The table::get_hit_rate needs gossiper to get hitrates state from.
There's no way to carry gossiper reference on the table itself, so it's
up to the callers of that method to provide it. Fortunately, there's
only one caller -- the proxy -- but the call chain to carry the
reference it not very short ... oh, well.
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.
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.
Returning a function parameter guarantees copy elision and does not
require a std::move(). Enable -Wredundant-move to warn us that the
move is unneeded, and gain slightly more readable code. A few violations
are trivially adjusted.
Closes#9004
The write paths in storage_proxy pass replica sets as
std::unordered_set<gms::inet_address>. This is a complex type, with
N+1 allocations for N members, so we change it to a small_vector (via
inet_address_vector_replica_set) which requires just one allocation, and
even zero when up to three replicas are used.
This change is more nuanced than the corresponding change to the read path
abe3d7d7 ("Merge 'storage_proxy: use small_vector for vectors of
inet_address' from Avi Kivity"), for two reasons:
- there is a quadratic algorithm in
abstract_write_response_handler::response(): it searches for a replica
and erases it. Since this happens for every replica, it happens N^2/2
times.
- replica sets for writes always include all datacenters, while reads
usually involve just one datacenter.
So, a write to a keyspace that has 5 datacenters will invoke 15*(15-1)/2
=105 compares.
We could remove this by sending the index of the replica in the replica
set to the replica and ask it to include the index in the response, but
I think that this is unnecessary. Those 105 compares need to be only
105/15 = 7 times cheaper than the corresponding unordered_set operation,
which they surely will. Handling a response after a cross-datacenter round
trip surely involves L3 cache misses, and a small_vector reduces these
to a minimum compared to an unordered_set with its bucket table, linked
list walking and managent, and table rehashing.
Tests using perf_simple_query --write --smp 1 --operations-per-shard 1000000
--task-quota-ms show two allocations removed (as expected) and a nice
reduction in instructions executed.
before: median 204842.54 tps ( 54.2 allocs/op, 13.2 tasks/op, 49890 insns/op)
after: median 206077.65 tps ( 52.2 allocs/op, 13.2 tasks/op, 49138 insns/op)
Closes#8847
Consider two nodes with almost-100% cache hit ratio, but not exactly
100%: one has 99.9% cache hits, the second 99.8%. Normally in HWLB we
want to equalize the miss rate in both nodes. So we send the first node
twice the number of requests we send to the second. But unless the disks
are extremely limited, this doesn't make sense: As a numeric example,
consider that we send 2000 requests to the first node and 1000 to the
second, just so the number of misses will be the same - 2 (0.1% and 0.2%
misses, respectively). At such low miss numbers, the assumption that the
disk reads are the slowest part of the operation is wrong, so trying to
equalize only this part is wrong.
So above some threshold hit rate, we should treat all hit rates as
equivalent. In the code we already had such a threshold - max_hit_rate,
but it was set to the incredibly high 0.999. We saw in actual user
runs (see issue #8815) that this threshold was too high - one node
received twice the amount of requests that another did - although both
had near-100% cache hit rates.
So in this patch we lower the max_hit_rate to 0.95. This will have two
consequences:
1. Two nodes with hit rates above 0.95 will be considered to have the
same hit rate, so they will get equal amount of work - even if one
has hit rate 0.98 and the other 0.99.
2. A cold node with it rate 0.0 will get 5% of the work of a node with
the perfect hit rate limited to 0.95. This will allow the cold node to
slowly warm up its cache. Before this patch, if the hot node happened
to have a hit rate of 0.999 (the previous maximum), the cold node would
get just 0.1% of the work and remain almost idle and fill its cache
extremely slowly - which is a waste.
Fixes#8815.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210616180732.125295-1-nyh@scylladb.com>
assure_sufficient_live_nodes() is a huge template calling other
huge templates, and requires "network_topology_strategy.hh". It is
inlined in consistency_level.hh. This increases compile time and recompiles.
Move the template out-of-line and use "extern template" to instantiate it.
This is not ideal as new callers would require updates to the
instantiated signatures, but I think our goal should be to de-template
it completely instead. Meanwhile, this reduces some pain.
Ref #1.
Closes#8637
Replace std::vector<inet_address> with a small_vector of size 3 for
replica sets (reflecting the common case of local reads, and the somewhat
less common case of single-datacenter writes). Vectors used to
describe topology changes are of size 1, reflecting that up to one
node is usually involved with topology changes. At those counts and
below we save an allocation; above those counts everything still works,
but small_vector allocates like std::vector.
In a few places we need to convert between std::vector and the new types,
but these are all out of the hot paths (or are in a hot path, but behind a
cache).
storage_proxy works with vectors of inet_addresses for replica sets
and for topology changes (pending endpoints, dead nodes). This patch
introduces new names for these (without changing the underlying
type - it's still std::vector<gms::inet_address>). This is so that
the following patch, that changes those types to utils::small_vector,
will be less noisy and highlight the real changes that take place.
We used to calculate the number of endpoints for quorum and local_quorum
unconditionally as ((rf / 2) + 1). This formula doesn't take into
account the corner case where RF = 0, in this situation quorum should
also be 0.
This commit adds the missing corner case.
Tests: Unit Tests (dev)
Fixes#6905Closes#7296
Rename inherited metrics cas_propose and cas_commit
to cas_accept and cas_learn respectively.
A while ago we made a decision to stick to widely accepted
terms for Paxos rounds: prepare, accept, learn. The rest
of the code is using these terms, so rename the metrics
to avoid confusion/technical debt.
While at it, rename a few internal methods and functions.
Fixes#6169
Message-Id: <20200414213537.129547-1-kostja@scylladb.com>
This patch resurrects Cassandra's code validating a consistency level
for CAS requests. Basically, it makes CAS requests use a special
function instead of validate_for_write to make error messages more
coherent.
Note, we don't need to resurrect requireNetworkTopologyStrategy as
EACH_QUORUM should work just fine for both CAS and non-CAS writes.
Looks like it is just an artefact of a rebase in the Cassandra
repository.
Support single-statement conditional updates and as well as batches.
This patch almost fully rewrites column_condition.cc, implementing
is_satisfied_by().
Most of the remaining complications in column_condition implementation
come from the need to properly handle frozen and multi-cell
collection in predicates - up until now it was not possible
to compare entire collection values between each other. This is further
complicated since multi-cell lists and sets are returned as maps.
We can no longer assume that the columns fetched by prefetch operation
are non-frozen collections. IF EXISTS/IF NOT EXISTS condition
fetches all columns, besides, a column may be needed to check other
condition.
When fetching the old row for LWT or to apply updates on list/columns,
we now calculate precisely the list of columns to fetch.
The primary key columns are also included in CAS batch result set,
and are thus also prefetched (the user needs them to figure out which
statements failed to apply).
The patch is cross-checked for compatibility with cassandra-3.11.4-1545-g86812fa502
but does deviate from the origin in handling of conditions on static
row cells. This is addressed in future series.
It has two unrelated users: cql for validation, and storage_proxy for
complicated calculations. Split the simple stuff into a new header to reduce
dependencies.
* seastar d59fcef...b924495 (2):
> build: Fix protobuf generation rules
> Merge "Restructure files" from Jesse
Includes fixup patch from Jesse:
"
Update Seastar `#include`s to reflect restructure
All Seastar header files are now prefixed with "seastar" and the
configure script reflects the new locations of files.
Signed-off-by: Jesse Haber-Kucharsky <jhaberku@scylladb.com>
Message-Id: <5d22d964a7735696fb6bb7606ed88f35dde31413.1542731639.git.jhaberku@scylladb.com>
"
sprint() recently became more strict, throwing on sprint("%s", 5). Replace
with the more modern format().
Mechanically converted with https://github.com/avikivity/unsprint.
Propagate the preferred_replicas to db::filter_for_query() and consider
them when selecting the endpoints. The algoritm for selecting the
endpoints is as follows:
* Compute the intersection of the endpoint candidates and the
preferred endpoints.
* If this yields a set of endpoints that already satisfies the CL
requirements use this set.
* Otherwise select the remaining endpoints according to the
load-balancing strategy, just like before.
This patch makes storage proxy to choose replicas to read from base on
their cache hit rates. Replicas with higher cache hit rates will see
more requests while replicas with lower hit rates will see less. Local
node has a special bonus and will get more requests even if another node
has slightly higher cache hit rate (same goes for local vs remote DC),
but after the patch it is no longer guarantied that a coordinator node
will be chosen as a replica for the read (if the feature is enabled).
Currently storage proxy has to loop over remaining replicas to search
for suitable extra replica, but doing it in filter_for_query() is
extremely easy, so do it there instead.
Merge filter_for_query_dc_local() functionality into filter_for_query().
This is more efficient since filter_for_query_dc_local() partitions
endpoints into 'local' and 'remote' set but filter_for_query() already
does it for CL=LOCAL so for such queries we needlessly do it twice.
filter_for_query() gets sorted by preference list of endpoints and
should preserve that order after filtering out non local endpoints for
local query. partition() does not guaranty this while stable_partition()
does, so use it instead.
Fixes#1450.
Message-Id: <20160713100909.GM10767@scylladb.com>
This is kind of sorting, so it belongs there, but it also fixes a bug in
storage_proxy::get_read_executor() that assumes filter_for_query() do
not change order of nodes in all_nodes when extra replica is chosen.
Otherwise if coordinator ip happens to be last in all_nodes then it will
be chosen as extra replica and will be quired twice.
Message-Id: <1460549369-29523-1-git-send-email-gleb@scylladb.com>
During bootstrapping additional copies of data has to be made to ensure
that CL level is met (see CASSANDRA-833 for details). Our code does
that, but it does not take into account that bootstraping node can be
dead which may cause request to proceed even though there is no
enough live nodes for it to be completed. In such a case request neither
completes nor timeouts, so it appear to be stuck from CQL layer POV. The
patch fixes this by taking into account pending nodes while checking
that there are enough sufficient live nodes for operation to proceed.
Fixes#965
Message-Id: <20160303165250.GG2253@scylladb.com>
