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50cfe81331
Since token representation is fixed now, all the partitioners will share the sharding logic. It makes sense now to keep the logic in common super class and separate header that's included only in i_partitioner.cc. shard_of and token_for_next_shard are now implemented in i_partitioner. They would be non-virtual but we have to keep them virtual because one test is overriding them to enforce some specific sharding. Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
93 lines
3.9 KiB
C++
93 lines
3.9 KiB
C++
/*
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* Copyright (C) 2019 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 <map>
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#include "db_clock.hh"
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#include "timestamp.hh"
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namespace dht {
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class token;
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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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/* Represents the node's knowledge about CDC generations used in the cluster.
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* Used during writes to pick streams to which CDC log writes should be sent to
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* (i.e., to pick partition keys for these writes).
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*/
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class metadata final {
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// Note: we use db_clock (1ms resolution) for generation timestaps
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// (because we need to insert them into tables using columns of timestamp types,
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// and the native type of our columns' timestamp_type is db_clock::time_point).
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// On the other hand, timestamp_clock (1us resolution) is used for mutation timestamps,
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// and api::timestamp_type represents the number of ticks of a timestamp_clock::time_point since epoch.
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using container_t = std::map<api::timestamp_type, std::optional<topology_description>>;
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container_t _gens;
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/* The timestamp used in the last successful `get_stream` call. */
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api::timestamp_type _last_stream_timestamp = api::missing_timestamp;
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container_t::const_iterator gen_used_at(api::timestamp_type ts) const;
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public:
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/* Is a generation with the given timestamp already known or superseded by a newer generation? */
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bool known_or_obsolete(db_clock::time_point) const;
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/* Return the stream for the base partition whose token is `tok` to which a corresponding log write should go
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* according to the generation used at time `ts` (i.e, the latest generation whose timestamp is less or equal to `ts`).
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*
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* If the provided timestamp is too far away "into the future" (where "now" is defined according to our local clock),
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* we reject the get_stream query. This is because the resulting stream might belong to a generation which we don't
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* yet know about. The amount of leeway (how much "into the future" we allow `ts` to be) is defined
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* by the `cdc::generation_leeway` constant.
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*/
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stream_id get_stream(api::timestamp_type ts, dht::token tok);
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/* Insert the generation given by `gen` with timestamp `ts` to be used by the `get_stream` function,
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* if the generation is not already known or older than the currently known ones.
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*
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* Returns true if the generation was inserted,
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* meaning that `get_stream` might return a stream from this generation (at some time points).
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*/
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bool insert(db_clock::time_point ts, topology_description&& gen);
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/* Prepare for inserting a new generation whose timestamp is `ts`.
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* This method is not required to be called before `insert`, but it's here
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* to increase safety of `get_stream` calls in some situations. Use it if you:
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* 1. know that there is a new generation, but
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* 2. you didn't yet retrieve the generation's topology_description.
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*
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* After preparing a generation, if `get_stream` is supposed to return a stream from this generation
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* but we don't yet have the generation's data, it will reject the query to maintain consistency of streams.
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*
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* Returns true iff this generation is not obsolete and wasn't previously prepared nor inserted.
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*/
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bool prepare(db_clock::time_point ts);
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};
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} // namespace cdc
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