[GitHub] nickva commented on a change in pull request #1824: Clean rexi stream workers when coordinator process is killed

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

nickva commented on a change in pull request #1824: Clean rexi stream workers when coordinator process is killed
URL: https://github.com/apache/couchdb/pull/1824#discussion_r243377610
 
 

 ##########
 File path: src/fabric/src/fabric_streams.erl
 ##########
 @@ -0,0 +1,215 @@
+% 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_streams).
+
+-export([
+    start/2,
+    start/4,
+    cleanup/1
+]).
+
+-include_lib("fabric/include/fabric.hrl").
+-include_lib("mem3/include/mem3.hrl").
+
+
+-define(WORKER_CLEANER, fabric_worker_cleaner).
+
+
+start(Workers, Keypos) ->
+    start(Workers, Keypos, undefined, undefined).
+
+start(Workers0, Keypos, StartFun, Replacements) ->
+    Fun = fun handle_stream_start/3,
+    Acc = #stream_acc{
+        workers = fabric_dict:init(Workers0, waiting),
+        start_fun = StartFun,
+        replacements = Replacements
+    },
+    spawn_worker_cleaner(self(), Workers0),
+    Timeout = fabric_util:request_timeout(),
+    case rexi_utils:recv(Workers0, Keypos, Fun, Acc, Timeout, infinity) of
+        {ok, #stream_acc{workers=Workers}} ->
+            true = fabric_view:is_progress_possible(Workers),
+            AckedWorkers = fabric_dict:fold(fun(Worker, From, WorkerAcc) ->
+                rexi:stream_start(From),
+                [Worker | WorkerAcc]
+            end, [], Workers),
+            {ok, AckedWorkers};
+        Else ->
+            Else
+    end.
+
+
+cleanup(Workers) ->
+    % Stop the auxiliary cleaner process as we got to the point where cleanup
+    % happesn in the regular fashion so we don't want to send 2x the number kill
+    % messages
+    case get(?WORKER_CLEANER) of
+        CleanerPid when is_pid(CleanerPid) ->
+            exit(CleanerPid, kill);
+        _ ->
+            ok
+    end,
+    fabric_util:cleanup(Workers).
+
+
+handle_stream_start({rexi_DOWN, _, {_, NodeRef}, _}, _, St) ->
+    case fabric_util:remove_down_workers(St#stream_acc.workers, NodeRef) of
+    {ok, Workers} ->
+        {ok, St#stream_acc{workers=Workers}};
+    error ->
+        Reason = {nodedown, <<"progress not possible">>},
+        {error, Reason}
+    end;
+
+handle_stream_start({rexi_EXIT, Reason}, Worker, St) ->
+    Workers = fabric_dict:erase(Worker, St#stream_acc.workers),
+    Replacements = St#stream_acc.replacements,
+    case {fabric_view:is_progress_possible(Workers), Reason} of
+    {true, _} ->
+        {ok, St#stream_acc{workers=Workers}};
+    {false, {maintenance_mode, _Node}} when Replacements /= undefined ->
+        % Check if we have replacements for this range
+        % and start the new workers if so.
+        case lists:keytake(Worker#shard.range, 1, Replacements) of
+            {value, {_Range, WorkerReplacements}, NewReplacements} ->
+                FinalWorkers = lists:foldl(fun(Repl, NewWorkers) ->
+                    NewWorker = (St#stream_acc.start_fun)(Repl),
+                    fabric_dict:store(NewWorker, waiting, NewWorkers)
+                end, Workers, WorkerReplacements),
+                % Assert that our replaced worker provides us
+                % the oppurtunity to make progress.
+                true = fabric_view:is_progress_possible(FinalWorkers),
+                NewRefs = fabric_dict:fetch_keys(FinalWorkers),
+                {new_refs, NewRefs, St#stream_acc{
+                    workers=FinalWorkers,
+                    replacements=NewReplacements
+                }};
+            false ->
+                % If we progress isn't possible and we don't have any
+                % replacements then we're dead in the water.
+                Error = {nodedown, <<"progress not possible">>},
+                {error, Error}
+        end;
+    {false, _} ->
+        {error, fabric_util:error_info(Reason)}
+    end;
+
+handle_stream_start(rexi_STREAM_INIT, {Worker, From}, St) ->
+    case fabric_dict:lookup_element(Worker, St#stream_acc.workers) of
+    undefined ->
+        % This worker lost the race with other partition copies, terminate
+        rexi:stream_cancel(From),
+        {ok, St};
+    waiting ->
+        % Don't ack the worker yet so they don't start sending us
+        % rows until we're ready
+        Workers0 = fabric_dict:store(Worker, From, St#stream_acc.workers),
+        Workers1 = fabric_view:remove_overlapping_shards(Worker, Workers0),
+        case fabric_dict:any(waiting, Workers1) of
+            true ->
+                {ok, St#stream_acc{workers=Workers1}};
+            false ->
+                {stop, St#stream_acc{workers=Workers1}}
+        end
+    end;
+
+handle_stream_start({ok, ddoc_updated}, _, St) ->
+    cleanup(St#stream_acc.workers),
+    {stop, ddoc_updated};
+
+handle_stream_start(Else, _, _) ->
+    exit({invalid_stream_start, Else}).
+
+
+% Spawn an auxiliary rexi worker cleaner. This will be used in cases
+% when the coordinator (request) process is forceably killed and doesn't
+% get a chance to process its `after` fabric:clean/1 clause.
+spawn_worker_cleaner(Coordinator, Workers) ->
 
 Review comment:
   Updated to add replacement workers

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services