fcb8d040e8
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
85 lines
3.5 KiB
C++
85 lines
3.5 KiB
C++
/*
|
|
* Copyright (C) 2019-present ScyllaDB
|
|
*/
|
|
|
|
/*
|
|
* SPDX-License-Identifier: AGPL-3.0-or-later
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <map>
|
|
|
|
#include "db_clock.hh"
|
|
#include "timestamp.hh"
|
|
#include "cdc/generation.hh"
|
|
|
|
namespace dht {
|
|
class token;
|
|
}
|
|
|
|
namespace cdc {
|
|
|
|
class stream_id;
|
|
class topology_description;
|
|
|
|
/* Represents the node's knowledge about CDC generations used in the cluster.
|
|
* Used during writes to pick streams to which CDC log writes should be sent to
|
|
* (i.e., to pick partition keys for these writes).
|
|
*/
|
|
class metadata final {
|
|
// Note: we use db_clock (1ms resolution) for generation timestaps
|
|
// (because we need to insert them into tables using columns of timestamp types,
|
|
// and the native type of our columns' timestamp_type is db_clock::time_point).
|
|
// On the other hand, timestamp_clock (1us resolution) is used for mutation timestamps,
|
|
// and api::timestamp_type represents the number of ticks of a timestamp_clock::time_point since epoch.
|
|
|
|
using container_t = std::map<api::timestamp_type, std::optional<topology_description>>;
|
|
container_t _gens;
|
|
|
|
/* The timestamp used in the last successful `get_stream` call. */
|
|
api::timestamp_type _last_stream_timestamp = api::missing_timestamp;
|
|
|
|
container_t::const_iterator gen_used_at(api::timestamp_type ts) const;
|
|
public:
|
|
/* Is a generation with the given timestamp already known or superseded by a newer generation? */
|
|
bool known_or_obsolete(db_clock::time_point) const;
|
|
|
|
/* Are there streams available. I.e. valid for time == now. If this is false, any writes to
|
|
* CDC logs will fail fast.
|
|
*/
|
|
bool streams_available() const;
|
|
/* Return the stream for the base partition whose token is `tok` to which a corresponding log write should go
|
|
* according to the generation used at time `ts` (i.e, the latest generation whose timestamp is less or equal to `ts`).
|
|
*
|
|
* If the provided timestamp is too far away "into the future" (where "now" is defined according to our local clock),
|
|
* we reject the get_stream query. This is because the resulting stream might belong to a generation which we don't
|
|
* yet know about. The amount of leeway (how much "into the future" we allow `ts` to be) is defined
|
|
* by the `cdc::generation_leeway` constant.
|
|
*/
|
|
stream_id get_stream(api::timestamp_type ts, dht::token tok);
|
|
|
|
/* Insert the generation given by `gen` with timestamp `ts` to be used by the `get_stream` function,
|
|
* if the generation is not already known or older than the currently known ones.
|
|
*
|
|
* Returns true if the generation was inserted,
|
|
* meaning that `get_stream` might return a stream from this generation (at some time points).
|
|
*/
|
|
bool insert(db_clock::time_point ts, topology_description&& gen);
|
|
|
|
/* Prepare for inserting a new generation whose timestamp is `ts`.
|
|
* This method is not required to be called before `insert`, but it's here
|
|
* to increase safety of `get_stream` calls in some situations. Use it if you:
|
|
* 1. know that there is a new generation, but
|
|
* 2. you didn't yet retrieve the generation's topology_description.
|
|
*
|
|
* After preparing a generation, if `get_stream` is supposed to return a stream from this generation
|
|
* but we don't yet have the generation's data, it will reject the query to maintain consistency of streams.
|
|
*
|
|
* Returns true iff this generation is not obsolete and wasn't previously prepared nor inserted.
|
|
*/
|
|
bool prepare(db_clock::time_point ts);
|
|
};
|
|
|
|
} // namespace cdc
|