[GitHub] iilyak commented on issue #501: Fix error on race condition in mem3 startup

[gi...@git.apache.org]

iilyak commented on issue #501: Fix error on race condition in mem3 startup
URL: https://github.com/apache/couchdb/pull/501#issuecomment-298691336
 
 
   > Question: Why not call couch_db:open/2 with Options including create_if_missing once, and if that fails with file_exists, just call it again without that option?
   
   Thank you @wohali your suggestion is great. Following works locally:
   ```
   diff --git a/src/mem3/src/mem3_util.erl b/src/mem3/src/mem3_util.erl
   index 2cd444d..71ef5b6 100644
   --- a/src/mem3/src/mem3_util.erl
   +++ b/src/mem3/src/mem3_util.erl
   @@ -214,11 +214,12 @@ shard_info(DbName) ->
    ensure_exists(DbName) when is_list(DbName) ->
        ensure_exists(list_to_binary(DbName));
    ensure_exists(DbName) ->
   -    case couch_db:open(DbName, [nologifmissing, sys_db | [?ADMIN_CTX]]) of
   +    Options = [nologifmissing, sys_db, {create_if_missing, true}, ?ADMIN_CTX],
   +    case couch_db:open(DbName, Options) of
        {ok, Db} ->
            {ok, Db};
   -    _ ->
   -        couch_server:create(DbName, [?ADMIN_CTX])
   +    file_exists ->
   +        couch_db:open(DbName, [sys_db, ?ADMIN_CTX])
        end.
   ```
 
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