445eece95b
If the starting of a transaction was interrupted by a server failure, the query needs to be retried. This needs to be done as a transaction replay to keep the routing logic consistent and simple. When a non-autocommit transaction is interrupted, there will be no query in progress and no replaying is needed. To handle this case, the replay initialization logic needed to be altered to treat truly empty transactions as a success case.
148 lines
3.3 KiB
C++
148 lines
3.3 KiB
C++
#pragma once
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/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2020-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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#include <maxscale/cppdefs.hh>
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#include <list>
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#include <maxscale/buffer.hh>
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#include <maxscale/utils.hh>
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// A transaction
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class Trx
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{
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public:
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// A log of executed queries, for transaction replay
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typedef std::list<mxs::Buffer> TrxLog;
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Trx():
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m_size(0)
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{
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}
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/**
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* Add a statement to the transaction
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*
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* @param buf Statement to add
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*/
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void add_stmt(GWBUF* buf)
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{
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m_size += gwbuf_length(buf);
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m_log.emplace_back(buf);
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}
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/**
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* Add a result to the transaction
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*
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* The result is used to update the checksum.
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*
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* @param buf Result to add
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*/
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void add_result(GWBUF* buf)
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{
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m_checksum.update(buf);
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}
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/**
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* Releases the oldest statement in this transaction
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*
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* This reduces the size of the transaction by one and should only be used
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* to replay a transaction.
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*
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* @return The oldest statement in this transaction
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*/
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GWBUF* pop_stmt()
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{
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ss_dassert(!m_log.empty());
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GWBUF* rval = m_log.front().release();
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m_log.pop_front();
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return rval;
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}
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/**
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* Finalize the transaction
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*
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* This function marks the transaction as completed be that by a COMMIT
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* or by a failure of the current server where the transaction was being
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* executed.
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*/
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void finalize()
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{
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m_checksum.finalize();
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}
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/**
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* Check if transaction has statements
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*
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* @return True if transaction has statements
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*
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* @note This function should only be used when checking whether a transaction
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* that is being replayed has ended. The empty() method can be used
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* to check whether statements were added to the transaction.
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*/
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bool have_stmts() const
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{
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return !m_log.empty();
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}
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/**
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* Check whether the transaction is empty
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*
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* @return True if no statements have been added to the transaction
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*/
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bool empty() const
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{
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return m_size == 0;
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}
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/**
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* Get transaction size in bytes
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*
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* @return Size of the transaction in bytes
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*/
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size_t size() const
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{
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return m_size;
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}
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/**
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* Close the transaction
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*
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* This clears out the stored statements and resets the checksum state.
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*/
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void close()
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{
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m_checksum.reset();
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m_log.clear();
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m_size = 0;
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}
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/**
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* Return the current checksum
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*
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* finalize() must be called before the return value of this function is used.
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*
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* @return The checksum of the transaction
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*/
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const mxs::SHA1Checksum& checksum() const
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{
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return m_checksum;
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}
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private:
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mxs::SHA1Checksum m_checksum; /**< Checksum of the transaction */
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TrxLog m_log; /**< The transaction contents */
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size_t m_size; /**< Transaction size in bytes */
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};
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