104 lines
2.7 KiB
Elixir
104 lines
2.7 KiB
Elixir
defmodule HAHandler.Control do
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@moduledoc """
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This module handles the decision-logic and actions to be
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taken regarding the current state of the infrastructure.
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"""
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@haproxy_pgsql_backend "pgsql"
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use GenServer
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require Logger
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alias HAHandler.{PGSQL, HAProxy}
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# How much do we wait (ms) between each check/decision-making round?
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@refresh 15_000
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def start_link(opts) do
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GenServer.start_link(__MODULE__, opts, name: __MODULE__)
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end
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@impl true
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def init(_opts) do
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state = []
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# Let's skip the initial startup round so that other components are all up
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# and running.
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Process.send_after(self(), :sync, @refresh)
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{:ok, state}
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end
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@impl true
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def handle_info(:sync, state) do
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Logger.debug("Executing control logic.")
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# Fetch PGSQL state, make sure HAProxy routes to the master
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# process.
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pgsql_state =
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PGSQL.get_instances()
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|> Enum.map(fn {hostname, pid} = instance ->
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haproxy_server =
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HAHandler.pgsql_instances()
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|> Enum.filter(fn opts -> Keyword.get(opts, :hostname) == hostname end)
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|> Enum.at(0)
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|> Keyword.get(:haproxy_server)
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%{
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haproxy_server: haproxy_server,
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pgsql_watcher_pid: pid,
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pgsql_operation_mode: PGSQL.get_operation_mode(instance)
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}
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end)
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haproxy_state =
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HAProxy.get_stats()
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|> Map.get("Server", [])
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|> Enum.filter(fn mapping -> mapping["pxname"] == @haproxy_pgsql_backend end)
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|> Enum.map(fn mapping -> %{mapping["svname"] => mapping["status"]} end)
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|> Enum.reduce(&Map.merge/2)
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for pgsql_instance <- pgsql_state do
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haproxy_state = Map.get(haproxy_state, pgsql_instance.haproxy_server)
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case {pgsql_instance.pgsql_operation_mode, haproxy_state} do
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{:primary, "UP"} ->
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:noop
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{:primary, "MAINT"} ->
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Logger.info("Enabling routing PGSQL to (now) primary #{pgsql_instance.haproxy_server}.")
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HAProxy.set_server(
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@haproxy_pgsql_backend,
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pgsql_instance.haproxy_server,
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"state",
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"ready"
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)
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{:secondary, "UP"} ->
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Logger.info(
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"Disabling routing PGSQL to (now) secondary #{pgsql_instance.haproxy_server}."
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)
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HAProxy.set_server(
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@haproxy_pgsql_backend,
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pgsql_instance.haproxy_server,
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"state",
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"maint"
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)
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{:secondary, "MAINT"} ->
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:noop
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unknown ->
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Logger.warning("Unhandled PGSQL/HAProxy state: #{inspect(unknown)}")
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end
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end
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# Schedule next round.
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Process.send_after(self(), :sync, @refresh)
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{:noreply, state}
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end
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end
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