[couchdb] 08/10: make sure peruser listeners are only initialised once per node

[ja...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

jan pushed a commit to branch 749-fix-couch_peruser-app-structure
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 736c26984907116eff8a5b0dac705b9cfee4a714
Author: Jan Lehnardt <ja...@apache.org>
AuthorDate: Sun Oct 8 15:36:31 2017 +0200

    make sure peruser listeners are only initialised once per node
---
 src/couch_peruser/src/couch_peruser.erl | 59 ++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 23 deletions(-)

diff --git a/src/couch_peruser/src/couch_peruser.erl b/src/couch_peruser/src/couch_peruser.erl
index 791431c..e722b7e 100644
--- a/src/couch_peruser/src/couch_peruser.erl
+++ b/src/couch_peruser/src/couch_peruser.erl
@@ -32,7 +32,14 @@
     cluster_unstable/1
 ]).
 
--record(state, {parent, db_name, delete_dbs, changes_pid, changes_ref}).
+-record(state, {
+    parent,
+    db_name,
+    delete_dbs,
+    changes_pid,
+    changes_ref
+}).
+
 -record(clusterState, {
     parent,
     db_name,
@@ -47,6 +54,9 @@
 -define(DEFAULT_QUIET_PERIOD, 60). % seconds
 -define(DEFAULT_START_PERIOD, 5). % seconds
 
+%%
+%% Please leave in the commented-out couch_log:debug calls, thanks! — Jan
+%%
 
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
@@ -72,8 +82,6 @@ init() ->
         {ok, Mem3Cluster} = mem3_cluster:start_link(?MODULE, self(), StartPeriod,
             Period),
 
-        couch_log:debug("peruser: registered for cluster event on node ~p", [node()]),
-
         #clusterState{
             parent = self(),
             db_name = DbName,
@@ -86,11 +94,14 @@ init() ->
 % Cluster membership change notification callback
 -spec notify_cluster_event(pid(), {cluster, any()}) -> ok.
 notify_cluster_event(Server, {cluster, _} = Event) ->
-    couch_log:debug("peruser: received cluster event ~p on node ~p", [Event, node()]),
+    % couch_log:debug("peruser: received cluster event ~p on node ~p", [Event, node()]),
     gen_server:cast(Server, Event).
 
+start_listening(#clusterState{states=States}=ClusterState) when length(States) > 0 ->
+    % couch_log:debug("peruser: start_listening() already run on node ~p in pid ~p", [node(), self()]),
+    ClusterState;
 start_listening(#clusterState{db_name=DbName, delete_dbs=DeleteDbs} = ClusterState) ->
-    couch_log:debug("peruser: start_listening() on node ~p", [node()]),
+    % couch_log:debug("peruser: start_listening() on node ~p", [node()]),
     try
         States = lists:map(fun (A) ->
             S = #state{parent = ClusterState#clusterState.parent,
@@ -100,6 +111,7 @@ start_listening(#clusterState{db_name=DbName, delete_dbs=DeleteDbs} = ClusterSta
                 ?MODULE, init_changes_handler, [S], [link, monitor]),
             S#state{changes_pid=Pid, changes_ref=Ref}
         end, mem3:local_shards(DbName)),
+        % couch_log:debug("peruser: start_listening() States ~p", [States]),
 
         ClusterState#clusterState{states = States, cluster_stable = true}
     catch error:database_does_not_exist ->
@@ -108,7 +120,6 @@ start_listening(#clusterState{db_name=DbName, delete_dbs=DeleteDbs} = ClusterSta
     end.
 
 init_changes_handler(#state{db_name=DbName} = State) ->
-    % leave for debugging
     % couch_log:debug("peruser: init_changes_handler() on DbName ~p", [DbName]),
     try
         {ok, Db} = couch_db:open_int(DbName, [?ADMIN_CTX, sys_db]),
@@ -123,7 +134,6 @@ init_changes_handler(#state{db_name=DbName} = State) ->
 
 
 changes_handler({change, {Doc}, _Prepend}, _ResType, State=#state{db_name=DbName}) ->
-    % leave for debugging
     % couch_log:debug("peruser: changes_handler() on DbName/Doc ~p/~p", [DbName, Doc]),
 
     case couch_util:get_value(<<"id">>, Doc) of
@@ -155,28 +165,31 @@ changes_handler({change, {Doc}, _Prepend}, _ResType, State=#state{db_name=DbName
 changes_handler(_Event, _ResType, State) ->
     State.
 
+
 should_handle_doc(ShardName, DocId) ->
-    should_handle_doc_int(ShardName, DocId, is_stable()).
-
-should_handle_doc_int(ShardName, DocId, false) ->
-    % when the cluster is unstable, we have already stopped all Listeners
-    % the next stable event will restart all listeners and pick up this
-    % doc change
-    couch_log:debug("peruser: skipping, cluster unstable ~s/~s", [ShardName, DocId]),
-    false;
-should_handle_doc_int(ShardName, DocId, true) ->
+    case is_stable() of
+    false ->
+        % when the cluster is unstable, we have already stopped all Listeners
+        % the next stable event will restart all listeners and pick up this
+        % doc change
+        couch_log:debug("peruser: skipping, cluster unstable ~s/~s", [ShardName, DocId]),
+        false;
+    true ->
+        should_handle_doc_int(ShardName, DocId)
+    end.
+
+should_handle_doc_int(ShardName, DocId) ->
     DbName = mem3:dbname(ShardName),
     Live = [erlang:node() | erlang:nodes()],
     Shards = mem3:shards(DbName, DocId),
     Nodes = [N || #shard{node=N} <- Shards, lists:member(N, Live)],
     case mem3:owner(DbName, DocId, Nodes) of
-        ThisNode when ThisNode =:= node() ->
-            couch_log:debug("peruser: handling ~s/~s", [DbName, DocId]),
-            % do the deed
-            true;
-        _OtherNode ->
-            couch_log:debug("peruser: skipping ~s/~s", [DbName, DocId]),
-            false
+    ThisNode when ThisNode =:= node() ->
+        couch_log:debug("peruser: handling ~s/~s", [DbName, DocId]),
+        true; % do the database action
+    _OtherNode ->
+        couch_log:debug("peruser: skipping ~s/~s", [DbName, DocId]),
+        false
   end.
 
 

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