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Split interface and implementation into seperate files.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| %% @doc kvs_server implements a distributed key-value store. | ||
| -module(kvs_server). | ||
| -include("kvs.hrl"). | ||
| -export([store/1]). | ||
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| %% @doc implementation of distributed key-value store | ||
| %% @spec store(proplist()) -> term() | ||
| %% proplist = [{term(), term()}] | ||
| store(Store) -> | ||
| receive | ||
| {Sender, get, Key} -> | ||
| message_get(Store, Sender, Key); | ||
| {Sender, retrieve, Client, Key} -> | ||
| message_retrieve(Store, Sender, Client, Key); | ||
| {Sender, retrieved, Client, Key, Value} -> | ||
| message_retrieved(Store, Sender, Client, Key, Value); | ||
| {Sender, set, Key, Value} -> | ||
| message_set(Store, Sender, Key, Value); | ||
| {Sender, update, Client, Key, Value} -> | ||
| message_update(Store, Sender, Client, Key, Value); | ||
| {Sender, updated, Client, Key, Value} -> | ||
| message_updated(Store, Sender, Client, Key, Value); | ||
| stop -> | ||
| ok | ||
| after | ||
| ?KVS_POLL_PENDING -> | ||
| Writes2 = lists:filter(fun filter_writes/1, Store#kvs_store.pending_writes), | ||
| Reads2 = lists:filter(fun filter_reads/1, Store#kvs_store.pending_reads), | ||
| store(Store#kvs_store{pending_writes=Writes2, pending_reads=Reads2}) | ||
| end. | ||
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| %% @doc filter expired writes from pending_writes. | ||
| filter_writes({{Client, _Key}, {_Count, Ts}}) -> | ||
| Now = ts(), | ||
| if Now > Ts + ?KVS_WRITE_TIMEOUT -> | ||
| Client ! {error, write_failed}, | ||
| false; | ||
| true -> | ||
| true | ||
| end. | ||
|
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| %% @doc filter expired reads from pending_reads. | ||
| filter_reads({{Client, _Key}, {_Count, _Values, Ts}}) -> | ||
| Now = ts(), | ||
| if Now > Ts + ?KVS_READ_TIMEOUT -> | ||
| Client ! {error, read_failed}, | ||
| false; | ||
| true -> | ||
| true | ||
| end. | ||
|
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| %% | ||
| %% Message Handling Functions | ||
| %% | ||
|
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| message_get(Store = #kvs_store{pending_reads=Reads}, Sender, Key) -> | ||
| % client interface for retrieving values | ||
| lists:foreach(fun(Pid) -> | ||
| Pid ! {self(), retrieve, Sender, Key} | ||
| end, pg2:get_members(kvs)), | ||
| % ?KVS_READS is required # of nodes to read from | ||
| % [] is used to collect read values | ||
| Reads2 = [{{Sender, Key}, {?KVS_READS, [], ts()}} | Reads], | ||
| store(Store#kvs_store{pending_reads=Reads2}). | ||
|
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| message_retrieve(Store = #kvs_store{data=Data}, Sender, Client, Key) -> | ||
| Sender ! {self(), retrieved, Client, Key, proplists:get_value(Key, Data)}, | ||
| store(Store). | ||
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| message_retrieved(Store = #kvs_store{pending_reads=Reads}, _Sender, Client, Key, Value) -> | ||
| case proplists:get_value({Client, Key}, Reads) of | ||
| undefined -> | ||
| store(Store); | ||
| {0, Values, _Timestamp} -> | ||
| Freq = lists:foldr(fun(X, Acc) -> | ||
| case proplists:get_value(X, Acc) of | ||
| undefined -> [{X, 1} | Acc]; | ||
| N -> [{X, N+1} | proplists:delete(X, Acc)] | ||
| end | ||
| end, [], Values), | ||
| [{Popular, _} | _ ] = lists:reverse(lists:keysort(2, Freq)), | ||
| Client ! {self(), got, Popular}, | ||
| store(Store#kvs_store{ | ||
| pending_reads=proplists:delete({Key, Value}, Reads)}); | ||
| {Count, Values, Timestamp} -> | ||
| store(Store#kvs_store{ | ||
| pending_reads=[{{Client, Key}, {Count-1, [Value | Values], Timestamp}} | | ||
| proplists:delete({Client, Key}, Reads)]}) | ||
| end. | ||
|
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| message_set(Store = #kvs_store{pending_writes=Writes}, Sender, Key, Value) -> | ||
| % client interface for updating values | ||
| lists:foreach(fun(Pid) -> | ||
| Pid ! {self(), update, Sender, Key, Value} | ||
| end, pg2:get_members(kvs)), | ||
| Writes2 = [{{Sender, Key}, {?KVS_WRITES, ts()}} | Writes], | ||
| store(Store#kvs_store{pending_writes=Writes2}). | ||
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| message_update(Store = #kvs_store{data=Data}, Sender, Client, Key, Value) -> | ||
| % sent to all nodes by first receiving node | ||
| Sender ! {self(), updated, Client, Key, Value}, | ||
| store(Store#kvs_store{data=[{Key, Value} | proplists:delete(Key, Data)]}). | ||
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| message_updated(Store = #kvs_store{pending_writes=Writes}, _Sender, Client, Key, Value) -> | ||
| {Count, Timestamp} = proplists:get_value({Client, Key}, Writes), | ||
| case Count of | ||
| undefined -> | ||
| store(Store); | ||
| 0 -> | ||
| Client ! {self(), received, {set, Key, Value}}, | ||
| store(Store#kvs_store{ | ||
| pending_writes=proplists:delete({Key, Value}, Writes)}); | ||
| _ -> | ||
| store(Store#kvs_store{ | ||
| pending_writes=[{{Client, Key}, {Count-1, Timestamp}} | | ||
| proplists:delete({Client, Key}, Writes)]}) | ||
| end. | ||
|
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| %% | ||
| %% Utility functions | ||
| %% | ||
|
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| ts() -> | ||
| {Mega, Sec, _} = erlang:now(), | ||
| (Mega * 1000000) + Sec. |