[GitHub] [couchdb] nickva edited a comment on pull request #3050: Do not check db instance UUID in fabric2_fdb:reopen/1 call

[GitBox <gi...@apache.org>]

nickva edited a comment on pull request #3050:
URL: https://github.com/apache/couchdb/pull/3050#issuecomment-666737359


   Saw some unexpected success test failures:
   
   ```
      fabric2_db_crud_tests:40: crud_test_ (recreate_db)...*failed*
   in function fabric2_db_crud_tests:'-recreate_db/1-fun-4-'/1 (test/fabric2_db_crud_tests.erl, line 160)
   in call from fabric2_db_crud_tests:recreate_db/1 (test/fabric2_db_crud_tests.erl, line 160)
   **error:{assertException,
       [{module,fabric2_db_crud_tests},
        {line,160},
        {expression,"fabric2_db : get_db_info ( Db1 )"},
        {pattern,"{ error , database_does_not_exist , [...] }"},
        {unexpected_success,
            {ok,[{cluster,{[{n,0},{q,0},{r,...},{...}]}},
                 {compact_running,false},
                 {data_size,0},
                 {db_name,<<"eunit-te"...>>},
                 {disk_format_version,0},
                 {disk_size,0},
                 {instance_start_time,...},
                 {...}|...]}}]}
     output:<<"">>
   
   ```
   
   From https://github.com/apache/couchdb/blob/prototype/fdb-layer/src/fabric/test/fabric2_db_crud_tests.erl#L160
   
   So perhaps the existing code wasn't totally wrong. The question is what should happen if we end up finding a previous instance of a db in the cache.  With the current PR we'll let the user roll with the old db, and when they perform a transaction operation, we'd silently upgrade it to the new db version. And then they can keep holding on that stale handle and be none the wiser.
   
   In the previous scheme, any old db handles immediately threw a `database_does_not_exist` error which bubbled up to the client right away. That wasn't correct either, since a user may delete and recreate the db on node1 then make a re-quest for db_info to node2, get the previous db instance, then get a 404 response, which is wrong.


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