fdb-erlang

Erlang bindings for FoundationDB.

This is still very early alpha.

Todo

• A non-VM-blocking fdb_nif:fdb_future_block_until_ready using enif_send and fdb_future_set_callback. More inspiration here.
• Conversion from Erlang terms to keys using the FDB tuple layer.
• Map most-used functionality. (A lot of function calls return not_implemented.)
• Feature-complete tests.
• Fix memory leaks in case of non-happy paths.

Prerequisites

Developed and tested on ubuntu only (for now). It requires you to have Erlang and the FoundationDB client libraries installed.

Due to the way enif_send is implemented in Erlang NIFs, your system needs to run with at least 2 core's.

Update

Apparently you can also work around this by using erl -smp enable.

Big thanks to Valery Meleshkin for the tip!

Compilation and testing

git clone [email protected]:HappyPancake/fdb-erlang.git
cd fdb-erlang
chmod u+x rebar
./rebar get-deps compile eunit -v

Example usage

This is the simplest possible usage:

tojans@ubuntu:/tmp/fdb-erlang$ erl -pa ebin
Erlang R16B02 (erts-5.10.3) [source-5d89ddd] [64-bit] [async-threads:10] [kernel-poll:false]

Eshell V5.10.3  (abort with ^G)
1> fdb:init().
ok
2> fdb:api_version(100).
0
3> DB = fdb:open().
{db,<<>>}
4> fdb:get(DB,<<"Hello">>).
not_found
5> fdb:set(DB,<<"Hello">>,<<"World">>).
ok
6> fdb:get(DB,<<"Hello">>).            
<<"World">>
7> fdb:get(DB,<<"Hello2">>,some_default_value).
some_default_value
8> fdb:clear(DB,<<"Hello">>).
ok
9> fdb:get(DB,<<"Hello">>).
not_found
10>

If you want to have a transaction, you need to invoke code like this:

10> fdb:transact(DB, fun(Tx) ->                         
10>   fdb:set(Tx,<<"Hello">>,<<"World">>),            
10>   fdb:set(Tx,<<"xyz">>,<<"abc">>),                
10>   [fdb:get(Tx,<<"xyz">>)|fdb:get(Tx,<<"Hello">>)]   
10> end).
[<<"abc">>|<<"World">>]
11>

It will invoke the lambda multiple times until the whole action succeeds or it seems unreasonable to try any longer. If the code in the lambda crashes, the transaction will be rolled back.