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Cisco Bug: CSCur40497 - HTTP Progressive download Content is Incomplete in CA but complete in SE

Last Modified

Jun 21, 2020

Products (1)

  • Cisco Content Delivery Engine Series

Known Affected Releases

3.1(2)

Description (partial)

Symptom:
On CA "Content is Incomplete" and on SE "Content is Complete".

Conditions:
1, Client sent a request to SE-03;
2, Web engine served this request and sent a command to UKSE to pull data from upstreams(SE-01, CA);
3, Client aborted;
4, Web engine stopped serving this request and sent a command to UKSE to abort data feeding;
5, UKSE kept pulling and writing data to cached content until came to the boundary of n*4MB, in other words, UKSE managed the cached contents in the unit of 4MB. It might take as long as tends of seconds depending on network speed, cached content size and current writing postion;
6, During the time period of #5, client issued another request;
7, Web engine served this request without sending another command to UKSE to pull data, because there's already one, which was to be aborted later;
8, UKSE finally ended data feeding, note that the content was still incomplete;
9, Web engine encountered the edge of the incomplete content, so it sent another command to UKSE to pull data from upstreams. Because it just needed the data unavailable, so it issued a range request to upstream(SE-01);
10, Web engine got requested data(206 response) and in the end, all the data of the content was available, so it just marked the content as complete;
11, For SE-01 and CA, they firstly got the incomplete content after #2, then, the cached content expired, so when range request came in due to #9, they issued range &IMS request to upstream. Since both SE-01 and CA got 206, they deleted old content and cached the 206 response, as a result, SE-01 and CA had incomplete cached content;
12, In the end, we have SE-03 complete content, while SE-01 and CA incomplete content.
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