# CloudWatch Logs

* You can use CloudWatch Logs to **monitor, store, and access your log files** from EC2 instances, CloudTrail, Route 53, and other sources.

* CloudWatch Logs enables you to **centralize the logs from all of your systems, applications, and AWS services that you use**, in a single, highly scalable service.<br>

* You can then **easily view them, search them for specific error codes or patterns**, filter them based on specific fields, or archive them securely for future **analysis**.

## Log streams

* A log stream is a **sequence of log events that share the same source**.

## Log groups

* A log group is a **group of log streams that share the same settings**, such as retention, monitoring, and access control.<br>
* You **define log groups and specify which streams to put into each group**.<br>
* There is **no limit on the number of log streams that can belong to one log group**.

## Metric filters

* You can use metric filters to **extract metric observations from ingested events and transform them to data points in a CloudWatch metric**.<br>
* Metric filters are assigned to log groups, and all of the filters assigned to a log group are applied to their log streams.

## Retention settings

* Retention settings can be used to **specify how long log events are kept** in CloudWatch Logs.<br>
* Retention settings are also **assigned to log groups**.

## Logs Insights

* Logs Insights enables you to interactively **search and analyse your log data in Amazon CloudWatch Logs**.<br>
* You can **perform queries to help you more efficiently and effectively respond to operational issues**.<br>
* Logs Insights **includes a purpose-built query language**.
