[GitHub] [couchdb] nickva commented on a change in pull request #2051: CouchDB background jobs

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nickva commented on a change in pull request #2051: CouchDB background jobs
URL: https://github.com/apache/couchdb/pull/2051#discussion_r299683197
 
 

 ##########
 File path: src/couch_jobs/src/couch_jobs_activity_monitor.erl
 ##########
 @@ -0,0 +1,133 @@
+% Licensed under the Apache License, Version 2.0 (the "License"); you may not
+% use this file except in compliance with the License. You may obtain a copy of
+% the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+% License for the specific language governing permissions and limitations under
+% the License.
+
+-module(couch_jobs_activity_monitor).
+
+-behaviour(gen_server).
+
+
+-export([
+    start_link/1
+]).
+
+-export([
+    init/1,
+    terminate/2,
+    handle_call/3,
+    handle_cast/2,
+    handle_info/2,
+    code_change/3
+]).
+
+-record(st, {
+    jtx,
+    type,
+    tref,
+    timeout = 0,
+    vs = not_found
+}).
+
+
+-define(MAX_JITTER_DEFAULT, 10000).
+-define(MISSING_TIMEOUT_CHECK, 5000).
+
+
+start_link(Type) ->
+    gen_server:start_link(?MODULE, [Type], []).
+
+
+%% gen_server callbacks
+
+init([Type]) ->
+    St = #st{jtx = couch_jobs_fdb:get_jtx(), type = Type},
+    {ok, schedule_check(St)}.
+
+
+terminate(_, _St) ->
+    ok.
+
+
+handle_call(Msg, _From, St) ->
+    {stop, {bad_call, Msg}, {bad_call, Msg}, St}.
+
+
+handle_cast(Msg, St) ->
+    {stop, {bad_cast, Msg}, St}.
+
+
+handle_info(check_activity, St) ->
+    St1 = check_activity(St),
+    St2 = schedule_check(St1),
+    {noreply, St2};
+
+handle_info({Ref, ready}, St) when is_reference(Ref) ->
+    % Don't crash out couch_jobs_server and the whole application would need to
+    % eventually do proper cleanup in erlfdb:wait timeout code.
+    LogMsg = "~p : spurious erlfdb future ready message ~p",
+    couch_log:error(LogMsg, [?MODULE, Ref]),
 
 Review comment:
   I think these are coming from the `erlfdb:wait`'s `is_ready` call https://github.com/cloudant-labs/couchdb-erlfdb/commit/11df0ac4c2e1024f3e71e124dd90da49e7a126a9#diff-5d6e935fc45cb6d387c9f7a8e4516411R228 when we don't wait for message. This commit hopefully should reduce the chance of it happening https://github.com/cloudant-labs/couchdb-erlfdb/commit/11df0ac4c2e1024f3e71e124dd90da49e7a126a9 but it's still not a 100% thing

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