src/mem3_util.erl - couchdb-mem3 - Git at Google

 % Licensed 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 "AS IS" BASIS, WITHOUT
 % WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 % License for the specific language governing permissions and limitations under
 % the License.

 -module(mem3_util).

 -export([hash/1, name_shard/2, create_partition_map/5, build_shards/2,
     n_val/2, to_atom/1, to_integer/1, write_db_doc/1, delete_db_doc/1,
     shard_info/1, ensure_exists/1, open_db_doc/1]).
 -export([owner/2, is_deleted/1]).

 -export([create_partition_map/4, name_shard/1]).
 -deprecated({create_partition_map, 4, eventually}).
 -deprecated({name_shard, 1, eventually}).

 -define(RINGTOP, 2 bsl 31).  % CRC32 space

 -include_lib("mem3/include/mem3.hrl").
 -include_lib("couch/include/couch_db.hrl").

 hash(Item) when is_binary(Item) ->
     erlang:crc32(Item);
 hash(Item) ->
     erlang:crc32(term_to_binary(Item)).

 name_shard(Shard) ->
     name_shard(Shard, "").

 name_shard(#shard{dbname = DbName, range=[B,E]} = Shard, Suffix) ->
     Name = ["shards/", couch_util:to_hex(<<B:32/integer>>), "-",
         couch_util:to_hex(<<E:32/integer>>), "/", DbName, Suffix],
     Shard#shard{name = ?l2b(Name)}.

 create_partition_map(DbName, N, Q, Nodes) ->
     create_partition_map(DbName, N, Q, Nodes, "").

 create_partition_map(DbName, N, Q, Nodes, Suffix) ->
     UniqueShards = make_key_ranges((?RINGTOP) div Q, 0, []),
     Shards0 = lists:flatten([lists:duplicate(N, S) || S <- UniqueShards]),
     Shards1 = attach_nodes(Shards0, [], Nodes, []),
     [name_shard(S#shard{dbname=DbName}, Suffix) || S <- Shards1].

 make_key_ranges(_, CurrentPos, Acc) when CurrentPos >= ?RINGTOP ->
     Acc;
 make_key_ranges(Increment, Start, Acc) ->
     case Start + 2*Increment of
     X when X > ?RINGTOP ->
         End = ?RINGTOP - 1;
     _ ->
         End = Start + Increment - 1
     end,
     make_key_ranges(Increment, End+1, [#shard{range=[Start, End]} | Acc]).

 attach_nodes([], Acc, _, _) ->
     lists:reverse(Acc);
 attach_nodes(Shards, Acc, [], UsedNodes) ->
     attach_nodes(Shards, Acc, lists:reverse(UsedNodes), []);
 attach_nodes([S | Rest], Acc, [Node | Nodes], UsedNodes) ->
     attach_nodes(Rest, [S#shard{node=Node} | Acc], Nodes, [Node | UsedNodes]).

 open_db_doc(DocId) ->
     DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
     {ok, Db} = couch_db:open(DbName, []),
     try couch_db:open_doc(Db, DocId, [ejson_body]) after couch_db:close(Db) end.

 write_db_doc(Doc) ->
     DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
     write_db_doc(DbName, Doc, true).

 write_db_doc(DbName, #doc{id=Id, body=Body} = Doc, ShouldMutate) ->
     {ok, Db} = couch_db:open(DbName, []),
     try couch_db:open_doc(Db, Id, [ejson_body]) of
     {ok, #doc{body = Body}} ->
         % the doc is already in the desired state, we're done here
         ok;
     {not_found, _} when ShouldMutate ->
         try couch_db:update_doc(Db, Doc, []) of
         {ok, _} ->
             ok
         catch conflict ->
             % check to see if this was a replication race or a different edit
             write_db_doc(DbName, Doc, false)
         end;
     _ ->
         % the doc already exists in a different state
         conflict
     after
         couch_db:close(Db)
     end.

 delete_db_doc(DocId) ->
     gen_server:cast(mem3_shards, {cache_remove, DocId}),
     DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
     delete_db_doc(DbName, DocId, true).

 delete_db_doc(DbName, DocId, ShouldMutate) ->
     {ok, Db} = couch_db:open(DbName, []),
     {ok, Revs} = couch_db:open_doc_revs(Db, DocId, all, []),
     try [Doc#doc{deleted=true} || {ok, #doc{deleted=false}=Doc} <- Revs] of
     [] ->
         not_found;
     Docs when ShouldMutate ->
         try couch_db:update_docs(Db, Docs, []) of
         {ok, _} ->
             ok
         catch conflict ->
             % check to see if this was a replication race or if leafs survived
             delete_db_doc(DbName, DocId, false)
         end;
     _ ->
         % we have live leafs that we aren't allowed to delete. let's bail
         conflict
     after
         couch_db:close(Db)
     end.

 build_shards(DbName, DocProps) ->
     {ByNode} = couch_util:get_value(<<"by_node">>, DocProps, {[]}),
     Suffix = couch_util:get_value(<<"shard_suffix">>, DocProps, ""),
     lists:flatmap(fun({Node, Ranges}) ->
         lists:map(fun(Range) ->
             [B,E] = string:tokens(?b2l(Range), "-"),
             Beg = httpd_util:hexlist_to_integer(B),
             End = httpd_util:hexlist_to_integer(E),
             name_shard(#shard{
                 dbname = DbName,
                 node = to_atom(Node),
                 range = [Beg, End]
             }, Suffix)
         end, Ranges)
     end, ByNode).

 to_atom(Node) when is_binary(Node) ->
     list_to_atom(binary_to_list(Node));
 to_atom(Node) when is_atom(Node) ->
     Node.

 to_integer(N) when is_integer(N) ->
     N;
 to_integer(N) when is_binary(N) ->
     list_to_integer(binary_to_list(N));
 to_integer(N) when is_list(N) ->
     list_to_integer(N).

 n_val(undefined, NodeCount) ->
     n_val(config:get("cluster", "n", "3"), NodeCount);
 n_val(N, NodeCount) when is_list(N) ->
     n_val(list_to_integer(N), NodeCount);
 n_val(N, NodeCount) when is_integer(NodeCount), N > NodeCount ->
     couch_log:error("Request to create N=~p DB but only ~p node(s)", [N, NodeCount]),
     NodeCount;
 n_val(N, _) when N < 1 ->
     1;
 n_val(N, _) ->
     N.

 shard_info(DbName) ->
     [{n, mem3:n(DbName)},
      {q, length(mem3:shards(DbName)) div mem3:n(DbName)}].

 ensure_exists(DbName) when is_list(DbName) ->
     ensure_exists(list_to_binary(DbName));
 ensure_exists(DbName) ->
     Options = [{user_ctx, #user_ctx{roles=[<<"_admin">>]}}],
     case couch_db:open(DbName, [nologifmissing | Options]) of
     {ok, Db} ->
         {ok, Db};
     _ ->
         couch_server:create(DbName, Options)
     end.


 owner(DbName, DocId) ->
     Shards = mem3:shards(DbName, DocId),
     Nodes = [node()|nodes()],
     LiveShards = [S || #shard{node=Node} = S <- Shards, lists:member(Node, Nodes)],
     [#shard{node=Node}] = lists:usort(fun(#shard{name=A}, #shard{name=B}) ->
                                               A =< B  end, LiveShards),
     node() =:= Node.

 is_deleted(Change) ->
     case couch_util:get_value(<<"deleted">>, Change) of
     undefined ->
         % keep backwards compatibility for a while
         couch_util:get_value(deleted, Change, false);
     Else ->
         Else
     end.
	% Licensed 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 "AS IS" BASIS, WITHOUT
	% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	% License for the specific language governing permissions and limitations under
	% the License.

	-module(mem3_util).

	-export([hash/1, name_shard/2, create_partition_map/5, build_shards/2,
	n_val/2, to_atom/1, to_integer/1, write_db_doc/1, delete_db_doc/1,
	shard_info/1, ensure_exists/1, open_db_doc/1]).
	-export([owner/2, is_deleted/1]).

	-export([create_partition_map/4, name_shard/1]).
	-deprecated({create_partition_map, 4, eventually}).
	-deprecated({name_shard, 1, eventually}).

	-define(RINGTOP, 2 bsl 31). % CRC32 space

	-include_lib("mem3/include/mem3.hrl").
	-include_lib("couch/include/couch_db.hrl").

	hash(Item) when is_binary(Item) ->
	erlang:crc32(Item);
	hash(Item) ->
	erlang:crc32(term_to_binary(Item)).

	name_shard(Shard) ->
	name_shard(Shard, "").

	name_shard(#shard{dbname = DbName, range=[B,E]} = Shard, Suffix) ->
	Name = ["shards/", couch_util:to_hex(<<B:32/integer>>), "-",
	couch_util:to_hex(<<E:32/integer>>), "/", DbName, Suffix],
	Shard#shard{name = ?l2b(Name)}.

	create_partition_map(DbName, N, Q, Nodes) ->
	create_partition_map(DbName, N, Q, Nodes, "").

	create_partition_map(DbName, N, Q, Nodes, Suffix) ->
	UniqueShards = make_key_ranges((?RINGTOP) div Q, 0, []),
	Shards0 = lists:flatten([lists:duplicate(N, S) \|\| S <- UniqueShards]),
	Shards1 = attach_nodes(Shards0, [], Nodes, []),
	[name_shard(S#shard{dbname=DbName}, Suffix) \|\| S <- Shards1].

	make_key_ranges(_, CurrentPos, Acc) when CurrentPos >= ?RINGTOP ->
	Acc;
	make_key_ranges(Increment, Start, Acc) ->
	case Start + 2*Increment of
	X when X > ?RINGTOP ->
	End = ?RINGTOP - 1;
	_ ->
	End = Start + Increment - 1
	end,
	make_key_ranges(Increment, End+1, [#shard{range=[Start, End]} \| Acc]).

	attach_nodes([], Acc, _, _) ->
	lists:reverse(Acc);
	attach_nodes(Shards, Acc, [], UsedNodes) ->
	attach_nodes(Shards, Acc, lists:reverse(UsedNodes), []);
	attach_nodes([S \| Rest], Acc, [Node \| Nodes], UsedNodes) ->
	attach_nodes(Rest, [S#shard{node=Node} \| Acc], Nodes, [Node \| UsedNodes]).

	open_db_doc(DocId) ->
	DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
	{ok, Db} = couch_db:open(DbName, []),
	try couch_db:open_doc(Db, DocId, [ejson_body]) after couch_db:close(Db) end.

	write_db_doc(Doc) ->
	DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
	write_db_doc(DbName, Doc, true).

	write_db_doc(DbName, #doc{id=Id, body=Body} = Doc, ShouldMutate) ->
	{ok, Db} = couch_db:open(DbName, []),
	try couch_db:open_doc(Db, Id, [ejson_body]) of
	{ok, #doc{body = Body}} ->
	% the doc is already in the desired state, we're done here
	ok;
	{not_found, _} when ShouldMutate ->
	try couch_db:update_doc(Db, Doc, []) of
	{ok, _} ->
	ok
	catch conflict ->
	% check to see if this was a replication race or a different edit
	write_db_doc(DbName, Doc, false)
	end;
	_ ->
	% the doc already exists in a different state
	conflict
	after
	couch_db:close(Db)
	end.

	delete_db_doc(DocId) ->
	gen_server:cast(mem3_shards, {cache_remove, DocId}),
	DbName = ?l2b(config:get("mem3", "shard_db", "dbs")),
	delete_db_doc(DbName, DocId, true).

	delete_db_doc(DbName, DocId, ShouldMutate) ->
	{ok, Db} = couch_db:open(DbName, []),
	{ok, Revs} = couch_db:open_doc_revs(Db, DocId, all, []),
	try [Doc#doc{deleted=true} \|\| {ok, #doc{deleted=false}=Doc} <- Revs] of
	[] ->
	not_found;
	Docs when ShouldMutate ->
	try couch_db:update_docs(Db, Docs, []) of
	{ok, _} ->
	ok
	catch conflict ->
	% check to see if this was a replication race or if leafs survived
	delete_db_doc(DbName, DocId, false)
	end;
	_ ->
	% we have live leafs that we aren't allowed to delete. let's bail
	conflict
	after
	couch_db:close(Db)
	end.

	build_shards(DbName, DocProps) ->
	{ByNode} = couch_util:get_value(<<"by_node">>, DocProps, {[]}),
	Suffix = couch_util:get_value(<<"shard_suffix">>, DocProps, ""),
	lists:flatmap(fun({Node, Ranges}) ->
	lists:map(fun(Range) ->
	[B,E] = string:tokens(?b2l(Range), "-"),
	Beg = httpd_util:hexlist_to_integer(B),
	End = httpd_util:hexlist_to_integer(E),
	name_shard(#shard{
	dbname = DbName,
	node = to_atom(Node),
	range = [Beg, End]
	}, Suffix)
	end, Ranges)
	end, ByNode).

	to_atom(Node) when is_binary(Node) ->
	list_to_atom(binary_to_list(Node));
	to_atom(Node) when is_atom(Node) ->
	Node.

	to_integer(N) when is_integer(N) ->
	N;
	to_integer(N) when is_binary(N) ->
	list_to_integer(binary_to_list(N));
	to_integer(N) when is_list(N) ->
	list_to_integer(N).

	n_val(undefined, NodeCount) ->
	n_val(config:get("cluster", "n", "3"), NodeCount);
	n_val(N, NodeCount) when is_list(N) ->
	n_val(list_to_integer(N), NodeCount);
	n_val(N, NodeCount) when is_integer(NodeCount), N > NodeCount ->
	couch_log:error("Request to create N=~p DB but only ~p node(s)", [N, NodeCount]),
	NodeCount;
	n_val(N, _) when N < 1 ->
	1;
	n_val(N, _) ->
	N.

	shard_info(DbName) ->
	[{n, mem3:n(DbName)},
	{q, length(mem3:shards(DbName)) div mem3:n(DbName)}].

	ensure_exists(DbName) when is_list(DbName) ->
	ensure_exists(list_to_binary(DbName));
	ensure_exists(DbName) ->
	Options = [{user_ctx, #user_ctx{roles=[<<"_admin">>]}}],
	case couch_db:open(DbName, [nologifmissing \| Options]) of
	{ok, Db} ->
	{ok, Db};
	_ ->
	couch_server:create(DbName, Options)
	end.


	owner(DbName, DocId) ->
	Shards = mem3:shards(DbName, DocId),
	Nodes = [node()\|nodes()],
	LiveShards = [S \|\| #shard{node=Node} = S <- Shards, lists:member(Node, Nodes)],
	[#shard{node=Node}] = lists:usort(fun(#shard{name=A}, #shard{name=B}) ->
	A =< B end, LiveShards),
	node() =:= Node.

	is_deleted(Change) ->
	case couch_util:get_value(<<"deleted">>, Change) of
	undefined ->
	% keep backwards compatibility for a while
	couch_util:get_value(deleted, Change, false);
	Else ->
	Else
	end.