1、首先添加依赖，启动项

{deps, [
  jsx,
  {poolboy, {git, "https://github.com/devinus/poolboy.git", {tag, "1.5.2"}}},
  {mysql, {git, "https://github.com/mysql-otp/mysql-otp.git", {tag, "1.4.0"}}},
  {cowboy, {git, "https://github.com/ninenines/cowboy.git", {tag, "2.6.1"}}}
]}.

{relx, [{release, {hope, "1.0.0"},
         [jsx,poolboy,mysql,cowlib,ranch,cowboy,
           hope,
          sasl]},

        {sys_config, "./config/sys.config"},
        {vm_args, "./config/vm.args"},

        {dev_mode, true},
        {include_erts, false},

        {extended_start_script, true}]
}.

jsx 是用来json编解码

2、进程池和mysql配置信息放入sys.config

[
  {hope, [
    {sqlPool, [
      {name, mysql},
      {poolConf, [
        {name, {local, mysql}},
        {worker_module, mysql},
        {size, 10},
        {max_overflow, 5}
      ]},
      
      {sqlConf, [
        {host, "127.0.0.1"},
        {port, 3306},
        {user, "root"},
        {password, "123456"},
        {database, "hope"}
      ]}
    ]}
  ]}
].

name 是 子进程ID
poolConf 里面的
name 是 注册名
worker_module 是 启动哪个工作模块
size 启动的进程数
max_overflow 当超过最大进程数时，临时启动的最大进程数（当空闲时，会回收）

3、启动进程池连接数据库

修改hope_sup

init([]) ->
    {ok, SqlPool} = application:get_env(hope, sqlPool),
    Name = proplists:get_value(name, SqlPool),
    PoolArgs = proplists:get_value(poolConf, SqlPool),
    WorkerArgs = proplists:get_value(sqlConf, SqlPool),
    Mysql = poolboy:child_spec(Name, PoolArgs, WorkerArgs),
    
    {ok, {{one_for_all, 5, 10}, [Mysql]}}.

4、查询数据库代码

新建一个处理sql模块hope_sql

-module(hope_sql).

-export([query/1]).


query(Sql) ->
    poolboy:transaction(mysql, fun(Pid) -> mysql:query(Pid, Sql) end).

5、修改接口数据

-module(hope_main).

-export([init/2]).

init(Req0, Opts) ->
    {ok, FieldList, UserList} = hope_sql:query("select * from user"),
    DataList = [lists:zip(FieldList, User) || User <- UserList],
    RespBody = jsx:encode([{<<"status">>, <<"ok">>}, {<<"data">>, DataList}]),
        Req = cowboy_req:reply(200, #{
        <<"content-type">> => <<"application/json; charset=utf-8">>
    }, RespBody, Req0),
    {ok, Req, Opts}.

6、rebar3 release

7、./_build/default/rel/hope/bin/hope console

8、看效果

image.png