Log routers in Google Cloud Platform are a fundamental component of Cloud Logging that determine how log entries are processed, stored, and exported within your cloud environment. They act as the central routing mechanism that evaluates every log entry generated by your resources and decides what h…Log routers in Google Cloud Platform are a fundamental component of Cloud Logging that determine how log entries are processed, stored, and exported within your cloud environment. They act as the central routing mechanism that evaluates every log entry generated by your resources and decides what happens to each entry based on configured rules called sinks.
When log entries are written to Cloud Logging, the log router receives them and processes them through a series of sinks. Each sink consists of three main elements: a filter that determines which logs match specific criteria, a destination where matching logs should be sent, and optional exclusion filters to prevent certain logs from being processed.
The log router supports several destination types for your logs. You can route logs to Cloud Logging buckets for storage and analysis, BigQuery datasets for advanced querying and analytics, Cloud Storage buckets for long-term archival, or Pub/Sub topics for streaming to external systems or custom applications.
Every Google Cloud project comes with two default sinks: the _Required sink that captures audit logs and system events that cannot be disabled, and the _Default sink that sends logs to the _Default logging bucket. You can create custom sinks to meet specific requirements such as compliance, cost optimization, or integration needs.
For Associate Cloud Engineer certification, understanding log routers is essential for several operational tasks. You need to know how to create and manage sinks, configure appropriate filters using the Logging query language, set up exclusion filters to reduce storage costs by filtering out unnecessary logs, and troubleshoot logging issues when expected logs are not appearing in designated destinations.
Proper configuration of log routers helps organizations maintain visibility into their cloud operations, meet regulatory compliance requirements, optimize logging costs by routing only necessary logs to expensive storage solutions, and integrate cloud logs with external monitoring and security tools.
Log Routers in Google Cloud Platform
Why Log Routers Are Important
Log routers are a fundamental component of Cloud Logging in Google Cloud Platform. They determine where your log entries go after they are received by Cloud Logging. Understanding log routers is essential for managing costs, ensuring compliance, maintaining security, and organizing your logging infrastructure effectively. In production environments, proper log routing can significantly reduce storage costs while ensuring critical logs reach the appropriate destinations.
What Are Log Routers?
A log router is the mechanism within Cloud Logging that processes every log entry and determines its destination based on configured sinks. Each Google Cloud project, folder, billing account, and organization has its own log router. The log router evaluates incoming log entries against all configured sinks and routes copies of the logs to the appropriate destinations.
Key components of log routing include:
Sinks: Rules that define where log entries should be sent. Each sink contains a filter that determines which logs match and a destination where matching logs are exported.
Inclusion Filters: Determine which log entries are captured by a sink.
Exclusion Filters: Prevent specific log entries from being ingested or routed, helping reduce costs and noise.
Destinations: Where logs are sent, including Cloud Storage buckets, BigQuery datasets, Pub/Sub topics, and other Cloud Logging buckets.
How Log Routers Work
1. Log Entry Reception: When a log entry is generated, it arrives at the Cloud Logging API.
2. Router Processing: The log router receives the entry and checks it against all configured sinks.
3. Filter Evaluation: Each sink's inclusion filter is evaluated. If a log entry matches multiple sinks, copies are sent to each matching destination.
4. Exclusion Processing: Exclusion filters are applied to prevent certain logs from being stored or routed.
5. Routing to Destinations: Matching log entries are sent to their configured destinations asynchronously.
Default Sinks
Every project comes with two default sinks: - _Default sink: Routes logs to the _Default log bucket with 30-day retention - _Required sink: Routes Admin Activity and System Event audit logs to the _Required bucket with 400-day retention (cannot be modified)
Common Sink Destinations
- Cloud Storage: For long-term archival and compliance requirements - BigQuery: For log analysis and querying - Pub/Sub: For streaming logs to external systems or custom applications - Cloud Logging Buckets: For organizing logs within Cloud Logging with different retention periods - Splunk: For integration with third-party SIEM solutions
Creating and Managing Sinks
Sinks can be created using: - Google Cloud Console - gcloud logging sinks create command - Cloud Logging API - Terraform or other IaC tools
When creating a sink, you must grant the sink's service account appropriate permissions on the destination resource.
Exam Tips: Answering Questions on Log Routers
1. Remember the _Required sink: This sink cannot be disabled or modified. It always captures Admin Activity and System Event audit logs with 400-day retention.
2. Understand filter syntax: Know that sinks use Cloud Logging query language for filters. Questions may test whether you can identify correct filter expressions.
3. Know destination permissions: When routing to a destination, the sink's writer identity needs appropriate IAM roles on the destination resource.
4. Cost optimization scenarios: Questions about reducing logging costs often involve creating exclusion filters or modifying the _Default sink.
5. Aggregated sinks: For organization-wide or folder-wide log collection, aggregated sinks at the organization or folder level can capture logs from child resources.
6. Sink scope: Remember that sinks can be created at project, folder, billing account, or organization levels, each with different visibility into logs.
7. Order of operations: Exclusion filters are processed before logs are written to destinations, making them effective for cost control.
8. BigQuery for analysis: When questions mention log analysis, querying, or creating dashboards from logs, BigQuery is typically the correct destination choice.
9. Real-time processing: When questions involve real-time log processing or streaming to external systems, Pub/Sub is the appropriate destination.
10. Retention requirements: Match retention period requirements with appropriate destinations - Cloud Storage for very long retention, custom buckets for specific retention periods.