The feature listener callbacks are waited upon to finish in the
middle of the cluster joining process. I particular -- before
actually joining the cluster the format should have being selected.
For that there's a .sync() method that locks the semaphore thus
making sure that any update is finished and it's called right after
the wait_for_gossip_to_settle() finishes.
However, features are enabled inside the wait_for_gossip_to_settle()
in a seastar::async() context that's also waited upon to finish. This
waiting makes it possible for any feature listener to .get() any of
its futures that should be resolved until gossip is settled.
Said that, the format selection barrier can be moved -- instead of
waiting on the semaphore, the respective part of the selection code
can be .get()-ed (it all runs in async context). One thing to care
about -- the remainder should continue running with the gate held.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This method is run when a feature is enabled. It's a bit trickier than
the others, also there are two methods actually, that are merged into
one by this patch. By and large most of the care is about the _sel
gate and _sem semaphore.
The gate protects the whole selection code from the selector being freed
from underneath it on stop. The semaphore is only needed to keep two
different format selections from each other -- each update the system
keyspace, local variable and replica::database instance on all shards.
In the end there's a gossiper update, but it happens outside of the
semaphore.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Each feature has a private variable and a public accessor. Since the
accessor effectively makes the variable public, avoid the intermediary
and make the variable public directly.
To ease mechanical translation, the variable name is chosen as
the function name (without the cluster_supports_ prefix).
References throughout the codebase are adjusted.
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.
These features have been around for over 2 years and every reasonable
deployment should have them enabled.
The only case when those features could be not enabled is when the user
has used enable_sstables_mc_format config flag to disable MC sstable
format. This case has been eliminated by removing
enable_sstables_mc_format config flag.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Make the database be the format_selector target, so
when the format is selected its set on database which
in turn just forwards the selection into sstables
managers. All users of the format are already patched
to read it from those managers.
The initial value for the format is the highest, which
is needed by tests. When scylla starts the format is
updated by format_selector, first after reading from
system tables, then by selectiing it from features.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Remove the selector from storage_service and introduce
an instance in main.cc that starts soon after the gossiper
and feature_service, starts listening for features and
sets the selected format on storage_service.
This change includes
- Removal of for_testing bit from format_selector constructor,
now tests just do not use it
- Adding a gate to selection routine to make sure on exit all
the selection stuff is done. Although before the cluster join
the selector waits for the feature listeners to finish (the
.sync() method) this gate is still required to handle aborted
start cases and wait for gossiper announcement from selector
to complete.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
