Added support to BACKUP STAGE to maria-backup
This is a port of the code from ES 10.6
See MDEV-5336 for backup stages description.
The following old options are not supported by the new code:
--rsync ; This is because rsync will not work on tables
that are in used.
--no-backup-locks ; This is disabled as mariadb-backup will always
use backup locks for better performance.
Even though commit b817afaa1c passed
the test mariabackup.compress_qpress, that test turned out to be
too small to reveal one more problem that had previously been prevented
by the existence of ctrl_mutex. I did not realize that there can be
multiple concurrent callers to compress_write(). One of them is the
log copying thread; further callers are data file copying threads
(default: --parallel=1).
By default, there is only one compression worker thread
(--compress-threads=1).
compress_write(): Fix a race condition between threads that would
use the same worker thread object. Make thd->data_avail contain the
thread identifier of the submitter, and add thd->avail_cond to
notify other compress_write() threads that are waiting for a slot.
This reverts the revert 4f62dfe676
and fixes the hang that was introduced when ctrl_mutex was removed.
The test mariabackup.compress_qpress covers this code, but the
test is skipped if a stand-alone qpress executable is not available.
It is not available in many software repositories, possibly because
the code base has not been updated since 2010.
This was tested with an executable that was compile from the source
code at http://www.quicklz.com/qpress-11-source.zip (after adding
a missing #include <unistd.h> for the definition of isatty()).
Compared to the grandparent commit (before the revert), the changes
are as follows:
comp_thread_ctxt_t::done_cond: A separate condition for completed
compression, signaling that thd->to_len has been updated.
compress_write(): Replace some threads[i] with thd.
Reset thd->to_len = 0 after consuming the compressed data.
compress_worker_thread_func(): After consuming the uncompressed
data, set thd->data_avail = FALSE. After compressing, signal
thd->done_cond.
comp_thread_ctxt_t: Remove ctrl_mutex, ctrl_cond, started. We do not
actually need them for anything.
destroy_worker_thread(): Split from destroy_worker_threads().
create_worker_threads(): We already initialize
thd->data_avail=FALSE and thd->cancelled=FALSE before
invoking pthread_create(). If any thread creation fails,
clean up by destroy_worker_thread().
compress_worker_thread_func(): Assume that thd->started and
thd->data_avail are already initialized.
Reviewed by: Vladislav Vaintroub
The previous threads locked need to be released too.
This occurs if the initialization of any of the non-first
mutex/conditition variables errors occurs.
