### 2023-05-11 Logstash, which is a popular open-source log processing tool, is designed to handle logs in various formats. It provides a flexible pipeline architecture that can parse and process logs in different formats. However, there are some commonly used log formats that are widely supported and recommended when working with Logstash. 1. **JSON format**: Logstash has excellent support for logs in JSON format. JSON logs have a structured format that makes it easy to extract fields and perform further analysis. Each log entry is represented as a JSON object with key-value pairs, allowing for easy querying and filtering. Many libraries and frameworks provide JSON logging out of the box, making it a popular choice. ```json {"timestamp": "2023-05-09T10:15:30Z", "level": "INFO", "message": "User logged in", "user_id": 12345} ``` 2. **Common Event Format (CEF)**: CEF is a standardized log format developed by ArcSight (now Micro Focus) and is widely used in security event logging. It follows a key-value format where each log entry consists of predefined fields such as timestamp, severity, source IP, destination IP, etc. Logstash has a CEF codec plugin that can parse CEF logs and extract the relevant fields. ```bash CEF:0|Vendor|Product|Version|Signature ID|Name|Severity|Extension ``` 3. **Syslog**: Syslog is a standard logging protocol widely used across various operating systems and network devices. It has a well-defined format that includes a timestamp, hostname, application name, process ID, and log message. Logstash has built-in support for parsing syslog messages using the syslog input plugin. ```bash May 9 10:15:30 hostname application_name[PID]: Log message goes here ``` 4. **Apache/Nginx access logs**: For web server logs, Logstash provides specific plugins to parse common web server log formats like Apache's Combined Log Format and Nginx's Combined Log Format. These plugins can extract fields such as the client IP, request method, URL, status code, and more. ```bash 192.168.0.1 - - [09/May/2023:10:15:30 +0000] "GET /index.html HTTP/1.1" 200 1234 ``` 5. **NDJSON:** Each log entry is represented as a separate JSON object, separated by newline characters. According to elastic, this is the preferred method of log ingestion for Logstash: ```json {"timestamp": "2024-01-13T14:30:00", "severity": "INFO", "message": "User logged in successfully"} {"timestamp": "2024-01-13T15:15:00", "severity": "ERROR", "message": "Failed to connect to database"} {"timestamp": "2024-01-13T16:00:00", "severity": "DEBUG", "message": "API request received"} ``` While these formats are commonly used, Logstash's flexibility allows you to parse and process logs in custom formats as well. You can define custom grok patterns, use regular expressions, or write custom parsing logic using plugins to handle logs in formats specific to your application or infrastructure. In real-world scenarios, the logs may contain additional fields or details based on the specific application or system generating the logs. **If you need any help or want to get in contact with me, Click [[🌱 The Syntax Garden]] where I have my contact details.**