[ts-gen] Downstream architecture (3rd)

Bill Pippin pippin at owlriver.net
Fri Aug 28 20:53:56 EDT 2009


Ken,

With respect to your questions about downstream architectural
approaches to the IB tws api, this post focuses on the following
question: 

    How might a ruby sample client, an example program to interface
    with the shim, be designed, what parts of the code would be
    provided, what parts would be supplied by client users, and in
    the absence of such a sample client in the shim tarball for now,
    what might users write in its place?

To recap, such a program would apply user-specific criteria to perform
the following types of tasks:

    * ask for market data;
    * interpret such data;
    * generate orders; and
    * manage positions.

Once given an IB tws account, and the shim, then the shim command
language would be used to generate api requests, and the shim cout
option could be used to ensure that the resulting message traffic,
and indeed the entire integrated event stream, were accessible to
the client.  That much is obvious, and leaves us a long reach from
the task goals above.  What else?

A.  Main.

Once given initialization, about which more later, there would be
a main loop to process events; input for that loop would be read
via the select() system call, provided in ruby; and the two input
streams from the shim provided via the popen3() system call, the
stdin and stderr, would be multiplexed via select() .  The input
would be selectively converted to event objects via table-driven
code, which brings us back to initialization.

B.  Init

Prior to entering the main loop, event descriptions from a sql
database would be read in, and used to generate: event classes, the
related data members, and constructor code which would take as
input a split array from a text input line.  The result would be an
admittedly large quantity of automatically generated boilerplate
none of which would need or warrant human maintenance.

C.  Processing

The client user would still be responsible for writing: the
definitions of non-empty process operations for each message event;
as well as strategy code that would use input from such processing,
presumably to generate signals and/or orders.

D.  User input

The client user would still be responsible for writing: gui screens,
or code to accept yet another layer of downstream command input, if
so desired.  As previously noted, the select() system call could be
used to multiplex the three input streams of other client/human
control, events from the shim cout, and exceptional messages from
the shim stderr.

E.  What for now?

As for (c) and (d), above, that's the user's responsibility in any
case, and so about which no more.

As for (a), users should already be using popen3() or its equivalent
in their favorite scripting language, and select() ditto, in any case;
or else they may choose threads, in which case that's their business,
and outside the scope of these list messages.

It would be nice to provide example code via a ruby sample client,
and that's just one of many things we haven't completed yet.

As for (b), this is the serious gap, and all I can say is that study
of rule.c and apis.c may help, but is a non-trivial effort.  I fully
intend to define sql create table and insert statements to provide
table definition of the api events, but such work is intimately coupled
with versioned api-level event processing, our next major work effort.
It's just not done yet.  Sorry.  Feel free to read rule.c, and apis.c,
and for that matter EClientSocket.java and EReader.java.

Thanks,

Bill



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