Generic KVS feed-server

Feed server for KVS abstract database middleware.

Implements database queries in the form of atomic operations or in other words, provides transaction for KVS-feeds logic.

• kvs – Database middleware.
• n2o – n2o_async needed.

• log :: {Mod,Fun} – Custom logging function/3, default: {wf,info}
• feed_timeout :: non_neg_integer() – Pool worker timeout, in ms, default: 600000 (10 min)
• feed_timeout_action :: hibernate | stop – Action for inactive pool workers, default: hibernate

• append(Record) – Add Record to database.
• delete(Record) – Remove Record from database.
• update(Record,Fun) – Update Record with Fun/1 which takes Record2 (at the time of execution) and should return {ok,Record3} (modified) if surgery is to be performed, or anything else to cancel.
• relink(Record) – Bring Record to top in Record feed.
• purge(Record,Fun) – Remove Record and related feeds with Fun/0 which should return a list of feeds, example: kvs_feeds:purge(E,fun() -> [{feed,attachments,fun kvs_feed:delete/1}] end), feed_id to be deleted will be generated as {attachment,element(2,E)} for feed container table.
• eval(Record,Fun) – Eval custom Fun/1 which takes Record2 (at the time of execution), like as update/2.

R=#post{},
{ok,R2}=kvs_feeds:append(R),
Link = 1000,
FunUpdate=fun(#post{links=Links}=P) -> {ok,P#post{links=lists:usort([Link | Links])}} end,
{ok,R3}=kvs_feeds:update(R2,FunUpdate),
     ok=kvs_feeds:delete(R3),
        kvs_feeds:purge(R3,fun() -> [{feed,attachment,fun kvs_feeds:delete/1}] end),

• @m-2k