Everything you need to know about log parsing
Feb 10, 2022 6 min read
Log parsing is the process of splitting unstructured log data and converting it into a structured format. This makes it easier to understand, analyze, and store logs.
For example, consider this sample windows event log, 21/1/2022 08:14:29 AM 1102 Application Information 'The audit log was cleared' Test-PC - None Windows Update Success
A log parsing tool analyses this log and splits it into different fields like date and time, event ID, type, level, source, computer name, user, task category, and message for easy understanding.
There are two methods to parse logs: RegEx and Delimiter parsing.
RegEx stands for Regular Expressions, which is a domain specific language used for pattern searches and replacements.
RegEx expressions let you create custom queries using patterns that will extract data from the log events. It helps you extract unique fields like date, time, and log type from unstructured data, making it easier for you to sort, filter and work with them.
Log parsing tools help you create RegEx patterns seamlessly with the help of sophisticated built-in modules.
For example, look at the same sample Windows event log from before.
21/1/2022 08:14:29 AM 1102 Application Information 'The audit log was cleared' Test-PC - None Windows Update Success
To extract the date field from this event log, the following reg expression can be used.
^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]))\1|(?:(?:29|30)(\/|-|\.)(?:0?[13-9]|1[0-2])\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.)0?2\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.)(?:(?:0?[1-9])|(?:1[0-2]))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$
This regular expression can find dates in the dd/mm/yyyy, dd-mm-yyyy or dd.mm.yyyy format.
A log consists of different information like log type, date, time, and errors in a single line. We can split this data with the help of a delimiter character such as commas (,), semicolon (;), braces ({}) and pipes (|). This type of parsing makes the process of sorting and filtering the required data more efficient.
When you use a delimiter character, you do not have to rely on fixed widths in the text. The delimiter character lets you break the information from a log at the right place even if the information is not symmetrical or follows a pattern, to help sort and filter the data.
While working with complex data, the ability to transform a delimited string into a dataset is highly beneficial.
Eg: apple, orange, mango, [grapes]10/10, banana
In this example "," can be the delimiter parser for the first 3 attributes. For the 4th attribute, if you need to get the value between "[ ]", while defining the fourth attribute, assign a separator type Begin and End Text with begin and end text values of "[" and "]".
Analyzing or debugging an issue from a log file is a tedious process. Using a log parser, you can organize the logs and troubleshoot issues quickly.
A powerful log parsing application can use forensic analysis to search through a massive amount of log data with wild cards, phrases, and boolean operators along with grouped searches and range searches.
A log parser will help you to understand your logs better. The better understanding and structured categorization of logs will simplify the process of log analysis.
A log parser has many features to make sorting and analyzing data more efficient, which helps in improving the security posture of your organization. . Some of the important ways log parsing can help with log management are:
A log parsing tool allows you to streamline the whole process of collecting and analysing log data by automation, relieving you of the tedious process of going over raw logs for analysis.
When you use a traditional log viewer, the log parsing has to be carried out manually. In today's world where thousands of log files are generated every minute, it becomes impossible to parse all the data. A log parser will help you manage your logs more effectively while you do not have to worry about the scale.
A reliable log parser can create custom rules for parsing your data, and select the most important log events to make log management easier by prioritizing what's needed and leaving out the rest.
A log management tool like EventLog Analyzer with powerful parsing features can simplify the process of extracting all the relevant information from your logs and help you understand network events with ease. If you're looking for a reliable log parsing tool that can streamline and simplify your logs check out EventLog Analyzer from ManageEngine.
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