What is Amazon CloudWatch Logs?

Two log classes for flexibility – CloudWatch Logs offers two log classes so that you can have a cost-effective option for logs that you access infrequently. You also have a full-featured option for logs that require real-time monitoring or other features. For more information, see Log classes.

Query your log data – You can use CloudWatch Logs Insights to interactively search and analyze your log data. You can perform queries to help you more efficiently and effectively respond to operational issues. CloudWatch Logs Insights includes a purpose-built query language with a few simple but powerful commands. We provide sample queries, command descriptions, query autocompletion, and log field discovery to help you get started. Sample queries are included for several types of AWS service logs. To get started, see Analyzing log data with CloudWatch Logs Insights.

Create field indexes to make queries more efficient – You can create field indexes of fields in your log events. When you then use a field index in a CloudWatch Logs Insights query, the query attempts to skip processing log events that are known to not include the indexed field. This query reduces the scan volume of your queries, making it possible to return results faster. To get started, see Create field indexes to improve query performance and reduce scan volume.

Detect and debug using Live Tail – You can use Live Tail to quickly troubleshoot incidents by viewing a streaming list of new log events as they are ingested. You can view, filter, and highlight ingested logs in near real time, helping you to detect and resolve issues quickly. You can filter the logs based on terms you specify, and also highlight logs that contain specified terms to help you quickly find what you are looking for. For more information, see Troubleshoot with CloudWatch Logs Live Tail.

Monitor logs from Amazon EC2 instances – You can use CloudWatch Logs to monitor applications and systems using log data. For example, CloudWatch Logs can track the number of errors that occur in your application logs and send you a notification whenever the rate of errors exceeds a threshold you specify. CloudWatch Logs uses your log data for monitoring; so, no code changes are required. For example, you can monitor application logs for specific literal terms (such as "NullReferenceException") or count the number of occurrences of a literal term at a particular position in log data (such as "404" status codes in an Apache access log). When the term you are searching for is found, CloudWatch Logs reports the data to a CloudWatch metric that you specify. Log data is encrypted while in transit and while it is at rest. To get started, see Getting started with CloudWatch Logs.

Monitor AWS CloudTrail logged events – You can create alarms in CloudWatch and receive notifications of particular API activity as captured by CloudTrail and use the notification to perform troubleshooting. To get started, see Sending CloudTrail Events to CloudWatch Logs in the AWS CloudTrail User Guide.

Audit and mask sensitive data – If you have sensitive data in your logs, you can help safeguard it with data protection policies. These policies let you audit and mask the sensitive data. If you enable data protection, then by default, sensitive data that matches the data identifiers you select is masked. For more information, see Help protect sensitive log data with masking.

Log retention – By default, logs are kept indefinitely and never expire. You can adjust the retention policy for each log group, keeping the indefinite retention, or choosing a retention period between 10 years and one day.

Archive log data – You can use CloudWatch Logs to store your log data in highly durable storage. The CloudWatch Logs agent makes it easy to quickly send both rotated and non-rotated log data off of a host and into the log service. You can then access the raw log data when you need it.

Log Route 53 DNS queries – You can use CloudWatch Logs to log information about the DNS queries that Route 53 receives. For more information, see Logging DNS Queries in the Amazon Route 53 Developer Guide.

AWS CloudTrail is a web service that enables you to monitor the calls made to the CloudWatch Logs API for your account, including calls made by the AWS Management Console, AWS Command Line Interface (AWS CLI), and other services. When CloudTrail logging is turned on, CloudTrail captures API calls in your account and delivers the log files to the Amazon S3 bucket that you specify. Each log file can contain one or more records, depending on how many actions must be performed to satisfy a request. For more information about AWS CloudTrail, see What Is AWS CloudTrail? in the AWS CloudTrail User Guide. For an example of the type of data that CloudWatch writes into CloudTrail log files, see Logging CloudWatch Logs API and console operations in AWS CloudTrail.

AWS Identity and Access Management (IAM) is a web service that helps you securely control access to AWS resources for your users. Use IAM to control who can use your AWS resources (authentication) and what resources they can use in which ways (authorization). For more information, see What Is IAM? in the IAM User Guide.

Amazon Kinesis Data Streams is a web service you can use for rapid and continuous data intake and aggregation. The type of data used includes IT infrastructure log data, application logs, social media, market data feeds, and web clickstream data. Because the response time for the data intake and processing is in real time, processing is typically lightweight. For more information, see What is Amazon Kinesis Data Streams? in the Amazon Kinesis Data Streams Developer Guide.

AWS Lambda is a web service you can use to build applications that respond quickly to new information. Upload your application code as Lambda functions and Lambda runs your code on high-availability compute infrastructure and performs all the administration of the compute resources, including server and operating system maintenance, capacity provisioning and automatic scaling, code and security patch deployment, and code monitoring and logging. All you need to do is supply your code in one of the languages that Lambda supports. For more information, see What is AWS Lambda? in the AWS Lambda Developer Guide.