[GitHub] obi458 commented on issue #1182: fixed race is_idle

[GitBox]

obi458 commented on issue #1182: fixed race is_idle
URL: https://github.com/apache/couchdb/pull/1182#issuecomment-368962363
 
 
   One solution may be:
   
   If we are going to close the Db(couch_file) we try:
   
   ```
   is_idle() ->
   ....
   andalso ets:insert_new(couch_dbs,self()).
   ```
   
   
   Further if we are going to monitor the Fd:
   
    ```
   incref(#db{fd = Fd} = Db) ->
     incref(Db,ets:insert_new(couch_dbs,Fd)).
   
   incref(#db{fd = Fd} = Db, true = _Ready) ->
       % first monitor
       Ref = erlang:monitor(process, Fd),
       % than release the lock
       ets:delete(couch_dbs,Fd),
       {ok, Db#db{fd_monitor = Ref}};
   % we are not able to write the lock,
   % either the file will be closed or another process want to monitor
   % we will try it again
   incref(#db{fd = _Fd} = Db, false = _Ready) ->
       retry.
   ```
   
   and 
   
   ```
   ...
   case couch_db:incref(Db0) of
                   retry -> open(DbName, Options0);
                   {ok, Db1} -> couch_db:set_user_ctx(Db1, Ctx)
               end;
   ...
   
   ...
   case couch_db:incref(Db0) of
                   retry -> create(DbName, Options0);
                   {ok, Db1} -> couch_db:set_user_ctx(Db1, Ctx)
               end;
   ...
   
   ```
   
   
   

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