This patch moves the resharding process to use the new
directory_with_sstables_handler infrastructure. There is no longer
a clear reshard step, and that just becomes a natural part of
populate_column_family.
In main.cc, a couple of changes are necessary to make that happen.
The first one obviously is to stop calling reshard. We also need to
make sure that:
- The compaction manager is started much earlier, so we can register
resharding jobs with it.
- auto compactions are disabled in the populate method, so resharding
doesn't have to fight for bandwidth with auto compactions.
Now that we are resharding through the sstable_directory, the old
resharding code can be deleted. There is also no need to deal with
the resharding backlog either, because the SSTables are not yet
added to the sstable set at this point.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Uploading of SSTables is problematic: for historical reasons it takes a
lock that may have to wait for ongoing compactions to finish, then it
disables writes in the table, and then it goes loading SSTables as if it
knew nothing about them.
With the sstable_directory infrastructure we can do much better:
* we can reshard and reshape the SSTables in place, keeping the number
of SSTables in check. Because this is an background process we can be
fairly aggressive and set the reshape mode to strict.
* we can then move the SSTables directly into the main directory.
Because we know they are few in number we can call the more elegant
add_sstable_and_invalidate_cache instead of the open coding currently
done by load_new_sstables
* we know they are not shared (if they were, we resharded them),
simplifying the load process even further.
The major changes after this patch is applied is that all compactions
(resharding and reshape) needed to make the SSTables in-strategy are
done in the streaming class, which reduces the impact of this operation
on the node. When the SSTables are loaded, subsequent reads will not
suffer as we will not be adding shared SSTables in potential high
numbers, nor will we reshard in the compaction class.
There is also no more need for a lock in the upload process so in the
fast path where users are uploading a set of SSTables from a backup this
should essentially be instantaneous. The lock, as well as the code to
disable and enable table writes is removed.
A future improvement is to bypass the staging directory too, in which
case the reshaping compaction would already generate the view updates.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Before moving SSTables to the main directory, we may need to reshape them
into in-strategy. This patch provides helper code that reshapes the SSTables
that are known to be unshared local in the sstable directory, and updates the
sstable directory with the result.
Rehaping can be made more or less aggressive by passing a reshape mode
(relaxed or strict), which will influence the amount of SSTables reshape
can tolerate to consider a particular slice of the SSTable set
offstrategy.
Because the compaction expects an std::vector everywhere, we changed
our chunked vector for the unshared sstables to a std::vector so we
can more easily pass it around without conversions.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
In a later patch we will be able move files directly from upload
into the main directory. However for now, for the benefit of doing
this incrementally, we will first reshard in place with our new
reshard infrastructure.
load_new_sstables can then move the SSTables directly, without having
to worry about resharding. This has the immediate benefit that the
resharding happens:
- in the streaming group, without affecting compaction work
- without waiting for the current locks (which are held by compactions)
in load_new_sstables to release.
We could, at this point, just move the SSTables to the main directory
right away.
I am not doing this in this patch, and opting to keep the rest of upload
process unchanged. This will be fixed later when we enable offstrategy
compactions: we'll then compact the SSTables generated into the main
directory.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Off-strategy SSTables are SSTables that do not conform to the invariants
that the compaction strategies define. Examples of offstrategy SSTables
are SSTables acquired over bootstrap, resharding when the cpu count
changes or imported from other databases through our upload directory.
This patch introduces a new class, sstable_directory, that will
handle SSTables that are present in a directory that is not one of the
directories where the table expects its SSTables.
There is much to be done to support off-strategy compactions fully. To
make sure we make incremental progress, this patch implements enough
code to handle resharding of SSTables in the upload directory. SSTables
are resharded in place, before we start accessing the files.
Later, we will take other steps before we finally move the SSTables into
the main directory. But for now, starting with resharding will not only
allow us to start small, but it will also allow us to start unleashing
much needed cleanups in many places. For instance, once we start
resharding on boot before making the SSTables available, we will be able
to expurge all places in Scylla where, during normal operations, we have
extra handler code for the fact that SSTables could be shared.
Tests: a new test is added and it passes in debug mode.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Fixes#6202
Distributed loader sstable opening is gated through the
database::sstable_load_concurrency_sem() semaphore
(at a concurrency of 3).
This is (according to creation comment) to reduce memory footprint
during bootstrap, by partially serializing the actual opening of
existing sstables.
However, in certain versions of the product, there exist circular
dependencies between data in some sstables and the ability to actually
read others. Thus when gated as above, we can end up with the
dependents acquiring the semaphore fully, and once stuck waiting for
population of their dependency effectively blocking this from ever
happening.
Since we probably do not want to remove the concurrency control,
and increasing it would only push the problem further away,
we solve the issue by adding the ability to mark certain keyspaces
as "prioritized" (pre-bootstrap), and allow them to populate outside
the normal concurrency control semaphore. Concurrency increase is
however limited to one extra sstable per shard and prio keyspace.
Message-Id: <20200415102431.20816-1-calle@scylladb.com>
This is the last place where database code needs the migration_manager
instance to be alive, so now the mutual dependency between these two
is gone, only the migration_manager needs the database, but not the
vice-versa.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Files and directories must be owned by the process uid.
Files must have read access and directories must have
read, write, and execute access.
Refs #3117
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Scan the table's pending_delete sub-directory if it exists.
Remove any temporary pending_delete log files to roll back the respective
delete_atomically operation.
Replay completed pending_delete log files to roll forward the respective
delete_atomically operation, and finally delete the log files.
Cleanup of temporary sstable directories and pending_delete
sstables are done in a preliminary scan phase when populating the column family
so that we won't attempt to load the to-be-deleted sstables.
Fixes#4082
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
In preparation for replaying pending_delete log files,
we would like to first remove any temporary sst dirs
and later handle pending_delete log files, and only
then populate the column family.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
SSTables loaded to the system via /upload dir may sometimes be needed
to generate view updates from them (if their table has accompanying
views).
Fixes#4047
distributed_loader is a sizeable fraction of database.cc, so moving it
out reduces compile time and improves readability.
Message-Id: <20181230200926.15074-1-avi@scylladb.com>
