Commit aab6b0ee27 introduced the
controversial new IMR format, which relied on a very template-heavy
infrastructure to generate serialization and deserialization code via
template meta-programming. The promise was that this new format, beyond
solving the problems the previous open-coded representation had (working
on linearized buffers), will speed up migrating other components to this
IMR format, as the IMR infrastructure reduces code bloat, makes the code
more readable via declarative type descriptions as well as safer.
However, the results were almost the opposite. The template
meta-programming used by the IMR infrastructure proved very hard to
understand. Developers don't want to read or modify it. Maintainers
don't want to see it being used anywhere else. In short, nobody wants to
touch it.
This commit does a conceptual revert of
aab6b0ee27. A verbatim revert is not
possible because related code evolved a lot since the merge. Also, going
back to the previous code would mean we regress as we'd revert the move
to fragmented buffers. So this revert is only conceptual, it changes the
underlying infrastructure back to the previous open-coded one, but keeps
the fragmented buffers, as well as the interface of the related
components (to the extent possible).
Fixes: #5578
The main motivation for this patchset is to prepare
for adding a async close() method to flat_mutation_reader.
In order to close the reader before destroying it
in all paths we need to make next_partition asynchronous
so it can asynchronously close a current reader before
destoring it, e.g. by reassignment of flat_mutation_reader_opt,
as done in scanning_reader::next_partition.
Test: unit(release, debug)
* git@github.com:bhalevy/scylla.git futurize-next-partition-v1:
flat_mutation_reader: return future from next_partition
multishard_mutation_query: read_context: save_reader: destroy reader_meta from the calling shard
mutation_reader: filtering_reader: fill_buffer: futurize inner loop
flat_mutation_reader::impl: consumer_adapter: futurize handle_result
flat_mutation_reader: consume_pausable/in_thread: futurize_invoke consumer
flat_mutation_reader: FlatMutationReaderConsumer: support also async consumer
flat_mutation_reader:impl: get rid of _consume_done member
The keys classes (partition_key et al) already use managed_bytes,
but they assume the data is not fragmented and make liberal use
of that by casting to bytes_view. The view classes use bytes_view.
Change that to managed_bytes_view, and adjust return values
to managed_bytes/managed_bytes_view.
The callers are adjusted. In some places linearization (to_bytes())
is needed, but this isn't too bad as keys are always <= 64k and thus
will not be fragmented when out of LSA. We can remove this
linearization later.
The serialize_value() template is called from a long chain, and
can be reached with either bytes_view or managed_bytes_view.
Rather than trace and adjust all the callers, we patch it now
with constexpr if.
operator bytes_view (in keys) is converted to operator
managed_bytes_view, allowing callers to defer or avoid
linearization.
This reverts commit dc77d128e9. It was reverted
due to a strange and unexplained diff, which is now explained. The
HEAD on the working directory being pulled from was set back, so git
thought it was merging the intended commits, plus all the work that was
committed from HEAD to master. So it is safe to restore it.
This reverts commit 0aa1f7c70a, reversing
changes made to 72c59e8000. The diff is
strange, including unrelated commits. There is no understanding of the
cause, so to be safe, revert and try again.
1. sstables: move `sstable_set` implementations to a separate module
All the implementations were kept in sstables/compaction_strategy.cc
which is quite large even without them. `sstable_set` already had its
own header file, now it gets its own implementation file.
The declarations of implementation classes and interfaces (`sstable_set_impl`,
`bag_sstable_set`, and so on) were also exposed in a header file,
sstable_set_impl.hh, for the purposes of potential unit testing.
2. mutation_reader: move `mutation_reader::forwarding` to flat_mutation_reader.hh
Files which need this definition won't have to include
mutation_reader.hh, only flat_mutation_reader.hh (so the inclusions are
in total smaller; mutation_reader.hh includes flat_mutation_reader.hh).
3. sstables: move sstable reader creation functions to `sstable_set`
Lower level functions such as `create_single_key_sstable_reader`
were made methods of `sstable_set`.
The motivation is that each concrete sstable_set
may decide to use a better sstable reading algorithm specific to the
data structures used by this sstable_set. For this it needs to access
the set's internals.
A nice side effect is that we moved some code out of table.cc
and database.hh which are huge files.
4. sstables: pass `ring_position` to `create_single_key_sstable_reader`
instead of `partition_range`.
It would be best to pass `partition_key` or `decorated_key` here.
However, the implementation of this function needs a `partition_range`
to pass into `sstable_set::select`, and `partition_range` must be
constructed from `ring_position`s. We could create the `ring_position`
internally from the key but that would involve a copy which we want to
avoid.
5. sstable_set: refactor `filter_sstable_for_reader_by_pk`
Introduce a `make_pk_filter` function, which given a ring position,
returns a boolean function (a filter) that given a sstable, tells
whether the sstable may contain rows with the given position.
The logic has been extracted from `filter_sstable_for_reader_by_pk`.
Split from #7437.
Closes#7655
* github.com:scylladb/scylla:
sstable_set: refactor filter_sstable_for_reader_by_pk
sstables: pass ring_position to create_single_key_sstable_reader
sstables: move sstable reader creation functions to `sstable_set`
mutation_reader: move mutation_reader::forwarding to flat_mutation_reader.hh
sstables: move sstable_set implementations to a separate module
Lower level functions such as `create_single_key_sstable_reader`
were made methods of `sstable_set`.
The motivation is that each concrete sstable_set
may decide to use a better sstable reading algorithm specific to the
data structures used by this sstable_set. For this it needs to access
the set's internals.
A nice side effect is that we moved some code out of table.cc
and database.hh which are huge files.
If a list of target endpoints for sending view updates contains
duplicates, it results in benign (but annoying) broken promise
errors happening due to duplicated write response handlers being
instantiated for a single endpoint.
In order to avoid such errors, target remote endpoints are deduplicated
from the list of pending endpoints.
A similar issue (#5459) solved the case for duplicated local endpoints,
but that didn't solve the general case.
Fixes#7572Closes#7641
When a missing base column happens to be named `idx_token`,
an additional helper message is printed in logs.
This additional message does not need to have `error` severity,
since the previous, generic message is already marked as `error`.
This patch simply makes it easier to write tests, because in case
this error is expected, only one message needs to be explicitly
ignored instead of two.
Closes#7597
Raname token_column_computation to legacy_token_column_computation, as
it will be replaced with new column_computation. The reason is that this
computation returns bytes, but all tokens in Scylla can now be
represented by int64_t. Moreover, returning bytes causes invalid token
ordering as bytes comparison is done in unsigned way (not signed as
int64_t). See issue:
https://github.com/scylladb/scylla/issues/7443
When an out-of-sync view is attempted to be used in a write operation,
the whole operation needs to be aborted with an error. After this patch,
the error contains more context - namely, the missing column.
The code which created base-dependent info for materialized views
can be expressed with fewer branches. Also, the constructor
which takes a single parameter is made explicit.
When Scylla finds out that a materialized view contains columns
which are not present in the base table (and they are not computed),
it now presents comprehensible errors in the log.
only reading from view.
The current implementation of materialized views does
no keep the version to which a specific version of materialized
view schema corresponds to. This complicate things especially on
old views versions that the schema doesn't support anymore. However,
the views, being also an independent table should allow reading from
them as long as they exist even if the base table changed since then.
For the reading purpose, we don't need to know the exact composition
of view primary key columns that are not part of the base primary
key, we only need to know that there are any, and this is a much
looser constrain on the schema.
We can rely on a table invariants such as the fact that pk columns are
not going to disappear on newer version of the table.
This means that if we don't find a view column in the base table, it is
not a part of the base table primary key.
This information is enough for us to perform read on the view.
This commit adds support for being able to rely on such partial
information along with a validation that it is not going to be used for
writes. If it is, we simply abort since this means that our schema
integrity is compromised.
The change's purpose is to guard against segfault that is the
result of dereferencing the _base_info member when it is
uninitialized. We already know this can happen (#7420).
The only purpose of this change is to treat this condition as
an internal error, the reason is that it indicates a schema integrity
problem.
Besides this change, other measures should be taken to ensure that
the _base_table member is initialized before calling methods that
rely on it.
We call the internal_error as a last resort.
Require a schema and an operation name to be given to each permit when
created. The schema is of the table the read is executed against, and
the operation name, which is some name identifying the operation the
permit is part of. Ideally this should be different for each site the
permit is created at, to be able to discern not only different kind of
reads, but different code paths the read took.
As not all read can be associated with one schema, the schema is allowed
to be null.
The name will be used for debugging purposes, both for coredump
debugging and runtime logging of permit-related diagnostics.
We want to start tracking the memory consumption of mutation fragments.
For this we need schema and permit during construction, and on each
modification, so the memory consumption can be recalculated and pass to
the permit.
In this patch we just add the new parameters and go through the insane
churn of updating all call sites. They will be used in the next patch.
We will soon want to update the memory consumption of mutation fragment
after each modification done to it, to do that safely we have to forbid
direct access to the underlying data and instead have callers pass a
lambda doing their modifications.
Uses where this method was just used to move the fragment away are
converted to use `as_clustering_row() &&`.
Not used yet, this patch does all the churn of propagating a permit
to each impl.
In the next patch we will use it to track to track the memory
consumption of `_buffer`.
sstable_manager will soon wait for all sstables under its
control to be deleted (if so marked), but that can't happen
if someone is holding on to references to those sstables.
To allow sstables_manager::stop() to work, drop remaining
queued work when terminating.
We use class template argument deduction (CTAD) in a few places, but it appears
not to work for alias templates in clang. While it looks like a clang bug, using
the class name is an improvement, so let's do that.
"
Before seastar is updated with the {fmt} engine under the
logging hood, some changes are to be made in scylla to
conform to {fmt} standards.
Compilation and tests checked against both -- old (current)
and new seastar-s.
tests: unit(dev), manual
"
* 'br-logging-update' of https://github.com/xemul/scylla:
code: Force formatting of pointer in .debug and .trace
code: Format { and } as {fmt} needs
streaming: Do not reveal raw pointer in info message
mp_row_consumer: Provide hex-formatting wrapper for bytes_view
heat_load_balance: Include fmt/ranges.h
The lockup:
When view_builder starts all shards at some point get to a
barrier waiting for each other to pass. If any shard misses
this checkpoint, all others stuck forever. As this barrier
lives inside the _started future, which in turn is waited
on stop, the stop stucks as well.
Reasons to miss the barrier -- exception in the middle of the
fun^w start or explicit abort request while waiting for the
schema agreement.
Fix the "exception" case by unlocking the barrier promise with
exception and fix the "abort request" case by turning it into
an exception.
The bug can be reproduced by hands if making one shard never
see the schema agreement and continue looping until the abort
request.
The crash:
If the background start up fails, then the _started future is
resolved into exception. The view_builder::stop then turns this
future into a real exception caught-and-rethrown by main.cc.
This seems wrong that a failure in a background fiber aborts
the regular shutdown that may proceed otherwise.
tests: unit(dev), manual start-stop
branch: https://github.com/xemul/scylla/tree/br-view-builder-shutdown-fix-3fixes: #7077
Patch #5 leaves the seastar::async() in the 1-st phase of the
start() although can also be tuned not to produce a thread.
However, there's one more (painless) issue with the _sem usage,
so this change appears too large for the part of the bug-fix
and will come as a followup.
* 'br-view-builder-shutdown-fix-3' of git://github.com/xemul/scylla:
view_builder: Add comment about builder instances life-times
view_builder: Do sleep abortable
view_builder: Wakeup barrier on exception
view_builder: Always resolve started future to success
view_builder: Re-futurize start
view_builder: Split calculate_shard_build_step into two
view_builder: Populate the view_builder_init_state
view_builder: Fix indentation after previous patch
view_builder: Introduce view_builder_init_state
... and tests. Printin a pointer in logs is considered to be a bad practice,
so the proposal is to keep this explicit (with fmt::ptr) and allow it for
.debug and .trace cases.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
If one shard delays in seeing the schema agreement and returns on
abort request, other shards may get stuck waiting for it on the
status read barrier. Luckily with the previous patch the barrier
is exception-proof, so we may abort the waiting loop with exception
and handle the lock-up.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
If an exception pops up during the view_builder::start while some
shards wait for the status-read barrier, these shards are not woken
up, thus causing the shutdown to stuck.
Fix this by setting exception on the barrier promise, resolving all
pending and on-going futures.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
If the view builder background start fails, the _started future resolves
to exceptional state. In turn, stopping the view builder keeps this state
through .finally() and aborts the shutdown very early, while it may and
should proceed.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Step two turning the view_builder::start() into a chain of lambdas --
rewrite (most of) the seastar::async()'s lambda into a more "classical"
form.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The calculate_shard_build_step() has a cross-shard barrier in the middle and
passing the barrier is broken wrt exceptions that may happen before it. The
intention is to prepare this barrier passing for exception handling by turning
the view_builder::start() into a dedicated continuation lambda.
Step one in this campaign -- split the calculate_shard_build_step() into
steps called by view_builder::start():
- before the barrier
- barrier
- after the barrier
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Keep the internal calculate_shard_build_step()'s stuff on the init helper
struct, as the method in question is about to be split into a chain of
continuation lambdas.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This is the helper initialization struct that will carry the needed
objects accross continuation lambdas.
The indentation in ::start() will be fixed in the next patch.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
It is no longer called once for a given view_info, so the name
"initialize" is not appropriate.
This patch splits the "initialize" method into the "make" part, which
makes a new base_info object, and the "set" part, which changes the
current base_info object attached to the view.
The view building process was accessing mutation fragments using
current table's schema. This is not correct, fragments must be
accessed using the schema of the generating reader.
This could lead to undefined behavior when the column set of the base
table changes. out_of_range exceptions could be observed, or data in
the view ending up in the wrong column.
Refs #7061.
The fix has two parts. First, we always use the reader's schema to
access fragments generated by the reader.
Second, when calling populate_views() we upgrade the fragment-wrapping
reader's schema to the base table schema so that it matches the base
table schema of view_and_base snapshots passed to populate_views().
The view_info object, which is attached to the schema object of the
view, contains a data structure called
"base_non_pk_columns_in_view_pk". This data structure contains column
ids of the base table so is valid only for a particular version of the
base table schema. This data structure is used by materialized view
code to interpret mutations of the base table, those coming from base
table writes, or reads of the base table done as part of view updates
or view building.
The base table schema version of that data structure must match the
schema version of the mutation fragments, otherwise we hit undefined
behavior. This may include aborts, exceptions, segfaults, or data
corruption (e.g. writes landing in the wrong column in the view).
Before this patch, we could get schema version mismatch here after the
base table was altered. That's because the view schema does not change
when the base table is altered.
Part of the fix is to extract base_non_pk_columns_in_view_pk into a
third entitiy called base_dependent_view_info, which changes both on
base table schema changes and view schema changes.
It is managed by a shared pointer so that we can take immutable
snapshots of it, just like with schema_ptr. When starting the view
update, the base table schema_ptr and the corresponding
base_dependent_view_info have to match. So we must obtain them
atomically, and base_dependent_view_info cannot change during update.
Also, whenever the base table schema changes, we must update
base_dependent_view_infos of all attached views (atomically) so that
it matches the base table schema.
Refs #7061.
fea83f6 introduced a race between processing (and hence removing)
sstables from `_sstables_with_tables` and registering new ones. This
manifested in sstables that were added concurrently with processing a
batch for the same sstables being dropped and the semaphore units
associated with them not returned. This resulted in repairs being
blocked indefinitely as the units of the semaphore were effectively
leaked.
This patch fixes this by moving the contents of `_sstables_with_tables`
to a local variable before starting the processing. A unit test
reproducing the problem is also added.
Fixes: #6892
Tests: unit(dev)
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20200817160913.2296444-1-bdenes@scylladb.com>
C++17 introduced try_emplace for maps to replace a pattern:
if(element not in a map) {
map.emplace(...)
}
try_emplace is more efficient and results in a more concise code.
This commit introduces usage of try_emplace when it's appropriate.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <4970091ed770e233884633bf6d46111369e7d2dd.1597327358.git.piotr@scylladb.com>
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
`count` function was often used in various ways.
`contains` does not only express the intend of the code better but also
does it in more unified way.
This commit replaces all the occurences of the `count` with the
`contains`.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <b4ef3b4bc24f49abe04a2aba0ddd946009c9fcb2.1597314640.git.piotr@scylladb.com>
Merged pull request https://github.com/scylladb/scylla/pull/7018
by Piotr Sarna:
This series addresses various issues with metrics and semaphores - it mainly adds missing metrics, which makes it possible to see the length of the queues attached to the semaphores. In case of view building and view update generation, metrics was not present in these services at all, so a first, basic implementation is added.
More precise semaphore metrics would ease the testing and development of load shedding and admission control.
view_builder: add metrics
db, view: add view update generator metrics
hints: track resource_manager sending queue length
hints: add drain queue length to metrics
table: add metrics for sstable deletion semaphore
database: remove unused semaphore
C++20 introduced `contains` member functions for maps and sets for
checking whether an element is present in the collection. Previously
the code pattern looked like:
<collection>.find(<element>) != <collection>.end()
In C++20 the same can be expressed with:
<collection>.contains(<element>)
This is not only more concise but also expresses the intend of the code
more clearly.
This commit replaces all the occurences of the old pattern with the new
approach.
Tests: unit(dev)
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <f001bbc356224f0c38f06ee2a90fb60a6e8e1980.1597132302.git.piotr@scylladb.com>
Move the classes representing CQL expressions (and utility functions
on them) from the `restrictions` namespace to a new namespace `expr`.
Most of the restriction.hh content was moved verbatim to
expression.hh. Similarly, all expression-related code was moved from
statement_restrictions.cc verbatim to expression.cc.
As suggested in #5763 feedback
https://github.com/scylladb/scylla/pull/5763#discussion_r443210498
Tests: dev (unit)
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
"
While working on another patch I was getting odd compiler errors
saying that a call to ::make_shared was ambiguous. The reason was that
seastar has both:
template <typename T, typename... A>
shared_ptr<T> make_shared(A&&... a);
template <typename T>
shared_ptr<T> make_shared(T&& a);
The second variant doesn't exist in std::make_shared.
This series drops the dependency in scylla, so that a future change
can make seastar::make_shared a bit more like std::make_shared.
"
* 'espindola/make_shared' of https://github.com/espindola/scylla:
Everywhere: Explicitly instantiate make_lw_shared
Everywhere: Add a make_shared_schema helper
Everywhere: Explicitly instantiate make_shared
cql3: Add a create_multi_column_relation helper
main: Return a shared_ptr from defer_verbose_shutdown
It is important that all replicas participating in a read use the same
memory limits to avoid artificial differences due to different amount of
results. The coordinator now passes down its own memory limit for reads,
in the form of max_result_size (or max_size). For unpaged or reverse
queries this has to be used now instead of the locally set
max_memory_unlimited_query configuration item.
To avoid the replicas accidentally using the local limit contained in
the `query_class_config` returned from
`database::make_query_class_config()`, we refactor the latter into
`database::get_reader_concurrency_semaphore()`. Most of its callers were
only interested in the semaphore only anyway and those that were
interested in the limit as well should get it from the coordinator
instead, so this refactoring is a win-win.
