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.
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
Eliminate not used includes and replace some more includes
with forward declarations where appropriate.
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@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
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.
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.
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.
DowngradingConsistencyRetryPolicy uses live replicas count from
Unavailable exception to adjust CL for retry, but when there are pending
nodes CL is increased internally by a coordinator and that may prevent
retried query from succeeding. Adjust live replica count in case of
pending node presence so that retried query will be able to proceed.
Fixes#2535
Message-Id: <20170710085238.GY2324@scylladb.com>
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.
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>
Move unavailable_exception to exceptions.hh where other CQL transport
level exceptions are defined in.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Move 'consistency_level' enumeration to a separate header file to fix
dependency issues that arise when we move 'unavailable_exception' to
exceptions.hh.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Cleanup consistency_level.hh by removing untranslated code that's been
sitting in the tree for a while.
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Transport layer expects to get error code in an exception of type
exceptions::cassandra_exception. Fix code to use it as a base for
all user visible exceptions and put correct error code there.
Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
New in v2:
- Use std::partition_copy() and boost::range::algorithm::partition().
- Don't use std::move() when returning a local vector variable.
Works only if all replicas (participating in CL) has the same live
data. Does not detects mismatch in tombstones (no infrastructure yet).
Does not report timeout yet.
