feat: read only transaction #303
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When both ReadWriteSplittingPolicy and ReadOnlyTransactionPolicy are enabled, the function suggestTabletType will return TabletType_REPLICA for all SQLs during read-only transaction. But I notice that there is another value of TabletType which is topodatapb.TabletType_RDONLY, and actually I don't know the exact difference between them. |
go/vt/vtgate/executor.go
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| @@ -607,6 +607,12 @@ func (e *Executor) handleBegin(ctx context.Context, safeSession *SafeSession, lo | |||
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| begin := stmt.(*sqlparser.Begin) | |||
| err := e.txConn.Begin(ctx, safeSession, begin.TxAccessModes) | |||
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| // verify read only tx | |||
| if len(begin.TxAccessModes) == 1 && begin.TxAccessModes[0] == sqlparser.ReadOnly { | |||
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Is it possible that begin.TxAccessModes > 1?
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yeah~ the transaction can start with both read only and with consistent snapshot!
| @@ -127,3 +127,24 @@ func ToLoadBalancePolicy(s string) querypb.ExecuteOptions_LoadBalancePolicy { | |||
| return querypb.ExecuteOptions_RANDOM | |||
| } | |||
| } | |||
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| type ReadOnlyTransactionPolicy string | |||
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I think you should use a better name.
Maybe EnableReadWriteSplitForReadOnlyTxn=true/false?
go/vt/vtgate/read_write_splitter.go
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| @@ -49,24 +62,33 @@ func randomPickTabletType(ratio int32) topodatapb.TabletType { | |||
| } | |||
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| // IsReadOnly : whether the query should be routed to a read-only vttablet | |||
| func isReadOnly(query string) (bool, error) { | |||
| // return : -1 means error occurs; 0 means is not read-only; 1 means read-only tx; 2 means read-only but not in a read-only tx; | |||
| func isReadOnly(query string) (int, error) { | |||
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It is not a good idea that using int to replace bool as the return value type, it makes this function hard to understand.
In golang, we use error to represtent something wrong happens, we don't use int(-1).
go/vt/vtgate/read_write_splitter.go
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| // if the sql is in transaction and its transaction access mode is read-only, then suggest type should be read-only tablet | ||
| if isReadOnlyTx && schema.NewReadOnlyTransactionPolicy(readOnlyTransactionPolicy).IsEnable() { | ||
| return topodatapb.TabletType_REPLICA, nil | ||
| } |
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I think these can be moved into isReadOnly
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Finally we found that it will be more readable if we leave this code in suggestTabletType function and let isSQLSupportReadWriteSplit (which is the new name of isReadOnly) to decide whether the SQL can be send to read-only nodes
Signed-off-by: newborn22 <[email protected]>
Signed-off-by: newborn22 <[email protected]>
…er read only transaction and should be routed to PRIMARY node Signed-off-by: newborn22 <[email protected]>
…napshot both are enabled. And adjusted the order of the code to make it more readable Signed-off-by: newborn22 <[email protected]>
Signed-off-by: newborn22 <[email protected]>
Signed-off-by: newborn22 <[email protected]>
Signed-off-by: newborn22 <[email protected]>
…dWriteSplitForReadOnlyTxn to false Signed-off-by: newborn22 <[email protected]>
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…out read only transaction begin sql Signed-off-by: newborn22 <[email protected]>
Description
Add two fields to Session: TransactionAccessMode and ReadOnlyTransactionPolicy.
If both ReadWriteSplittingPolicy and ReadOnlyTransactionPolicy are enabled, the function suggestTabletType will return TabletType_REPLICA for all SQLs during read-only transaction including the SQL "start transaction read only".
The function handleTransactions will mark or unmark read-only transactions on TransactionAccessMode field of the Session.
Related Issue(s)
#146
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