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Treat offline hosts as unpreferred #5798

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407ef89
Treat offline hosts as unpreferred
vonzshik Aug 1, 2024
e666ebc
Fix test
vonzshik Aug 1, 2024
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3 changes: 2 additions & 1 deletion src/Npgsql/DatabaseState.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,5 +6,6 @@ enum DatabaseState : byte
Offline = 1,
PrimaryReadWrite = 2,
PrimaryReadOnly = 3,
Standby = 4
Standby = 4,
UnknownAfterError = 5
}
4 changes: 3 additions & 1 deletion src/Npgsql/NpgsqlDataSource.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -385,7 +385,9 @@ internal DatabaseState GetDatabaseState(bool ignoreExpiration = false)

return ignoreExpiration || !databaseStateInfo.Timeout.HasExpired
? databaseStateInfo.State
: DatabaseState.Unknown;
: databaseStateInfo.State == DatabaseState.Offline
? DatabaseState.UnknownAfterError
: DatabaseState.Unknown;
}

internal DatabaseState UpdateDatabaseState(
Expand Down
72 changes: 49 additions & 23 deletions src/Npgsql/NpgsqlMultiHostDataSource.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,7 @@ static bool IsPreferred(DatabaseState state, TargetSessionAttributes preferredTy
=> state switch
{
DatabaseState.Offline => false,
DatabaseState.UnknownAfterError => false, // We will check compatibility only if we don't find preferred
DatabaseState.Unknown => true, // We will check compatibility again after refreshing the database state

DatabaseState.PrimaryReadWrite when preferredType is
Expand All @@ -150,21 +151,49 @@ TargetSessionAttributes.PreferStandby or
_ => preferredType == TargetSessionAttributes.Any
};

static bool IsOnline(DatabaseState state, TargetSessionAttributes preferredType)
{
Debug.Assert(preferredType is TargetSessionAttributes.PreferPrimary or TargetSessionAttributes.PreferStandby);
return state != DatabaseState.Offline;
}
static bool IsUnpreferred(DatabaseState state, TargetSessionAttributes preferredType)
=> state switch
{
DatabaseState.Offline => false,
DatabaseState.UnknownAfterError => true,
DatabaseState.Unknown => true, // We will check compatibility again after refreshing the database state

DatabaseState.PrimaryReadWrite when preferredType is
TargetSessionAttributes.Primary or
TargetSessionAttributes.PreferPrimary or
TargetSessionAttributes.ReadWrite or
TargetSessionAttributes.PreferStandby
=> true,

DatabaseState.PrimaryReadOnly when preferredType is
TargetSessionAttributes.Primary or
TargetSessionAttributes.PreferPrimary or
TargetSessionAttributes.ReadOnly or
TargetSessionAttributes.PreferStandby
=> true,

DatabaseState.Standby when preferredType is
TargetSessionAttributes.Standby or
TargetSessionAttributes.PreferStandby or
TargetSessionAttributes.ReadOnly or
TargetSessionAttributes.PreferPrimary
=> true,

_ => preferredType == TargetSessionAttributes.Any
};

async ValueTask<NpgsqlConnector?> TryGetIdleOrNew(
NpgsqlConnection conn,
TimeSpan timeoutPerHost,
bool async,
TargetSessionAttributes preferredType, Func<DatabaseState, TargetSessionAttributes, bool> stateValidator,
TargetSessionAttributes preferredType,
bool preferred,
int poolIndex,
IList<Exception> exceptions,
CancellationToken cancellationToken)
{
Func<DatabaseState, TargetSessionAttributes, bool> stateValidator = preferred ? IsPreferred : IsUnpreferred;

var pools = _pools;
for (var i = 0; i < pools.Length; i++)
{
Expand All @@ -183,7 +212,7 @@ static bool IsOnline(DatabaseState state, TargetSessionAttributes preferredType)
{
if (pool.TryGetIdleConnector(out connector))
{
if (databaseState == DatabaseState.Unknown)
if (databaseState == DatabaseState.Unknown || !preferred && databaseState == DatabaseState.UnknownAfterError)
{
databaseState = await connector.QueryDatabaseState(new NpgsqlTimeout(timeoutPerHost), async, cancellationToken).ConfigureAwait(false);
Debug.Assert(databaseState != DatabaseState.Unknown);
Expand All @@ -201,11 +230,11 @@ static bool IsOnline(DatabaseState state, TargetSessionAttributes preferredType)
connector = await pool.OpenNewConnector(conn, new NpgsqlTimeout(timeoutPerHost), async, cancellationToken).ConfigureAwait(false);
if (connector is not null)
{
if (databaseState == DatabaseState.Unknown)
if (databaseState == DatabaseState.Unknown || !preferred && databaseState == DatabaseState.UnknownAfterError)
{
// While opening a new connector we might have refreshed the database state, check again
databaseState = pool.GetDatabaseState();
if (databaseState == DatabaseState.Unknown)
if (databaseState == DatabaseState.Unknown || !preferred && databaseState == DatabaseState.UnknownAfterError)
databaseState = await connector.QueryDatabaseState(new NpgsqlTimeout(timeoutPerHost), async, cancellationToken).ConfigureAwait(false);
Debug.Assert(databaseState != DatabaseState.Unknown);
if (!stateValidator(databaseState, preferredType))
Expand Down Expand Up @@ -235,11 +264,13 @@ static bool IsOnline(DatabaseState state, TargetSessionAttributes preferredType)
TimeSpan timeoutPerHost,
bool async,
TargetSessionAttributes preferredType,
Func<DatabaseState, TargetSessionAttributes, bool> stateValidator,
bool preferred,
int poolIndex,
IList<Exception> exceptions,
CancellationToken cancellationToken)
{
Func<DatabaseState, TargetSessionAttributes, bool> stateValidator = preferred ? IsPreferred : IsUnpreferred;

var pools = _pools;
for (var i = 0; i < pools.Length; i++)
{
Expand All @@ -257,11 +288,11 @@ static bool IsOnline(DatabaseState state, TargetSessionAttributes preferredType)
try
{
connector = await pool.Get(conn, new NpgsqlTimeout(timeoutPerHost), async, cancellationToken).ConfigureAwait(false);
if (databaseState == DatabaseState.Unknown)
if (databaseState == DatabaseState.Unknown || !preferred && databaseState == DatabaseState.UnknownAfterError)
{
// Get might have opened a new physical connection and refreshed the database state, check again
databaseState = pool.GetDatabaseState();
if (databaseState == DatabaseState.Unknown)
if (databaseState == DatabaseState.Unknown || !preferred && databaseState == DatabaseState.UnknownAfterError)
databaseState = await connector.QueryDatabaseState(new NpgsqlTimeout(timeoutPerHost), async, cancellationToken).ConfigureAwait(false);

Debug.Assert(databaseState != DatabaseState.Unknown);
Expand Down Expand Up @@ -299,16 +330,11 @@ internal override async ValueTask<NpgsqlConnector> Get(

var timeoutPerHost = timeout.IsSet ? timeout.CheckAndGetTimeLeft() : TimeSpan.Zero;
var preferredType = GetTargetSessionAttributes(conn);
var checkUnpreferred = preferredType is TargetSessionAttributes.PreferPrimary or TargetSessionAttributes.PreferStandby;

var connector = await TryGetIdleOrNew(conn, timeoutPerHost, async, preferredType, IsPreferred, poolIndex, exceptions, cancellationToken).ConfigureAwait(false) ??
(checkUnpreferred ?
await TryGetIdleOrNew(conn, timeoutPerHost, async, preferredType, IsOnline, poolIndex, exceptions, cancellationToken).ConfigureAwait(false)
: null) ??
await TryGet(conn, timeoutPerHost, async, preferredType, IsPreferred, poolIndex, exceptions, cancellationToken).ConfigureAwait(false) ??
(checkUnpreferred ?
await TryGet(conn, timeoutPerHost, async, preferredType, IsOnline, poolIndex, exceptions, cancellationToken).ConfigureAwait(false)
: null);
var connector = await TryGetIdleOrNew(conn, timeoutPerHost, async, preferredType, preferred: true, poolIndex, exceptions, cancellationToken).ConfigureAwait(false) ??
await TryGetIdleOrNew(conn, timeoutPerHost, async, preferredType, preferred: false, poolIndex, exceptions, cancellationToken).ConfigureAwait(false) ??
await TryGet(conn, timeoutPerHost, async, preferredType, preferred: true, poolIndex, exceptions, cancellationToken).ConfigureAwait(false) ??
await TryGet(conn, timeoutPerHost, async, preferredType, preferred: false, poolIndex, exceptions, cancellationToken).ConfigureAwait(false);

return connector ?? throw NoSuitableHostsException(exceptions);
}
Expand Down Expand Up @@ -421,7 +447,7 @@ internal override bool TryRentEnlistedPending(

// Can't get valid preferred connector. Try to get an unpreferred connector, if supported.
if ((preferredType == TargetSessionAttributes.PreferPrimary || preferredType == TargetSessionAttributes.PreferStandby)
&& TryGetValidConnector(list, preferredType, IsOnline, out connector))
&& TryGetValidConnector(list, preferredType, IsUnpreferred, out connector))
{
return true;
}
Expand All @@ -437,7 +463,7 @@ bool TryGetValidConnector(List<NpgsqlConnector> list, TargetSessionAttributes pr
{
connector = list[i];
var lastKnownState = connector.DataSource.GetDatabaseState(ignoreExpiration: true);
Debug.Assert(lastKnownState != DatabaseState.Unknown);
Debug.Assert(lastKnownState != DatabaseState.Unknown && lastKnownState != DatabaseState.UnknownAfterError);
if (validationFunc(lastKnownState, preferredType))
{
list.RemoveAt(i);
Expand Down
4 changes: 2 additions & 2 deletions test/Npgsql.Tests/MultipleHostsTests.cs
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Expand Up @@ -878,12 +878,12 @@ await firstServer
await secondServer.SendMockState(Primary);

await Task.Delay(TimeSpan.FromSeconds(10));
Assert.That(firstDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.Unknown));
Assert.That(firstDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.UnknownAfterError));
Assert.That(secondDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.Unknown));

await conn.OpenAsync();
Assert.That(conn.Port, Is.EqualTo(secondPostmaster.Port));
Assert.That(firstDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.Standby));
Assert.That(firstDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.UnknownAfterError));
Assert.That(secondDataSource.GetDatabaseState(), Is.EqualTo(DatabaseState.PrimaryReadWrite));
}

Expand Down