This is experimental software. While it is now mostly functional, it is not yet fully complete.
Until such time as the EtaMOO database format is well tested and considered stable, please make and keep LambdaMOO-format backup copies of your EtaMOO databases.
EtaMOO is a new implementation of the LambdaMOO server written in Haskell.
LambdaMOO is a network-accessible, multi-user, programmable, interactive system well-suited to the construction of text-based adventure games, conferencing systems, and other collaborative software.
EtaMOO differs from LambdaMOO in a few significant ways:
EtaMOO is multi-threaded. MOO tasks run concurrently, producing network output and changes to the database in isolated transactions that are committed only when not in conflict with any other transaction. (In cases of conflict, transactions are automatically retried.) Separate threads are also used for network connection management, so for example name lookups do not block the entire server.
EtaMOO uses LMDB as a persistent backing store for the MOO database. Changes are committed on an ongoing basis for instantaneous crash recovery; checkpoints perform a quick synchronization for guaranteed durability, but are otherwise unnecessary. The persistence layer includes an automatic value cache with implicit structure sharing, so the entire database need not be in memory at once, and duplicate values are stored only once. EtaMOO provides mechanisms for importing and exporting LambdaMOO-format databases to and from the EtaMOO-native format.
EtaMOO is Unicode-aware, and will eventually include support for Unicode MOO strings via compile-time build option.
EtaMOO supports 64-bit MOO integers via compile-time build option.
EtaMOO supports the lightweight object WAIF datatype via compile-time build option.
EtaMOO natively supports string-key association lists with efficient lookup and update operations; the list index syntax has been extended to allow
valuefor string *
alistis a well-formed association list.
EtaMOO supports several additional hashing algorithms besides MD5, including SHA-1, SHA-2, SHA-3, and RIPEMD-160, via optional argument to
value_hash(). Hash digests may also optionally be returned as binary strings.
EtaMOO internally handles binary strings in an efficient manner, and only translates to and from the special MOO binary string syntax upon demand. For example, passing a binary string read from the network directly to
decode_binary()does not suffer a round trip through the binary string representation.
EtaMOO supports fractional second delays in
EtaMOO supports IPv6.
The implementation of EtaMOO otherwise closely follows the specifications of the LambdaMOO Programmer's Manual, and should be compatible with most LambdaMOO databases as of about version 1.8.3 of the LambdaMOO server code.
EtaMOO is built with Cabal, the Haskell package manager. In the simplest case, running:
cabal install EtaMOO
should automatically download, build, and install the
after doing the same for all of its Haskell dependencies.
Cabal itself is part of the Haskell Platform which is available for many distributions and platforms.
There are a few options you can give to
cabal install to customize your
||Build in parallel using multiple processors|
||Use GHC's LLVM backend to compile the code|
||Enable 64-bit MOO integers|
||Enable the lightweight object WAIF datatype|
EtaMOO has non-Haskell dependencies on three external libraries: liblmdb for
database persistence, libpcre (with UTF-8 support enabled) for regular
expression matching, and, possibly, libcrypt (often part of the standard
libraries) for the MOO
crypt() built-in function. You should ensure you have
these available before installing EtaMOO (e.g. on Debian-derived systems,
sudo apt-get install liblmdb-dev libpcre3-dev).
etamoo is nearly a drop-in replacement for the LambdaMOO
the main difference is that
etamoo takes a single database path, rather than
both input and output paths. You can run
etamoo --help for a command-line
EtaMOO uses a native binary database format that allows quick loading and
checkpointing, and instantaneous crash recovery. You can create a native
database from a LambdaMOO-format database by using
etamoo --import. You can
also go the other way and convert an EtaMOO database back to a
LambdaMOO-format database with
If you don't already have a database, you can find LambdaMOO-format cores for various MOOs online -- for example there is the venerable LambdaCore, or an alternative JHCore. You can also request a character on Waterpoint and then perform a live JHCore extraction. (Note that Waterpoint's core extraction process requires running an actual LambdaMOO server executable on the precore database to obtain the final core database; EtaMOO cannot yet do this itself.)
By default, EtaMOO will make use of all available CPUs for maximum
parallelism. If you'd rather limit the number of processors EtaMOO uses, you
can use the command-line option
n is the
number of processors to use.
If you want to enable statistics from the
memory_usage() built-in function,
you will need to add
+RTS -T -RTS to the command line options.
The following LambdaMOO features are currently unsupported:
- Importing, exporting, or checkpointing of queued tasks in the database file
- Task time limits (ticks are counted, but seconds are not)
NP_LOCALnetwork protocols (i.e. stdin/stdout, UNIX-domain sockets, and/or named pipes; only TCP/IP is supported)
OUT_OF_BAND_QUOTE_PREFIX(these are currently fixed as
See also the
DIFFERENCES.md file for other differences between EtaMOO and
Documentation is available for the various types, data structures, and functions used internally by EtaMOO.