riak / src / riak_connect.erl

justin 1c37b76 

Rusty Klophaus c16aea7 

justin 1c37b76 

Rusty Klophaus c16aea7 

justin 1c37b76 
Andy Gross 4b70143 
Rusty Klophaus c804506 
Andy Gross 4b70143 
Rusty Klophaus c16aea7 

justin 1c37b76 

Rusty Klophaus c16aea7 

justin 1c37b76 
Rusty Klophaus c16aea7 
Andy Gross 4b70143 
justin 1c37b76 
Rusty Klophaus c16aea7 

Rusty Klophaus c804506 
Rusty Klophaus c16aea7 

justin 1c37b76 
Rusty Klophaus c16aea7 

justin 1c37b76 

Rusty Klophaus c16aea7 

justin 1c37b76 

Rusty Klophaus c16aea7 

jus...@basho.com 2ec123e 

jus...@basho.com 6af4d75 
Rusty Klophaus c16aea7 
justin 1c37b76 
Rusty Klophaus c16aea7 

Bryan Fink b8e14ea 
Rusty Klophaus c16aea7 
Bryan Fink b8e14ea 

Rusty Klophaus c16aea7 
jus...@basho.com 2ec123e 
Rusty Klophaus c16aea7 

Bryan Fink b8e14ea 
Rusty Klophaus c16aea7 
jus...@basho.com 2ec123e 
Bryan Fink b8e14ea 

jus...@basho.com 8f3c439 

Bryan Fink b8e14ea 

jus...@basho.com 8f3c439 

Bryan Fink b8e14ea 

%% This file is provided to you under the Apache License,
%% Version 2.0 (the "License"); you may not use this file
%% except in compliance with the License.  You may obtain
%% a copy of the License at

%%   http://www.apache.org/licenses/LICENSE-2.0

%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% KIND, either express or implied.  See the License for the
%% specific language governing permissions and limitations
%% under the License.    

%% @doc
%% riak_connect takes care of the mechanics of shuttling a
%% from one node to another upon request by other
%% Riak processes.
%% Additionally, it occasionally checks to make sure the current
%% node has its fair share of partitions, and also sends
%% a copy of the ring to some other random node, ensuring
%% that all nodes eventually synchronize on the same understanding
%% of the Riak cluster. This interval is configurable, but defaults
%% to once per minute.


-export([start_link/0, stop/0]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
-export ([send_ring/1, send_ring/2, remove_from_cluster/1]).

-define (SERVER, ?MODULE).

%% send_ring/1 -
%% Send the current node's ring to some other node.
send_ring(ToNode) -> send_ring(node(), ToNode).

%% send_ring/2 -
%% Send the ring from one node to another node. 
%% Does nothing if the two nodes are the same.
send_ring(Node, Node) -> ok;
send_ring(FromNode, ToNode) ->
    gen_server:cast({?SERVER, FromNode}, {send_ring_to, ToNode}).

%% @private
start_link() -> 
    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
%% @private
init(_State) -> 
    {ok, false}.
schedule_next_gossip() ->
    MaxInterval = riak:get_app_env(gossip_interval),
    Interval = random:uniform(MaxInterval),
    timer:apply_after(Interval, gen_server, cast, [?SERVER, gossip_ring]). 

stop() -> gen_server:cast(?SERVER, stop).

%% @private
handle_cast({send_ring_to, Node}, RingChanged) ->
    riak_eventer:notify(riak_connect, send_ring_to, Node),
    {ok, MyRing} = riak_ring_manager:get_my_ring(),    
    gen_server:cast({?SERVER, Node}, {reconcile_ring, MyRing}),
    {noreply, RingChanged};
handle_cast({reconcile_ring, OtherRing}, RingChanged) ->
    % Compare the two rings, see if there is anything that
    % must be done to make them equal...
    {ok, MyRing} = riak_ring_manager:get_my_ring(),
    case riak_ring:reconcile(OtherRing, MyRing) of
        {no_change, _} -> 
            {noreply, RingChanged};
        {new_ring, ReconciledRing} ->
            BalancedRing = claim_until_balanced(ReconciledRing),
            RandomNode = riak_ring:random_node(BalancedRing),
            send_ring(node(), RandomNode),
            riak_eventer:notify(riak_connect, changed_ring, gossip_changed),
            {noreply, true}
handle_cast(gossip_ring, RingChanged) ->
    % First, schedule the next round of gossip...
    riak_eventer:notify(riak_connect, interval, interval),
    % Make sure all vnodes are started...
    {ok, MyRing} = riak_ring_manager:get_my_ring(),
    % If the ring has changed since our last write,
    % then rewrite the ring...
    case RingChanged of
        true ->
        false -> 
    % Finally, gossip the ring to some random other node...
    RandomNode = riak_ring:index_owner(MyRing, riak_ring:random_other_index(MyRing)),
    send_ring(node(), RandomNode),
    {noreply, false};                         

handle_cast(_, State) -> 
    {noreply, State}.

%% @private
handle_info(_Info, State) -> {noreply, State}.

%% @private
handle_call(_, _From, State) -> {reply, ok, State}.

%% @private
terminate(_Reason, _State) -> ok.

%% @private
code_change(_OldVsn, State, _Extra) ->  {ok, State}.

claim_until_balanced(Ring) ->
    {WMod, WFun} = riak:get_app_env(wants_claim_fun),
    NeedsIndexes = apply(WMod, WFun, [Ring]),
    case NeedsIndexes of
        no -> 
        {yes, _NumToClaim} ->
            {CMod, CFun} = riak:get_app_env(choose_claim_fun),
            NewRing = CMod:CFun(Ring),

ensure_vnodes_started(Ring) ->
    VNodes2Start = case length(riak_ring:all_members(Ring)) of
       1 -> riak_ring:my_indices(Ring);
       _ -> [riak_ring:random_other_index(Ring)| riak_ring:my_indices(Ring)]
        gen_server:cast({riak_vnode_master, node()}, {start_vnode, I}) 
    end|| I <- VNodes2Start].

remove_from_cluster(ExitingNode) ->
    % Set the remote node to stop claiming.
    % Ignore return of rpc as this should succeed even if node is offline
    rpc:call(ExitingNode, application, set_env, [riak, wants_claim_fun, {riak_claim, never_wants_claim}]),
    % Get a list of indices owned by the ExitingNode...
    {ok, Ring} = riak_ring_manager:get_my_ring(),
    AllOwners = riak_ring:all_owners(Ring),
    AllIndices = [I || {I,_Owner} <- AllOwners],
    Indices = [I || {I,Owner} <- AllOwners, Owner =:= ExitingNode],
    riak_eventer:notify(riak_connect, remove_from_cluster,
                        {ExitingNode, length(Indices)}),

    % Transfer indexes to other nodes...
    ExitRing = 
        case attempt_simple_transfer(Ring, AllOwners, ExitingNode) of
            {ok, NR} -> NR;
            target_n_fail ->
                %% re-diagonalize
                %% first hand off all claims to *any* one else,
                %% just so rebalance doesn't include exiting node
                Other = hd(lists:delete(ExitingNode, riak_ring:all_members(Ring))),
                TempRing = lists:foldl(fun({I,N}, R) when N == ExitingNode ->
                                                 I, Other, R);
                                          (_, R) -> R
                riak_claim:claim_rebalance_n(TempRing, Other)

    % Send the ring to all other rings...
    [send_ring(X) || X <- riak_ring:all_members(Ring)],
    %% This line is right!
    [gen_server:cast({riak_vnode_master, ExitingNode}, {start_vnode, P}) ||
        P <- AllIndices].    

attempt_simple_transfer(Ring, Owners, ExitingNode) ->
    attempt_simple_transfer(Ring, Owners,
                            riak:get_app_env(target_n_val, 3),
                            ExitingNode, 0, []).
attempt_simple_transfer(Ring, [{P, Exit}|Rest], TargetN, Exit, Idx, Last) ->
    %% handoff
    case [ N || {N, I} <- Last, Idx-I >= TargetN ] of
        [] ->
        Candidates ->
            %% these nodes don't violate target_n in the reverse direction
            StepsToNext = fun(Node) ->
                                           fun({_, Owner}) -> Node /= Owner end,
            case lists:filter(fun(N) -> 
                                 Next = StepsToNext(N),
                                 (Next >= TargetN) orelse (Next == length(Rest))
                              Candidates) of
                [] ->
                Qualifiers ->
                    %% these nodes don't violate target_n forward
                    Chosen = lists:nth(crypto:rand_uniform(
                                         1, length(Qualifiers)+1),
                    %% choose one, and do the rest of the ring
                      riak_ring:transfer_node(P, Chosen, Ring),
                      Rest, TargetN, Exit, Idx+1,
                      lists:keyreplace(Chosen, 1, Last, {Chosen, Idx}))
attempt_simple_transfer(Ring, [{_, N}|Rest], TargetN, Exit, Idx, Last) ->
    %% just keep track of seeing this node
    attempt_simple_transfer(Ring, Rest, TargetN, Exit, Idx+1,
                            lists:keyreplace(N, 1, Last, {N, Idx}));
attempt_simple_transfer(Ring, [], _, _, _, _) ->
    {ok, Ring}.
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