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|
%%% membership module
%%%
%%% State of the gen_server is a #mem record
%%%
%%% Nodes and Gossip are the same thing, and are a list of three-tuples like:
%%%
%%% [ {Pos,NodeName,Options} | _ ]
%%%
%%% Position is 1-based incrementing in order of node joining
%%%
%%% Options is a proplist, with [{hints, [Part1|_]}] denoting that the node
%%% is responsible for the extra partitions too.
%%%
%%% TODO: dialyzer type specs
%%%
-module(mem3).
-author('brad@cloudant.com').
-behaviour(gen_server).
%% API
-export([start_link/0, start_link/1, stop/0, stop/1, reset/0]).
-export([join/3, clock/0, state/0, states/0, nodes/0, fullnodes/0,
start_gossip/0]).
%-export([partitions/0, fullmap/0]).
%-export([nodes/0, nodes_for_part/1, nodes_for_part/2, all_nodes_parts/1]).
%-export([parts_for_node/1]).
%% for testing more than anything else
-export([merge_nodes/2, next_up_node/1, next_up_node/3]).
%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
%% includes
-include_lib("eunit/include/eunit.hrl").
%% version 3 of membership state
-record(mem, {header=3,
nodes=[],
clock=[],
args
}).
-define(SERVER, membership).
-define(STATE_FILE_PREFIX, "membership").
%% types - stick somewhere in includes?
-type join_type() :: init | join | replace | leave.
-type join_order() :: non_neg_integer().
-type options() :: list().
-type mem_node() :: {join_order(), node(), options()}.
-type mem_node_list() :: [mem_node()].
-type arg_options() :: {test, boolean()}.
-type args() :: [] | [arg_options()].
-type mem_state() :: #mem{}.
-type test() :: undefined | node().
-type epoch() :: float().
-type clock() :: {node(), epoch()}.
-type vector_clock() :: [clock()].
-type ping_node() :: node() | nil.
%%====================================================================
%% API
%%====================================================================
-spec start_link() -> {ok, pid()}.
start_link() ->
start_link([]).
-spec start_link(args()) -> {ok, pid()}.
start_link(Args) ->
gen_server:start_link({local, ?SERVER}, ?MODULE, Args, []).
-spec stop() -> ok.
stop() ->
stop(?MODULE).
-spec stop(atom()) -> ok.
stop(Server) ->
gen_server:cast(Server, stop).
-spec join(join_type(), mem_node_list(), node() | nil) -> ok.
join(JoinType, Nodes, PingNode) ->
gen_server:call(?SERVER, {join, JoinType, Nodes, PingNode}).
-spec clock() -> vector_clock().
clock() ->
gen_server:call(?SERVER, clock).
-spec state() -> mem_state().
state() ->
gen_server:call(?SERVER, state).
-spec states() -> {ok, [mem_state()]}.
states() ->
{ok, Nodes} = mem3:nodes(),
case rpc:multicall(Nodes, ?MODULE, state, []) of
{States, []} -> {ok, lists:map(fun({ok,S}) -> S end, States)};
{Good, Bad} -> {error, {[{good,Good},{bad,Bad}]}}
end.
-spec start_gossip() -> ok.
start_gossip() ->
gen_server:call(?SERVER, start_gossip).
-spec reset() -> ok | not_reset.
reset() ->
gen_server:call(?SERVER, reset).
%% @doc get the list of cluster nodes (according to membership module)
%% This may differ from erlang:nodes()
%% Guaranteed to be in order of State's node list (1st elem in 3-tuple)
-spec nodes() -> {ok, [node()]}.
nodes() ->
gen_server:call(?SERVER, nodes).
%% @doc get the list of cluster nodes (according to membership module)
%% This may differ from erlang:nodes()
%% Guaranteed to be in order of State's node list (1st elem in 3-tuple)
-spec fullnodes() -> {ok, [mem_node()]}.
fullnodes() ->
gen_server:call(?SERVER, fullnodes).
%%====================================================================
%% gen_server callbacks
%%====================================================================
%% start up membership server
-spec init(args()) -> {ok, mem_state()}.
init(Args) ->
process_flag(trap_exit,true),
Test = get_test(Args),
OldState = read_latest_state_file(Test),
showroom_log:message(info, "membership: membership server starting...", []),
net_kernel:monitor_nodes(true),
State = handle_init(Test, OldState),
{ok, State#mem{args=Args}}.
%% new node(s) joining to this node
handle_call({join, JoinType, ExtNodes, PingNode}, _From, State) ->
% {ok, NewState} = handle_join(JoinType, ExtNodes, PingNode, State),
% {reply, ok, NewState};
try
case handle_join(JoinType, ExtNodes, PingNode, State) of
{ok, NewState} -> {reply, ok, NewState};
Other -> {reply, Other, State}
end
catch _:Error ->
showroom_log:message(error, "~p", [Error]),
{reply, Error, State}
end;
%% clock
handle_call(clock, _From, #mem{clock=Clock} = State) ->
{reply, {ok, Clock}, State};
%% state
handle_call(state, _From, State) ->
{reply, {ok, State}, State};
%% reset - but only if we're in test mode
handle_call(reset, _From, #mem{args=Args} = State) ->
Test = get_test(Args),
case Test of
undefined -> {reply, not_reset, State};
_ -> {reply, ok, int_reset(Test, State)}
end;
%% nodes
handle_call(nodes, _From, #mem{nodes=Nodes} = State) ->
{_,NodeList,_} = lists:unzip3(lists:keysort(1, Nodes)),
{reply, {ok, NodeList}, State};
%% fullnodes
handle_call(fullnodes, _From, #mem{nodes=Nodes} = State) ->
{reply, {ok, Nodes}, State};
%% gossip
handle_call({gossip, RemoteState}, {Pid,_Tag} = From, LocalState) ->
showroom_log:message(info, "membership: received gossip from ~p",
[erlang:node(Pid)]),
handle_gossip(From, RemoteState, LocalState);
% start_gossip
handle_call(start_gossip, _From, State) ->
NewState = gossip(State),
{reply, ok, NewState};
%% ignored call
handle_call(Msg, _From, State) ->
showroom_log:message(info, "membership: ignored call: ~p", [Msg]),
{reply, ignored, State}.
%% stop
handle_cast(stop, State) ->
{stop, normal, State};
%% ignored cast
handle_cast(Msg, State) ->
showroom_log:message(info, "membership: ignored cast: ~p", [Msg]),
{noreply, State}.
%% @doc handle nodedown messages because we have
%% net_kernel:monitor_nodes(true)
handle_info({nodedown, Node}, State) ->
showroom_log:message(alert, "membership: nodedown ~p", [Node]),
{noreply, State};
%% @doc handle nodeup messages because we have
%% net_kernel:monitor_nodes(true)
handle_info({nodeup, Node}, State) ->
showroom_log:message(alert, "membership: nodeup ~p", [Node]),
{noreply, State};
%% ignored info
handle_info(Info, State) ->
showroom_log:message(info, "membership: ignored info: ~p", [Info]),
{noreply, State}.
% terminate
terminate(_Reason, _State) ->
ok.
% ignored code change
code_change(OldVsn, State, _Extra) ->
io:format("Unknown Old Version~nOldVsn: ~p~nState : ~p~n", [OldVsn, State]),
{ok, State}.
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
%% @doc if Args has config use it, otherwise call configuration module
%% most times Args will have config during testing runs
%get_config(Args) ->
% case proplists:get_value(config, Args) of
% undefined -> configuration:get_config();
% Any -> Any
% end.
get_test(Args) ->
proplists:get_value(test, Args).
%% @doc handle_init starts a node
%% Most of the time, this puts the node in a single-node cluster setup,
%% But, we could be automatically rejoining a cluster after some downtime.
%% See handle_join for initing, joining, leaving a cluster, or replacing a
%% node.
%% @end
handle_init(Test, nil) ->
int_reset(Test);
handle_init(_Test, #mem{nodes=Nodes, args=Args} = OldState) ->
% there's an old state, let's try to rejoin automatically
% but only if we can compare our old state to other available
% nodes and get a match... otherwise get a human involved
{_, NodeList, _} = lists:unzip3(Nodes),
ping_all_yall(NodeList),
{RemoteStates, _BadNodes} = get_remote_states(NodeList),
Test = get_test(Args),
case compare_state_with_rest(OldState, RemoteStates) of
match ->
showroom_log:message(info, "membership: rejoined successfully", []),
OldState;
Other ->
showroom_log:message(error, "membership: rejoin failed: ~p", [Other]),
int_reset(Test)
end.
%% @doc handle join activities, return {ok,NewState}
-spec handle_join(join_type(), [mem_node()], ping_node(), mem_state()) ->
{ok, mem_state()}.
% init
handle_join(init, ExtNodes, nil, State) ->
{_,Nodes,_} = lists:unzip3(ExtNodes),
ping_all_yall(Nodes),
int_join(ExtNodes, State);
% join
handle_join(join, ExtNodes, PingNode, #mem{args=Args} = State) ->
NewState = case get_test(Args) of
undefined -> get_pingnode_state(PingNode);
_ -> State % testing, so meh
end,
% now use this info to join the ring
int_join(ExtNodes, NewState);
% replace
handle_join(replace, OldNode, PingNode, State) when is_atom(OldNode) ->
handle_join(replace, {OldNode, []}, PingNode, State);
handle_join(replace, [OldNode | _], PingNode, State) ->
handle_join(replace, {OldNode, []}, PingNode, State);
handle_join(replace, {OldNode, NewOpts}, PingNode, _State) ->
OldState = #mem{nodes=OldNodes} = get_pingnode_state(PingNode),
{Order, OldNode, _OldOpts} = lists:keyfind(OldNode, 2, OldNodes),
NewNodes = lists:keyreplace(OldNode, 2, OldNodes, {Order, node(), NewOpts}),
int_join([], OldState#mem{nodes=NewNodes});
% leave
handle_join(leave, [_OldNode | _], _PingNode, _State) ->
% TODO implement me
ok;
handle_join(JoinType, _, PingNode, _) ->
showroom_log:message(info, "membership: unknown join type: ~p "
"for ping node: ~p", [JoinType, PingNode]),
{error, unknown_join_type}.
%% @doc common operations for all join types
int_join(ExtNodes, #mem{nodes=Nodes, clock=Clock} = State) ->
NewNodes = lists:foldl(fun({Pos, N, _Options}=New, AccIn) ->
check_pos(Pos, N, Nodes),
[New|AccIn]
end, Nodes, ExtNodes),
NewNodes1 = lists:sort(NewNodes),
NewClock = vector_clock:increment(node(), Clock),
NewState = State#mem{nodes=NewNodes1, clock=NewClock},
install_new_state(NewState),
{ok, NewState}.
install_new_state(#mem{args=Args} = State) ->
Test = get_test(Args),
save_state_file(Test, State),
gossip(Test, State).
get_pingnode_state(PingNode) ->
% ping the PingNode and get its state
pong = net_adm:ping(PingNode),
timer:sleep(1000), % let dist. erl get set up... sigh.
{ok, RemoteState} = rpc:call(PingNode, mem3, state, []),
RemoteState.
%% @doc handle the gossip messages
%% We're not using vector_clock:resolve b/c we need custom merge strategy
handle_gossip(From, RemoteState=#mem{clock=RemoteClock},
LocalState=#mem{clock=LocalClock}) ->
case vector_clock:compare(RemoteClock, LocalClock) of
equal ->
{reply, ok, LocalState};
less ->
% remote node needs updating
{reply, {new_state, LocalState}, LocalState};
greater ->
% local node needs updating
gen_server:reply(From, ok), % reply to sender first
{noreply, install_new_state(RemoteState)};
concurrent ->
% ick, so let's resolve and merge states
showroom_log:message(info,
"membership: Concurrent Clocks~n"
"RemoteState : ~p~nLocalState : ~p~n"
, [RemoteState, LocalState]),
MergedState = merge_states(RemoteState, LocalState),
gen_server:reply(From, {new_state, MergedState}), % reply to sender
{noreply, install_new_state(MergedState)}
end.
merge_states(#mem{clock=RemoteClock, nodes=RemoteNodes} = _RemoteState,
#mem{clock=LocalClock, nodes=LocalNodes} = LocalState) ->
MergedClock = vector_clock:merge(RemoteClock, LocalClock),
MergedNodes = merge_nodes(RemoteNodes, LocalNodes),
LocalState#mem{clock=MergedClock, nodes=MergedNodes}.
%% this will give one of the lists back, deterministically
merge_nodes(Remote, Local) ->
% get rid of the initial 0 node if it's still there, and sort
Remote1 = lists:usort(lists:keydelete(0,1,Remote)),
Local1 = lists:usort(lists:keydelete(0,1,Local)),
% handle empty lists as well as other cases
case {Remote1, Local1} of
{[], L} -> L;
{R, []} -> R;
_ -> erlang:min(Remote1, Local1)
end.
gossip(#mem{args=Args} = NewState) ->
Test = get_test(Args),
gossip(Test, NewState).
-spec gossip(test(), mem_state()) -> mem_state().
gossip(undefined, #mem{nodes=StateNodes} = State) ->
{_, Nodes, _} = lists:unzip3(StateNodes),
TargetNode = next_up_node(Nodes),
showroom_log:message(info, "membership: firing gossip from ~p to ~p",
[node(), TargetNode]),
case gen_server:call({?SERVER, TargetNode}, {gossip, State}) of
ok -> State;
{new_state, NewState} -> NewState;
Error -> throw({unknown_gossip_response, Error})
end;
gossip(_,_) ->
% testing, so don't gossip
ok.
next_up_node(Nodes) ->
Node = node(),
next_up_node(Node, Nodes, up_nodes()).
next_up_node(Node, Nodes, UpNodes) ->
{A, [Node|B]} = lists:splitwith(fun(N) -> N /= Node end, Nodes),
List = lists:append(B, A), % be sure to eliminate Node
DownNodes = Nodes -- UpNodes,
case List -- DownNodes of
[Target|_] -> Target;
[] -> throw({error, no_gossip_targets_available})
end.
up_nodes() ->
% TODO: implement cache (fb 9704 & 9449)
erlang:nodes().
%% @doc find the latest state file on disk
find_latest_state_filename() ->
Dir = couch_config:get("couchdb", "database_dir"),
case file:list_dir(Dir) of
{ok, Filenames} ->
Timestamps = [list_to_integer(TS) || {?STATE_FILE_PREFIX, TS} <-
[list_to_tuple(string:tokens(FN, ".")) || FN <- Filenames]],
SortedTimestamps = lists:reverse(lists:sort(Timestamps)),
case SortedTimestamps of
[Latest | _] ->
{ok, Dir ++ "/" ++ ?STATE_FILE_PREFIX ++ "." ++
integer_to_list(Latest)};
_ ->
throw({error, mem_state_file_not_found})
end;
{error, Reason} ->
throw({error, Reason})
end.
%% (Test, Config)
read_latest_state_file(undefined) ->
try
{ok, File} = find_latest_state_filename(),
case file:consult(File) of
{ok, [#mem{}=State]} -> State;
_Else ->
throw({error, bad_mem_state_file})
end
catch _:Error ->
showroom_log:message(info, "membership: ~p", [Error]),
nil
end;
read_latest_state_file(_) ->
nil.
%% @doc save the state file to disk, with current timestamp.
%% thx to riak_ring_manager:do_write_ringfile/1
-spec save_state_file(test(), mem_state()) -> ok.
save_state_file(undefined, State) ->
Dir = couch_config:get("couchdb", "database_dir"),
{{Year, Month, Day},{Hour, Minute, Second}} = calendar:universal_time(),
TS = io_lib:format("~B~2.10.0B~2.10.0B~2.10.0B~2.10.0B~2.10.0B",
[Year, Month, Day, Hour, Minute, Second]),
FN = Dir ++ "/" ++ ?STATE_FILE_PREFIX ++ "." ++ TS,
ok = filelib:ensure_dir(FN),
{ok, File} = file:open(FN, [binary, write]),
io:format(File, "~w.~n", [State]),
file:close(File);
save_state_file(_,_) -> ok. % don't save if testing
check_pos(Pos, Node, Nodes) ->
Found = lists:keyfind(Pos, 1, Nodes),
case Found of
false -> ok;
_ ->
{_,OldNode,_} = Found,
if
OldNode =:= Node ->
Msg = "node_exists_at_position_" ++ integer_to_list(Pos),
throw({error, list_to_binary(Msg)});
true ->
Msg = "position_exists_" ++ integer_to_list(Pos),
throw({error, list_to_binary(Msg)})
end
end.
int_reset(Test) ->
int_reset(Test, #mem{}).
int_reset(_Test, State) ->
State#mem{nodes=[], clock=[]}.
ping_all_yall(Nodes) ->
lists:foreach(fun(Node) ->
net_adm:ping(Node)
end, Nodes),
timer:sleep(500). % sigh.
get_remote_states(NodeList) ->
NodeList1 = lists:delete(node(), NodeList),
{States1, BadNodes} = rpc:multicall(NodeList1, mem3, state, [], 5000),
{_Status, States2} = lists:unzip(States1),
NodeList2 = NodeList1 -- BadNodes,
{lists:zip(NodeList2,States2), BadNodes}.
%% @doc compare state with states based on vector clock
%% return match | {bad_state_match, Node, NodesThatDontMatch}
compare_state_with_rest(#mem{clock=Clock} = _State, States) ->
Results = lists:map(fun({Node, #mem{clock=Clock1}}) ->
{vector_clock:equals(Clock, Clock1), Node}
end, States),
BadResults = lists:foldl(fun({true, _N}, AccIn) -> AccIn;
({false, N}, AccIn) -> [N | AccIn]
end, [], Results),
if
length(BadResults) == 0 -> match;
true -> {bad_state_match, node(), BadResults}
end.
|