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Support for detaching prepared XA transactions

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Add support for detaching XA transactions. This is useful for handling
the case where the DBMS client has a transaction in prepared state and
disconnects. Before disconnect, the DBMS calls the newly introduced
client_state::xa_detach(), to cleanup the local transaction and
convert it to a high priority transaction. The DBMS may later attempt
to terminate the transaction through client_state::commit_by_xid() or
client_state::rollback_by_xid().

Also in this patch:

- Fix client_state::close() so that it does not rollback transactions
  in prepared state
- Changed class wsrep::xid representation to hold enough information
  so that DBMS can convert to its native representation
- Fix potential infinite loop in
  server_state::find_streaming_applier(wsrep:xid&)
- Append SR keys on prepare fragment and make it pa_unsafe
- Handle one phase commit (simply fall back to two phase)
- Do not rollback prepared streaming clients in
  server_state::close_orphaned_transactions()
This commit is contained in:
Daniele Sciascia
2020-03-25 15:40:24 +01:00
parent 2da6e4894e
commit 965642eded
9 changed files with 167 additions and 29 deletions
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9
include/wsrep/buffer.hpp
View File

@ -66,6 +66,10 @@ namespace wsrep
: buffer_()
{ }
mutable_buffer(const mutable_buffer& b)
: buffer_(b.buffer_)
{ }
void resize(size_t s) { buffer_.resize(s); }
void clear()
@ -111,6 +115,11 @@ namespace wsrep
buffer_ = other.buffer_;
return *this;
}
bool operator==(const mutable_buffer& other) const
{
return buffer_ == other.buffer_;
}
private:
std::vector<char> buffer_;
};

15
include/wsrep/client_state.hpp
View File

@ -589,6 +589,21 @@ namespace wsrep
return transaction_.commit_or_rollback_by_xid(xid, false);
}
/**
* Detach a prepared XA transaction
*
* This method cleans up a local XA transaction in prepared state
* and converts it to high priority mode.
* This can be used to handle the case where the client of a XA
* transaction disconnects, and the transaction must not rollback.
* After this call, a different client may later attempt to terminate
* the transaction by calling method commit_by_xid() or rollback_by_xid().
*/
void xa_detach()
{
transaction_.xa_detach();
}
//
// BF aborting
//

8
include/wsrep/transaction.hpp
View File

@ -125,17 +125,17 @@ namespace wsrep
bool is_xa() const
{
return !xid_.empty();
return !xid_.is_null();
}
void assign_xid(const wsrep::xid& xid)
{
assert(active());
assert(xid_.empty());
assert(!is_xa());
xid_ = xid;
}
const wsrep::xid xid() const
const wsrep::xid& xid() const
{
return xid_;
}
@ -144,6 +144,8 @@ namespace wsrep
int commit_or_rollback_by_xid(const wsrep::xid& xid, bool commit);
void xa_detach();
bool pa_unsafe() const { return pa_unsafe_; }
void pa_unsafe(bool pa_unsafe) { pa_unsafe_ = pa_unsafe; }

75
include/wsrep/xid.hpp
View File

@ -21,23 +21,80 @@
#define WSREP_XID_HPP
#include <iosfwd>
#include <string>
#include "buffer.hpp"
namespace wsrep
{
class xid
{
public:
xid() : xid_() { }
xid(const std::string& str) : xid_(str) { }
xid(const char* s) : xid_(s) { }
bool empty() const { return xid_.empty(); }
void clear() { xid_.clear(); }
bool operator==(const xid& other) const { return xid_ == other.xid_; }
xid()
: format_id_(-1)
, gtrid_len_(0)
, bqual_len_(0)
, data_()
{ }
xid(long format_id, long gtrid_len,
long bqual_len, const char* data)
: format_id_(format_id)
, gtrid_len_(gtrid_len)
, bqual_len_(bqual_len)
, data_()
{
const long len = gtrid_len_ + bqual_len_;
if (len > 0)
{
data_.push_back(data, data + len);
}
}
xid(const xid& xid)
: format_id_(xid.format_id_)
, gtrid_len_(xid.gtrid_len_)
, bqual_len_(xid.bqual_len_)
, data_(xid.data_)
{ }
bool is_null() const
{
return format_id_ == -1;
}
void clear()
{
format_id_ = -1;
data_.clear();
}
xid& operator= (const xid& other)
{
format_id_ = other.format_id_;
gtrid_len_ = other.gtrid_len_;
bqual_len_ = other.bqual_len_;
data_ = other.data_;
return *this;
}
bool operator==(const xid& other) const
{
if (format_id_ != other.format_id_ ||
gtrid_len_ != other.gtrid_len_ ||
bqual_len_ != other.bqual_len_ ||
data_.size() != other.data_.size())
{
return false;
}
return data_ == other.data_;
}
friend std::string to_string(const wsrep::xid& xid);
friend std::ostream& operator<<(std::ostream& os, const wsrep::xid& xid);
private:
std::string xid_;
protected:
long format_id_;
long gtrid_len_;
long bqual_len_;
mutable_buffer data_;
};
std::string to_string(const wsrep::xid& xid);

4
src/client_state.cpp
View File

@ -50,7 +50,9 @@ void wsrep::client_state::close()
debug_log_state("close: enter");
state(lock, s_quitting);
lock.unlock();
if (transaction_.active())
if (transaction_.active() &&
(mode_ != m_local ||
transaction_.state() != wsrep::transaction::s_prepared))
{
client_service_.bf_rollback();
transaction_.after_statement();

22
src/server_state.cpp
View File

@ -1297,6 +1297,7 @@ wsrep::high_priority_service* wsrep::server_state::find_streaming_applier(
{
return sa;
}
i++;
}
return NULL;
}
@ -1425,6 +1426,19 @@ void wsrep::server_state::recover_streaming_appliers_if_not_recovered(
streaming_appliers_recovered_ = true;
}
class transaction_state_cmp
{
public:
transaction_state_cmp(const enum wsrep::transaction::state s) : state_(s)
{ }
bool operator()(std::pair<const wsrep::client_id, wsrep::client_state*>& vt) const
{
return vt.second->transaction().state() == state_;
}
private:
enum wsrep::transaction::state state_;
};
void wsrep::server_state::close_orphaned_sr_transactions(
wsrep::unique_lock<wsrep::mutex>& lock,
wsrep::high_priority_service& high_priority_service)
@ -1445,9 +1459,13 @@ void wsrep::server_state::close_orphaned_sr_transactions(
if (current_view_.own_index() == -1 || equal_consecutive_views)
{
while (streaming_clients_.empty() == false)
streaming_clients_map::iterator i;
transaction_state_cmp prepared_state_cmp(wsrep::transaction::s_prepared);
while ((i = std::find_if_not(streaming_clients_.begin(),
streaming_clients_.end(),
prepared_state_cmp))
!= streaming_clients_.end())
{
streaming_clients_map::iterator i(streaming_clients_.begin());
wsrep::client_id client_id(i->first);
wsrep::transaction_id transaction_id(i->second->transaction().id());
// It is safe to unlock the server state temporarily here.

34
src/transaction.cpp
View File

@ -326,6 +326,8 @@ int wsrep::transaction::before_prepare(
{
// Force fragment replication on XA prepare
flags(flags() | wsrep::provider::flag::prepare);
flags(flags() | wsrep::provider::flag::pa_unsafe);
append_sr_keys_for_commit();
const bool force_streaming_step = true;
ret = streaming_step(lock, force_streaming_step);
if (ret == 0)
@ -423,9 +425,20 @@ int wsrep::transaction::before_commit()
switch (client_state_.mode())
{
case wsrep::client_state::m_local:
if (state() == s_prepared)
if (is_xa() &&
(state() == s_prepared || state() == s_executing))
{
assert(is_xa());
ret = 0;
if (state() == s_executing)
{
// XA COMMIT in one phase
// This optimization is not supported...
// fall back to prepare + commit
ret = before_prepare(lock) || after_prepare(lock);
}
if (!ret)
{
assert(state() == s_prepared);
ret = certify_commit(lock);
assert((ret == 0 && state() == s_committing) ||
(state() == s_must_abort ||
@ -433,6 +446,7 @@ int wsrep::transaction::before_commit()
state() == s_cert_failed ||
state() == s_prepared));
}
}
else if (state() == s_executing)
{
ret = before_prepare(lock) || after_prepare(lock);
@ -1084,6 +1098,20 @@ int wsrep::transaction::commit_or_rollback_by_xid(const wsrep::xid& xid,
}
}
void wsrep::transaction::xa_detach()
{
assert(state() == s_prepared);
wsrep::server_state& server_state(client_state_.server_state());
server_state.convert_streaming_client_to_applier(&client_state_);
client_service_.cleanup_transaction();
wsrep::unique_lock<wsrep::mutex> lock(client_state_.mutex_);
streaming_context_.cleanup();
state(lock, s_aborting);
state(lock, s_aborted);
provider().release(ws_handle_);
cleanup();
}
////////////////////////////////////////////////////////////////////////////////
// Private //
////////////////////////////////////////////////////////////////////////////////
@ -1470,7 +1498,7 @@ int wsrep::transaction::certify_commit(
state(lock, s_certifying);
lock.unlock();
if (is_streaming())
if (is_streaming() && !is_xa())
{
append_sr_keys_for_commit();
flags(flags() | wsrep::provider::flag::pa_unsafe);

4
src/xid.cpp
View File

@ -22,10 +22,10 @@
std::string wsrep::to_string(const wsrep::xid& xid)
{
return xid.xid_;
return std::string(xid.data_.data(), xid.data_.size());
}
std::ostream& wsrep::operator<<(std::ostream& os, const wsrep::xid& xid)
{
return os << xid.xid_;
return os << to_string(xid);
}

13
test/transaction_test_xa.cpp
View File

@ -7,8 +7,10 @@
BOOST_FIXTURE_TEST_CASE(transaction_xa,
replicating_client_fixture_sync_rm)
{
wsrep::xid xid(1, 9, 0, "test xid");
BOOST_REQUIRE(cc.start_transaction(wsrep::transaction_id(1)) == 0);
cc.assign_xid("test xid");
cc.assign_xid(xid);
BOOST_REQUIRE(tc.active());
BOOST_REQUIRE(tc.id() == wsrep::transaction_id(1));
@ -52,8 +54,10 @@ BOOST_FIXTURE_TEST_CASE(transaction_xa,
BOOST_FIXTURE_TEST_CASE(transaction_xa_applying,
applying_client_fixture)
{
wsrep::xid xid(1, 9, 0, "test xid");
start_transaction(wsrep::transaction_id(1), wsrep::seqno(1));
cc.assign_xid("test xid");
cc.assign_xid(xid);
BOOST_REQUIRE(cc.before_prepare() == 0);
BOOST_REQUIRE(tc.state() == wsrep::transaction::s_preparing);
@ -85,8 +89,11 @@ BOOST_FIXTURE_TEST_CASE(transaction_xa_applying,
BOOST_FIXTURE_TEST_CASE(transaction_xa_sr,
streaming_client_fixture_byte)
{
wsrep::xid xid(1, 9, 0, "test xid");
BOOST_REQUIRE(cc.start_transaction(wsrep::transaction_id(1)) == 0);
cc.assign_xid("test xid");
cc.assign_xid(xid);
cc.bytes_generated_ = 1;
BOOST_REQUIRE(cc.after_row() == 0);
BOOST_REQUIRE(tc.streaming_context().fragments_certified() == 1);