Logging

The Fusion Metadata Registry logs information regarding the requests made to it and the work that it is performing. These logs can be long and complicated, but this document aims to explain the logging process.

Logging information is stored in the filesystem as well as in database tables. The files on your system are possibly more transient so unless you take action these will likely be replaced with more recent log information. This is to prevent the size of the log files consuming all of your disk space.

File-based logging

During operation the FMR writes information to its logs. The level of logging is controlled by a system setting in the FMR which directly relates to the logging tool that the FMR uses, which is called Logback. The files generated are also affected by the Java Web-Application Server you are running (for example Apache Tomcat). For the rest of this section, only the scenario when running on Tomcat will be detailed.

Since log files will naturally grow larger over time, if allowed to grow indefinitely, their size would become a problem consuming all the available disk space. This is addressed using rolling file appenders, which automatically “roll” or archive the current log file, and resume logging in a new file when certain predefined conditions occur.

Logback

The logging is controlled by a file called "logback.xml" which is located in the WEB-INF\classes directory under the installed FusionRegistry web application. For example this could be: C:\tomcats\apache-tomcat-9.0.58\webapps\FusionRegistry\WEB-INF\classes

Configuration can be performed by modifying this file. There are different levels of logging:

TRACE: This is for extremely detailed and potentially high volume logs that you don’t typically want enabled even during normal development.
DEBUG: Helpful in tracking the flow through the system and isolating issues, especially during the development and QA phases.
INFO: Used for system lifecycle events (system start, stop) and significant boundary events (e.g., database calls, remote API calls). Typical business exceptions can go here.
WARN: An unexpected technical or business event happened, customers may be affected, but probably no immediate human intervention is required.
ERROR: The system is in distress, customers are probably being affected (or will soon be) and the fix probably requires human intervention.
OFF: This level is intended to turn off logging.

It is not recommended to switch to TRACE or DEBUG level unless specifically requested to by the development team, since the amount of logging produced can be excessive and can cause performance issues.

Tomcat files

In Apache Tomcat, various log files are generated during the execution of a Java web application. These log files provide valuable information about the application's behavior, errors, and performance. Here's a summary of some common log files in Tomcat:

   catalina.log:
       Purpose: General logging for the Tomcat server.
       Contents: Includes information about server startup, shutdown, and any errors that occur during the server's operation.

   catalina.<date>.log:
       Purpose: Daily rotating log file for Catalina.
       Contents: Includes information specific to the Catalina component of Tomcat. Useful for troubleshooting Catalina-related issues.

   localhost.log:
       Purpose: Logs information related to the default "localhost" context.
       Contents: Records information about the deployment and undeployment of web applications under the default context.

   localhost.<date>.log:
       Purpose: Daily rotating log file for the default "localhost" context.
       Contents: Contains information specific to the default web application context. Useful for troubleshooting application-specific issues.

   localhost_access_log.txt:
       Purpose: Records access information, such as requests made to the Tomcat server.
       Contents: Contains details like client IP address, request date and time, HTTP status, and bytes sent.

   localhost_access_log.<date>.txt:
       Purpose: Daily rotating log file for localhost_access_log
       Contents: The daily rotation of the localhost_access_log

   manager.log:
       Purpose: Logs information about the Tomcat Manager application.
       Contents: Records deployment and undeployment activities performed through the Tomcat Manager.

   host-manager.log:
       Purpose: Logs information about the Host Manager application.
       Contents: Records deployment and undeployment activities performed through the Host Manager.

Database Logging

There are also log tables within the database which persist some but not all of the logged information.

• Log Tables
• Audit Tables