[squid-users] What is the ICAP chain exactly?

[Alex Rousskov]

I'v read some documents but I don't understand yet about ICAP chain how to
work and how to setup in the squid.cof.
I wonder if the squid can control sequence of connecting to some ICAP
service.
It's not only processing ICAP services in a row, but also controls sequence
of ICAP services.
Do my thoughts make sense? Or Is it possible?

For a given HTTP message, Squid 3.0 can select zero or one ICAP service.

Future Squid versions will probably be able to select a list of ICAP
services for a given HTTP message. The services would then be applied
one after another, in a chain- or pipe-like manner, where the output of
the previous service becomes the input of the next one. Developers are
looking for those who need that kind of functionality.

Sorry, I do not know what you mean by "not only processing ICAP services
in a row, but also controls sequence of ICAP services". An example might
help.

Thank you,

Alex.
P.S. Squid2 with some ICAP patches can support ICAP service chaining,
but poorly.

[Alex Rousskov]

I almost clear "chain" now however I have a bit more questions.
My thoughts "not only processing ICAP...." is as bellow.
ICAP chain has only ability to connect to next service, or before go to next
service, squid or previous service can control whether connect to next
service or not (bypass).
icap_service_1 ---> icap_service_2 --> and more. (only sequential process.)
Or
icap_service_1 ---> icap_service_3 --> .. (icap_service_1 can chose the next
service.)
Does that work for you?

I believe you are talking about "dynamic" chaining of ICAP services
(using previous ICAP response headers) as opposed to "static" chaining
(via squid.conf ACLs).

AFAIK, dynamic chaining is not supported by Squid2 ICAP patches. Its
Squid3 status is the same as general chaining support described below.
That is, developers are looking for those who need that kind of
functionality to provide patches or sponsorship.

HTH,

Alex.

-----Original Message-----
Sent: Wednesday, February 20, 2008 3:38 PM
To: S.KOBAYASHI
Cc: 'Squid Users'
Subject: Re: [squid-users] What is the ICAP chain exactly?

I'v read some documents but I don't understand yet about ICAP chain how to
work and how to setup in the squid.cof.
I wonder if the squid can control sequence of connecting to some ICAP
service.
It's not only processing ICAP services in a row, but also controls

sequence

of ICAP services.
Do my thoughts make sense? Or Is it possible?

For a given HTTP message, Squid 3.0 can select zero or one ICAP service.
Future Squid versions will probably be able to select a list of ICAP
services for a given HTTP message. The services would then be applied
one after another, in a chain- or pipe-like manner, where the output of
the previous service becomes the input of the next one. Developers are
looking for those who need that kind of functionality.
Sorry, I do not know what you mean by "not only processing ICAP services
in a row, but also controls sequence of ICAP services". An example might
help.
Thank you,
Alex.
P.S. Squid2 with some ICAP patches can support ICAP service chaining,
but poorly.