibana tracing error.png

Search records using request ID in kibana

Kibana search req id.png

Searching records using unity id in kibana

Kibana search using unityid.png
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