It is essential to have readable log files. Having loads of information that can’t be used because it is incomprehensible makes no sense, isn’t it? Hence, considering the importance of log formatting is a quintessential part of getting human-readable log files. Well, just having machine-readable log files is not enough, although it is a fact that machine-readable logs facilitate the usage of tools that automatically process and parse precious information. However, the human-readable log files are critical when post-mortem debugging comes into the picture. Admins would want to check the log entries to extract vital information. So, the information should be easily readable, or else they won’t understand what went wrong with the software.

Maintaining appropriate log file formats is mandatory to make the cumbersome job less of a challenge for admins. This is why, in the upcoming sections, the tips to achieve human-readable log files will be discussed:

• Standard date and time format: Your log entries are meaningless without the standard date and time stamps. You need to know when the issue popped up. Among so many dates and time formats, which one should you choose? Always choose the one that is universally accepted; the ISO standard (ISO-8601) is the one you are looking for. So, to keep confusion at bay, use it!
• Log entries aligned well with the context: Adding detailed context to your log entry can help you identify the minute details of what happened. Such a lucid log entry will only facilitate the admins to effectively and quickly solve the problem. The utility of adding context comes into play when you need to get access to distinguishable messages readily.
• Logging levels: You want the parsers to analyze and process the information correctly, right? So, do not neglect to employ logging levels correctly. Humans can search log files easily when the logging levels are mentioned correctly. These labels help you segregate each log entry from one another based on the urgency or severity of each. Filtering log entries would otherwise become a challenging task. But the logging levels make it easily searchable. In fact, the logging levels show the context and details of each entry categorically and based on their level type. So here’s what you can do:
• Enter the log level within your log entries.
• The level should be displayed in uppercase, i.e., “ERROR” and not “error.” This helps the log level to appear unique among the other information within the entry.
• Each event should have a dedicated and correct level.
• The timestamps should be in line with the time zone: While it’s helpful to implement ISO-8601 to standardize the timestamps format on your log entries, addressing time is challenging in general. It is not merely restricted to various formats that are available. Time zones and Daylight Saving Time must also be considered. Users will refer to their time zone while communicating, i.e., while reporting a problem, they will indicate the time zone they are in such as EST. Thus, having the timestamps displayed as per the users’ time zone will make more sense. This approach simplifies the process of locating the pertinent log entries during post-mortem debugging. You must use the local time along with the offset from UTC to address the DST and time zone issues while maintaining the timestamps as per the user’s local time.
• Mention the thread name if logging from an application having multiple threads: The thread name is vital because it tells its readers about the event location. So, what it does is it facilitates easy searching or filtering. Furthermore, the entries can be parsed quickly by making them lucid for humans to read and understand.
• Using stack trace for logging exceptions: Try not to make this section verbose. The title will do the talking. However, any exception should be logged in along with its stack trace. Post-mortem debugging cannot be performed correctly if the stack trace information is not included because this information helps the admin bridge the gap.

When it comes to production environments, fewer events are usually logged depending on the relevant user activity. Nobody logs each interaction of the user with the UI. Hence, when it comes to debugging, the specific destination of the logs according to their granularity can help you massively. This means you will not get lost in the ocean of debugging entries while trying to find out a log.