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Logging

🕓 10 minutes

What you’ll learn​

How to use logs of your application for monitoring, debugging, and better understanding of the process behind the code.

Logging helps you to:

  • follow the system actions and information about user,
  • and reveal application problems together with the place where they occur.

Prerequisites​

Overview​

Loki tool​

CodeNow is using the Loki tool for logs, which is a horizontally scalable log aggregation system.

  • Loki comes with its own language for queries called LogQL.
  • LogQL uses labels and operators for filtering.

Steps​

  1. Find the "Logging&Tracing" section in the sidebar menu and go to the "Logging" option.
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  1. You have different options to enter a query:
  • You can use "Log browser" button to automatically generate a query:
    • Select some labels and then select values for each of these labels.
    • Tool will automatically generate the query, which you can see as "Resulting selector" at the bottom of log browser.
    • Press "Show logs" button.
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  • You can write your own queries from basic queries and then click on the "Run Query" button.:
    • Logs for your namespace: {namespace="_name_of_the_namespace_"}
    • Logs for the specific application: {app="_name_of_the_application_", namespace="_name_of_the_namespace_"}
    • NOTE: You can't use traceID for application logs.
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  • To understand how to write more complex queries, please refer to LogQL's online documentation.

  • To understand how to write queries for the Loki tool, please refer to "Loki Cheat Sheet".

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  1. The appeared graph shows you the request statistics in time. Below it you will find application logs.
  • You can also set the appearance of the logs: time, unique labels, wrap lines or dedup. You can additionally flip the results' order.
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  1. You can expand the log to see more details
  • You can click on "Jaeger" button to see the corresponding trace
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  1. You can set the time range for your application and see the corresponding logs.
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  1. For live monitoring of your application, click on the "Live" button.
    • For pausing or stopping the live monitoring, simply click on the "Live" button again.
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  1. If you want to add another query and run both the original query and the new query at the same time, you can click on the "Add query" button.
    • You can simply disable or remove a query by clicking on buttons in the right side of the query
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  1. You can split your screen in two by clicking on the "split" sign.
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  1. Here we described the basics of using Logging in Grafana. For more details visit the corresponding section of Grafana's online documentation.