When a node notices that a new CDC generation was introduced in
`storage_service::topology_state_load`, it updates its internal data
structures that are used when coordinating writes to CDC log tables.
The service uses system keyspace to, e.g., manage the generation id,
thus it depends on the system_keyspace instance and deserves the
explicit reference.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
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.
If we're upgrading from an older version with the previous CDC streams
format, we'll upgrade it in the background. Background update is needed
since we need the cluster to be available when performing the upgrade,
but at this point we're just starting a node, and may not succeed in
forming a cluster before we shut down.
However, running in the background is dangerous since the objects we
use may stop existing. The code is careful to use reference counting,
but this does not guarantee that other dependencies are still alive,
especially since not all dependencies are expressed via constructor
parameters.
Fix by waiting for the rewrite work in generation_service::stop(). As
long as generation_service is up, the required dependencies should be
working too.
Note that there is another change here besides limiting the background
work: checks that were previously done in the foreground (limited to
local tables) are now also done in the background. I don't think
this has any impact.
Note: I expect this to have no real impact. Any CDC users will have
long since ugpraded. This is just preparing for other patches that
bring in other dependencies, which cannot be passed via reference
counted pointers, so they expose the existing problem.
This is to push the service towards general idea that each
component should have its own config and db::config to stay
in main.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
All of them are references taken from 'this', since the function is
the generation_service method it can use 'this' directly.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The generation service already has all it needs to do it. This
keeps storage_service smaller and less aware about cdc internals.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The recently introduced make_new_generation() method just calls
another one by passing more this->... stuff as arguments. Relax
the flow by teaching the latter to use 'this' directly.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
It has everything needed onboard. Only two arguments are required -- the
booststrap tokens and whether or not to inject a delay.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This is a follow-up to the previous commit.
Each CDC generation has a timestamp which denotes a logical point in time
when this generation starts operating. That same timestamp is
used to identify the CDC generation. We use this identification scheme
to exchange CDC generations around the cluster.
However, the fact that a generation's timestamp is used as an ID for
this generation is an implementation detail of the currently used method
of managing CDC generations.
Places in the code that deal with the timestamp, e.g. functions which
take it as an argument (such as handle_cdc_generation) are often
interested in the ID aspect, not the "when does the generation start
operating" aspect. They don't care that the ID is a `db_clock::time_point`.
They may sometimes want to retrieve the time point given the ID (such as
do_handle_cdc_generation when it calls `cdc::metadata::insert`),
but they don't care about the fact that the time point actually IS the ID.
In the future we may actually change the specific type of the ID if we
modify the generation management algorithms.
This commit is an intermediate step that will ease the transition in the
future. It introduces a new type, `cdc::generation_id`. Inside it contains
the timestamp, so:
1. if a piece of code doesn't care about the timestamp, it just passes
the ID around
2. if it does care, it can simply access it using the `get_ts` function.
The fact that `get_ts` simply accesses the ID's only field is an
implementation detail.
Using the occasion, we change the `do_handle_cdc_generation_intercept...`
function to be a standard function, not a coroutine. It turns out that -
depending on the shape of the passed-in argument - the function would
sometimes miscompile (the compiled code would not copy the argument to the
coroutine frame).
Each CDC generation always has a timestamp, but the fact that the
timestamp identifies the generation is an implementation detail.
We abstract away from this detail by using a more generic naming scheme:
a generation "identifier" (whatever that is - a timestamp or something
else).
It's possible that a CDC generation will be identified by more than a
timestamp in the (near) future.
The actual string gossiped by nodes in their application state is left
as "CDC_STREAMS_TIMESTAMP" for backward compatibility.
Some stale comments have been updated.
Currently all management of CDC generations happens in storage_service,
which is a big ball of mud that does many unrelated things.
Previous commits have introduced a new service for managing CDC
generations. This code moves most of the relevant code to this new
service.
However, some part still remains in storage_service: the bootstrap
procedure, which happens inside storage_service, must also do some
initialization regarding CDC generations, for example: on restart it
must retrieve the latest known generation timestamp from disk; on
bootstrap it must create a new generation and announce it to other
nodes. The order of these operations w.r.t the rest of the startup
procedure is important, hence the startup procedure is the only right
place for them.
Still, what remains in storage_service is a small part of the entire
CDC generation management logic; most of it has been moved to the
new service. This includes listening for generation changes and
updating the data structures for performing CDC log writes (cdc::metadata).
Furthermore these functions now return futures (and are internally
coroutines), where previously they required a seastar::async context.
This commit introduces a new service crafted to handle CDC generation
management: listening and reacting to generation changes in the cluster.
The implementation is a stub for now, the service reacts to generation
changes by simply logging the event.
The commit plugs the service in, initializing it in main and test code,
passing a reference to storage_service and having storage_service start
the service (using the `after_join` method): the service only starts
doing its job after the node joins the token ring (either on bootstrap
or restart).
