131 lines
4.1 KiB
Elixir
131 lines
4.1 KiB
Elixir
defmodule HAHandler.HAProxy do
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@moduledoc """
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Interface to HAProxy's runtime API:
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https://www.haproxy.com/documentation/hapee/latest/api/runtime-api/
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"""
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# TODO: can we keep the socket open by keeping the port state in a GenServer
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# and abusing the prompt mode of HAProxy's socket somehow? The later is
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# somewhat clunky, but I'm not sure if there is a way around it since HAProxy
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# seems to return EOF once a command is executed (unless prompt mode is
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# enabled).
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import HAHandler, only: [haproxy_socket: 0]
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alias :procket, as: Socket
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# How long do we wait for an answer - in milliseconds.
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@socket_read_timeout 5_000
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@doc """
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Sends a command to HAProxy's socket - please refer to HAProxy's runtime API
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documentation for available commands (see moduledoc).
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This method will either return an answer with `{:ok, answer}` or error with
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`{:error, err}`.
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"""
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def execute(command) when is_binary(command) do
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case open_socket(haproxy_socket()) do
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{:ok, socket} ->
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send(socket, {self(), {:command, command <> "\n"}})
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read_from_socket(socket)
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{:error, err} ->
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{:error, err}
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end
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end
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@doc """
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Executes and parse the output of the `show stats` HAProxy command, returning
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a list of Maps.
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TODO: extract more informations from stats output.
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"""
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def get_stats() do
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case execute("show stat json") do
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{:ok, raw} ->
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case Poison.decode(raw) do
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{:ok, data} ->
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for entry <- data do
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attrs =
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entry
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|> Enum.filter(fn m -> get_in(m, ["field", "name"]) == "pxname" end)
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|> Enum.at(0)
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%{
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type: attrs |> Map.get("objType"),
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name: get_in(attrs, ["value", "value"])
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}
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end
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{:error, err} ->
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{:error, err}
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end
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{:error, err} ->
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{:error, err}
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end
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end
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# Opens an UNIX socket - there is no built-in support in Elixir/Erlang so we
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# use low-level C bindings provided by :procket
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# (https://github.com/msantos/procket).
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#
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# Heavily inspired by the `NVim.Link` module:
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# https://github.com/kbrw/neovim-elixir/blob/master/lib/link.ex
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defp open_socket(path) do
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family = Socket.family(:unix)
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type = :stream
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# 0 means use the default protocol in the family.
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protocol = 0
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pad = 8 * (Socket.unix_path_max() - byte_size(path))
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sockaddr = Socket.sockaddr_common(family, byte_size(path)) <> path <> <<0::size(pad)>>
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{:ok, socket} = Socket.socket(family, type, protocol)
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case Socket.connect(socket, sockaddr) do
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:ok ->
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# We connect our UNIX socket to an erlang Port:
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#
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# > Ports provide a mechanism to start operating system processes
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# > external to the Erlang VM and communicate with them via message
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# > passing.
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# See https://hexdocs.pm/elixir/Port.html for details.
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#
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# See https://www.erlang.org/doc/man/erlang.html#open_port-2 for more
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# port options.
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#
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# * :binary: all I/O from the port is binary data objects as opposed to
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# lists of bytes.
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# * Messages are delivered on a per line basis. Each line (delimited by
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# the OS-dependent newline sequence) is delivered in a single message.
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# The message data format is {Flag, Line}, where Flag is eol or noeol,
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# and Line is the data delivered (without the newline sequence).
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{fdin, fdout} = {socket, socket}
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port = Port.open({:fd, fdin, fdout}, [{:line, 10_000}, :binary])
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{:ok, port}
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{:error, err} ->
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{:error, err}
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end
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end
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# Messages may be split due to the `{:line, L}` option specific in
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# `open_socket/1`.
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defp read_from_socket(socket, acc \\ "") do
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receive do
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{_port, {:data, {:noeol, data}}} ->
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read_from_socket(socket, acc <> data)
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{_port, {:data, {:eol, data}}} ->
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{:ok, acc <> data}
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msg ->
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{:error, {:unexpected_message, msg}}
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after
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@socket_read_timeout ->
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{:error, :timeout}
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end
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end
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end
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