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fix(dcl): capture adapter into locals before background tasks — no off-thread reads of the mutable _adapter field (S7)

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This commit is contained in:
Joseph Doherty
2026-07-09 00:44:09 -04:00
parent ef69fab6f6
commit f294b46263
2 changed files with 97 additions and 6 deletions
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src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Actors/DataConnectionActor.cs
+26 -6
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@@ -678,6 +678,13 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
// Capture the current adapter generation so callbacks
// from this adapter can be distinguished from a later (post-failover) adapter.
var generation = _adapterGeneration;
// Capture the adapter reference on the actor thread too (S7). The background task
// below iterates multiple tags with an await between each SubscribeAsync — a failover
// that swaps the mutable _adapter field mid-loop would otherwise make later iterations
// (and the SeedTagsAsync read) run against the NEW adapter while carrying the OLD
// generation. The in-flight subscribe must finish against the adapter that started it;
// the generation guard drops any value the swapped-out adapter later produces.
var adapter = _adapter;
// Partition tags on the actor thread into "this
// request will issue _adapter.SubscribeAsync" vs. "already subscribed (by us
@@ -718,7 +725,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
{
try
{
var subId = await _adapter.SubscribeAsync(tagPath, (path, value) =>
var subId = await adapter.SubscribeAsync(tagPath, (path, value) =>
{
self.Tell(new TagValueReceived(path, value, generation));
});
@@ -752,7 +759,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
// SeedTagsAsync retries the still-empty reads so a
// seed that races the just-created advise (returns VT_EMPTY) is not silently
// dropped, and logs any tag that never yields a value.
var seedValues = await SeedTagsAsync(_adapter, tagsToSeed);
var seedValues = await SeedTagsAsync(adapter, tagsToSeed);
return new SubscribeCompleted(request, sender, results, seedValues);
}).PipeTo(self);
@@ -1119,8 +1126,12 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
// failed WriteTagResponse so the failure is returned synchronously.
var cts = new CancellationTokenSource(_options.WriteTimeout);
// Capture the adapter on the actor thread (S7) so the write completes against the
// adapter that started it even if a failover swaps the _adapter field mid-flight.
var adapter = _adapter;
// Write through DCL to device, failure returned synchronously
_adapter.WriteAsync(request.TagPath, request.Value, cts.Token).ContinueWith(t =>
adapter.WriteAsync(request.TagPath, request.Value, cts.Token).ContinueWith(t =>
{
cts.Dispose();
if (t.IsCompletedSuccessfully)
@@ -1158,11 +1169,16 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
var sender = Sender;
var cts = new CancellationTokenSource(_options.WriteTimeout);
// Capture the adapter on the actor thread (S7). The trigger write below runs AFTER
// the batch await, so re-reading the _adapter field there could hit a post-failover
// adapter; both legs must use the adapter that started this batch.
var adapter = _adapter;
async Task<WriteTagBatchResponse> RunAsync()
{
try
{
var results = await _adapter.WriteBatchAsync(
var results = await adapter.WriteBatchAsync(
new Dictionary<string, object?>(request.Values), cts.Token);
var failed = results.Values.Where(r => !r.Success).Select(r => r.ErrorMessage).ToList();
if (failed.Count > 0)
@@ -1172,7 +1188,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
if (!string.IsNullOrEmpty(request.TriggerTagPath))
{
var tr = await _adapter.WriteAsync(request.TriggerTagPath, request.TriggerValue, cts.Token);
var tr = await adapter.WriteAsync(request.TriggerTagPath, request.TriggerValue, cts.Token);
if (!tr.Success)
return new WriteTagBatchResponse(
request.CorrelationId, false,
@@ -1591,9 +1607,13 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
_healthCollector.UpdateTagQuality(_connectionName, _tagsGoodQuality, _tagsBadQuality, _tagsUncertainQuality);
var generation = _adapterGeneration;
// Capture the adapter up front (S7), symmetric with reseedAdapter below. This loop
// runs on the actor thread so a mid-loop swap can't happen, but reading the local
// keeps every adapter access in this method tied to one generation.
var subscribeAdapter = _adapter;
foreach (var tagPath in allTags)
{
_adapter.SubscribeAsync(tagPath, (path, value) =>
subscribeAdapter.SubscribeAsync(tagPath, (path, value) =>
{
self.Tell(new TagValueReceived(path, value, generation));
}).ContinueWith(t =>