December 6, 2000www.eecs.tufts.edu/~couch/babble An Expectant Chat about Script Maturity Dr. Alva L. Couch Electrical Engineering and Computer Science Tufts University ~couch/babble

December 6, ~couch/babble My original goals manage user privileges on a LightWave 3200 Console Switch using convergent administration scripts that make minimal changes create a more powerful ‘expect’ with modal awareness/exception handling

December 6, ~couch/babble Convergence “If it ain’t broke, don’t fix it.” If it is “broke”, disrupt service as little as possible in fixing it.

December 6, ~couch/babble Convergent account administration Not what but how Non-convergent: erase and start over –erase all users –build new user table Convergent: make minimal changes –leave appropriately configured users alone –add, remove, modify others

December 6, ~couch/babble Epiphany! Expressive power is not empowerment. Making ‘expect’ more powerful won’t help. Convergence is complex –high environmental coupling –high branch complexity Must attack the root of the problem...

December 6, ~couch/babble Get your pies ready to throw! I challenge the most basic of tenets that we must make life easier for us. I’ll make your lives more difficult. Make the pies Chocolate Cream.

December 6, ~couch/babble Let’s get this over with...

December 6, ~couch/babble Scripting is double-edged short term win: – easy tasks become easier long term loss: –poorly documented –difficult for others to use –difficult to validate

December 6, ~couch/babble Why scripting is a weak practice scripts execute in a highly modal environment but are typically not modally aware. If they break we “page the author” instead of questioning why they break.

December 6, ~couch/babble Scripts as documentation Shift responsibility for modal awareness away from the script, into the script interpreter. Instead of telling ‘what to do’, tell ‘how to do it’. Allow the interpreter to decide ‘when to do what’. Declarative programming.

December 6, ~couch/babble Babble Instead of writing scripts, document device interactions in XML. To make documentation reusable, bind things that vary to values listed in a configuration file. To handle modal interactions, allow documentation to branch when device responses differ from the norm.

December 6, ~couch/babble Configuration JOHN foo 4 1,4, Y

December 6, ~couch/babble Adding a user adduser\s foo \r \n Enter\scase\ssensitive\spassword\s |\sPASSWORD\s>\s *** \r \n Re-enter\scase\ssensitive\spassword\s |\sPASSWORD\s>\s *** \r \n...

December 6, ~couch/babble Configuration discovery listusers\r\n User\sId\s>\s<var name="username" pattern="[A-Z0-9]+">FOO \s More \s

December 6, ~couch/babble Convergence

December 6, ~couch/babble This is not a script... This may look like a script but this is documentation, not a program. Not what but how. The interpreter exploits rather than simply interpreting –‘Paranoic’ validation –Built-in convergence and error handling

December 6, ~couch/babble Experience In production use for account management. Easy ‘rote’ script development process. ‘Paranoic’ error checking speeds development.

December 6, ~couch/babble Big ideas Babble scripts : –‘are closer to real practice than scripts’ –‘document best practices’ –‘describe debugging processes’ The Babble interpreter –detects many common scripting errors –encapsulates complex convergent processes

December 6, ~couch/babble Future Uses Planned future use: automating service monitoring and validation. Unlike a traditional script, Babble can easily cross server boundaries. To validate a service, ssh or telnet to another machine and try the service from there!

December 6, ~couch/babble Waxing philosophical... We need to allow our interpreters to become more aware and responsible. They can only transcend us if we give them choices to make. They can only make correct choices if they are educated on our best practices.

December 6, ~couch/babble Conclusions Babble is one small step on the path to total automation of administration. Takes away responsibility for execution. Grants much more important responsibility of `education’. Not scripting, but `teaching’.

December 6, ~couch/babble Availability Freely available from ~couch/babble Revision 0.1-Alpha. ~ 4000 lines of Perl “more bugs than features” but already solves some difficult problems.

December 6, ~couch/babble An Expectant Chat URL: ~couch/babble (We have an opening for a junior sysadmin!)