[couchdb] branch fix-concurrent-db-creation-2613-3.x created (now 553767c)

[va...@apache.org]

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

vatamane pushed a change to branch fix-concurrent-db-creation-2613-3.x
in repository https://gitbox.apache.org/repos/asf/couchdb.git.


      at 553767c  Handle race condition during concurrent db creation

This branch includes the following new commits:

     new 553767c  Handle race condition during concurrent db creation

The 1 revisions listed above as "new" are entirely new to this
repository and will be described in separate emails.  The revisions
listed as "add" were already present in the repository and have only
been added to this reference.

[couchdb] 01/01: Handle race condition during concurrent db creation

[va...@apache.org]

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

vatamane pushed a commit to branch fix-concurrent-db-creation-2613-3.x
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 553767c3194cd81e861949d9780d9a33ad8c59de
Author: Nick Vatamaniuc <va...@apache.org>
AuthorDate: Fri Feb 28 13:30:44 2020 -0500

    Handle race condition during concurrent db creation
    
    Previously concurrent db creation requests could get past db_exists/1 and try
    to create the shard document. The first one would succeed but the others would
    fail with a `500 {"error":"error", "reason":"conflict"}` error instead of
    `412`.
    
    Handle the race condition by checking if db exists after getting a conflict
    error and return a 412 response.
    
    Fixes: #2613
---
 src/fabric/src/fabric_db_create.erl              |  6 +++
 src/fabric/test/eunit/fabric_db_create_tests.erl | 53 ++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/src/fabric/src/fabric_db_create.erl b/src/fabric/src/fabric_db_create.erl
index 03fabb4..1048cb0 100644
--- a/src/fabric/src/fabric_db_create.erl
+++ b/src/fabric/src/fabric_db_create.erl
@@ -37,6 +37,12 @@ go(DbName, Options) ->
                 case {CreateShardResult, create_shard_db_doc(Doc)} of
                 {ok, {ok, Status}} ->
                     Status;
+                {ok, {error, conflict} = ShardDocError} ->
+                    % Check if it is just a race to create the shard doc
+                    case db_exists(DbName) of
+                        true -> {error, file_exists};
+                        false -> ShardDocError
+                    end;
                 {file_exists, {ok, _}} ->
                     {error, file_exists};
                 {_, Error} ->
diff --git a/src/fabric/test/eunit/fabric_db_create_tests.erl b/src/fabric/test/eunit/fabric_db_create_tests.erl
new file mode 100644
index 0000000..8e5b108
--- /dev/null
+++ b/src/fabric/test/eunit/fabric_db_create_tests.erl
@@ -0,0 +1,53 @@
+% 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(fabric_db_create_tests).
+
+
+-include_lib("couch/include/couch_eunit.hrl").
+-include_lib("couch/include/couch_db.hrl").
+-include_lib("mem3/include/mem3.hrl").
+
+
+-define(TDEF(A), {atom_to_list(A), fun A/0}).
+
+
+main_test_() ->
+    {
+        setup,
+        fun setup/0,
+        fun teardown/1,
+        [
+            ?TDEF(t_handle_shard_doc_conflict)
+        ]
+    }.
+
+
+setup() ->
+    test_util:start_couch([fabric]).
+
+
+teardown(Ctx) ->
+    meck:unload(),
+    test_util:stop_couch(Ctx).
+
+
+t_handle_shard_doc_conflict() ->
+    DbName = ?tempdb(),
+    meck:new(mem3, [passthrough]),
+    meck:new(fabric_util, [passthrough]),
+    ok = meck:sequence(mem3, shards, 1, [
+        fun(_) -> meck:raise(error, database_does_not_exist) end,
+        [#shard{dbname = DbName}]
+    ]),
+    meck:expect(fabric_util, recv, 4, {error, conflict}),
+    ?assertEqual({error, file_exists}, fabric_db_create:go(DbName, [])).