[infinispan-dev] Hot Rod - pt3

Mon Jan 4 12:17:53 EST 2010

On 29 Dec 2009, at 18:56, Alex Kluge wrote:

> Hi,
> 
>  I hope you have all enjoyed the holiday season.
> 
>  The protocol is an interesting read. There are a few things that stand
> out.
> 
>  - No events. I used events, that is asynchronous messages originating
>    from the server when certain conditions are met, to notify clients
>    that data was written to the server.  This was mostly driven by the
>    need to notify an L1 cache of a write to the cache server. It would
>    be good to allow for this usage in this protocol. Note that this is
>    another case where the op code is useful to have as part of the
>    message.

Isn't this expensive?  Doesn't this mean the server has to fire off messages to each and every connected client, whether the clients are interested in these messages or not?

>  - What happens if the key or the value is not text? I have a way of
>    representing the data to allow for a wide variety of data types,
>    even allowing for arrays or maps. This will make the protocol more
>    complex, but the assumption that the data is a string is rather
>    limiting. This is already sketched out in the wiki.

There is some work around non-text data in the RESTful cache server.  Adding MIME types to any opaque data allows us to attach handlers to this data, such as XML or JSON data.  What do you have in mind?

>  - Is the full message size still there as a header field? Is this
>    necessary? It precludes you from generating messages where you
>    don't know the full size of the message beforehand. For example,
>    in the future you might want to write a map of the data in the
>    cache. I do this, and can chunk the data, thus allowing me to send
>    an arbitrarily large map. This becomes, to put it mildly, difficult
>    if you need the size of the request as a header field.

+1.  If there is a way to work without this size header that would be better.

Cheers
Manik

> 
>                                  Thanks,
>                                       Alex
> 
> --- On Mon, 12/21/09, Manik Surtani <manik at jboss.org> wrote:
> 
>> From: Manik Surtani <manik at jboss.org>
>> Subject: Re: [infinispan-dev] Hot Rod - pt3
>> To: "infinispan -Dev List" <infinispan-dev at lists.jboss.org>
>> Date: Monday, December 21, 2009, 5:36 AM
>> 
>> On 21 Dec 2009, at 11:08, Galder Zamarreno wrote:
>> 
>>> Hi all,
>>> 
>>> Re: http://community.jboss.org/wiki/HotRodProtocol
>>> 
>>> First, I've made the corresponding changes based on
>> the feedback I got 
>>> from pt2. This included reducing the response header
>> since clients are 
>>> already aware of what they sent, addition of topology
>> view id to to non 
>>> dumb requests and further specification in responses
>> when topology 
>>> changes have happened...etc.
>>> 
>>> I've also added flags to the request header that allow
>> sending 
>>> Infinispan flags like: skip cache store, zero lock
>> acquisition 
>>> timeout...etc.
>> 
>>> Note that I've noted this as being N * 1 byte where
>> each byte represents 
>>> a flag. However, I think this could maybe be sent more
>> efficiently by 
>>> using XOR, i.e.
>>> 
>>> 0x00 -> no flag
>>> 0x01 (0000 0001) -> zero lock acquisition
>>> 0x02 (0000 0010) -> cache mode local
>>> 0x03 (0000 0011) -> zero lock acquisition + cache
>> mode local
>>> 0x04 (0000 0100) -> skip locking
>>> ...etc.
>>> 
>>> With 2 bytes, we could implement 16 Flags, we
>> currently 11. However, we 
>>> could use vint as well, making sure that the most
>> significant bit does 
>>> not mean anything flag wise. Iow, with vint, in 1 byte
>> we'd be able to 
>>> define 7 diff flags. Thoughts?
>> 
>> +1
>> 
>>> I've also added the quit command that disconnects
>> clients.
>> 
>> Does this have any effect on the servers?
>> 
>>> Finally, as far as I'm concerned, the specification is
>> complete. I'm 
>>> leaving the quiet commands out of this initial scope
>> (see 
>>> http://code.google.com/p/memcached/wiki/MemcacheBinaryProtocol).
>> 
>>> Remember that quiet commands could be used so that the
>> server buffers 
>>> responses and only when you send a non-quiet command,
>> the server replies 
>>> with all the pending answers.
>>> 
>>> As you can see at the bottom of the wiki, I've added a
>> local only put 
>>> request/response example so that readers get an idea
>> of what a full 
>>> command looks like. I had received some feedback from
>> readers saying 
>>> that it was difficult to understand how it all fit
>> together.
>> 
>> The examples look good, however I would not use the
>> LOCAL_ONLY flag since that flag really only has meaning in a
>> p2p context.  In a client-server context, this flag is
>> useless, and probably meaningless.  I would suggest a
>> different flag for the example, e.g., ZERO_LOCK_TIMEOUT.
>> 
>>> I'll probably add a couple more examples for
>> non-so-dumb and clever 
>>> request/responses but I'll held them until we have a
>> final round of 
>>> feedback and people can indicate whether they want any
>> other examples 
>>> appearing in the wiki.
>>> 
>>> Cheers,
>>> -- 
>>> Galder Zamarreño
>>> Sr. Software Engineer
>>> Infinispan, JBoss Cache
>>> _______________________________________________
>>> infinispan-dev mailing list
>>> infinispan-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>> 
>> --
>> Manik Surtani
>> manik at jboss.org
>> Lead, Infinispan
>> Lead, JBoss Cache
>> http://www.infinispan.org
>> http://www.jbosscache.org
>> 
>> 
>> 
>> 
>> 
>> _______________________________________________
>> infinispan-dev mailing list
>> infinispan-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>> 
> 
> 
> 
> 
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--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org