PASSEDcloud / azure_appgw

Azure: Azure Application Gateway 502 — Backend Pool Empty

Azure Application Gateway returning 502 because all backends were removed from the pool during a scale-in event.

Pattern

AZURE_CLOUD

Expected: AZURE_APPGW_502

Severity

HIGH

Confidence

68%

Remediation

Auto-Heal

Test Results

Metric	Expected	Actual
Pattern Recognition	AZURE_APPGW_502	AZURE_CLOUD
Severity Assessment	CRITICAL	HIGH
Incident Correlation	N/A	None
Cascade Escalation	N/A	No
Remediation	—	Auto-Heal — Corax resolves autonomously

Scenario Conditions

Azure Application Gateway v2. Backend pool 'api-pool' has 0 healthy targets. Scale-in removed all instances. Min instance count set to 0 in auto-scale.

Injected Error Messages (1)

Azure App Gateway 502 — backend pool 'api-pool' empty, auto-scale set min instances to 0, all backends removed during scale-in, 100% of requests returning 502

Neural Engine Root Cause Analysis

Azure cloud infrastructure event detected — an Azure resource may be failing, an App Service is unhealthy, Azure AD authentication is disrupted, or a Service Bus queue is backed up. Azure outages can cascade across dependent services and affect both cloud-hosted applications and hybrid on-premises integrations relying on Azure AD.

Remediation Plan

1. Check Azure Service Health (status.azure.com) for any active incidents in your region. 2. Review Azure Monitor alerts and resource health for the affected service. 3. For App Service issues, check the Kudu console for application logs and restart the app if needed. 4. For Azure AD issues, verify conditional access policies and check the Azure AD sign-in logs for failure reasons. 5. For Service Bus, check dead-letter queues and verify the sending/receiving applications are connected and processing messages.

Improvements Applied

Pattern classified as AZURE_CLOUD (expected AZURE_APPGW_502)
Severity: HIGH (expected CRITICAL)

Tested: 2026-04-02Monitors: 1 | Incidents: 1Test ID: cmnhnr9bk09c7lig7byul2gx2