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|
-module(couch_prometheus_http).
-compile(tuple_calls).
-export([
start_link/0,
handle_request/1
]).
-include("couch_prometheus.hrl").
-include_lib("couch/include/couch_db.hrl").
start_link() ->
IP = case config:get("prometheus", "bind_address", "any") of
"any" -> any;
Else -> Else
end,
Port = config:get("prometheus", "port"),
ok = couch_httpd:validate_bind_address(IP),
Options = [
{name, ?MODULE},
{loop, fun ?MODULE:handle_request/1},
{ip, IP},
{port, Port}
],
case mochiweb_http:start(Options) of
{ok, Pid} ->
{ok, Pid};
{error, Reason} ->
io:format("Failure to start Mochiweb: ~s~n", [Reason]),
{error, Reason}
end.
handle_request(MochiReq) ->
RawUri = MochiReq:get(raw_path),
{"/" ++ Path, _, _} = mochiweb_util:urlsplit_path(RawUri),
PathParts = string:tokens(Path, "/"), try
case PathParts of
["_node", Node, "_prometheus"] ->
send_prometheus(MochiReq, Node);
_ ->
send_error(MochiReq, 404, <<"not_found">>, <<>>)
end
catch T:R ->
Body = list_to_binary(io_lib:format("~p:~p", [T, R])),
send_error(MochiReq, 500, <<"server_error">>, Body)
end.
send_prometheus(MochiReq, Node) ->
Type = "text/plain; version=" ++ ?PROMETHEUS_VERSION,
Headers = couch_httpd:server_header() ++ [
{<<"Content-Type">>, ?l2b(Type)}
],
Body = call_node(Node, couch_prometheus_server, scrape, []),
send_resp(MochiReq, 200, Headers, Body).
send_resp(MochiReq, Status, ExtraHeaders, Body) ->
Headers = couch_httpd:server_header() ++ ExtraHeaders,
MochiReq:respond({Status, Headers, Body}).
send_error(MochiReq, Code, Error, Reason) ->
Headers = couch_httpd:server_header() ++ [
{<<"Content-Type">>, <<"application/json">>}
],
JsonError = {[{<<"error">>, Error},
{<<"reason">>, Reason}]},
Body = ?JSON_ENCODE(JsonError),
MochiReq:respond({Code, Headers, Body}).
call_node("_local", Mod, Fun, Args) ->
call_node(node(), Mod, Fun, Args);
call_node(Node0, Mod, Fun, Args) when is_list(Node0) ->
Node1 = try
list_to_existing_atom(Node0)
catch
error:badarg ->
NoNode = list_to_binary(Node0),
throw({not_found, <<"no such node: ", NoNode/binary>>})
end,
call_node(Node1, Mod, Fun, Args);
call_node(Node, Mod, Fun, Args) when is_atom(Node) ->
case rpc:call(Node, Mod, Fun, Args) of
{badrpc, nodedown} ->
Reason = list_to_binary(io_lib:format("~s is down", [Node])),
throw({error, {nodedown, Reason}});
Else ->
Else
end.
|
