Packages
macula
17.2.0
17.2.0
17.1.1
17.1.0
17.0.0
16.1.0
16.0.1
16.0.0
15.6.0
15.5.0
15.4.0
15.3.0
15.2.0
15.1.0
15.0.0
15.0.0-rc.3
15.0.0-rc.2
15.0.0-rc.1
14.11.0
14.10.0
14.9.0
14.8.2
14.8.1
14.8.0
14.7.0
14.6.0
14.5.0
14.4.0
14.3.0
14.2.1
14.2.0
14.1.0
14.0.0
13.6.0
13.5.0
13.4.0
13.3.0
13.2.2
13.2.1
13.2.0
13.1.0
13.0.1
13.0.0
12.12.0
12.11.1
12.11.0
12.10.0
12.9.1
12.9.0
12.8.0
12.7.0
12.6.0
12.5.1
12.5.0
12.4.0
12.3.0
12.2.1
12.2.0
12.1.0
12.0.0
11.5.0
11.4.0
11.3.1
11.3.0
11.2.0
11.1.0
11.0.0
10.25.0
10.24.0
10.23.0
10.22.0
10.21.0
10.20.3
10.20.2
10.20.0
10.19.2
10.19.1
10.19.0
10.18.0
10.17.0
10.16.0
10.15.0
10.14.5
10.14.4
10.14.2
10.14.1
10.14.0
10.13.2
10.13.1
10.11.0
10.10.2
10.10.1
10.10.0
10.9.1
10.9.0
10.8.0
10.7.0
10.5.8
10.5.7
10.5.6
10.5.5
10.5.4
10.5.3
10.5.2
10.5.1
10.5.0
10.4.0
10.2.0
10.1.1
10.1.0
10.0.2
10.0.1
10.0.0
9.13.8
9.8.2
9.8.1
9.8.0
9.5.0
9.4.0
9.3.1
9.3.0
9.2.0
9.1.1
9.1.0
9.0.0
8.7.0
8.6.0
8.5.0
8.4.1
8.4.0
8.3.0
8.2.0
8.1.0
8.0.2
8.0.1
8.0.0
7.1.0
7.0.0
6.0.0
5.2.2
5.2.1
5.2.0
5.1.0
5.0.0
4.8.0
4.7.1
4.7.0
4.6.0
4.5.0
4.4.10
4.4.9
4.4.8
4.4.7
4.4.6
4.4.5
4.4.4
4.4.3
4.4.2
4.4.1
4.4.0
4.3.1
4.3.0
4.2.9
4.2.8
4.2.7
4.2.6
4.2.5
4.2.4
4.2.3
4.2.2
4.2.1
4.2.0
4.1.1
4.1.0
4.0.0
3.16.0
3.15.3
3.15.2
3.15.1
3.14.0
3.13.0
3.12.1
3.12.0
3.11.1
3.11.0
3.10.3
3.10.2
3.10.1
3.9.0
3.8.0
3.7.0
3.5.0
3.4.0
3.3.0
3.2.0
3.1.0
3.0.0
2.1.1
2.1.0
2.0.0
1.5.2
1.5.1
1.4.30
1.4.29
1.4.28
1.4.27
1.4.26
1.4.25
1.4.24
1.4.23
1.4.22
1.4.21
1.4.20
1.4.19
1.4.18
1.4.17
1.4.16
1.4.15
1.4.14
1.4.13
1.4.11
1.4.10
1.4.9
1.4.8
1.4.7
1.4.6
1.4.5
1.4.4
1.4.3
1.4.2
1.4.1
1.4.0
1.3.1
1.3.0
1.2.0
1.1.0
1.0.10
1.0.9
1.0.8
1.0.7
1.0.6
1.0.5
1.0.4
1.0.3
1.0.2
1.0.1
1.0.0
0.48.6
0.48.5
0.48.4
0.48.3
0.48.2
0.48.1
0.48.0
0.47.1
0.47.0
0.46.3
0.46.1
0.46.0
0.45.3
0.45.2
0.45.1
0.45.0
0.44.2
0.44.1
0.44.0
0.43.3
0.43.2
0.43.1
0.43.0
0.42.9
0.42.8
0.42.7
0.42.6
0.42.5
0.42.4
0.42.3
0.42.2
0.42.1
0.42.0
0.41.1
0.41.0
0.40.1
0.40.0
0.39.9
0.39.8
0.39.7
0.39.6
0.39.5
0.39.4
0.39.3
0.39.2
0.39.1
0.39.0
0.38.8
0.38.7
0.38.6
0.38.5
0.38.4
0.38.3
0.38.2
0.38.1
0.38.0
0.37.7
0.37.6
0.37.5
0.37.4
0.37.3
0.37.2
0.37.1
0.37.0
0.36.6
0.36.5
0.36.4
0.36.3
0.36.2
0.36.1
0.36.0
0.35.4
0.35.3
0.35.2
0.35.1
0.35.0
0.34.1
0.34.0
0.33.1
0.33.0
0.32.5
0.32.4
0.32.3
0.32.2
0.32.1
0.32.0
0.31.9
0.31.8
0.31.7
0.31.6
0.31.5
0.31.4
0.31.3
0.31.2
0.31.1
0.31.0
0.30.10
0.30.9
0.30.8
0.30.7
0.30.6
0.30.5
0.30.4
0.30.3
0.30.2
0.30.1
0.30.0
0.29.0
0.28.3
0.28.2
0.28.1
0.28.0
0.27.1
0.27.0
0.26.1
0.26.0
0.25.6
0.25.5
0.25.4
0.25.3
0.25.2
0.25.1
0.25.0
0.24.6
0.24.5
0.24.4
0.24.3
0.24.2
0.24.1
0.24.0
0.23.3
0.23.2
0.23.1
0.23.0
0.22.12
0.22.11
0.22.10
0.22.9
0.22.8
0.22.7
0.22.6
0.22.5
0.22.4
0.22.3
0.22.2
0.22.1
0.22.0
0.21.7
0.21.6
0.21.5
0.21.4
0.21.2
0.21.1
0.21.0
0.20.25
0.20.24
0.20.23
0.20.22
0.20.21
0.20.20
0.20.19
0.20.18
0.20.17
0.20.16
0.20.15
0.20.14
0.20.13
0.20.12
0.20.11
0.20.10
0.20.9
0.20.8
0.20.7
0.20.6
0.20.5
0.20.3
0.20.2
0.20.1
0.20.0
0.19.2
0.19.1
0.19.0
0.18.1
0.18.0
0.17.4
0.17.3
0.17.2
0.17.1
0.17.0
0.16.6
0.16.5
0.16.4
0.16.3
0.16.2
0.16.1
0.16.0
0.15.1
0.15.0
0.14.3
0.14.2
0.14.1
0.14.0
0.12.6
0.12.5
0.12.3
0.11.3
0.10.2
0.10.1
0.10.0
0.9.2
0.9.1
0.9.0
0.8.25
0.8.24
0.8.23
0.8.22
0.8.21
0.8.20
0.8.19
0.8.18
0.8.17
0.8.16
0.8.15
0.8.14
0.8.13
0.8.12
0.8.11
0.8.10
0.8.9
0.8.8
0.8.7
0.8.6
0.8.5
0.8.4
0.8.3
0.8.2
0.8.1
0.8.0
0.7.30
0.7.29
0.7.28
0.7.27
0.7.26
0.7.25
0.7.24
0.7.23
0.7.22
0.7.21
0.7.20
0.7.19
0.7.18
0.7.17
0.7.16
0.7.15
0.7.14
0.7.13
0.7.12
0.7.11
0.7.10
0.7.9
0.7.8
0.7.7
0.7.6
0.7.5
0.7.4
0.7.3
0.7.2
0.7.1
0.7.0
0.6.7
0.6.6
0.6.5
0.6.4
0.6.3
0.6.2
0.6.1
0.6.0
0.5.0
0.4.4
0.4.3
0.4.2
0.4.1
0.4.0
0.3.4
0.3.3
0.3.2
0.3.1
Macula HTTP/3 Mesh SDK — connect, subscribe, publish, call, advertise
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Files
src/macula_provider_standing.erl
%% @doc The node's last reading of each provider's delegation slot, shared by every stream that follows that provider
%% (macula#120): a node holding N streams to one provider under one org key reads the slot once per re-check, not N
%% times.
%%
%% A follower asks read/3 with its key, {Provider, OrgKeyId}, the read it would make and its re-check interval. A
%% reading younger than half the interval is answered as it is, and the follower asks again one interval later, so
%% the withdrawal reaches it within one and a half re-checks plus a lookup: the worst case is a reading taken just
%% before the tombstone landed and answered when almost half an interval old. A missing or older one is claimed by
%% the first asker, atomically, and that asker makes the one read and stores its answer; every other asker
%% meanwhile waits for that answer rather than taking the last one, so no follower learns of a withdrawal later than
%% the one that read it. A read that raises is stored as lookup_failed, and an asker that waits longer than a lookup can
%% take answers lookup_failed: neither is evidence of revocation. A claim older than that wait, its claimant gone
%% mid-read, is claimed again by the next asker. Callers read and write the table themselves; this process owns
%% it and sweeps readings older than ten minutes. Without the table, between an owner's exit and its restart, read/3
%% reads directly.
-module(macula_provider_standing).
-behaviour(gen_server).
-export([start_link/0, read/3]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2]).
%% Started from macula_root's child spec, which xref does not count as a call.
-ignore_xref([{macula_provider_standing, start_link, 0}]).
-define(TABLE, ?MODULE).
%% A reading older than this is swept.
-define(KEEP_MS, 600_000).
-define(SWEEP_MS, 60_000).
%% An asker waits this long at most for another asker's read, longer than a lookup's own deadline.
-define(AWAIT_MS, 15_000).
-define(AWAIT_POLL_MS, 20).
-type key() :: {<<_:256>>, <<_:256>>}.
-type standing() :: ok | {error, term()}.
-spec start_link() -> {ok, pid()} | {error, term()}.
start_link() ->
gen_server:start_link(?MODULE, [], []).
%% @doc The standing of the provider and org key `Key', from a reading younger than `MaxAgeMs', or from `Read()'.
-spec read(key(), fun(() -> standing()), pos_integer()) -> standing().
read(Key, Read, MaxAgeMs) when is_function(Read, 0), is_integer(MaxAgeMs), MaxAgeMs > 0 ->
held(ets:whereis(?TABLE), Key, Read, MaxAgeMs).
held(undefined, _Key, Read, _MaxAgeMs) ->
Read();
held(Table, Key, Read, MaxAgeMs) ->
Now = now_ms(),
reading(ets:lookup(Table, Key), Table, Key, Read, MaxAgeMs, Now).
%% A row is {Key, ReadAt, Standing}, where Standing is `reading' while its claimant reads, ReadAt then being the claim's
%% time.
reading([{Key, ClaimedAt, reading}], Table, Key, _Read, _MaxAgeMs, Now) when Now - ClaimedAt < ?AWAIT_MS ->
awaited(Table, Key, Now + ?AWAIT_MS);
reading([{Key, ReadAt, Standing}], _Table, Key, _Read, MaxAgeMs, Now)
when Standing =/= reading, Now - ReadAt < MaxAgeMs div 2 ->
Standing;
reading([{Key, ReadAt, Standing}], Table, Key, Read, _MaxAgeMs, Now) ->
claimed(ets:select_replace(Table, [{{Key, ReadAt, Standing}, [], [{{{const, Key}, Now, reading}}]}]), Table, Key,
Read, Now);
reading([], Table, Key, Read, _MaxAgeMs, Now) ->
claimed(boolean_to_count(ets:insert_new(Table, {Key, Now, reading})), Table, Key, Read, Now).
boolean_to_count(true) -> 1;
boolean_to_count(false) -> 0.
%% The asker whose claim landed owns the read; another asker got there first, and this one waits for its answer.
claimed(1, Table, Key, Read, _Now) -> stored(Table, Key, read_once(Read));
claimed(0, Table, Key, _Read, Now) -> awaited(Table, Key, Now + ?AWAIT_MS).
read_once(Read) ->
try Read()
catch _:_ -> {error, lookup_failed}
end.
stored(Table, Key, Standing) ->
true = ets:insert(Table, {Key, now_ms(), Standing}),
Standing.
awaited(Table, Key, Deadline) ->
awaited(ets:lookup(Table, Key), Table, Key, Deadline, now_ms()).
awaited([{Key, _ReadAt, reading}], Table, Key, Deadline, Now) when Now < Deadline ->
timer:sleep(?AWAIT_POLL_MS),
awaited(Table, Key, Deadline);
awaited([{Key, _ReadAt, reading}], _Table, Key, _Deadline, _Now) ->
{error, lookup_failed};
awaited([{Key, _ReadAt, Standing}], _Table, Key, _Deadline, _Now) ->
Standing;
awaited([], _Table, _Key, _Deadline, _Now) ->
{error, lookup_failed}.
init([]) ->
Table = ets:new(?TABLE, [named_table, public, set, {write_concurrency, true}]),
_ = erlang:send_after(?SWEEP_MS, self(), sweep),
{ok, #{table => Table}}.
handle_call(_Request, _From, State) ->
{reply, {error, unknown_call}, State}.
handle_cast(_Message, State) ->
{noreply, State}.
handle_info(sweep, #{table := Table} = State) ->
_ = ets:select_delete(Table, [{{'_', '$1', '_'}, [{'<', '$1', now_ms() - ?KEEP_MS}], [true]}]),
_ = erlang:send_after(?SWEEP_MS, self(), sweep),
{noreply, State};
handle_info(_Message, State) ->
{noreply, State}.
now_ms() ->
erlang:system_time(millisecond).