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From =?ks_c_5601-1987?B?v8DA57Dm?= <genex...@gmail.com>
Subject RE: why does a range request get in CACHE_EVENT_OPEN_WRITE?
Date Fri, 31 May 2013 08:32:44 GMT
I found a tricky solution.

 

Just let background_fill_completed work. That is the plugin disconnect
right after get some from origin.

 

Even if download happens a couple of times in stress test its better than
the plugin keeps downloading again and again.

 

Thanks.

 

From:  [mailto:genextoh@gmail.com] 
Sent: Thursday, May 30, 2013 4:06 PM
To: users@trafficserver.apache.org
Subject: why does a range request get in CACHE_EVENT_OPEN_WRITE?

 

Hi. how are you?

 

I converted rfc5861 plugin to a plugin that triggers a download from origin
server when it gets cache miss about the range request.

 

But the problem is background download hardly get cached at once. usually
it gets cached after 5~10 times background download.

 

So i traced the full debug log of ATS.

 

i found a range request also get in CACHE_EVENT_OPEN_WRITE, which finally
comes to "[is_response_cacheable] Partial content response - don't cache".

 

Meanwhile the triggered full contents download fails to get "(http_cache)
[41] [&HttpCacheSM::state_cache_open_write, CACHE_EVENT_OPEN_WRITE_FAILED]".

 

That happens several times until background download get cached and gives
heavy traffic to origin server.

 

Why does a range request get in CACHE_EVENT_OPEN_WRITE none the less it
won't be cached?

 

How can i force ATS to cache the background download at the first time? or
is there any way ATS have range request not get in CACHE_EVENT_OPEN_WRITE?

 

 

Thanks in advance.

 

P.S. i'm afraid it happens also in the case we use
background_fill_completed option. if there are many traffic i think ATS
can't assure the background_fill will be cached at once because of the
cache open write lock.


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