How to make multiple clients can get the response at the same time by stream.
Per Buer
perbu at varnish-software.com
Sat Feb 2 13:58:32 CET 2013
That is an interesting use case. So, if I understand it correctly what
would happen would be something like this:
1. Client requests /foo
2. Varnish goes to backend and asks for /foo
3. Backend responds and notifies that this would be accessed in the future
as /bar
4. Varnish changes the object in memory or maybe copies it.
I'm guessing that would not be possible as the hashing happens quite early
and you would have to alter the hash before looking it up. It might be
easier to maintain a map of various rewrites in memory, memcache or redis
and lookup the rewrite in vcl_recv.
On Sat, Feb 2, 2013 at 3:35 AM, Xianzhe Wang <wxz19861013 at gmail.com> wrote:
> Hi,
> I'm sorry, I wasn't being clear. Thank you for your patience.
> I'm trying to estimate the response header from backend, if the
> "content-type:" is " image/*", we know that the response body is image.
> Then I'll rewrite
> the image and insert it into varnish cache. Subsequent request will hit
> the rewritten image.
> That's I wanna to do. Fetch backend response, rewrite image and insert
> into varnish cache.
>
> Regards,
> --
> Shawn Wang
>
>
>
>
>
> 2013/2/1 Per Buer <perbu at varnish-software.com>
>
>> Hi,
>>
>> I don't quite understand what you're trying to do. Varnish will store the
>> jpg together with the response headers in memory. When you request the
>> object Varnish will deliver it verbatim along with the HTTP headers. What
>> exactly are you trying to do?
>>
>>
>> PS: I see we haven't built packages of 3.0.3-plus, yet. This should pop
>> up in the repo next week. Until then 3.0.2s might suffice.
>>
>>
>> On Fri, Feb 1, 2013 at 8:01 AM, Xianzhe Wang <wxz19861013 at gmail.com>wrote:
>>
>>> Hi,
>>> Thanks for clarification. What you say is very clear.
>>> I am sorry to show my poor English, but I have tried my best to
>>> communicate.
>>>
>>> There is another question.For example, if we request a .jpg
>>> file(cacheable), varnish will encapsulation it as an object and insert
>>> into memory. How can we get the .jpg file from the object?
>>>
>>> Thank you for help again.
>>>
>>> -Shawn Wang
>>>
>>>
>>> 2013/1/30 Per Buer <perbu at varnish-software.com>
>>>
>>>> Hi,
>>>>
>>>> I was a bit quick and I didn't read the whole email the first time.
>>>> Sorry about that. You're actually using the streaming branch, already I
>>>> see. What you're writing is really, really odd. There is a slight lock
>>>> while the "first" object is being fetched where other requests will be put
>>>> on the waiting list. However, when the hit-for-pass object is created these
>>>> should be released and pass'ed to the clients.
>>>>
>>>> If the backend takes forever coming back with the response headers then
>>>> the situation would be something like what you describe. However, that
>>>> would be odd and doesn't make much sense.
>>>>
>>>> PS: The streaming branch was renamed "plus" when it got other
>>>> experimental features. You'll find source
>>>> https://github.com/mbgrydeland/varnish-cache and packages at
>>>> repo.varnish-cache.org/test if I recall correctly.
>>>>
>>>>
>>>>
>>>>
>>>> On Wed, Jan 30, 2013 at 3:32 AM, Xianzhe Wang <wxz19861013 at gmail.com>wrote:
>>>>
>>>>>
>>>>> Hi,
>>>>> Thanks a lot.
>>>>>
>>>>> I tried option
>>>>> "set req.hash_ignore_busy = true;"
>>>>> in vlc_recv.
>>>>> I think it works. But there are side effects: it would increase
>>>>> backend load.
>>>>>
>>>>> I have an idea about it in my previous email. what do you think about
>>>>> it?
>>>>>
>>>>> Another question is that where can I find the "plus" branch of Varnish
>>>>> which matches this issue.
>>>>>
>>>>> Any suggestions will be appreciate.
>>>>> Thanks again for help.
>>>>>
>>>>> Regards,
>>>>> --
>>>>> Shawn Wang
>>>>>
>>>>>
>>>>> ---------- Forwarded message ----------
>>>>> From: Xianzhe Wang <wxz19861013 at gmail.com>
>>>>> Date: 2013/1/30
>>>>> Subject: Re: How to make multiple clients can get the response at the
>>>>> same time by stream.
>>>>> To: Jakub Słociński <kuba at ovh.net>
>>>>>
>>>>>
>>>>> Hi Jakub S.
>>>>> Thank you very much.
>>>>> I tried, and take a simple test, two client request the big file at
>>>>> the same time, they get the response stream immediately, so it works.
>>>>> In that case, multiple requests will go directly to "pass", they do
>>>>> not need to wait, but it would increase backend load.
>>>>> We need to balance the benefits and drawbacks.
>>>>>
>>>>> I wanna is that:
>>>>> Client 1 requests url /foo
>>>>> Client 2..N request url /foo
>>>>> Varnish tasks a worker to fetch /foo for Client 1
>>>>> Client 2..N are now queued pending response from the worker
>>>>> Worker fetch response header(just header not include body) from
>>>>> backend, and find it non-cacheable, then make the remaining
>>>>> requests(Client 2..N) go directly to "pass". And creat the hit_for_pass
>>>>> object synchronously in the first request(Client 1).
>>>>> Subsequent requests are now given the hit_for_pass object
>>>>> instructing them to go to the backend as long as the hit_for_pass object
>>>>> exists.
>>>>>
>>>>> As I mentioned below, is it feasible? Or do you have any Suggestions?
>>>>>
>>>>> Thanks again for help.
>>>>>
>>>>> Regards,
>>>>> --
>>>>> Shawn Wang
>>>>>
>>>>>
>>>>>
>>>>> 2013/1/29 Jakub Słociński <kuba at ovh.net>
>>>>>
>>>>>> Hi Xianzhe Wang,
>>>>>> you should try option
>>>>>> "set req.hash_ignore_busy = true;"
>>>>>> in vlc_recv.
>>>>>>
>>>>>> Regards,
>>>>>> --
>>>>>> Jakub S.
>>>>>>
>>>>>>
>>>>>> Xianzhe Wang napisał(a):
>>>>>> > Hello everyone,
>>>>>> > My varnish version is 3.0.2-streaming release.And I set
>>>>>> > "beresp.do_stream = true" in vcl_fetch in order to "Deliver the
>>>>>> object to
>>>>>> > the client directly without fetching the whole object into varnish";
>>>>>> >
>>>>>> > This is a part of my *.vcl file:
>>>>>> >
>>>>>> > sub vcl_fetch {
>>>>>> > set beresp.grace = 30m;
>>>>>> >
>>>>>> > set beresp.do_stream = true;
>>>>>> >
>>>>>> > if (beresp.http.Content-Length && beresp.http.Content-Length ~
>>>>>> > "[0-9]{8,}") {
>>>>>> > return (hit_for_pass);
>>>>>> > }
>>>>>> >
>>>>>> > if (beresp.http.Pragma ~ "no-cache" ||
>>>>>> beresp.http.Cache-Control ~
>>>>>> > "no-cache" || beresp.http.Cache-Control ~ "private") {
>>>>>> > return (hit_for_pass);
>>>>>> > }
>>>>>> >
>>>>>> > if (beresp.ttl <= 0s ||
>>>>>> > beresp.http.Set-Cookie ||
>>>>>> > beresp.http.Vary == "*") {
>>>>>> >
>>>>>> > set beresp.ttl = 120 s;
>>>>>> > return (hit_for_pass);
>>>>>> > }
>>>>>> >
>>>>>> > return (deliver);
>>>>>> > }
>>>>>> >
>>>>>> > Then I request a big file(about 100M+) like "xxx.zip" from
>>>>>> clients.There is
>>>>>> > only one client can access the object.because "the object will
>>>>>> marked as
>>>>>> > busy as it is delivered."
>>>>>> >
>>>>>> > But if the request goes directly to “pass” ,multiple clients can
>>>>>> get the
>>>>>> > response at the same time.
>>>>>> >
>>>>>> > Also if I remove
>>>>>> > if (beresp.http.Content-Length && beresp.http.Content-Length ~
>>>>>> > "[0-9]{8,}") {
>>>>>> > return (hit_for_pass);
>>>>>> > }
>>>>>> > to make the file cacheable,multiple clients can get the response at
>>>>>> the
>>>>>> > same time.
>>>>>> >
>>>>>> > Now I want "multiple clients can get the response at the same
>>>>>> time." in all
>>>>>> > situations("pass","hit","hit_for_pass").
>>>>>> >
>>>>>> > What can I do for it?
>>>>>> > Any suggestions will be appreciate.
>>>>>> > Thank you.
>>>>>> >
>>>>>> > -Shawn Wang
>>>>>>
>>>>>> > _______________________________________________
>>>>>> > varnish-misc mailing list
>>>>>> > varnish-misc at varnish-cache.org
>>>>>> > https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> <http://www.varnish-software.com/> *Per Buer*
>>>>
>>>> CEO | Varnish Software AS
>>>> Phone: +47 958 39 117 | Skype: per.buer
>>>> We Make Websites Fly!
>>>>
>>>>
>>>
>>
>>
>> --
>> <http://www.varnish-software.com/> *Per Buer*
>> CEO | Varnish Software AS
>> Phone: +47 958 39 117 | Skype: per.buer
>> We Make Websites Fly!
>>
>>
>
--
<http://www.varnish-software.com/> *Per Buer*
CEO | Varnish Software AS
Phone: +47 958 39 117 | Skype: per.buer
We Make Websites Fly!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.varnish-cache.org/lists/pipermail/varnish-misc/attachments/20130202/c521f695/attachment.html>
More information about the varnish-misc
mailing list