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Motivation

Currently transactions are not supported by thin client protocol. 

Description

There are changes needed for protocol, server side, and client side to support transactions.

Protocol changes

Add new operations to the thin client protocol:

OP_TX_START message format

OP_TX_END message format

Empty response.

Cache operations

We need to add a new field to requests header of all cache data manipulation operations (opcodes 1000-1020, 2000, 2002, 2004) to bind these operations with the transaction.

We also can remove deprecated "flag" field in this protocol version. "Flag" field is only used by OP_QUERY_SCAN operation. So, we need to add a new field "keepBinary" to OP_QUERY_SCAN request.

Proposed changes to cache operations request header format:

Proposed changes to OP_QUERY_SCAN request format:

Server-side changes

On the server side, we need to have the ability to decouple transactions from threads. We can do this by using transaction suspend/resume methods. Suspend/resume methods are only implemented for optimistic transactions now, so we need to implement this mechanism for pessimistic transactions first.

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When the client sends OP_TX_END request, thread served this request resumes the transaction and commit or rollback it.

Client-side changes

The client must bind transaction and all cache operations which was made within this explicitly started transaction. We can implement transaction per thread approach on the thin client side as implemented now for the thick client. In this case, each transaction on the thin client side will be bound to a thread started this transaction. And each cache operation performed by this thread will be bound to the same transaction until the transaction is completed.

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public interface ClientTransactions {
    public ClientTransaction txStart(); // Start tx with client default values of concurrency, isolation and timeout properties.
    public ClientTransaction txStart(TransactionConcurrency concurrency, TransactionIsolation isolation); // Start tx with default timeout.
    public ClientTransaction txStart(TransactionConcurrency concurrency, TransactionIsolation isolation, long timeout);
    public ClientTransactions withLabel(String lb);
}

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public interface ClientTransaction extends AutoCloseable {
    public void commit();
    public void rollback();
    public void close();
}

To configure client default concurrency, isolation and timeout values for connection it is proposed to create new configuration class:

public class ClientTransactionConfiguration {
    public static final TransactionConcurrency DFLT_TX_CONCURRENCY = TransactionConcurrency.PESSIMISTIC;
    public static final TransactionIsolation DFLT_TX_ISOLATION = TransactionIsolation.REPEATABLE_READ;
    public static final long DFLT_TRANSACTION_TIMEOUT = 0;

    public TransactionConcurrency getDefaultTxConcurrency();
	public ClientTransactionConfiguration setDefaultTxConcurrency(TransactionConcurrency dfltConcurrency)

    public TransactionIsolation getDefaultTxIsolation();
    public ClientTransactionConfiguration setDefaultTxIsolation(TransactionIsolation dfltIsolation);

    public long getDefaultTxTimeout();
	public ClientTransactionConfiguration setDefaultTxTimeout(long dfltTxTimeout);
}

This transaction configuration can be used when the client connection is created (as a property of ClientConfiguration class).

Risks and Assumptions

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Discussion Links

http://apache-ignite-developers.2346864.n4.nabble.com/Thin-client-transactions-support-td27761.html

Reference Links

// Links to various reference documents, if applicable.

Tickets