Design Cross Project Log Based Monitoring Alerting

What this solution is

This architecture combines user-defined counter log-based metrics with Cloud Monitoring metrics scopes to enable centralized, multi-project security observability and automated threshold alerting over Cloud Audit Logs.

How it meets all requirements

• Rate of failed access attempts: User-defined counter log-based metrics count log entries matching specific audit log filter criteria (such as severity>=ERROR or specific gRPC/HTTP status codes) as they are ingested by Cloud Logging.
• Granular trend analysis via metadata: Counter metrics support user-defined labels extracted directly from fields in matching log entries (such as protoPayload.authenticationInfo.principalEmail and protoPayload.serviceName), allowing Cloud Monitoring to record separate time series for each combination of label values.
• Centralized dashboard and cross-project alerting: By establishing a multi-project metrics scope hosted by a dedicated scoping project, all metrics from the 20 monitored projects become visible to the scoping project. Metric-based alerting policies and custom dashboards created in the scoping project operate across all projects within its metrics scope, eliminating the need to duplicate alerting rules across projects.

Key advantages and capabilities

• Cross-project scalability: Alerting policies evaluated over metrics scopes dynamically aggregate time series across all attached projects.
• Custom dimensional charting: Extracted labels allow dashboard widgets to group, break down, and filter by principal, service, or project.
• Standardized incident workflow: Incidents generated from metric-based alerts integrate directly with notification channels (such as PagerDuty, Slack, Webhooks, or SIEM ingestion pipelines).

Why this is optimal

Metric-based alerting policies built on log-based metrics leverage the full aggregation, grouping, and cross-project scoping capabilities of Cloud Monitoring. In contrast, log-based alerting policies operate only within individual project boundaries and cannot leverage multi-project metrics scopes.