erlang real system sizing and metrics.
Wed Dec 16 08:44:39 CET 1998
> In a recent post to the mailing list it was mentioned that erlang has
> been used in large systems within Ericsson. Without gettin into the
> proprietary details of these projects would it be possible to get
> some detail that addresses:
> 1. The General Applications (or Systems) that were built or are
> being built.
For obvious reasons we can only point you at the open literature.
A good source of information is
In particular browse the stuff in the archive and
in "CeBit'98 Special" - this is a special issue of Erlang news describing
products built in Erlang and presented at CeBit.
Another good jumping off place is
> 4. Complexity of developed systems i.e. use of supervisors,
> event handing, fault tolerance & load sharing behaviors,
> number of nodes involved in distributed system.
This is difficult to answer. One of the the design goals of the
supervisors, client-server behaviours etc. was to "abstract out the
details of the concurrency" - It's *much* easier to understand
sequential code than concurrent code. Our goal was that 95% of all the
application programmers would never "see" a process (or the
concurrency structures used).
This has turned out rather well - It appears that a small number
of design patterns (supervision trees, client-server, event-handler,
etc.) suffice for a high percentage of all the application code
(whether it's 95% or not I don't know - but it is large) - the
exceptions are sufficiently small that they can easily be handled by a
System design then becomes "choosing from a number of
pre-defined design patterns" rather than a totally unconstrained process.
The design patterns that have evolved (and which are included in
the distribution) are those we have found useful in build large
The Complexity of these systems is "manageable" is the sense that
to understand the design you first have to understand the design
patterns and what they are good for and then you have to understand
how the problem maps onto the design.
As for the number of nodes in an application this ranges from 1 to
a max of round about 40 (from memory the 40 were two clusters one of 5
nodes the other of 35 - the clusters where in two different towns),
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