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HTTP 502 when accessing Cognos through IIS when partial server farm is unhealthy

Troubleshooting


Problem

Accessing Cognos through IIS portal intermittently throws HTTP 502 when there are unhealthy 'server farm' node where the expectation should be that IIS should not send the request to an unhealthy 'server farm' node.

Symptom

IIS Access Logs:
HTTP subcode shows 502.3 which confirms this is a timeout error
SERVER-ROUTED shows the endpoint it used. This confirms the endpoint was unhealthy at the time of the route.
Example:
2022-09-07 00:53:42 Web_server1_IP_Address GET /ibmcognos/bi/v1/plugins/themes/current/css/palette.css v=1662511981405&X-ARR-CACHE-HIT=0&SERVER-ROUTED=ServerFarmEndpoint1&X-ARR-LOG-ID=6c0e4241-5f1e-4849-b40b-14c1f7a246a3 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/104.0.5112.81+Safari/537.36+Edg/104.0.1293.47 http://Web_server1/ibmcognos/bi/?perspective=home 502 3 12002 42064
IIS Server Farm -> Health Test:
image-20230126113429-3
IIS Server Farm -> Monitoring and Management 
image-20230126113529-4

Document Location

Worldwide

[{"Type":"MASTER","Line of Business":{"code":"LOB76","label":"Data Platform"},"Business Unit":{"code":"BU048","label":"IBM Software"},"Product":{"code":"SSTSF6","label":"IBM Cognos Analytics"},"ARM Category":[{"code":"a8m50000000Cl6dAAC","label":"Install-\u003EGateway\/Web Server"}],"ARM Case Number":"TS010303329","Platform":[{"code":"PF033","label":"Windows"}],"Version":"All Versions"},{"Product":{"code":"SS6G84","label":"IBM Cognos Analytics on Cloud"},"Business Unit":{"code":"BU048","label":"IBM Software"},"Component":" ","Platform":[{"code":"","label":""}],"Version":"","Edition":"","Line of Business":{"code":"LOB76","label":"Data Platform"}}]

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Document Information

Modified date:
06 May 2025

UID

ibm16857789

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