balsoft/ligo
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Distributed_db: fix concurency issue

Browse Source 
Some `events` might be lost in case of the timeout happens before
concomitantly. We avoid this by storing the `events` promise into the
worker state.
This commit is contained in:
Grégoire Henry 2017-09-29 18:43:13 +02:00 committed by Benjamin Canou
parent 5c03d92457
commit 79ae54625d
1 changed files with 49 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

97
src/node/shell/distributed_db_functors.ml
View File

@ -281,6 +281,7 @@ end = struct
pending: status Table.t ;
cancelation: unit -> unit Lwt.t ;
wait_events: unit -> event list Lwt.t ;
mutable events: event list Lwt.t ;
}
and status = {
@ -329,62 +330,62 @@ end = struct
(* TODO *)
Lwt.return_unit
let worker_loop state =
let process = process_event state in
let rec loop () =
let shutdown = state.cancelation () >|= fun () -> `Shutdown
and timeout = compute_timeout state >|= fun () -> `Timeout
and events = state.wait_events () >|= fun events -> `Events events in
Lwt.pick [ timeout ; events ; shutdown ] >>= function
| `Shutdown -> Lwt.return_unit
| `Events events ->
Lwt_list.iter_s process events >>= fun () ->
loop ()
| `Timeout ->
let now = Unix.gettimeofday () in
let active_peers = Request.active state.param in
let requests =
Table.fold
(fun key { peers ; next_request ; delay } acc ->
if next_request > now +. 0.2 then
acc
else
let still_peers = P2p.Peer_id.Set.inter peers active_peers in
if P2p.Peer_id.Set.is_empty still_peers &&
not (P2p.Peer_id.Set.is_empty peers) then
( Table.remove state.pending key ; acc )
else
let requested_peers =
if P2p.Peer_id.Set.is_empty peers
then active_peers
else peers in
let next = { peers = still_peers ;
next_request = now +. delay ;
delay = delay *. 1.2 } in
Table.replace state.pending key next ;
P2p.Peer_id.Set.fold
(fun gid acc ->
let requests =
try key :: P2p_types.Peer_id.Map.find gid acc
with Not_found -> [key] in
P2p_types.Peer_id.Map.add gid requests acc)
requested_peers
acc)
state.pending P2p_types.Peer_id.Map.empty in
P2p_types.Peer_id.Map.iter (Request.send state.param) requests ;
loop ()
in
loop
let rec worker_loop state =
let shutdown = state.cancelation ()
and timeout = compute_timeout state in
Lwt.choose [ (state.events >|= fun _ -> ()) ; timeout ; shutdown ] >>= fun () ->
if Lwt.state shutdown <> Lwt.Sleep then
Lwt.return_unit
else if Lwt.state state.events <> Lwt.Sleep then
state.events >>= fun events ->
state.events <- state.wait_events () ;
Lwt_list.iter_s (process_event state) events >>= fun () ->
worker_loop state
else
let now = Unix.gettimeofday () in
let active_peers = Request.active state.param in
let requests =
Table.fold
(fun key { peers ; next_request ; delay } acc ->
if next_request > now +. 0.2 then
acc
else
let remaining_peers =
P2p.Peer_id.Set.inter peers active_peers in
if P2p.Peer_id.Set.is_empty remaining_peers &&
not (P2p.Peer_id.Set.is_empty peers) then
( Table.remove state.pending key ; acc )
else
let requested_peers =
if P2p.Peer_id.Set.is_empty remaining_peers
then active_peers
else remaining_peers
in
let next = { peers = remaining_peers ;
next_request = now +. delay ;
delay = delay *. 1.2 } in
Table.replace state.pending key next ;
P2p.Peer_id.Set.fold
(fun gid acc ->
let requests =
try key :: P2p_types.Peer_id.Map.find gid acc
with Not_found -> [key] in
P2p_types.Peer_id.Map.add gid requests acc)
requested_peers
acc)
state.pending P2p_types.Peer_id.Map.empty in
P2p_types.Peer_id.Map.iter (Request.send state.param) requests ;
worker_loop state
let create param =
let cancelation, cancel_worker, _ = Lwt_utils.canceler () in
let push_to_worker, wait_events = Lwt_utils.queue () in
let pending = Table.create 17 in
let worker_state =
{ cancelation ; wait_events ; pending ; param } in
{ cancelation ; wait_events ; pending ; param ; events = wait_events () } in
let worker =
Lwt_utils.worker "db_request_scheduler"
~run:(worker_loop worker_state)
~run:(fun () -> worker_loop worker_state)
~cancel:cancel_worker in
{ cancel_worker ; push_to_worker ; worker }