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alternator: use tablets by default, if available

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Before this patch, Alternator tables did not use tablets even if this
feature was available - tablets had to be manually enabled per table
by using a tag. But recently we changed CQL to enable tablets by default
on all keyspaces (when the experimental "tablets" option is turned on),
so this patch does the same for Alternator tables:

1. When the "tablets" experimental feature is on, new Alternator tables
   will use tablets instead of vnodes. They will use the default choice
   of initial_tablets.

2. The same tag that in the past could be used to enable tablets on a
   specific table, now can be used to disable tablets or change the
   default initial_tablets for a specific table at creation time.

Fixes #16355

Signed-off-by: Nadav Har'El <nyh@scylladb.com>
This commit is contained in:
Nadav Har'El
2024-01-21 16:38:58 +02:00
parent 36f14f89df
commit c496d60716
1 changed files with 24 additions and 9 deletions
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33
alternator/executor.cc
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@@ -8,6 +8,7 @@
#include <seastar/core/sleep.hh>
#include "alternator/executor.hh"
#include "db/config.hh"
#include "log.hh"
#include "schema/schema_builder.hh"
#include "exceptions/exceptions.hh"
@@ -4513,20 +4514,34 @@ static lw_shared_ptr<keyspace_metadata> create_keyspace_metadata(std::string_vie
keyspace_name, rf, endpoint_count);
}
auto opts = get_network_topology_options(sp, gossiper, rf);
std::optional<unsigned> initial_tablets;
// Tablets are not yet enabled by default on Alternator tables, because of
// missing support for CDC (see issue #16313). Until then, allow
// requesting tablets at table-creation time by supplying following tag,
// with an integer value. This is useful for testing Tablet support in
// Alternator even before it is ready for prime time.
// If the "tablets" experimental feature is available, we enable tablets
// by default on all Alternator tables. However, some Alternator features
// are not yet available with tablets (Streams #16313 and TTL #16567) so
// we allow disabling tablets at table-creation by supplying the following
// tags with any non-numeric value (e.g., empty string or the word "none").
// Supplying it with an integer value allows overriding the default choice
// of initial_tablets (setting the value to 0 asks for the default choice).
// If we make this tag a permanent feature, it will get a "system:" prefix -
// until then we give it the "experimental:" prefix to not commit to it.
static constexpr auto INITIAL_TABLETS_TAG_KEY = "experimental:initial_tablets";
if (tags_map.contains(INITIAL_TABLETS_TAG_KEY)) {
initial_tablets = std::stol(tags_map.at(INITIAL_TABLETS_TAG_KEY));
std::optional<unsigned> initial_tablets;
if (sp.get_db().local().get_config().check_experimental(db::experimental_features_t::feature::TABLETS)) {
auto it = tags_map.find(INITIAL_TABLETS_TAG_KEY);
if (it == tags_map.end()) {
// No tag - ask to choose a reasonable default number of tablets
initial_tablets = 0;
} else {
// Tag set. If it's a valid number, use it. If not - e.g., it's
// empty or a word like "none", disable tablets by setting
// initial_tablets to a disengaged optional.
try {
initial_tablets = std::stol(tags_map.at(INITIAL_TABLETS_TAG_KEY));
} catch(...) {
initial_tablets = std::nullopt;
}
}
}
return keyspace_metadata::new_keyspace(keyspace_name, "org.apache.cassandra.locator.NetworkTopologyStrategy", std::move(opts), initial_tablets);
}