1> Worker = poolboy:checkout(PoolName).
<0.9001.0>
2> gen_server:call(Worker, Request).
ok
3> poolboy:checkin(PoolName, Worker).
ok
This is an example application showcasing database connection pools using Poolboy and Will Glozer's epgsql.
{application, example, [
{description, "An example application"},
{vsn, "0.1"},
{applications, [kernel, stdlib, sasl, crypto, ssl]},
{modules, [example, example_worker]},
{registered, [example]},
{mod, {example, []}},
{env, [
{pools, [
{pool1, [
{size, 10},
{max_overflow, 20},
{hostname, "127.0.0.1"},
{database, "db1"},
{username, "db1"},
{password, "abc123"}
]},
{pool2, [
{size, 5},
{max_overflow, 10},
{hostname, "127.0.0.1"},
{database, "db2"},
{username, "db2"},
{password, "abc123"}
]}
]}
]}
]}.-module(example).
-behaviour(application).
-behaviour(supervisor).
-export([start/0, stop/0, squery/2, equery/3]).
-export([start/2, stop/1]).
-export([init/1]).
start() ->
application:start(?MODULE).
stop() ->
application:stop(?MODULE).
start(_Type, _Args) ->
supervisor:start_link({local, example_sup}, ?MODULE, []).
stop(_State) ->
ok.
init([]) ->
{ok, Pools} = application:get_env(example, pools),
PoolSpecs = lists:map(fun({PoolName, PoolConfig}) ->
Args = [{name, {local, PoolName}},
{worker_module, example_worker}]
++ PoolConfig,
poolboy:child_spec(PoolName, Args)
end, Pools),
{ok, {{one_for_one, 10, 10}, PoolSpecs}}.
squery(PoolName, Sql) ->
poolboy:transaction(PoolName, fun(Worker) ->
gen_server:call(Worker, {squery, Sql})
end).
equery(PoolName, Stmt, Params) ->
poolboy:transaction(PoolName, fun(Worker) ->
gen_server:call(Worker, {equery, Stmt, Params})
end).-module(example_worker).
-behaviour(gen_server).
-behaviour(poolboy_worker).
-export([start_link/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-record(state, {conn}).
start_link(Args) ->
gen_server:start_link(?MODULE, Args, []).
init(Args) ->
Hostname = proplists:get_value(hostname, Args),
Database = proplists:get_value(database, Args),
Username = proplists:get_value(username, Args),
Password = proplists:get_value(password, Args),
{ok, Conn} = pgsql:connect(Hostname, Username, Password, [
{database, Database}
]),
{ok, #state{conn=Conn}}.
handle_call({squery, Sql}, _From, #state{conn=Conn}=State) ->
{reply, pgsql:squery(Conn, Sql), State};
handle_call({equery, Stmt, Params}, _From, #state{conn=Conn}=State) ->
{reply, pgsql:equery(Conn, Stmt, Params), State};
handle_call(_Request, _From, State) ->
{reply, ok, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
terminate(_Reason, #state{conn=Conn}) ->
ok = pgsql:close(Conn),
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.name: the pool nameworker_module: the module that represents the workerssize: maximum pool sizemax_overflow: maximum number of workers created if pool is empty
- Devin Torres (devinus) devin@devintorres.com
- Andrew Thompson (Vagabond) andrew@hijacked.us
- Kurt Williams (onkel-dirtus) kurt.r.williams@gmail.com
Poolboy is available in the public domain (see UNLICENSE).
Poolboy is also optionally available under the Apache License (see LICENSE),
meant especially for jurisdictions that do not recognize public domain works.