99fd2244a3
This is a follow-up to the previous commit. Each CDC generation has a timestamp which denotes a logical point in time when this generation starts operating. That same timestamp is used to identify the CDC generation. We use this identification scheme to exchange CDC generations around the cluster. However, the fact that a generation's timestamp is used as an ID for this generation is an implementation detail of the currently used method of managing CDC generations. Places in the code that deal with the timestamp, e.g. functions which take it as an argument (such as handle_cdc_generation) are often interested in the ID aspect, not the "when does the generation start operating" aspect. They don't care that the ID is a `db_clock::time_point`. They may sometimes want to retrieve the time point given the ID (such as do_handle_cdc_generation when it calls `cdc::metadata::insert`), but they don't care about the fact that the time point actually IS the ID. In the future we may actually change the specific type of the ID if we modify the generation management algorithms. This commit is an intermediate step that will ease the transition in the future. It introduces a new type, `cdc::generation_id`. Inside it contains the timestamp, so: 1. if a piece of code doesn't care about the timestamp, it just passes the ID around 2. if it does care, it can simply access it using the `get_ts` function. The fact that `get_ts` simply accesses the ID's only field is an implementation detail. Using the occasion, we change the `do_handle_cdc_generation_intercept...` function to be a standard function, not a coroutine. It turns out that - depending on the shape of the passed-in argument - the function would sometimes miscompile (the compiled code would not copy the argument to the coroutine frame).
117 lines
4.0 KiB
C++
117 lines
4.0 KiB
C++
/*
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* Copyright (C) 2018 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "bytes.hh"
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#include "schema_fwd.hh"
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#include "service/migration_manager.hh"
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#include "utils/UUID.hh"
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#include "cdc/generation_id.hh"
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#include <seastar/core/future.hh>
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#include <seastar/core/sstring.hh>
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#include <unordered_map>
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namespace cql3 {
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class query_processor;
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}
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namespace cdc {
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class stream_id;
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class topology_description;
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class streams_version;
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} // namespace cdc
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namespace service {
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class storage_proxy;
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}
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namespace db {
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class system_distributed_keyspace {
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public:
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static constexpr auto NAME = "system_distributed";
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static constexpr auto VIEW_BUILD_STATUS = "view_build_status";
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/* Nodes use this table to communicate new CDC stream generations to other nodes. */
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static constexpr auto CDC_TOPOLOGY_DESCRIPTION = "cdc_generation_descriptions";
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/* This table is used by CDC clients to learn about available CDC streams. */
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static constexpr auto CDC_DESC_V2 = "cdc_streams_descriptions_v2";
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/* Used by CDC clients to learn CDC generation timestamps. */
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static constexpr auto CDC_TIMESTAMPS = "cdc_generation_timestamps";
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/* Previous version of the "cdc_streams_descriptions_v2" table.
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* We use it in the upgrade procedure to ensure that CDC generations appearing
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* in the old table also appear in the new table, if necessary. */
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static constexpr auto CDC_DESC_V1 = "cdc_streams_descriptions";
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/* Information required to modify/query some system_distributed tables, passed from the caller. */
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struct context {
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/* How many different token owners (endpoints) are there in the token ring? */
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size_t num_token_owners;
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};
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private:
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cql3::query_processor& _qp;
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service::migration_manager& _mm;
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service::storage_proxy& _sp;
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bool _started = false;
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bool _forced_cdc_timestamps_schema_sync = false;
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public:
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/* Should writes to the given table always be synchronized by commitlog (flushed to disk)
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* before being acknowledged? */
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static bool is_extra_durable(const sstring& cf_name);
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system_distributed_keyspace(cql3::query_processor&, service::migration_manager&, service::storage_proxy&);
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future<> start();
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future<> stop();
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bool started() const { return _started; }
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future<std::unordered_map<utils::UUID, sstring>> view_status(sstring ks_name, sstring view_name) const;
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future<> start_view_build(sstring ks_name, sstring view_name) const;
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future<> finish_view_build(sstring ks_name, sstring view_name) const;
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future<> remove_view(sstring ks_name, sstring view_name) const;
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future<> insert_cdc_topology_description(cdc::generation_id, const cdc::topology_description&, context);
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future<std::optional<cdc::topology_description>> read_cdc_topology_description(cdc::generation_id, context);
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future<> create_cdc_desc(db_clock::time_point, const cdc::topology_description&, context);
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future<bool> cdc_desc_exists(db_clock::time_point, context);
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/* Get all generation timestamps appearing in the "cdc_streams_descriptions" table
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* (the old CDC stream description table). */
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future<std::vector<db_clock::time_point>> get_cdc_desc_v1_timestamps(context);
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future<std::map<db_clock::time_point, cdc::streams_version>> cdc_get_versioned_streams(db_clock::time_point not_older_than, context);
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future<db_clock::time_point> cdc_current_generation_timestamp(context);
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};
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}
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