Web Cache Serves Stale Data As Third Party Module Is Setting Duplicate ETAG Values
Last updated on MARCH 08, 2017
Applies to:Web Cache - Version 184.108.40.206.0 to 220.127.116.11.0 [Release Oracle11g]
Information in this document applies to any platform.
- Oracle Webcache 11.1.1.X is installed
- Two Webcaches are configured in a cluster on seperate nodes
- Webcache is intermittently serving stale data when the cached object should have expired
- The issue can not be replicated if Webcaches are taken out of cluster
- The issue can still be replicated if only one Webcache is running in the cluster
- If all caching rules are disabled the problem does not occur
- Analysis of the problem via the log files shows:
a) The client makes a connection to Webcache for the page.
b) Webcache notices the page has expired and marks the cached version as garbage
c) Webcache goes off to OHS and fetches a new page.
d) Even though Webcache fetches a new page from OHS, and stores it in the cache , Webcache is sending back a 304 Not Modified back to the client, rather than the new page.
e) Because of the 304, the browser is using the original version that it has stored in it's own browser cache, and hence the browser is seeing stale data!
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