Concepts are easier to read and result in better error messages.
This change also tightens the constraint from "std::is_fundamental" to
"std::integral". The differences are floating point values, nullptr_t,
and void. The latter two are illegal/useless to write, and nobody uses
floating point values for list lengths, so everything still compiles.
Closes#8326
This series implements leader stepdown extension. See patch 4 for
justification for its existence. First three patches either implement
cleanups to existing code that future patch will touch or fix bugs
that need to be fixed in order for stepdown test to work.
* 'raft-leader-stepdown-v3' of github.com:scylladb/scylla-dev:
raft: add test for leader stepdown
raft: introduce leader stepdown procedure
raft: fix replication when leader is not part of current config
raft: do not update last election time if current leader is not a part of current configuration
raft: move log limiting semaphore into the leader state
"
Scylla suffers with aggressive compaction after repair-based operation has initiated. That translates into bad latency and slowness for the operation itself.
This aggressiveness comes from the fact that:
1) new sstables are immediately added to the compaction backlog, so reducing bandwidth available for the operation.
2) new sstables are in bad shape when integrated into the main sstable set, not conforming to the strategy invariant.
To solve this problem, new sstables will be incrementally reshaped, off the compaction strategy, until finally integrated into the main set.
The solution takes advantage there's only one sstable per vnode range, meaning sstables generated by repair-based operations are disjoint.
NOTE: off-strategy for repair-based decommission and removenode will follow this series and require little work as the infrastructure is introduced in this series.
Refs #5226.
"
* 'offstrategy_v7' of github.com:raphaelsc/scylla:
tests: Add unit test for off-strategy sstable compaction
table: Wire up off-strategy compaction on repair-based bootstrap and replace
table: extend add_sstable_and_update_cache() for off-strategy
sstables/compaction_manager: Add function to submit off-strategy work
table: Introduce off-strategy compaction on maintenance sstable set
table: change build_new_sstable_list() to accept other sstable sets
table: change non_staging_sstables() to filter out off-strategy sstables
table: Introduce maintenance sstable set
table: Wire compound sstable set
table: prepare make_reader_excluding_sstables() to work with compound sstable set
table: prepare discard_sstables() to work with compound sstable set
table: extract add_sstable() common code into a function
sstable_set: Introduce compound sstable set
reshape: STCS: preserve token contiguity when reshaping disjoint sstables
Section 3.10 of the PhD describes two cases for which the extension can
be helpful:
1. Sometimes the leader must step down. For example, it may need to reboot
for maintenance, or it may be removed from the cluster. When it steps
down, the cluster will be idle for an election timeout until another
server times out and wins an election. This brief unavailability can be
avoided by having the leader transfer its leadership to another server
before it steps down.
2. In some cases, one or more servers may be more suitable to lead the
cluster than others. For example, a server with high load would not make
a good leader, or in a WAN deployment, servers in a primary datacenter
may be preferred in order to minimize the latency between clients and
the leader. Other consensus algorithms may be able to accommodate these
preferences during leader election, but Raft needs a server with a
sufficiently up-to-date log to become leader, which might not be the
most preferred one. Instead, a leader in Raft can periodically check
to see whether one of its available followers would be more suitable,
and if so, transfer its leadership to that server. (If only human leaders
were so graceful.)
The patch here implements the extension and employs it automatically
when a leader removes itself from a cluster.
When a leader orchestrates its own removal from a cluster there is a
situation where the leader is still responsible for replication, but it
is no longer part of active configuration. Current code skips replication
in this case though. Fix it by always replicating in the leader state.
Since we use external failure detector instead of relying on empty
AppendRequests from a leader there can be a situation where a node
is no longer part of a certain raft group but is still alive (and also
may be part of other raft groups). In such case last election time
should not be updated even if the node is alive. It is the same as if
it would have stopped to send empty AppendRequests in original raft.
Since we switched scylla-python3 build directory to tools/python3/build
on Jenkins, we nolonger need compat-python3 targets, drop them.
Related scylladb/scylla-pkg#1554
Closes#8328
"
Due to bad interaction of recent changes (913d970 and 4c8ab10) inctive
readers that are not admitted have managed to completely fly under the
radar, avoiding any sort of limitation. The reason is that pre-admission
the permits don't forward their resource cost to the semaphore, to
prevent them possibly blocking their own admission later. However this
meant that if such a reader is registered as inactive, it completely
avoids the normal resource based eviction mechanism and can accumulate
without bounds.
The real solution to this is to move the semaphore before the cache and
make all reads pass admission before they get started (#4758). Although
work has been started towards this, it is still a while until it lands.
In the meanwhile this patchset provides a workaround in the form of a
new inactive state, which -- like admitted -- causes the permit to
forward its cost to the semaphore, making sure these un-admitted
inactive reads are accounted for and evicted if there is too much of
them.
Fixes: #8258
Tests: unit(release), dtest(oppartitions_test.py:TestTopPartitions.test_read_by_gause_key_distribution_for_compound_primary_key_and_large_rows_number)
"
* 'reader-concurrency-semaphore-limit-inactive-reads/v4' of https://github.com/denesb/scylla:
test: mutation_reader_test: add test for permit cleanup
test: querier_cache_test: add memory based cache eviction test
reader_permit: add inactive state
querier: insert(): account immediately evicted querier as resource based eviction
reader_concurrency_semaphore: fix clear_inactive_reads()
reader_concurrency_semaphore: make inactive_read_handle a weak reference
reader_concurrency_semaphore: make evict() noexcept
reader_concurrency_semaphore: update out-of-date comments
After commit 0bd201d3ca ("cql3: Skip indexed
column for CK restrictions") fixed issue #7888, the test
cassandra_tests/validation/entities/frozen_collections_test.py::testClusteringColumnFiltering
began passing, as expected. So we can remove its "xfail" label.
Refs #7888.
cassandra_tests/validation/entities/frozen_collections_test.py::testClusteringColumnFiltering
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210321080522.1831115-1-nyh@scylladb.com>
* seastar ea5e529f30...83339edb04 (21):
> cmake: filter out -Wno-error=#warnings from pkgconfig (seastar.pc)
> Merge 'utils/log.cc: fix nested_exception logging (again)' from Vlad Zolotarov
Fixes#8327.
> file: Add option to refuse the append-challenged file
> Merge "Teach io-tester to work on block device" from Pavel E
> Merge "Cleanup files code" from Pavel E
> install-dependencies: Support rhel-8.3
> install-dependencies: Add some missing rh packages
> file, reactor: reinstate RWF_NOWAIT support
> file: Prevent fsxattr.fsx_extsize from overflow
> cmake: enable clang's -Wno-error=#warnings if supported
> cmake: harden seastar_supports_flag aginst inputs with spaces or #
> cmake: fix seastar_supports_flag failing after first invocation
> thread: Stop backtraces in main() on s390x architecture
> intent: Explicitly declare constructors for references
> test: file_io_test: parallel_overwrite: use testing::local_random_engine
> util: log-impl: rework log_buf::inserter_iterator
> rwlock: pass timeout parameter to get_units
> concepts: require lib support to enable concepts
> rpc: print more info on bad protocol magic
> seastar-addr2line: strip input line to restore multiline support
> log: skip on unknown nested mixing instead of stopping the logging
Ref #8327.
This is a translation of Cassandra's CQL unit test source file
validation/entities/SecondaryIndexOnMapEntriesTest.java into our
our cql-pytest framework.
This test file checks various features of indexing (with secondary index)
individual entries of maps. All these tests pass on Cassandra, but fail on
Scylla because of issue #2962 - we do not yet support indexing of the content
of unfrozen collections. The failing test currently fail as soon as they
try to create the index, with the message:
"Cannot create secondary index on non-frozen collection or UDT column v".
Refs #2962.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210310124638.1653606-1-nyh@scylladb.com>
Thrift used to be quite unsafe with regard to its retry mechanism, which caused very rapid use of resources, namely the number of file descriptors. It was also prone to use-after-free due to spawning futures without guarding the captured objects with anything.
The mechanism is now cleaned up, and a simple exponential backoff replaced previous constant backoff policy.
Fixes#8317
Tests: unit(dev), manual(see #8317 for a simple reproducer)
Closes#8318
* github.com:scylladb/scylla:
thrift: add exponential backoff for retries
thrift: fix and simplify retry logic
When a tuple value is serialized, we go through every element type and
use it to serialize element values. But an element type can be
reversed, which is artificially different from the type of the value
being read. This results in a server error due to the type mismatch.
Fix it by unreversing the element type prior to comparing it to the
value type.
Fixes#7902
Tests: unit (dev)
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
Closes#8316
When querying an index table, we assemble clustering-column
restrictions for that query by going over the base table token,
partition columns, and clustering columns. But if one of those
columns is the indexed column, there is a problem; the indexed column
is the index table's partition key, not clustering key. We end up
with invalid clustering slice, which can cause problems downstream.
Fix this by skipping the indexed column when assembling the clustering
restrictions.
Tests: unit (dev)
Fixes#7888
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
Closes#8320
A trichotomic comparator returning an int an easily be mistaken
for a less comparator as the return types are convertible.
Use the new std::strong_ordering instead.
A caller in cql3's update_parameters.hh is also converted, following
the path of least resistance.
Ref #1449.
Test: unit (dev)
Closes#8323
Constrain inject() with a requires clause rather than enable_if,
simplifying the code and compiler diagnostics.
Note that the second instance could not have been called, since
the template argument does not appear in the function parameter
list and thus could not be deduced. This is corrected here.
Closes#8322
time_point_to_string ensures its input is a time_point with
millisecond resolution (though it neglects to verify the epoch
is what it expects). Change the test from a clunky enable_if to
a nicer concept.
Closes#8321
Currently send_snapshot is the only two-way RPC used by Raft.
However, the sender (the leader) does not look at the receiver's
reply, other than checks it's not an error. This has the following
issues:
- if the follower has a newer term and rejects the snapshot for
that reason, the leader will not learn about a newer follower
term and will not step down
- the send_snapshot message doesn't pass through a single-endpoint
fsm::step() and thus may not follow the general Raft rules
which apply for all messages.
- making a general purpose transport that simply calls fsm::step()
for every message becomes impossible.
Fix it by actually responding with snapshot_reply to send_snapshot
RPC, generating this reply in fsm::step() on the follower,
and feeding into fsm::step() on the leader.
* scylla-dev/raft-send-snapshot-v2:
raft: pass snapshot_reply into fsm::step()
raft: respond with snapshot_reply to send_snapshot RPC
raft: set follower's next_idx when switching to SNAPSHOT mode
raft: set the current leader upon getting InstallSnapshot
The original backoff mechanism which just retries after 1ms
may still lead to rapid resource depletion.
Instead, an exponential backoff is used, with a cap of ~2s.
Tests: manual, with cassandra-stress and browsing logs
The retry logic for Thrift frontend had two bugs:
1. Due to missing break in a switch statement,
two retry calls were always performed instead of one,
which acts a little bit like a Seastar forkbomb
2. The delayed action was not guarded with any gate,
so it was theoretically possible to access a captured `this`
pointer of an object which already got deallocated.
In order to fix the above, the logic is simplified to always
retry with backoff - it makes very little sense to skip the backoff
and immediate retries are not needed by anyone, while they cause
severe overload risk.
Tests: manual - a simple cassandra-stress invocation was able to crash
scylla with a segfault:
$ cassandra-stress write -mode thrift -rate threads=2000
Fixes#8317
enable_if is hard to understand, especially its error messages. Convert
enable_if in sstable code to concepts.
A new concept is introduced, self_describing, for the case of a type
that follows the obj.describe_type() protocol. Otherwise this is quite
straightforward.
Closes#8315
* github.com:scylladb/scylla:
sstables: vector write: convert to concepts
sstables: check_truncated_and_assign: convert to concept
sstables: convert write() to concepts
sstables: convert write_vint() to concepts
sstables: vector parse(): convert to concept
sstables: convert parse() for a self-describing type to concept
sstables: read_vint(): convert enable_if to concepts
sstables: add concept for self-describing type
We have an integral and a non-integral overload, each constrained
with enable_if. We use std::integral to constrain the integral
overload and leave the other unconstrained, as C++ will choose the
more constrained version when applicable.
There are three variants: integral, enum, and self-describing
(currently expressed as not integral and not enum). Convert to
concepts by using the standard concepts or the new self_describing
concept.
By default the boto3 library waits up to 60 second for a response,
and if got no response, it sends the same request again, multiple
times. We already noticed in the past that it retries too many times
thus slowing down failures, so in our test configuration lowered the
number of retries to 3, but the setting of 60-second-timeout plus
3 retries still causes two problems:
1. When the test machine and the build are extremely slow, and the
operation is long (usually, CreateTable or DeleteTable involving
multiple views), the 60 second timeout might not be enough.
2. If the timeout is reached, boto3 silently retries the same operation.
This retry may fail because the previous one really succeeded at
least partially! The symptom is tests which report an error when
creating a table which already exists, or deleting a table which
dooesn't exist.
The solution in this patch is first of all to never do retries - if
a query fails on internal server error, or times out, just report this
failure immediately. We don't expect to see transient errors during
local tests, so this is exactly the right behavior.
The second thing we do is to increase the default timeout. If 1 minute
was not enough, let's raise it to 5 minutes. 5 minutes should be enough
for every operation (famous last words...).
Even if 5 minutes is not enough for something, at least we'll now see
the timeout errors instead of some wierd errors caused by retrying an
operation which was already almost done.
Fixes#8135
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210222125630.1325011-1-nyh@scylladb.com>
The two vector parse() overloads select between integral members
and non-integral members. Use std::integral to constrain the
integral overload and leave the other unconstrained; C++ will choose
the more constrained version when it applies.
This parse() overload uses "not integral and not enum" to reject
non-self-describing types. Express it directly with the self_describing
concept instead.
Convert read_vint() to a concept. The explicitly deleted version
is no longer needed since wrongly-typed inputs will be rejected
by the constraint. Similarly the static assert can be dropped
for the same reason.
Our sstable parsing and writing code contains a self-describing
type concept, where a type can advertise its members via a
describe_types() member function with a specific protocol.
Formalize that into a C++ concept. This is a little tricky, since
describe_type() accepts a parameter that is itself a template, and
requires clauses only work with concrete type. To handle this problem,
create such a concrete example type and use it in the concept.
Now, sstables created by bootstrap and replace will be added to the
maintenance set, and once the operation completes, off-strategy compaction
will be started.
We wait until the end of operation to trigger off-strategy, as reshaping
can be more efficient if we wait for all sstables before deciding what
to compact. Also, waiting for completion is no longer an issue because
we're able to read from new sstables using partitioned_sstable_set and
their existence aren't accounted by the compaction backlog tracker yet.
Refs #5226.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This new variant will allow its caller to submit off-strategy job
asynchronously on behalf of a given table.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Off-strategy compaction is about incrementally reshaping the off-strategy
sstables in maintenance set, using our existing reshape mechanism, until
the set is ready for integration into the main sstable set.
The whole operation is done in maintenance mode, using the streaming
scheduling group.
We can do it this way because data in maintenance set is disjoint, so
effects on read amplification is avoided by using
partitioned_sstable_set, which is able to efficiently and incrementally
retrieve data from disjoint sstables.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
SSTables that are off-strategy should be excluded by this function as
it's used to select candidates for regular compaction.
So in addition to only returning candidates from the main set, let's
also rename it to precisely reflect its behavior.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This new sstable set will hold sstables created by repair-based
operations. A repair-based op creates 1 sstable per vrange (256),
so sstables added to this new set are disjoint, therefore they
can be efficiently read from using partitioned_sstable_set.
Compound set is changed to include this new set, so sstables in
this new set are automatically included when creating readers,
computing statistics, and so on.
This new set is not backlog tracked, so changes were needed to
prevent a sstable in this set from being added or removed from
the tracker.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
From now own, _sstables becomes the compound set, and _main_sstables refer
only to the main sstables of the table. In the near future, maintenance
set will be introduced and will also be managed by the compound set.
So add_sstable() and on_compaction_completion() are changed to
explicitly insert and remove sstables from the main set.
By storing compound set in _sstables, functions which used _sstables for
creating reader, computing statistics, etc, will not have to be changed
when we introduce the maintenance set, so code change is a lot minimized
by this approach.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Compound set will not be inserted or erased directly, so let's change
this function to build a new set from scratch instead.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
After compound set, discard_sstables() will have to prune each set
individually and later refresh the compound set. So let's change
the function to support multiple sstable sets, taking into account
that a sstable set may not want to be backlog tracked.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
The purpose is to allow the code to be eventually reused by maintenance
sstable set, which will be soon introduced.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
This new sstable set implementation is useful for combining operation of
multiple sstable sets, which can still be referenced individually via
its shared ptr reference.
It will be used when maintenance set is introduced in table, so a
compound set is required to allow both sets to have their operations
efficiently combined.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
When reshaping hundreds of disjoint sstables, like on bootstrap,
contiguity wasn't being preserved because the heuristic for picking
candidates didn't take into account their token range, which resulted
in reshape messing with the contiguity that could otherwise be
preserved by respecting the token order of the disjoint sstables.
In other words, sstables with the smallest first tokens should be
compacted first. By doing that, the contiguity is preserved even
across size tiers, after reshape has completed its possible multiple
rounds to get all the data in shape.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
