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https://issues.apache.org/jira/browse/TS-3665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14572947#comment-14572947
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Susan Hinrichs commented on TS-3665:
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So in the follow redirect case, we should ignore any 30x response that happens
to already be in the cache. Although we would have to look it up in the cache
(as part of normal operating procedure) to know it was a 30x.
So we do need to attempt to read from the cache for the initial request anyway.
After that, it seems reasonable to not attempt to write to the cache until the
"final" response that is sent back to the client. Again, we may want to be
reading from the cache on the intermediates, in case this is the final location
and has already been cached.
> Redirect logic causing debug asserts and leaking cache_vc's
> -----------------------------------------------------------
>
> Key: TS-3665
> URL: https://issues.apache.org/jira/browse/TS-3665
> Project: Traffic Server
> Issue Type: Bug
> Components: Cache
> Reporter: Susan Hinrichs
>
> This is related to TS-3140 and TS-3661. I spent this morning reviewing the
> issue addressed by TS-3140 after the fixes for TS-3661 were put in place.
> TS-3140 addresses the issue when the 301 is in cache, but I'm seeing asserts
> for both 301's in cache and 301's not in cache.
> My first assert was line 109 in HttpCacheSM.cc line 109,
> ink_assert(cache_read_vc == NULL). I added a cache_sm.close_read() to the
> HttpTransact::SM_ACTION_REDIRECT_READ: case of HttpSM::handle_api_return.
> While only debug assert, if we ignore it we will reassign cache_read_vc
> without freeing the previous.
> I addressed this by adding cache_sm.close_read() to the
> SM_ACTION_REDIRECT_READ case of HttpSM::handle_api_return.
> My second assert is in HttpSM::do_cache_prepare_action (line 4446 of
> HttpSM.cc). Before the changes for TS-3661, it was expressing itself in
> SM_ACTION_CACHE_ISSUE_WRITE case of HttpSM::cache_write_state(). In this
> case, do_cache_prepare_action will open a new cache_write_vc overwriting the
> original and losing the cache_vc memory.
> The original fix to TS-3140 addressed this by adding a cache_sm.close_write
> in the SM_ACTION_REDIRECT_READ case of HttpSM::handle_api_return. But this
> caused problems of TS-3661 causing the originally selected cache key to be
> lost, but if you pass through this logic, I assume that the original cache
> write vc will be lost anyway. [~sudheerv] and [~zwoop] does this situation
> not happen in your redirect use cases? I'm afraid that I'm not following how
> the original cache key is preserved in the second cache open only if the
> first cache write open is not cleaned up.
> My test URLs are:
> curl -v --proxy localhost:80
> http://whos.amung.us/cwidget/4s62rme9/007071fecc4e.png
> and
> curl -v --proxy localhost:80 http://docs.trafficserver.apache.org
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