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-module(mod_bosh_mnesia). |
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-behaviour(mod_bosh_backend). |
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%% mod_bosh_backend callbacks |
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-export([start/0, |
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create_session/1, |
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delete_session/1, |
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get_session/1, |
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get_sessions/0, |
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node_cleanup/1]). |
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-include("mod_bosh.hrl"). |
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-spec start() -> any(). |
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start() -> |
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mongoose_mnesia:create_table(bosh_session, |
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[{ram_copies, [node()]}, |
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{attributes, record_info(fields, bosh_session)}]). |
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%% The choice of the operation context here (transaction vs dirty, |
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%% see man on mnesia:activity/4 for description of contexts) and the deletion |
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%% in delete_session/1 below depends on the availability of a load balancer |
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%% capable of doing server/session affiliation. |
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%% |
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%% With affiliation, it suffices for this write to be synchronous, since the |
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%% client can issue no subsequent request without a session ID and the ID is |
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%% returned to the client only after the dirty synchronous write returns. |
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%% Other nodes in the cluster eventually will have the current view of the |
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%% database, possibly (significantly) later than the write returns. However, |
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%% the only node serving the client in question always operates on valid data. |
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%% |
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%% Without affiliation, each BOSH/HTTP request may be handled by a different |
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%% node in the cluster. Hence, we must guarantee that once the write |
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%% operation returns, all nodes in the cluster will have access to currently |
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%% valid data -- that's why a transaction is used instead of a dirty write. |
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-spec create_session(mod_bosh:session()) -> any(). |
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create_session(#bosh_session{} = Session) -> |
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mnesia:sync_transaction(fun mnesia:write/1, [Session]). |
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-spec delete_session(mod_bosh:sid()) -> any(). |
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delete_session(Sid) -> |
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mnesia:transaction(fun mnesia:delete/1, [{bosh_session, Sid}]). |
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-spec get_session(mod_bosh:sid()) -> [mod_bosh:session()]. |
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get_session(Sid) -> |
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mnesia:dirty_read(bosh_session, Sid). |
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-spec get_sessions() -> [mod_bosh:session()]. |
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get_sessions() -> |
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mnesia:dirty_match_object(mnesia:table_info(bosh_session, wild_pattern)). |
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-spec node_cleanup(atom()) -> any(). |
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node_cleanup(Node) -> |
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F = fun() -> |
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SIDs = mnesia:select( |
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bosh_session, |
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[{#bosh_session{sid = '$1', socket = '$2'}, |
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[{'==', {node, '$2'}, Node}], |
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['$1']}]), |
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lists:foreach(fun(SID) -> |
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:-( |
mnesia:delete({bosh_session, SID}) |
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end, SIDs) |
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end, |
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mnesia:async_dirty(F). |
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