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Merge branch 'master' of github.com:jeena/GGS-report

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Kallfaktorn 2011-04-07 12:19:34 +02:00
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@ -903,7 +903,53 @@ Same here it is simply not true for a generic server to chose one or the
\end_layout
\begin_layout Section
Fault Tolerant
Fault Tolerance
\end_layout
\begin_layout Standard
Fault tolerance is an important factor in all servers, a server that is
fault tolerant should be able to follow a given specification when parts
of the system failures.
This means that fault tolerance is different in each system depending on
what specification they have.
A system could be fault tolerant in different aspects, one is where the
system is guaranteed to be live but not safe and it could also be reversed,
that the system is safe but not guaranteed to be live.
Depending on the system one property may be more important(some example
here).
A system could also have non existent fault tolerance or it could be both
safe and guaranteed to be live.
It should be noted that it is not possible to achieve complete fault tolerance,
a system will always have a certain risk of failure.
With this in mind the goal is to make GGS as fault tolerant as possible.
\end_layout
\begin_layout Standard
In order to make GGS fault tolerant the programming language Erlang will
be used.
Erlang will not guarantee a fault tolerant system but it has features that
support and encourage the development of fault tolerant systems.
In GGS it is important that the system overall is fault tolerant.
Crashes of the whole system should be avoided as this would make the system
unusable for a time.
By using supervisor structures it is possible to crash and restart small
parts of the system, this is convenient as fault can be handled within
small modules thus never forcing a crash of the system.
\end_layout
\begin_layout Standard
Why is fault tolerance needed in game servers? This is an interesting question
because it is not so obvious as it is in many other cases.
In general all servers strive to be fault tolerant as fault tolerance means
more uptime and a safer system.
This is also the case when it comes to game servers, in short good fault
tolerance is a way of satisfying customers.
Game servers differ from many other fault tolerant systems in that high-availab
ility is more important than the safety of the system.
For example a simple calculation error will not be critical for a game
server but it may be in a life-critical system and then it is better that
the system crashes.
\end_layout
\begin_layout Subsubsection