varnishlog:tldr:ee412

The "varnishlog" command is a tool that allows you to monitor and analyze the traffic passing through the Varnish Cache server. Varnish Cache is a popular web application accelerator that sits between the client and server and can dramatically improve the performance of websites.

When you execute the "varnishlog" command, it opens a log stream in real-time, displaying a continuous flow of detailed information about each request and response handled by the Varnish Cache server. This information includes:

1. Timestamp: The exact time when each request was received or each response was sent.
2. Client IP address: The IP address of the client making the request.
3. Varnish request ID: A unique identifier assigned to each request.
4. HTTP request method: The HTTP method used, such as GET, POST, etc.
5. HTTP request URL: The URL of the requested resource.
6. HTTP status code: The response status code, indicating if the request was successful or encountered an error.
7. Backend server: The IP address and port of the server that Varnish Cache forwarded the request to.
8. Response time: The time taken by the backend server to process the request and send the response.
9. Referer and User-Agent: The referring website or page and the user agent of the client's browser.

By monitoring the varnishlog, you can gather valuable insights into the performance, behavior, and potential issues of your web applications. For example, you can identify slow backend response times, analyze cache hits and misses, debug configuration problems, and observe incoming traffic patterns.