MidWay: A Service Request Broker (SRB) Address: http://www.mid-way.org By: Terje Eggestad Address: Terje.Eggestad@iname.com
**** What is MidWay? ****
MidWay is a Service Request Broker. Not unlike an ORB (object Request Broker), but a SRB works by function passing, not method passing, there are no objects here in the sense OO describe it. An SRB are state less while an ORB is statefull.
In a SRB a process (called a server) provides a service given by a name. A client can now call the service and pass it input data, and it returns data. While commecial SRBs usually has some means to declare data types, in MidWay "data" means an octet string, think Perl scalars.
The providing of a service is a dynamic affair, no need for an ORB'like IDL. There are no limitation on how many servers that can provide the same service.
This parallellism gives a lot of scalability. You can do both fan-out and pipleline parallellism with MidWay. The purpose of a SRB is speed and scalability. Speed comes from the statelessness. (Se docs for details). Building applications that can handle 100 hits a second is simple.
SRB are traditionally called Transaction Processing Monitors or TP monitors. They earned that by providing transaction support, thus a clients could after calling n services either commit or rollback the work done in all the services. This fuctionallyit is not implemeted yet, and will only be if in demand.
MidWay is intended to be more WEB and internet orientated that its commercial cousins. Really easy since most TP Monitors have mainframe legacy in mind.
**** Running Midway ****
To do a quick test of MidWay, goto src and write make. There are no installation as of yet, this is alpha code. Either greate a soft link from /lib to src/lib/libMWipc.so, and do a ldconfig -v or include $PWD/src/lib/ in LD_LIBRARY_PATH.
goto src/mwd and start mwd by ./mwd -D, check ~/MidWay/userid/log/SYSTEM.date
goto src/lib and start testmidway
goto src/mwadm and start it, at prompt give the command:
MWADM> call test1 date
the test1 service in testmidway shall now give you the date.
Now read the docs!
**** A Note on Release Numbers. ****
In the CVS archive releasable versions are tagged with
STABILITY_M_N_P which are:
STABILITY: Alpha, Beta, Release, and possibly more.
Put simply it says what quality of code this is meant to be. M: Is the major version number that indicate that there are major changes
and most probably incompatibilities. N: Minor version number, indicate new fetues, but no incompatibilities. P: Patch number, bugs files only.
The rationale for using the STABILITY verb is that many projects are developing on 0.X.Y and releases on 1.0.0. Which is OK, but causes confusion later on when say 2.3.24 is experimental, while 2.2.15 is production. Observant readers may recognice that this is Linux kernel version numbers. Linus & co seem to prefer 2.even.patch for production, and 2.odd.patch for development. Not a bad plan either. I just really want the three numbers to have the meaning as indicated above, and the only way to indicate quality is to add a new indicator.
Terje