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Re: Interplatform (interprocess, interlanguage) communication

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On 12-02-08 04:41 AM, BGB wrote:
> On 2/7/2012 5:26 PM, Arved Sandstrom wrote:
>> On 12-02-07 07:38 PM, BGB wrote:
>>> On 2/7/2012 11:11 AM, jebblue wrote:
>> [ SNIP ]
>>>>
>>>> I recommend using sockets.
>>>>
>>>
>>> in general, I agree (sockets generally make the most sense), although
>>> there are cases where file-based communications can make sense, although
>>> probably not in the form as described in the OP.
>>>
>>>
>>> another issue (besides how to pass messages), is what sort of form to
>>> pass messages in.
>>>
>>> usually, in my case, if storing data in files, I tend to prefer
>>> ASCII-based formats.
>>>
>>> usually, for passing messages over sockets, I have used "compact"
>>> specialized binary formats, typically serialized data from some other
>>> form (such as XML nodes or S-Expressions). although "magic byte value"
>>> based message formats are initially simpler, they tend to be harder to
>>> expand later (whereas encoding/decoding some more generic form, though
>>> initially more effort, can turn out to be easier to maintain and extend
>>> later).
>>>
>>> note: this does not mean SOAP or CORBA or some other "standardized"
>>> messaging system, rather just that one initially builds and processes
>>> the messages in some form that is more high-level than spitting out
>>> bytes, and processing everything via a loop and a big "switch()" or
>>> similar (although this can be an initially fairly simple option, so has
>>> some merit due to ease of implementation).
>>>
>>>
>>> the main reason for picking a binary message-serialization format (for
>>> something like S-Expressions or XML nodes), would be mostly if there is
>>> a chance that the serialized data will go over the internet, and a
>>> textual format can be a bit bulkier (and thus slower to transmit over a
>>> slower connection), as well as typically being slower to decode (a
>>> sanely designed message format can be much more quickly unpacked than a
>>> textual format can be parsed).
>>>
>>> sending text over sockets may have merits as well, and is generally
>>> preferable for "open" protocols.
>>>
>>> or such...
>>
>> I've done a fair bit with sockets myself, including recently, in fact
>> including on a current gig. Some of the message formats have been
>> designed by others, some by me. A few of them are specialized industry
>> standards, some are very custom and bespoke.
>>
>> A few of the formats have been binary: fixed-length blocks of data with
>> fields at various offsets. Works well enough if it suits the data.
>>
>> A bunch of others have been text and line-oriented: a fixed number of
>> lines of data in known order, so that line 10 is always the data for a
>> particular field.
>>
>> Other things to consider: JAXB, JSON etc. Minimum coding fuss at the
>> endpoints if that's what's appropriate for constructing message payloads.
>>
>> I like text-based protocols, for some simple situations, that behave
>> like SMTP or POP. But it obviously depends on what you expect your
>> client and server to do, it's just another approach to be aware of.
>>
> 
> well, text need not be all that limiting.

You may have misunderstood something I said if you got that impression
from me, that text is all that limiting. :-)

[ SNIP ]

> note: my main way of working with XML is typically via DOM-style
> interfaces (if I am using it, it is typically because I am directly
> working with the data structure, and not as the result of some dumb-ass
> "data binding" crud...).

I haven't been able to completely avoid using the DOM, but I loathe the
API. If I'm using XML at all, and JAXB suits, I'll use JAXB. More
generally I'll use SAX or StAX.

I almost never encounter a situation where DOM is called for, simply
because no random access to the document is called for. When I send XML
back and forth as a payload, the entire thing is meant to be used, and
it makes sense to do the immediate and complete conversion into real
information rather than storing it into an opaque and kludgy DOM
representation.

For a lot of situations, not just message passing between endpoints, I
have backed away from XML anyway. For configuration files I have gotten
newly enthused by .properties files, because so often they fit the bill
much better than XML configuration files. And I mentioned JSON
previously, I prefer that to XML in many situations now.

[ SNIP ]

>> One of the big things in designing one's own messaging is error
>> handling. People generally do just fine with the happy path, but ignore
>> comprehensive error handling, or get wrapped around the axle trying to
>> do it.
> 
> yeah, but this applies to programming in general, so message-passing is
> likely nothing special here.

That's true, but it's maybe a bit more of an art form with messages.
Your message producer may be Java and produce beautiful exceptions in
your carefully designed exception hierarchy, but your clients may very
well not be Java at all, in which case you may end up with an error
message sub-protocol that borrows ideas from from HTTP status codes.

A lot of Java programmers these days maybe have never really dealt with
return codes, because we sort of tell them not to use them in Java, but
in the case of implementation-neutral status codes (including ones for
errors) that's really the design mindset that you need to be in: status
codes.

one issue maybe special to sockets though
> is the matter of whether or not the whole message has been received,
> often resulting in some annoying code to basically read messages from
> the socket and not decode them until the entire message has been received.

There is that. Although I find that once you've worked through one or
two socket implementations that you tend to devise some pretty re-usable
code for handling the incomplete message situations.
[ SNIP ]

AHS
-- 
...wherever the people are well informed they can be trusted with their
own government...
-- Thomas Jefferson, 1789

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Re: Interplatform (interprocess, interlanguage) communication jebblue <n@n.nnn> - 2012-02-07 12:11 -0600
  Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-07 16:38 -0700
    Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-07 20:26 -0400
      Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 01:41 -0700
        Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-08 07:19 -0400
          Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 12:07 -0700
            Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-08 21:16 -0500
              Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 19:50 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-09 06:24 -0400
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-09 09:15 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-09 18:58 -0400
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-09 16:15 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-09 18:50 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-09 21:40 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 14:47 -0500
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-11 12:06 -0800
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 15:18 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-11 23:03 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 09:27 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 13:33 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 15:50 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 14:34 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-09 18:48 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-09 21:46 -0700
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-10 08:51 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-10 10:43 -0700
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-10 13:15 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-10 14:50 -0700
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-10 14:32 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-10 17:10 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-10 22:08 -0400
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-11 00:49 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-11 14:04 -0400
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 14:55 -0500
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 14:52 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-11 20:06 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 22:41 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 00:46 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 09:29 -0500
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 09:31 -0500
                Re: Interplatform (interprocess, interlanguage) communication Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-12 16:02 +0000
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 11:16 -0500
                Re: Interplatform (interprocess, interlanguage) communication Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-12 22:46 +0000
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 11:33 -0700
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-11 20:18 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 01:36 -0700
                Re: Interplatform (interprocess, interlanguage) communication Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-02-12 13:52 -0600
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 14:43 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 14:49 -0500
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-09 18:46 -0500
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-09 18:45 -0500
        Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-08 14:02 -0800
          Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 18:49 -0700
            Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-08 21:14 -0500
              Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-08 20:07 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 23:29 -0700
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-09 09:40 -0800
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-09 17:02 -0700
              Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 21:10 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-09 18:54 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-10 10:25 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 14:45 -0500
                Re: Interplatform (interprocess, interlanguage) communication Lew <lewbloch@gmail.com> - 2012-02-11 12:14 -0800
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-11 15:20 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-11 22:20 -0700
                Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-12 09:23 -0500
                Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-12 12:13 -0700
    Re: Interplatform (interprocess, interlanguage) communication Arne Vajhøj <arne@vajhoej.dk> - 2012-02-07 20:24 -0500
    Re: Interplatform (interprocess, interlanguage) communication Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-08 01:31 +0000
      Re: Interplatform (interprocess, interlanguage) communication BGB <cr88192@hotmail.com> - 2012-02-08 00:55 -0700

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