GCP Cloud Logging

GCP Cloud Logging

MCP Server

• Endpoint: https://logging.googleapis.com/mcp (Streamable HTTP)
• Auth: OAuth 2.0 via Google IAM — service account key (GOOGLE_APPLICATION_CREDENTIALS) or gcloud auth application-default login
• Requires: GCP_PROJECT_ID environment variable

Available Tools (6)

Workflow: VPC Flow Log Analysis

When investigating GCP network traffic:

1. Discover logs: list_log_names — find compute.googleapis.com/vpc_flows
2. Query flow logs: list_log_entries filtered by:
   • Source/destination IP
   • Port and protocol
   • Action (ALLOWED/DENIED)
   • Time range
3. Denied traffic: Filter for reporter="DEST" and denied connections
4. Top talkers: Aggregate by source/destination IP and bytes
5. Cross-reference: Use gcp-cloud-monitoring for network metrics during the same period
6. Report: Traffic analysis with security findings

Workflow: Firewall Log Investigation

When investigating GCP firewall rule activity:

1. Discover logs: list_log_names — find compute.googleapis.com/firewall
2. Query firewall logs: list_log_entries filtered by:
   • Rule name
   • Action (ALLOWED/DENIED)
   • Source/destination IP
   • Port
3. Denied connections: Find blocked traffic patterns
4. Rule effectiveness: Which rules are hitting most frequently?
5. Report: Firewall activity summary with recommendations

Workflow: Audit Trail Investigation

When investigating GCP API activity (equivalent of AWS CloudTrail):

1. Admin activity logs: list_log_entries for cloudaudit.googleapis.com/activity — who created/modified/deleted resources?
2. Data access logs: list_log_entries for cloudaudit.googleapis.com/data_access — who read what?
3. Filter by principal: Narrow to specific user or service account
4. Filter by method: Narrow to specific API calls (e.g., compute.instances.delete)
5. Time window: Focus on the incident period
6. Report: Audit timeline with responsible principals and actions

Workflow: Troubleshooting with Logs

When debugging a GCP issue:

1. Application logs: list_log_entries for the affected service
2. Error filtering: Filter by severity (ERROR, CRITICAL, EMERGENCY)
3. Instance logs: Filter by resource.labels.instance_id for specific VMs
4. Correlate: Match timestamps with gcp-cloud-monitoring alert violations
5. Bucket check: list_buckets to verify log retention settings
6. Report: Root cause analysis with log evidence

Common GCP Log Sources

Log Query Filter Examples

# VPC flow logs — denied traffic to port 443
resource.type="gce_subnetwork"
logName="projects/PROJECT/logs/compute.googleapis.com%2Fvpc_flows"
jsonPayload.disposition="DENIED"
jsonPayload.connection.dest_port=443

# Firewall — denied SSH attempts
resource.type="gce_subnetwork"
logName="projects/PROJECT/logs/compute.googleapis.com%2Ffirewall"
jsonPayload.disposition="DENIED"
jsonPayload.connection.dest_port=22

# Audit — who deleted VMs in the last hour
logName="projects/PROJECT/logs/cloudaudit.googleapis.com%2Factivity"
protoPayload.methodName="compute.instances.delete"
timestamp>="2026-01-01T00:00:00Z"

# DNS queries from specific source
resource.type="dns_query"
jsonPayload.sourceIP="10.0.1.50"

Important Rules

• Remote MCP server — hosted by Google, no local install needed
• OAuth 2.0 authentication — uses IAM for access control
• Project-scoped — logs are scoped to the configured GCP project
• Log queries have cost implications — Cloud Logging charges for data scanned beyond free tier (50 GB/month free)
• Retention varies — Admin activity logs: 400 days, Data access logs: 30 days (default), VPC flow logs: depends on bucket config
• Record in GAIT — log all investigations for audit trail

Environment Variables

• GCP_PROJECT_ID — Google Cloud project ID
• GOOGLE_APPLICATION_CREDENTIALS — Path to service account key JSON file