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%%%-------------------------------------------------------------------
%%% File: cluster_ops.erl
%%% @author Brad Anderson <brad@cloudant.com> [http://cloudant.com]
%%% @copyright 2009 Brad Anderson
%%% @doc
%%%
%%% @end
%%%
%%% @since 2009-07-21 by Brad Anderson
%%%-------------------------------------------------------------------
-module(cluster_ops).
-author('brad@cloudant.com').
%% API
-export([key_lookup/3, key_lookup/5,
all_parts/4,
some_parts/4, some_parts/5,
quorum_from_each_part/3]).
-include("../include/common.hrl").
-include("../include/config.hrl").
-include("../include/profile.hrl").
%%====================================================================
%% API
%%====================================================================
%% @doc Get to the proper shard on N nodes by key lookup
%%
%% This fun uses quorum constants from config
key_lookup(Key, {M,F,A}, Access) ->
N = list_to_integer(couch_config:get("cluster", "n", "3")),
key_lookup(Key, {M,F,A}, Access, get_const(Access), N).
%% @doc Get to the proper shard on N nodes by key lookup
%%
%% This fun uses a provided quorum constant, possibly from request,
%% possibly from config
key_lookup(Key, {M,F,A}, Access, Const, N) ->
NodeParts = membership2:nodeparts_for_key(Key),
{ResolveFun, NotFoundFun} = case Access of
r -> {fun resolve_read/1, fun resolve_not_found/2};
w -> {fun resolve_write/1, fun(_,_) -> {false, notused, []} end}
end,
MapFun = fun({Node,Part}) ->
try
rpc:call(Node, M, F, [[Part | A]])
catch Class:Exception ->
{error, Class, Exception}
end
end,
{GoodReplies, Bad} = pcall(MapFun, NodeParts, N),
if length(Bad) > 0 -> ?LOG_DEBUG("~nBad: ~p~n", [Bad]); true -> ok end,
Good = lists:map(fun strip_ok/1, GoodReplies),
final_key_lookup(Good, Bad, N, Const, ResolveFun, NotFoundFun, Access).
%% @doc Do op on all shards (and maybe even replication partners)
all_parts({M,F,A}, Access, AndPartners, ResolveFun) ->
NodePartList = membership2:all_nodes_parts(AndPartners),
MapFun = fun({Node, Part}) ->
try
rpc:call(Node, M, F, [[Part | A]])
catch Class:Exception ->
{error, Class, Exception}
end
end,
Replies = ?PMAP(MapFun, NodePartList),
{Good, Bad} = lists:partition(fun valid/1, Replies),
final_all_parts(Good, Bad, length(NodePartList), ResolveFun, Access).
%% @doc Do op on some shards, depending on list of keys sent in.
%%
%% This fun uses quorum constants from config
some_parts(KeyFun, SeqsKVPairs, {M,F,A}, Access) ->
some_parts(KeyFun, SeqsKVPairs, {M,F,A}, Access, get_const(Access)).
%% @doc Do op on some shards, depending on list of keys sent in.
%%
%% This fun uses a provided quorum constant, possibly from request,
%% possibly from config
some_parts(KeyFun, SeqsKVPairs, {M,F,A}, _Access, Const) ->
TaskFun = fun({{Node,Part}, Values}) ->
try
rpc:call(Node, M, F, [[Part | [Values | A]]])
catch Class:Exception ->
{error, Class, Exception}
end
end,
% get tasks per node that are part / values for that partition
DistTasks = get_dist_tasks(KeyFun, SeqsKVPairs),
% With the distributed tasklist in hand, do the tasks per partition.
% For each partition, do the work on all nodes/parts.
TaskReplies = ?PMAP(TaskFun, DistTasks),
{GoodReplies, Bad} = lists:partition(fun valid/1, TaskReplies),
if length(Bad) > 0 -> ?LOG_DEBUG("~nBad: ~p~n", [Bad]); true -> ok end,
Good = lists:map(fun strip_ok/1, GoodReplies),
final_some_parts(Good, Bad, Const).
quorum_from_each_part({M,F,A}, Access, ResolveFun) ->
Const = get_const(Access),
{_, Parts} = lists:unzip(membership2:partitions()),
PartsMapFun = fun(Part) ->
Nodes = membership2:nodes_for_part(Part),
NodesMapFun = fun(Node) -> rpc:call(Node, M, F, [[Part | A]]) end,
{GoodReplies,BadReplies} = pcall(NodesMapFun, Nodes, Const),
Good1 = lists:map(fun strip_ok/1, GoodReplies),
Bad1 = case length(Good1) >= Const of
true -> [];
false -> BadReplies
end,
{Good1,Bad1}
end,
Results1 = ?PMAP(PartsMapFun, Parts),
{Good,Bad} = lists:foldl(fun({G,B}, {GAcc,BAcc}) ->
{lists:append(G,GAcc),lists:append(B,BAcc)}
end, {[],[]}, Results1),
if length(Bad) > 0 -> ?LOG_DEBUG("~nBad: ~p~n", [Bad]); true -> ok end,
final_quorum_from_each_part(Good, Bad, length(Parts), ResolveFun, Access).
%%--------------------------------------------------------------------
%% Internal functions
%%--------------------------------------------------------------------
final_key_lookup(Good, Bad, N, Const, ResolveFun, NotFoundFun, Access) ->
{NotFound, Return, Reasons} = NotFoundFun(Bad, Const),
if
length(Good) >= Const -> {ok, ResolveFun(Good)};
NotFound -> {ok, Return, Reasons};
true -> error_message(Good, Bad, N, Const, Access)
end.
final_all_parts(Good, Bad, Total, ResolveFun, Access) ->
case length(Good) =:= Total of
true -> {ok, ResolveFun(Good)};
_ -> error_message(Good, Bad, Total, Total, Access)
end.
final_some_parts(Good, _Bad, Const) ->
Good1 = lists:flatten(Good),
{Seqs, _} = lists:unzip(Good1),
{ResG,ResB} =
lists:foldl(
fun(Seq, {AccG,AccB}) ->
Vals = proplists:get_all_values(Seq, Good1),
case length(Vals) >= Const of
true -> {[{Seq, Vals}|AccG],AccB};
_ -> {AccG, [{Seq, Vals}|AccB]}
end
end, {[],[]}, lists:usort(Seqs)),
case length(ResB) of
0 -> {ok, ResG};
_ -> {error, ResB}
end.
final_quorum_from_each_part(Good, Bad, Total, ResolveFun, Access) ->
case length(Good) =:= Total of
true -> {ok, ResolveFun(Good)};
_ -> error_message(Good, Bad, Total, Total, Access)
end.
resolve_read([First|Responses]) ->
case First of
not_found -> not_found;
_ -> lists:foldr(fun vector_clock:resolve/2, First, Responses)
end.
resolve_write([First|Responses]) ->
case First of
not_found -> not_found;
_ -> lists:foldr(fun vector_clock:resolve/2, First, Responses)
end.
resolve_not_found(Bad, R) ->
{NotFoundCnt, DeletedCnt, OtherReasons} =
lists:foldl(fun({Error,Reason}, {NotFoundAcc, DeletedAcc, ReasonAcc}) ->
case {Error,Reason} of
{not_found, {_Clock, [missing|_Rest]}} ->
{NotFoundAcc+1, DeletedAcc, ReasonAcc};
{not_found, {_Clock, [deleted|_Rest]}} ->
{NotFoundAcc, DeletedAcc+1, ReasonAcc};
_ ->
{NotFoundAcc, DeletedAcc, [Reason|ReasonAcc]}
end
end, {0, 0, []}, Bad),
% TODO: is the comparison to R good here, or should it be N-R?
if
NotFoundCnt >= R -> {true, {not_found, missing}, OtherReasons};
DeletedCnt >= R -> {true, {not_found, deleted}, OtherReasons};
true -> {false, other, OtherReasons}
end.
error_message(Good, Bad, N, T, Access) ->
Msg = list_to_atom(lists:concat([atom_to_list(Access), "_quorum_not_met"])),
?LOG_ERROR("~p~nSuccess on ~p of ~p servers. Needed ~p. Errors: ~w"
, [Msg, length(Good), N, T, Bad]),
[{error, Msg}, {good, Good}, {bad, Bad}].
pcall(MapFun, Servers, Const) ->
Replies = lib_misc:pmap(MapFun, Servers, Const),
lists:partition(fun valid/1, Replies).
valid({ok, _}) -> true;
valid(ok) -> true;
valid(_) -> false.
strip_ok({ok, Val}) -> Val;
strip_ok(Val) -> Val.
%% @spec get_dist_tasks(KeyFun::function(), KVPairs::list()) ->
%% [{{Node::node(), Part::integer()}, SeqVals}]
%% Type - ordered | ??
%% SeqVals - [{Seq, Val}]
%% @doc builds a distributed task list of nodes with a list of shard/values.
%% This looks like a dict structure
%% but is a list so we can use ?PMAP with the results
%% @end
get_dist_tasks(KeyFun, SeqsKVPairs) ->
NPSV = lists:flatmap(fun({_,KVPair} = Elem) ->
[{NP, Elem} || NP <- membership2:nodeparts_for_key(KeyFun(KVPair))]
end, SeqsKVPairs),
group_by_key(NPSV).
group_by_key([]) ->
[];
group_by_key(List) ->
[{FirstK,FirstV} | Rest] = lists:keysort(1,List),
Acc0 = {FirstK, [FirstV], []},
FoldFun = fun({K,V}, {K,Vs,Acc}) ->
{K, [V|Vs], Acc};
({NewKey,V}, {OldKey,Vs,Acc}) ->
{NewKey, [V], [{OldKey,Vs}|Acc]}
end,
{LastK, LastVs, Acc} = lists:foldl(FoldFun, Acc0, Rest),
[{LastK, LastVs} | Acc].
get_const(r) ->
list_to_integer(couch_config:get("cluster", "r", "2"));
get_const(w) ->
list_to_integer(couch_config:get("cluster", "w", "2"));
get_const(r1) ->
1;
get_const(Other) ->
throw({bad_access_term, Other}).
|
