TD-929: add implementation

.gitignore

@@ -0,0 +1,18 @@
+# general
+log
+/_build/
+/_checkouts/
+*~
+erl_crash.dump
+rebar3.crashdump
+.tags*
+*.sublime-workspace
+.edts
+.DS_Store
+/.idea/
+*.beam
+/test/log/
+
+tags
+.image.dev
+bin

README.md

@@ -1,2 +1,2 @@
 # epg_connector
-Postgres connector fot Erlang
+Postgres connector for Erlang

config/sys.config

@@ -0,0 +1,28 @@
+[
+    {epg_connector, [
+        {databases, #{
+            default_db => #{
+                host =>"127.0.0.1",
+                port => 5432,
+                database => "db_name",
+                username => "postgres",
+                password => "postgres"
+            }
+        }},
+        {pools, #{
+            default_pool => #{
+                database => default_db,
+                size => 10
+            }
+        }},
+        %% Must specified for umbrella application
+        {vault_token_path, "/var/run/secrets/kubernetes.io/serviceaccount/token"},
+        {vault_role, "epg_connector"},
+        {vault_key_pg_creds, "epg_connector/pg_creds"}
+    ]},
+
+    {canal, [
+        {url, "http://vault:8200"},
+        {engine, kvv2}
+    ]}
+].

rebar.config

@@ -0,0 +1,13 @@
+{erl_opts, [debug_info]}.
+{deps, [
+    jsx,
+    {canal, {git, "https://github.com/valitydev/canal", {branch, master}}},
+    {epgsql, {git, "https://github.com/epgsql/epgsql.git", {tag, "4.7.1"}}},
+    {epgsql_pool, {git, "https://github.com/wgnet/epgsql_pool", {branch, "master"}}},
+    {herd, {git, "https://github.com/wgnet/herd.git", {tag, "1.3.4"}}}
+]}.
+
+{shell, [
+  % {config, "config/sys.config"},
+    {apps, [epg_connector]}
+]}.

src/epg_connector.app.src

@@ -0,0 +1,18 @@
+{application, epg_connector,
+ [{description, "An OTP application"},
+  {vsn, "0.1.0"},
+  {registered, []},
+  {mod, {epg_connector_app, []}},
+  {applications,
+   [kernel,
+    stdlib,
+    canal,
+    epgsql,
+    epgsql_pool
+   ]},
+  {env,[]},
+  {modules, []},
+
+  {licenses, ["MIT"]},
+  {links, []}
+ ]}.

src/epg_connector_app.erl

@@ -0,0 +1,101 @@
+%%%-------------------------------------------------------------------
+%% @doc epg_connector public API
+%% @end
+%%%-------------------------------------------------------------------
+
+-module(epg_connector_app).
+
+-behaviour(application).
+
+-define(VAULT_TOKEN_PATH, "/var/run/secrets/kubernetes.io/serviceaccount/token").
+-define(VAULT_ROLE, "api-key-mgmt-v2").
+-define(VAULT_KEY_PG_CREDS, "api-key-mgmt-v2/pg_creds").
+
+-export([start/2, stop/1]).
+
+start(_StartType, _StartArgs) ->
+    Databases = application:get_env(epg_connector, databases, #{}),
+    ok = maybe_set_secrets(Databases),
+    Pools = application:get_env(epg_connector, pools, #{}),
+    ok = start_pools(Pools, Databases),
+    epg_connector_sup:start_link().
+
+stop(_State) ->
+    ok.
+
+%% internal functions
+
+start_pools(Pools, Databases) ->
+    maps:fold(
+        fun(PoolName, Opts, _Acc) ->
+            #{
+                database := DB,
+                size := Size
+            } = Opts,
+            DbParams = maps:get(DB, Databases),
+            {ok, _} = epgsql_pool:start(PoolName, Size, Size, DbParams),
+            ok
+        end,
+        ok,
+        Pools
+    ).
+
+maybe_set_secrets(Databases) ->
+    TokenPath = application:get_env(epg_connector, vault_token_path, ?VAULT_TOKEN_PATH),
+    try vault_client_auth(TokenPath) of
+        ok ->
+            Key = unicode:characters_to_binary(
+                application:get_env(epg_connector, vault_key_pg_creds, ?VAULT_KEY_PG_CREDS)
+            ),
+            set_secrets(canal:read(Key), Databases);
+        Error ->
+            logger:error("can`t auth vault client with error: ~p", [Error]),
+            skip
+    catch
+        _:_ ->
+            logger:error("catch exception when auth vault client"),
+            skip
+    end,
+    ok.
+
+vault_client_auth(TokenPath) ->
+    case read_maybe_linked_file(TokenPath) of
+        {ok, Token} ->
+            Role = unicode:characters_to_binary(application:get_env(epg_connector, vault_role, ?VAULT_ROLE)),
+            canal:auth({kubernetes, Role, Token});
+        Error ->
+            Error
+    end.
+
+read_maybe_linked_file(MaybeLinkName) ->
+    case file:read_link(MaybeLinkName) of
+        {error, enoent} = Result ->
+            Result;
+        {error, einval} ->
+            file:read_file(MaybeLinkName);
+        {ok, Filename} ->
+            file:read_file(maybe_expand_relative(MaybeLinkName, Filename))
+    end.
+
+maybe_expand_relative(BaseFilename, Filename) ->
+    filename:absname_join(filename:dirname(BaseFilename), Filename).
+
+set_secrets({ok, #{<<"pg_creds">> := #{<<"pg_user">> := PgUser, <<"pg_password">> := PgPassword}}}, Databases) ->
+    logger:info("postgres credentials successfuly read from vault (as json)"),
+    NewDbConfig = maps:fold(fun(DbName, ConnOpts, Acc) ->
+        Acc#{
+            DbName => ConnOpts#{
+                username => unicode:characters_to_list(PgUser),
+                password => unicode:characters_to_list(PgPassword)
+            }
+        }
+    end, #{}, Databases),
+    application:set_env(epg_connector, databases, NewDbConfig),
+    ok;
+set_secrets({ok, #{<<"pg_creds">> := PgCreds}}, Databases) ->
+    logger:info("postgres credentials successfuly read from vault (as string)"),
+    set_secrets({ok, #{<<"pg_creds">> => jsx:decode(PgCreds, [return_maps])}}, Databases);
+set_secrets(Error, _Databases) ->
+    logger:error("can`t read postgres credentials from vault with error: ~p", [Error]),
+    skip.
+

src/epg_connector_sup.erl

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+%%%-------------------------------------------------------------------
+%% @doc epg_connector top level supervisor.
+%% @end
+%%%-------------------------------------------------------------------
+
+-module(epg_connector_sup).
+
+-behaviour(supervisor).
+
+-export([start_link/0]).
+
+-export([init/1]).
+
+-define(SERVER, ?MODULE).
+
+start_link() ->
+    supervisor:start_link({local, ?SERVER}, ?MODULE, []).
+
+init([]) ->
+    SupFlags = #{strategy => one_for_all,
+                 intensity => 0,
+                 period => 1},
+    ChildSpecs = [],
+    {ok, {SupFlags, ChildSpecs}}.
+
+%% internal functions