Armstrong Joe. Making reliable distributed systems in the presence of software errors

A Dissertation submitted to the Royal Institute of Technology in partial fulfilment of the requirements for the degree of Doctor of Technology The Royal Institute of Technology Stockholm, Sweden December 2003.
TRITA–IMIT–LECS AVH 03:09
ISSN 1651–4076
ISRN KTH/IMIT/LECS/AVH-03/09–SE
The work described in this thesis is the result of a research program
started in 1981 to ?nd better ways of programming Telecom applica-
tions. These applications are large programs which despite careful
testing will probably contain many errors when the program is put into
service. We assume that such programs do contain errors, and investigate
methods for building reliable systems despite such errors.
The research has resulted in the development of a new programming
language (called Erlang), together with a design methodology, and set of
libraries for building robust systems (called OTP). At the time of writing
the technology described here is used in a number of major Ericsson, and
Nortel products. A number of small companies have also been formed
which exploit the technology.
The central problem addressed by this thesis is the problem of con-
structing reliable systems from programs which may themselves contain
errors. Constructing such systems imposes a number of requirements on
any programming language that is to be used for the construction. I discuss
these language requirements, and show how they are satis?ed by Erlang.
Problems can be solved in a programming language, or in the stan-
dard libraries which accompany the language. I argue how certain of the
requirements necessary to build a fault-tolerant system are solved in the
language, and others are solved in the standard libraries. Together these
form a basis for building fault-tolerant sodware systems.
No theory is complete without proof that the ideas work in practice. To
demonstrate that these ideas work in practice I present a number of case
studies of large commercially successful products which use this technol-
ogy. At the time of writing the largest of these projects is a major Ericsson
product, having over a million lines of Erlang code. This product (the
AXD301) is thought to be one of the most reliable products ever made by
Ericsson.
Finally, I ask if the goal of inqluding better ways to program Telecom
applications was fulfilled—I also point to areas where I think the system
could be improved.