CloudWatch Logs subscriptions enable real-time streaming of log data from CloudWatch Logs to other AWS services for processing, analysis, or storage. This powerful feature allows you to create automated pipelines that react to log events as they occur.
A subscription filter defines the pattern use…CloudWatch Logs subscriptions enable real-time streaming of log data from CloudWatch Logs to other AWS services for processing, analysis, or storage. This powerful feature allows you to create automated pipelines that react to log events as they occur.
A subscription filter defines the pattern used to match log events and specifies the destination where matching events should be delivered. You can configure subscriptions to send data to three primary destinations: Amazon Kinesis Data Streams, Amazon Kinesis Data Firehose, or AWS Lambda functions.
When using Kinesis Data Streams, you can process high-volume log data in real-time and integrate with custom applications. Kinesis Data Firehose simplifies delivery to destinations like Amazon S3, Amazon Redshift, or Amazon OpenSearch Service, making it ideal for long-term storage and analytics. Lambda functions allow you to execute custom code in response to specific log patterns, enabling automated remediation workflows.
To create a subscription, you specify a filter pattern that determines which log events match. Filter patterns can be simple text strings or more complex pattern syntax to match specific fields in structured log data. Each log group can have up to two subscription filters.
Cross-account log data sharing is also supported through subscriptions. You can stream logs from one AWS account to a Kinesis stream or Firehose in another account, facilitating centralized logging architectures in multi-account environments.
The log data delivered through subscriptions is compressed in gzip format and base64 encoded, requiring appropriate decoding in your processing logic. For Lambda destinations, AWS handles this automatically.
Common use cases include security monitoring, where suspicious activity triggers alerts, operational dashboards that aggregate metrics from logs, and compliance archiving to S3. Subscriptions are essential for building reactive, event-driven architectures that respond to application and infrastructure events captured in CloudWatch Logs.
CloudWatch Logs Subscriptions
Why CloudWatch Logs Subscriptions Are Important
CloudWatch Logs Subscriptions enable real-time processing and analysis of log data as it flows into CloudWatch Logs. This capability is essential for building reactive systems, performing real-time analytics, and integrating log data with other AWS services or third-party tools. For SysOps administrators, understanding subscriptions is crucial for implementing automated monitoring and alerting solutions.
What Are CloudWatch Logs Subscriptions?
A CloudWatch Logs subscription is a configuration that streams log events from a log group to a destination in real-time. Subscriptions use subscription filters to define which log events are delivered to the destination. Each log group can have up to two subscription filters.
Supported Destinations: • Amazon Kinesis Data Streams - For real-time processing with custom applications • Amazon Kinesis Data Firehose - For loading data into S3, Redshift, OpenSearch, or Splunk • AWS Lambda - For custom processing and transformation of log data
How CloudWatch Logs Subscriptions Work
1. Create a Subscription Filter: Define a filter pattern that matches the log events you want to stream 2. Specify a Destination: Choose where the matching log events should be sent 3. Configure Permissions: Ensure the destination has the appropriate IAM permissions to receive data from CloudWatch Logs 4. Real-Time Streaming: Matching log events are streamed to the destination as they arrive
Key Components: • Filter Pattern - Defines which log events match (can be empty to match all events) • Destination ARN - The Amazon Resource Name of the target service • Role ARN - IAM role that grants CloudWatch Logs permission to put data to the destination
Cross-Account Log Subscriptions
CloudWatch Logs supports cross-account subscriptions, allowing you to stream logs from one AWS account to a destination in another account. This requires: • A destination policy in the receiving account that allows the sending account • Proper IAM permissions configured on both sides
Common Use Cases
• Real-time alerting: Stream logs to Lambda for custom alerting logic • Log aggregation: Centralize logs from multiple accounts using Kinesis Data Firehose to S3 • Security analysis: Stream logs to OpenSearch for security monitoring • Compliance archival: Archive logs to S3 through Kinesis Data Firehose
Exam Tips: Answering Questions on CloudWatch Logs Subscriptions
1. Remember the three destinations: Kinesis Data Streams, Kinesis Data Firehose, and Lambda are the only valid subscription destinations
2. Limit awareness: Each log group supports a maximum of two subscription filters - this is a commonly tested limit
3. Real-time scenarios: When questions mention real-time log processing or streaming, subscriptions are likely the answer
4. Cross-account questions: If asked about centralizing logs from multiple accounts, think of cross-account subscriptions with Kinesis Data Firehose to a central S3 bucket
5. Lambda for transformation: When questions involve transforming or enriching log data before storing, Lambda as a subscription destination is the answer
6. Kinesis Data Firehose for storage: For scenarios requiring log delivery to S3, Redshift, or OpenSearch, Kinesis Data Firehose is the appropriate choice
7. Permission requirements: Questions about subscription failures often relate to missing IAM permissions or incorrect destination policies
8. Filter patterns: Understand that an empty filter pattern matches all log events in the log group
9. Near real-time distinction: Kinesis Data Firehose provides near real-time delivery (with buffering), while Kinesis Data Streams and Lambda provide true real-time processing