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:
IIS Server Farm -> Monitoring and Management
Cause
IIS ARR module was not able to evaluate a request that uses a reverse proxy route to a server farm.
Diagnosing The Problem
FREB trace shows the exact IIS logic ARR has taken to route the requests and will show more information:
Resolving The Problem
There are multiple ways to tackle this:
1. Depending on the FREB trace results, you can move the Cognos application into the default application pool so that ARR can evaluate the condition of the server farm status.
2. Control the IIS Server Farm so that you mark unhealthy servers as unavailable.
Further questions regarding IIS should be discussed with Microsoft as this is an IIS issue and not one concerning Cognos.
Document Location
Worldwide
[{"Type":"MASTER","Line of Business":{"code":"LOB10","label":"Data and AI"},"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"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"}]
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Document Information
Modified date:
25 January 2023
UID
ibm16857789