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4b6937b570
DynamoDB Streams API can only convey a single parent per stream shard. Tablet merges produce 2 parents, which is incompatible. When streams are requested on a tablet table, block tablet merges via tablet_merge_blocked (the allocator suppresses new merge decisions and revokes any active merge decision). add_stream_options() sets tablet_merge_blocked=true alongside enabled=true, so CreateTable needs no special handling — the flag is inert on vnode tables and immediately effective on tablet tables. For UpdateTable, CDC enablement is deferred: store the user's intent via enable_requested, and let the topology coordinator finalize enablement once no in-progress merges remain. A new helper, defer_enabling_streams_block_tablet_merges(), amends the CDC options to this deferred state. Disabling streams clears all flags, immediately re-allowing merges. The tablet allocator accesses the merge-blocked flag through a schema::tablet_merges_forbidden() accessor rather than reaching into CDC options directly. Mark test_parent_children_merge as xfail and remove downward (merge) steps from tablet_multipliers in test_parent_filtering and test_get_records_with_alternating_tablets_count.
98 lines
3.7 KiB
C++
98 lines
3.7 KiB
C++
/*
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* Copyright (C) 2019-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
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*/
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#pragma once
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#include <map>
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#include <optional>
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#include <seastar/core/sstring.hh>
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#include "seastarx.hh"
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namespace cdc {
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enum class delta_mode : uint8_t {
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keys,
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full,
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};
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/**
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* (for now only pre-) image collection mode.
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* Stating how much info to record.
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* off == none
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* on == changed columns
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* full == all (changed and unmodified columns)
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*/
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enum class image_mode : uint8_t {
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off,
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on,
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full,
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};
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class options final {
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std::optional<bool> _enabled;
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bool _enable_requested = false;
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// When CDC is employed for the purpose of Alternator Streams and tablets are used,
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// tablet merges need to be blocked due to limitations of DynamoDB Streams API.
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// DynamoDB Streams allows to specify a single parent for a stream.
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// In ScyllaDB, there is a one-to-one association between streams and tablets,
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// so merging tablets means also merging streams. A merged stream has two parents and both
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// need to be done reading from before reading from the newly merged tablet. This is impossible
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// to be conveyed with DynamoDB Streams API and the result can be reordering of events in Streams.
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bool _tablet_merge_blocked = false;
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image_mode _preimage = image_mode::off;
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bool _postimage = false;
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delta_mode _delta_mode = delta_mode::full;
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int _ttl = 86400; // 24h in seconds
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public:
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options() = default;
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options(const std::map<sstring, sstring>& map);
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std::map<sstring, sstring> to_map() const;
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sstring to_sstring() const;
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bool enabled() const { return _enabled.value_or(false); }
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bool is_enabled_set() const { return _enabled.has_value(); }
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bool enable_requested() const { return _enable_requested; }
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bool tablet_merge_blocked() const { return _tablet_merge_blocked; }
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bool preimage() const { return _preimage != image_mode::off; }
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bool full_preimage() const { return _preimage == image_mode::full; }
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bool postimage() const { return _postimage; }
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delta_mode get_delta_mode() const { return _delta_mode; }
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void set_delta_mode(delta_mode m) { _delta_mode = m; }
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int ttl() const { return _ttl; }
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void enabled(bool b) { _enabled = b; }
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// For the cases when enabling cannot be immediately enforced, like with Alternator Streams
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// which is incompatible with tablet merges, we need to be able to defer actual enablement
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// until any in-progress tablet merges complete. We expect that finalization happens
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// promptly: on_update_column_family callback in topology_coordinator.cc wakes up
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// the topology coordinator to run maybe_finalize_pending_stream_enables shortly
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// after the DDL. However, there is SCYLLADB-1304
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void enable_requested(bool b = true) { _enable_requested = b; }
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// Persistent flag checked by the tablet allocator to suppress new merge
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// decisions. Always set when Alternator Streams are enabled; inert on
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// vnode tables.
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void tablet_merge_blocked(bool b = true) { _tablet_merge_blocked = b; }
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void preimage(bool b) { preimage(b ? image_mode::on : image_mode::off); }
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void preimage(image_mode m) { _preimage = m; }
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void postimage(bool b) { _postimage = b; }
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void ttl(int v) { _ttl = v; }
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bool operator==(const options& o) const;
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};
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} // namespace cdc
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template <> struct fmt::formatter<cdc::image_mode> : fmt::formatter<string_view> {
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auto format(cdc::image_mode, fmt::format_context& ctx) const -> decltype(ctx.out());
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};
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template <> struct fmt::formatter<cdc::delta_mode> : fmt::formatter<string_view> {
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auto format(cdc::delta_mode, fmt::format_context& ctx) const -> decltype(ctx.out());
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};
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