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-module(mem3_sync).
-behaviour(gen_server).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-export([start_link/0, get_active/0, get_queue/0, push/2, remove_node/1]).
-include_lib("../../couch/src/couch_db.hrl").
-record(state, {
active = [],
count = 0,
limit,
dict = dict:new(),
waiting = [],
update_notifier
}).
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
get_active() ->
gen_server:call(?MODULE, get_active).
get_queue() ->
gen_server:call(?MODULE, get_queue).
push(Db, Node) ->
gen_server:cast(?MODULE, {push, Db, Node}).
remove_node(Node) ->
gen_server:cast(?MODULE, {remove_node, Node}).
init([]) ->
process_flag(trap_exit, true),
Concurrency = couch_config:get("mem3", "sync_concurrency", "10"),
gen_event:add_handler(mem3_events, mem3_sync_event, []),
{ok, Pid} = start_update_notifier(),
spawn(fun initial_sync/0),
{ok, #state{limit = list_to_integer(Concurrency), update_notifier=Pid}}.
handle_call(get_active, _From, State) ->
{reply, State#state.active, State};
handle_call(get_queue, _From, State) ->
{reply, State#state.waiting, State}.
handle_cast({push, DbName, Node}, #state{count=Count, limit=Limit} = State)
when Count >= Limit ->
{noreply, add_to_queue(State, DbName, Node)};
handle_cast({push, DbName, Node}, State) ->
#state{active = L, count = C} = State,
case is_running(DbName, Node, L) of
true ->
{noreply, add_to_queue(State, DbName, Node)};
false ->
Pid = start_push_replication(DbName, Node),
{noreply, State#state{active=[{DbName, Node, Pid}|L], count=C+1}}
end;
handle_cast({remove_node, Node}, State) ->
Waiting = [{S,N} || {S,N} <- State#state.waiting, N =/= Node],
Dict = lists:foldl(fun(DbName,D) -> dict:erase({DbName,Node}, D) end,
State#state.dict, [S || {S,N} <- Waiting, N =:= Node]),
{noreply, State#state{dict = Dict, waiting = Waiting}}.
handle_info({'EXIT', Pid, _}, #state{update_notifier=Pid} = State) ->
{ok, NewPid} = start_update_notifier(),
{noreply, State#state{update_notifier=NewPid}};
handle_info({'EXIT', Active, normal}, State) ->
handle_replication_exit(State, Active);
handle_info({'EXIT', Active, Reason}, State) ->
case lists:keyfind(Active, 3, State#state.active) of
{OldDbName, OldNode, _} ->
?LOG_ERROR("~p replication ~s -> ~p died:~n~p", [?MODULE, OldDbName,
OldNode, Reason]),
timer:apply_after(5000, ?MODULE, push, [OldDbName, OldNode]);
false -> ok end,
handle_replication_exit(State, Active);
handle_info(Msg, State) ->
?LOG_ERROR("unexpected msg at replication manager ~p", [Msg]),
{noreply, State}.
terminate(_Reason, State) ->
[exit(Pid, shutdown) || {_,_,Pid} <- State#state.active],
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
handle_replication_exit(#state{waiting=[]} = State, Pid) ->
NewActive = lists:keydelete(Pid, 3, State#state.active),
{noreply, State#state{active=NewActive, count=length(NewActive)}};
handle_replication_exit(State, Pid) ->
#state{active=Active, limit=Limit, dict=D, waiting=Waiting} = State,
Active1 = lists:keydelete(Pid, 3, Active),
Count = length(Active1),
NewState = if Count < Limit ->
case next_replication(Active1, Waiting) of
nil -> % all waiting replications are also active
State#state{active = Active1, count = Count};
{DbName, Node, StillWaiting} ->
NewPid = start_push_replication(DbName, Node),
State#state{
active = [{DbName, Node, NewPid} | Active1],
count = Count+1,
dict = dict:erase({DbName,Node}, D),
waiting = StillWaiting
}
end;
true ->
State#state{active = Active1, count=Count}
end,
{noreply, NewState}.
start_push_replication(DbName, Node) ->
PostBody = {[
{<<"source">>, DbName},
{<<"target">>, {[{<<"node">>, Node}, {<<"name">>, DbName}]}},
{<<"continuous">>, false},
{<<"async">>, true}
]},
?LOG_INFO("starting ~s -> ~p internal replication", [DbName, Node]),
UserCtx = #user_ctx{name = <<"replicator">>, roles = [<<"_admin">>]},
case (catch couch_rep:replicate(PostBody, UserCtx)) of
Pid when is_pid(Pid) ->
link(Pid),
Pid;
{db_not_found, _Msg} ->
case couch_api:open_db(DbName, []) of
{ok, Db} ->
% source exists, let's (re)create the target
couch_api:close_db(Db),
case rpc:call(Node, couch_api, create_db, [DbName, []]) of
{ok, Target} ->
?LOG_INFO("~p successfully created ~s on ~p", [?MODULE, DbName,
Node]),
couch_api:close_db(Target),
start_push_replication(DbName, Node);
file_exists ->
start_push_replication(DbName, Node);
Error ->
?LOG_ERROR("~p couldn't create ~s on ~p because ~p",
[?MODULE, DbName, Node, Error]),
exit(shutdown)
end;
{not_found, no_db_file} ->
% source is gone, so this is a hack to skip it
?LOG_INFO("~p tried to push ~s to ~p but it was already deleted",
[?MODULE, DbName, Node]),
spawn_link(fun() -> ok end)
end;
{node_not_connected, _} ->
% we'll get this one when the node rejoins
?LOG_ERROR("~p exiting because ~p is not connected", [?MODULE, Node]),
spawn_link(fun() -> ok end);
CatchAll ->
?LOG_INFO("~p strange error ~p", [?MODULE, CatchAll]),
case lists:member(Node, nodes()) of
true ->
timer:apply_after(5000, ?MODULE, push, [DbName, Node]);
false ->
ok
end,
spawn_link(fun() -> ok end)
end.
add_to_queue(State, DbName, Node) ->
#state{dict=D, waiting=Waiting} = State,
case dict:is_key({DbName, Node}, D) of
true ->
State;
false ->
?LOG_DEBUG("adding ~s -> ~p to internal queue", [DbName, Node]),
State#state{
dict = dict:store({DbName,Node}, ok, D),
waiting = Waiting ++ [{DbName,Node}]
}
end.
initial_sync() ->
Db1 = ?l2b(couch_config:get("mem3", "node_db", "nodes")),
Db2 = ?l2b(couch_config:get("mem3", "shard_db", "dbs")),
Nodes = mem3:nodes(),
Live = nodes(),
[[push(Db, N) || Db <- [Db1,Db2]] || N <- Nodes, lists:member(N, Live)].
start_update_notifier() ->
Db1 = ?l2b(couch_config:get("mem3", "node_db", "nodes")),
Db2 = ?l2b(couch_config:get("mem3", "shard_db", "dbs")),
couch_db_update_notifier:start_link(fun
({updated, Db}) when Db == Db1; Db == Db2 ->
Nodes = mem3:nodes(),
Live = nodes(),
[?MODULE:push(Db, N) || N <- Nodes, lists:member(N, Live)];
(_) -> ok end).
%% @doc Finds the next {DbName,Node} pair in the list of waiting replications
%% which does not correspond to an already running replication
-spec next_replication(list(), list()) -> {binary(),node(),list()} | nil.
next_replication(Active, Waiting) ->
case lists:splitwith(fun({S,N}) -> is_running(S,N,Active) end, Waiting) of
{_, []} ->
nil;
{Running, [{DbName,Node}|Rest]} ->
{DbName, Node, Running ++ Rest}
end.
is_running(DbName, Node, ActiveList) ->
[] =/= [true || {S,N,_} <- ActiveList, S=:=DbName, N=:=Node].
|
