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Cache database state on the data source
Instead of a global, static cluster state cache. Closes #4727
1 parent 317a452 commit b61d2b9

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10 files changed

+319
-332
lines changed

10 files changed

+319
-332
lines changed

‎src/Npgsql/DatabaseState.cs‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,10 @@
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namespace Npgsql;
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enum DatabaseState : byte
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{
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Unknown = 0,
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Offline = 1,
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PrimaryReadWrite = 2,
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PrimaryReadOnly = 3,
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Standby = 4
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}

‎src/Npgsql/Internal/ClusterStateCache.cs‎

Lines changed: 0 additions & 77 deletions
This file was deleted.

‎src/Npgsql/Internal/NpgsqlConnector.cs‎

Lines changed: 12 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -603,7 +603,7 @@ await OpenCore(
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}
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}
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606-
internal async ValueTask<ClusterState> QueryClusterState(
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internal async ValueTask<DatabaseState> QueryDatabaseState(
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NpgsqlTimeout timeout, bool async, CancellationToken cancellationToken = default)
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{
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using var cmd = CreateCommand("select pg_is_in_recovery(); SHOW default_transaction_read_only");
@@ -629,9 +629,9 @@ internal async ValueTask<ClusterState> QueryClusterState(
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630630
_isTransactionReadOnly = reader.GetString(0) != "off";
631631

632-
var clusterState = UpdateClusterState();
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Debug.Assert(clusterState.HasValue);
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return clusterState.Value;
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var databaseState = UpdateDatabaseState();
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Debug.Assert(databaseState.HasValue);
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return databaseState.Value;
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}
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finally
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{
@@ -1934,8 +1934,7 @@ internal Exception Break(Exception reason)
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(ne.InnerException is not TimeoutException || Settings.CancellationTimeout != -1) ||
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reason is PostgresException pe && PostgresErrorCodes.IsCriticalFailure(pe))
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{
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ClusterStateCache.UpdateClusterState(Host, Port, ClusterState.Offline, DateTime.UtcNow,
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Settings.HostRecheckSecondsTranslated);
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DataSource.UpdateDatabaseState(DatabaseState.Offline, DateTime.UtcNow, Settings.HostRecheckSecondsTranslated);
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DataSource.Clear();
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}
19411940

@@ -2582,27 +2581,26 @@ void ReadParameterStatus(ReadOnlySpan<byte> incomingName, ReadOnlySpan<byte> inc
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case "default_transaction_read_only":
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_isTransactionReadOnly = value == "on";
2585-
UpdateClusterState();
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UpdateDatabaseState();
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return;
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case "in_hot_standby":
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_isHotStandBy = value == "on";
2590-
UpdateClusterState();
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UpdateDatabaseState();
25912590
return;
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}
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}
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2595-
ClusterState? UpdateClusterState()
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DatabaseState? UpdateDatabaseState()
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{
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if (_isTransactionReadOnly.HasValue && _isHotStandBy.HasValue)
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{
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var state = _isHotStandBy.Value
2600-
? ClusterState.Standby
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? DatabaseState.Standby
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: _isTransactionReadOnly.Value
2602-
? ClusterState.PrimaryReadOnly
2603-
: ClusterState.PrimaryReadWrite;
2604-
return ClusterStateCache.UpdateClusterState(Settings.Host!, Settings.Port, state, DateTime.UtcNow,
2605-
Settings.HostRecheckSecondsTranslated);
2601+
? DatabaseState.PrimaryReadOnly
2602+
: DatabaseState.PrimaryReadWrite;
2603+
return DataSource.UpdateDatabaseState(state, DateTime.UtcNow, Settings.HostRecheckSecondsTranslated);
26062604
}
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26082606
return null;

‎src/Npgsql/NpgsqlDataSource.cs‎

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -61,6 +61,8 @@ public abstract class NpgsqlDataSource : DbDataSource
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bool _isBootstrapped;
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64+
volatile DatabaseStateInfo _databaseStateInfo = new();
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// Note that while the dictionary is protected by locking, we assume that the lists it contains don't need to be
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// (i.e. access to connectors of a specific transaction won't be concurrent)
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private protected readonly Dictionary<Transaction, List<NpgsqlConnector>> _pendingEnlistedConnectors
@@ -315,6 +317,39 @@ internal abstract ValueTask<NpgsqlConnector> Get(
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316318
internal abstract bool OwnsConnectors { get; }
317319

320+
#region Database state management
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322+
internal DatabaseState GetDatabaseState(bool ignoreExpiration = false)
323+
{
324+
Debug.Assert(this is not NpgsqlMultiHostDataSource);
325+
326+
var databaseStateInfo = _databaseStateInfo;
327+
328+
return ignoreExpiration || !databaseStateInfo.Timeout.HasExpired
329+
? databaseStateInfo.State
330+
: DatabaseState.Unknown;
331+
}
332+
333+
internal DatabaseState UpdateDatabaseState(
334+
DatabaseState newState,
335+
DateTime timeStamp,
336+
TimeSpan stateExpiration,
337+
bool ignoreTimeStamp = false)
338+
{
339+
Debug.Assert(this is not NpgsqlMultiHostDataSource);
340+
341+
var databaseStateInfo = _databaseStateInfo;
342+
343+
if (!ignoreTimeStamp && timeStamp <= databaseStateInfo.TimeStamp)
344+
return _databaseStateInfo.State;
345+
346+
_databaseStateInfo = new(newState, new NpgsqlTimeout(stateExpiration), timeStamp);
347+
348+
return newState;
349+
}
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351+
#endregion Database state management
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318353
#region Pending Enlisted Connections
319354

320355
internal virtual void AddPendingEnlistedConnector(NpgsqlConnector connector, Transaction transaction)
@@ -399,4 +434,17 @@ private protected void CheckDisposed()
399434
}
400435

401436
#endregion
437+
438+
class DatabaseStateInfo
439+
{
440+
internal readonly DatabaseState State;
441+
internal readonly NpgsqlTimeout Timeout;
442+
// While the TimeStamp is not strictly required, it does lower the risk of overwriting the current state with an old value
443+
internal readonly DateTime TimeStamp;
444+
445+
public DatabaseStateInfo() : this(default, default, default) {}
446+
447+
public DatabaseStateInfo(DatabaseState state, NpgsqlTimeout timeout, DateTime timeStamp)
448+
=> (State, Timeout, TimeStamp) = (state, timeout, timeStamp);
449+
}
402450
}

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