Get all flush permits to serialize with any
ongoing flushes and preventing further flushes
during table::clear, in particular calling
discard_completed_segments for every table and
clearing the memtables in clear_and_add.
Fixes#10423
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Memtables are a replica-side entity, and so are moved to the
replica module and namespace.
Memtables are also used outside the replica, in two places:
- in some virtual tables; this is also in some way inside the replica,
(virtual readers are installed at the replica level, not the
cooordinator), so I don't consider it a layering violation
- in many sstable unit tests, as a convenient way to create sstables
with known input. This is a layering violation.
We could make memtables their own module, but I think this is wrong.
Memtables are deeply tied into replica memory management, and trying
to make them a low-level primitive (at a lower level than sstables) will
be difficult. Not least because memtables use sstables. Instead, we
should have a memtable-like thing that doesn't support merging and
doesn't have all other funky memtable stuff, and instead replace
the uses of memtables in sstable tests with some kind of
make_flat_mutation_reader_from_unsorted_mutations() that does
the sorting that is the reason for the use of memtables in tests (and
live with the layering violation meanwhile).
Test: unit (dev)
Closes#10120
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Move replica-oriented classes to the replica namespace. The main
classes moved are ::database, ::keyspace, and ::table, but a few
ancillary classes are also moved. There are certainly classes that
should be moved but aren't (like distributed_loader) but we have
to start somewhere.
References are adjusted treewide. In many cases, it is obvious that
a call site should not access the replica (but the data_dictionary
instead), but that is left for separate work.
scylla-gdb.py is adjusted to look for both the new and old names.
The database, keyspace, and table classes represent the replica-only
part of the objects after which they are named. Reading from a table
doesn't give you the full data, just the replica's view, and it is not
consistent since reconciliation is applied on the coordinator.
As a first step in acknowledging this, move the related files to
a replica/ subdirectory.
`segment_manager' now uses a decorated version of `timed_out_error'
with hardcoded name. On the other hand `region_group' uses named
`on_request_expiry' within its `expiring_fifo'.
Replace stdx::optional and stdx::string_view with the C++ std
counterparts.
Some instances of boost::variant were also replaced with std::variant,
namely those that called seastar::visit.
Scylla now requires GCC 8 to compile.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20190108111141.5369-1-duarte@scylladb.com>
We have found issues when a flush is requested outside the usual
memtable flush loop and because there is not a lot of data the
controller will not have a high amount of shares.
To prevent this, this patch guarantees some minimum amount of shares
when extraneous operations (nodetool flush, commitlog-driven flush, etc)
are requested.
Another option would be to add shares instead of guarantee a minimum.
But in my view the approach I am taking here has two main advantages:
1) It won't cause spikes when those operations are requested
2) It is cumbersome to add shares in the current infrastructure, as just
adding backlog can cause shares to spike. Consider this example:
Backlog is within the first range of very low backlog (~0.2). Shares
for this would be around ~20. If we want to add 200 shares, that is
equivalent to a backlog of 0.8. Once we add those two backlogs
together, we end up with 1 (max backlog).
Fixes#3761
Tests: unit (release)
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <20180927131904.8826-1-glauber@scylladb.com>
dirty memory managers run code on behalf of their callers
in a background fiber, so provide that background fiber with
the scheduling group appropriate to their caller.
- system: main (we want to let system writes through quickly)
- dirty: statement (normal user writes)
- streaming: streaming (streaming writes)
There are times in which we want to add and remove real dirty memory
without impacting virtual dirty. One such example is the cache update
process, where real dirty is the limiting factor.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Since we started accounting virtual dirty memory we no longer have a cap
on real dirty memory. In most situations that is not needed, since real
dirty will just be at most twice as much as virtual dirty (current
flushing memtable plus new memtable).
However, due to things like cache updates and component flushing we can
end up having a lot of memtables that are virtually freed but not yet
fully released, leading real dirty memory to explode using all the box'
memory.
This patch adds a cap on real dirty memory as well. Because of the
hierarchical nature of region_group, if the parent blocks due to memory
depletion, so will the child (virtual dirty region group).
A next step is to add a controller that will increase the priority of
the tasks involving in releasing real dirty memory if we get dangerously
close to the threshold.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
