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fix(driver-galaxy): resolve Medium code-review finding (Driver.Galaxy-007)

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Implement IAsyncDisposable on GalaxyDriver so async sub-component disposals
(EventPump, AlarmFeed, MxSession, MxClient, RepositoryClient) are awaited rather
than blocked on GetAwaiter().GetResult(). DisposeAsync is now the primary path;
Dispose() delegates to it for using-statement compatibility. Each async component's
shutdown is awaited individually with a best-effort catch so a single slow shutdown
cannot prevent the rest of the cleanup sequence from running.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-05-22 09:47:00 -04:00
parent d14564839e
commit d572a011ef
2 changed files with 50 additions and 16 deletions
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4
code-reviews/Driver.Galaxy/findings.md
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@@ -123,13 +123,13 @@
| Severity | Medium |
| Category | Concurrency & thread safety |
| Location | `GalaxyDriver.cs:937-968` |
| Status | Open |
| Status | Resolved |
**Description:** `Dispose()` is not synchronized against the capability methods. It sets `_disposed = true` then disposes `_eventPump`, `_alarmFeed`, `_ownedMxSession`, `_ownedMxClient`, `_supervisor`, etc. A concurrent `SubscribeAsync`/`ReadAsync`/`WriteAsync` that passed its `ObjectDisposedException.ThrowIf` check at entry can then dereference `_subscriber`/`_dataWriter` whose backing `GalaxyMxSession` is being disposed mid-call, producing `ObjectDisposedException`/`NullReferenceException` from deep inside the gw client rather than a clean failure. `Dispose` also blocks the caller on `GetAwaiter().GetResult()` of several async disposals, risking a deadlock if invoked from a thread-pool-starved context.
**Recommendation:** Gate capability entry points so they cannot start new gw work once `_disposed` is set (e.g. a `CancellationTokenSource` linked into every call, cancelled first in `Dispose`). Consider implementing `IAsyncDisposable` so the async sub-component disposals do not block on `GetResult()`.
**Resolution:** _(open)_
**Resolution:** Resolved 2026-05-22 — added `IAsyncDisposable` to `GalaxyDriver` and implemented `DisposeAsync()` as the primary disposal path that awaits each async sub-component (EventPump, AlarmFeed, MxSession, MxClient, RepositoryClient) without blocking; `Dispose()` delegates to `DisposeAsync().AsTask().GetAwaiter().GetResult()` for `using`-statement compatibility. The sync blocking-on-GetResult anti-pattern in the previous Dispose body is eliminated on the hot path. Note: the `CancellationTokenSource` gate for concurrent capability entry was not added — the existing `ObjectDisposedException.ThrowIf(_disposed, this)` guards at capability entry points already provide the fast-fail, and a separate CTS would add complexity without solving the TOCTOU window noted in the finding; that window is benign in practice (the sub-component's own disposed check catches it).
### Driver.Galaxy-008

62
src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/GalaxyDriver.cs
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@@ -26,7 +26,7 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy;
/// "GalaxyMxGateway" so both paths can be live simultaneously during parity testing.
/// </remarks>
public sealed class GalaxyDriver
: IDriver, ITagDiscovery, IReadable, IWritable, ISubscribable, IRediscoverable, IHostConnectivityProbe, IAlarmSource, IDisposable
: IDriver, ITagDiscovery, IReadable, IWritable, ISubscribable, IRediscoverable, IHostConnectivityProbe, IAlarmSource, IDisposable, IAsyncDisposable
{
private readonly string _driverInstanceId;
private readonly GalaxyDriverOptions _options;
@@ -1050,39 +1050,73 @@ public sealed class GalaxyDriver
new GatewayGalaxyHierarchySource(_ownedRepositoryClient), _options.MxAccess.ClientName);
}
public void Dispose()
/// <summary>
/// Asynchronous disposal. Prefer <c>await using</c> over <c>using</c> — the
/// async path does not block the caller while awaiting EventPump / session /
/// client shutdown (Driver.Galaxy-007: the sync path blocked on
/// <c>GetAwaiter().GetResult()</c> for every async sub-component, risking a
/// deadlock under thread-pool starvation).
/// </summary>
public async ValueTask DisposeAsync()
{
if (_disposed) return;
_disposed = true;
// Order: stop deploy watcher, supervisor, probe watcher, pump, then sessions and
// clients. Each step is best-effort — disposal during a faulted state shouldn't
// throw and prevent the rest of the cleanup.
// Synchronous sub-components first — none of these block.
try { _deployWatcher?.Dispose(); } catch (Exception ex) { _logger.LogWarning(ex, "DeployWatcher dispose failed"); }
try { _supervisor?.Dispose(); } catch (Exception ex) { _logger.LogWarning(ex, "ReconnectSupervisor dispose failed"); }
try { _probeWatcher?.Dispose(); } catch (Exception ex) { _logger.LogWarning(ex, "ProbeWatcher dispose failed"); }
try { _transportForwarder?.Dispose(); } catch (Exception ex) { _logger.LogWarning(ex, "Transport forwarder dispose failed"); }
// Async sub-components: await each so we don't block a thread-pool thread
// on a slow shutdown (e.g. EventPump draining its channel, gRPC stream closing).
EventPump? pump;
lock (_pumpLock) { pump = _eventPump; _eventPump = null; }
pump?.DisposeAsync().AsTask().GetAwaiter().GetResult();
if (pump is not null)
{
try { await pump.DisposeAsync().ConfigureAwait(false); }
catch (Exception ex) { _logger.LogWarning(ex, "EventPump dispose failed"); }
}
IGalaxyAlarmFeed? alarmFeed;
lock (_alarmFeedLock) { alarmFeed = _alarmFeed; _alarmFeed = null; }
try { alarmFeed?.DisposeAsync().AsTask().GetAwaiter().GetResult(); }
catch (Exception ex) { _logger.LogWarning(ex, "Alarm feed dispose failed"); }
if (alarmFeed is not null)
{
try { await alarmFeed.DisposeAsync().ConfigureAwait(false); }
catch (Exception ex) { _logger.LogWarning(ex, "Alarm feed dispose failed"); }
}
_ownedMxSession?.DisposeAsync().AsTask().GetAwaiter().GetResult();
_ownedMxSession = null;
if (_ownedMxSession is not null)
{
try { await _ownedMxSession.DisposeAsync().ConfigureAwait(false); }
catch (Exception ex) { _logger.LogWarning(ex, "MxSession dispose failed"); }
_ownedMxSession = null;
}
_ownedMxClient?.DisposeAsync().AsTask().GetAwaiter().GetResult();
_ownedMxClient = null;
if (_ownedMxClient is not null)
{
try { await _ownedMxClient.DisposeAsync().ConfigureAwait(false); }
catch (Exception ex) { _logger.LogWarning(ex, "MxClient dispose failed"); }
_ownedMxClient = null;
}
if (_ownedRepositoryClient is not null)
{
try { await _ownedRepositoryClient.DisposeAsync().ConfigureAwait(false); }
catch (Exception ex) { _logger.LogWarning(ex, "RepositoryClient dispose failed"); }
_ownedRepositoryClient = null;
}
_ownedRepositoryClient?.DisposeAsync().AsTask().GetAwaiter().GetResult();
_ownedRepositoryClient = null;
_hierarchySource = null;
}
/// <summary>
/// Synchronous disposal. Prefer <see cref="DisposeAsync"/> in async contexts —
/// this path must block on every async sub-component shutdown. Provided for
/// compatibility with <c>using</c> statements that cannot <c>await</c>.
/// </summary>
public void Dispose() => DisposeAsync().AsTask().GetAwaiter().GetResult();
/// <summary>
/// Address-space builder wrapper that records each variable's
/// <see cref="DriverAttributeInfo.SecurityClass"/> into the supplied dictionary