Erlang boss_db hello world? - postgresql

Question

Recently I tried to install and run a demo of boss_db ORM for Erlang.
Here is what I did:
clone the repository
cd boss_db/
rebar get-deps
put a simple mydb.erl file into src/:
-module(mydb).
-compile(export_all).
start() ->
DBOptions = [{adapter, pgsql},
{db_host, "localhost"},
{db_port, 5432},
{db_username, "postgres"},
{db_password, "mypass"},
{cache_enable, false},
{cache_exp_time, 0}],
boss_db:start(DBOptions).
rebar compile
cd ebin/
run erl
mydb:start()
Here is what I get:
** exception exit: shutdown
Whatam I doing wrong here? How is it supposed to be run?
P.S. I tried to run application:start(boss_db) as well, but the result is the same.
P.P.S. I have read the documentation twice, but I still have no idea how to run the whole thing.

Answer 1

You are not adding dependencies to the code path. That's why an exception is thrown when they are not found. Don't cd into ebin and erl. Instead run
erl -pa ebin -pa deps/*/ebin
from the current directory.
Btw this is not a good way to do this kind of stuff. Instead create a new empty app using rebar. Add boss_db as a dependency to your app in rebar.config. Put your own source files under src. And then
rebar get-deps compile
erl -pa ebin -pa deps/*/ebin

Answer 2

git clone git://github.com/evanmiller/boss_db.git
cd boss_db/
rebar get-deps
emacs src/mydb.erl
rebar compile
erl -pa ./ebin ./deps/*/ebin
These steps worked for me. code:is_loaded() will not work right after you run erl. Only when the module is invoked, the code is loaded.
I do get an application shutdown, but it is because the code is trying to connect to a Postgres DB and can't connect to it.
Erlang R15B02 (erts-5.9.2) [source] [smp:8:8] [async-threads:0] [hipe] [kernel-poll:false]
Eshell V5.9.2 (abort with ^G)
1> mydb:start().
** exception exit: shutdown
=ERROR REPORT==== 9-Oct-2012::12:13:07 ===
** Generic server <0.35.0> terminating
** Last message in was {'EXIT',<0.34.0>,
{{badmatch,
{error,
{{badmatch,
{error,
{{badmatch,{error,econnrefused}},
[{pgsql_sock,init,1,
[{file,"src/pgsql_sock.erl"},{line,51}]},
{gen_server,init_it,6,
[{file,"gen_server.erl"},{line,304}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}},
[{boss_db_controller,init,1,
[{file,"src/boss_db_controller.erl"},{line,31}]},
{gen_server,init_it,6,
[{file,"gen_server.erl"},{line,304}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}},
[{poolboy,new_worker,2,
[{file,"src/poolboy.erl"},{line,348}]},
{poolboy,prepopulate,4,
[{file,"src/poolboy.erl"},{line,370}]},
{poolboy,init,2,
[{file,"src/poolboy.erl"},{line,74}]},
{gen_fsm,init_it,6,
[{file,"gen_fsm.erl"},{line,361}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}
** When Server state == {state,
{<0.35.0>,poolboy_sup},
simple_one_for_one,
[{child,undefined,boss_db_controller,
{boss_db_controller,start_link,
[[{size,5},
{max_overflow,10},
{adapter,pgsql},
{db_host,"localhost"},
{db_port,5432},
{db_username,"postgres"},
{db_password,"mypass"},
{cache_enable,false},
{cache_exp_time,0}]]},
temporary,brutal_kill,worker,
[boss_db_controller]}],
{set,0,16,16,8,80,48,
{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],
[]},
{{[],[],[],[],[],[],[],[],[],[],[],[],[],[],
[],[]}}},
0,1,[],poolboy_sup,
{boss_db_controller,
[{size,5},
{max_overflow,10},
{adapter,pgsql},
{db_host,"localhost"},
{db_port,5432},
{db_username,"postgres"},
{db_password,"mypass"},
{cache_enable,false},
{cache_exp_time,0}]}}
** Reason for termination ==
** {{badmatch,
{error,
{{badmatch,
{error,
{{badmatch,{error,econnrefused}},
[{pgsql_sock,init,1,
[{file,"src/pgsql_sock.erl"},{line,51}]},
{gen_server,init_it,6,
[{file,"gen_server.erl"},{line,304}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}},
[{boss_db_controller,init,1,
[{file,"src/boss_db_controller.erl"},{line,31}]},
{gen_server,init_it,6,[{file,"gen_server.erl"},{line,304}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}},
[{poolboy,new_worker,2,[{file,"src/poolboy.erl"},{line,348}]},
{poolboy,prepopulate,4,[{file,"src/poolboy.erl"},{line,370}]},
{poolboy,init,2,[{file,"src/poolboy.erl"},{line,74}]},
{gen_fsm,init_it,6,[{file,"gen_fsm.erl"},{line,361}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]}