When shard splitting make sure to reset the targets before any retries

Previously the target was reset only when the whole job started, but not when
the initial copy phase restarted on its own. If that happened, we left the
target around so the retry failed always with the `eexist` error.

Target reset has a check to make sure the shards are not in the global shard
map, in case someone manually added them, for example. If they are found there
the job panics and exists.

2 files changed, 5 insertions, 15 deletions

diff --git a/src/mem3/src/mem3_reshard_job.erl b/src/mem3/src/mem3_reshard_job.erl
index d3a33d3f6..aedca21bb 100644
--- a/src/mem3/src/mem3_reshard_job.erl
+++ b/src/mem3/src/mem3_reshard_job.erl
@@ -184,19 +184,12 @@ run(#job{split_state = CurrState} = Job) ->
 
 
 set_start_state(#job{split_state = State} = Job) ->
-    case {State, maps:get(State, ?STATE_RESTART, undefined)} of
-        {_, undefined} ->
+    case maps:get(State, ?STATE_RESTART, undefined) of
+        undefined ->
             Fmt1 = "~p recover : unknown state ~s",
             couch_log:error(Fmt1, [?MODULE, jobfmt(Job)]),
             erlang:error({invalid_split_job_recover_state, Job});
-        {initial_copy, initial_copy} ->
-            % Since we recover from initial_copy to initial_copy, we need
-            % to reset the target state as initial_copy expects to
-            % create a new target
-            Fmt2 = "~p recover : resetting target ~s",
-            couch_log:notice(Fmt2, [?MODULE, jobfmt(Job)]),
-            reset_target(Job);
-        {_, StartState} ->
+        StartState->
             Job#job{split_state = StartState}
     end.
 
@@ -403,6 +396,7 @@ initial_copy_impl(#job{source = Source, target = Targets0} = Job) ->
     LogMsg1 = "~p initial_copy started ~s",
     LogArgs1 = [?MODULE, shardsstr(Source, Targets0)],
     couch_log:notice(LogMsg1, LogArgs1),
+    reset_target(Job),
     case couch_db_split:split(SourceName, TMap, fun pickfun/3) of
         {ok, Seq} ->
             LogMsg2 = "~p initial_copy of ~s finished @ seq:~p",
diff --git a/src/mem3/test/eunit/mem3_reshard_test.erl b/src/mem3/test/eunit/mem3_reshard_test.erl
index 1e89755a9..7cd6b1fe6 100644
--- a/src/mem3/test/eunit/mem3_reshard_test.erl
+++ b/src/mem3/test/eunit/mem3_reshard_test.erl
@@ -453,19 +453,15 @@ target_reset_in_initial_copy(#{db1 := Db}) ->
             job_state = running,
             split_state = initial_copy
         },
-        BogusParent = spawn(fun() -> receive {ack, _, _} -> ok end end),
-        put('$ancestors', [BogusParent]), % make prock_lib:ack not blow up
-        meck:expect(mem3_reshard, checkpoint, 2, ok),
         meck:expect(couch_db_split, cleanup_target, 2, ok),
         meck:expect(couch_server, exists, fun
             (<<"t1">>) -> true;
             (<<"t2">>) -> true;
             (DbName) -> meck:passthrough([DbName])
         end),
-        JobPid = spawn(fun() -> mem3_reshard_job:init(Job) end),
+        JobPid = spawn(fun() -> mem3_reshard_job:initial_copy_impl(Job) end),
         meck:wait(2, couch_db_split, cleanup_target, ['_', '_'], 5000),
         exit(JobPid, kill),
-        exit(BogusParent, kill),
         ?assertEqual(2, meck:num_calls(couch_db_split, cleanup_target, 2))
     end)}.