%% This Source Code Form is subject to the terms of the Mozilla Public %% License, v. 2.0. If a copy of the MPL was not distributed with this %% file, You can obtain one at https://mozilla.org/MPL/2.0/. %% %% Copyright © 2021-2023 Broadcom. All Rights Reserved. The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries. %% %% @doc %% Khepri private low-level API. %% %% This module exposes the private "low-level" API to the Khepri database and %% state machine. Main functions correspond to Ra commands implemented by the %% state machine. All functions in {@link khepri} are built on top of this %% module. %% %% This module is private. The documentation is still visible because it may %% help understand some implementation details. However, this module should %% never be called directly outside of Khepri. -module(khepri_machine). -behaviour(ra_machine). -include_lib("kernel/include/logger.hrl"). -include_lib("stdlib/include/assert.hrl"). -include_lib("horus/include/horus.hrl"). -include("include/khepri.hrl"). -include("src/khepri_cluster.hrl"). -include("src/khepri_error.hrl"). -include("src/khepri_evf.hrl"). -include("src/khepri_machine.hrl"). -include("src/khepri_ret.hrl"). -include("src/khepri_tx.hrl"). -include("src/khepri_projection.hrl"). -export([fold/5, put/4, delete/3, transaction/5, register_trigger/5, register_projection/4, unregister_projection/3]). -export([get_keep_while_conds_state/2, get_projections_state/2]). %% ra_machine callbacks. -export([init/1, init_aux/1, handle_aux/6, apply/3, state_enter/2, overview/1, version/0]). %% For internal use only. -export([clear_cache/1, ack_triggers_execution/2, split_query_options/1, split_command_options/1, split_put_options/1, insert_or_update_node/5, delete_matching_nodes/3, handle_tx_exception/1, process_query/3, process_command/3]). -ifdef(TEST). -export([get_tree/1, get_root/1, get_keep_while_conds/1, get_keep_while_conds_revidx/1, get_last_consistent_call_atomics/1]). -endif. -compile({no_auto_import, [apply/3]}). -type props() :: #{payload_version := khepri:payload_version(), child_list_version := khepri:child_list_version()}. %% Properties attached to each node in the tree structure. -type triggered() :: #triggered{}. -type command() :: #put{} | #delete{} | #tx{} | #register_trigger{} | #ack_triggered{} | #register_projection{} | #unregister_projection{}. %% Commands specific to this Ra machine. -type machine_init_args() :: #{store_id := khepri:store_id(), member := ra:server_id(), snapshot_interval => non_neg_integer(), commands => [command()], atom() => any()}. %% Structure passed to {@link init/1}. -type machine_config() :: #config{}. %% Configuration record, holding read-only or rarely changing fields. -type state() :: #?MODULE{}. %% State of this Ra state machine. -type aux_state() :: #khepri_machine_aux{}. %% Auxiliary state of this Ra state machine. -type query_fun() :: fun((state()) -> any()). %% Function representing a query and used {@link process_query/3}. -type common_ret() :: khepri:ok(khepri_adv:node_props_map()) | khepri:error(). -type tx_ret() :: khepri:ok(khepri_tx:tx_fun_result()) | khepri_tx:tx_abort() | no_return(). -type async_ret() :: ok. -type projection_tree() :: khepri_pattern_tree:tree( khepri_projection:projection()). %% A pattern tree that holds all registered projections in the machine's state. -export_type([common_ret/0, tx_ret/0, async_ret/0, state/0, machine_config/0, props/0, triggered/0, projection_tree/0]). -define(HAS_TIME_LEFT(Timeout), (Timeout =:= infinity orelse Timeout > 0)). -define(PROJECTION_PROPS_TO_RETURN, [payload_version, child_list_version, child_list_length, child_names, payload]). %% ------------------------------------------------------------------- %% Machine protocol. %% ------------------------------------------------------------------- %% TODO: Verify arguments carefully to avoid the construction of an invalid %% command. -spec fold(StoreId, PathPattern, Fun, Acc, Options) -> Ret when StoreId :: khepri:store_id(), PathPattern :: khepri_path:pattern(), Fun :: khepri:fold_fun(), Acc :: khepri:fold_acc(), Options :: khepri:query_options() | khepri:tree_options(), Ret :: khepri:ok(NewAcc) | khepri:error(), NewAcc :: Acc. %% @doc Returns all tree nodes matching the given path pattern. %% %% @param StoreId the name of the Ra cluster. %% @param PathPattern the path (or path pattern) to the nodes to get. %% @param Options query options such as `favor'. %% %% @returns an `{ok, NodePropsMap}' tuple with a map with zero, one or more %% entries, or an `{error, Reason}' tuple. fold(StoreId, PathPattern, Fun, Acc, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_function(Fun, 3) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), {QueryOptions, TreeOptions} = split_query_options(Options), Query = fun(#?MODULE{tree = Tree}) -> try khepri_tree:fold( Tree, PathPattern1, Fun, Acc, TreeOptions) catch Class:Reason:Stacktrace -> {exception, Class, Reason, Stacktrace} end end, case process_query(StoreId, Query, QueryOptions) of {exception, _, _, _} = Exception -> handle_tx_exception(Exception); Ret -> Ret end. -spec put(StoreId, PathPattern, Payload, Options) -> Ret when StoreId :: khepri:store_id(), PathPattern :: khepri_path:pattern(), Payload :: khepri_payload:payload(), Options :: khepri:command_options() | khepri:tree_options() | khepri:put_options(), Ret :: khepri_machine:common_ret() | khepri_machine:async_ret(). %% @doc Creates or modifies a specific tree node in the tree structure. %% %% @param StoreId the name of the Ra cluster. %% @param PathPattern the path (or path pattern) to the node to create or %% modify. %% @param Payload the payload to put in the specified node. %% @param Options command, tree and put options. %% %% @returns in the case of a synchronous put, an `{ok, NodePropsMap}' tuple %% with a map with zero, one or more entries, or an `{error, Reason}' tuple; %% in the case of an asynchronous put, always `ok' (the actual return value %% may be sent by a message if a correlation ID was specified). %% %% @private put(StoreId, PathPattern, Payload, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso ?IS_KHEPRI_PAYLOAD(Payload) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), Payload1 = khepri_payload:prepare(Payload), {CommandOptions, TreeAndPutOptions} = split_command_options(Options), Command = #put{path = PathPattern1, payload = Payload1, options = TreeAndPutOptions}, process_command(StoreId, Command, CommandOptions); put(_StoreId, PathPattern, Payload, _Options) -> ?khepri_misuse(invalid_payload, #{path => PathPattern, payload => Payload}). -spec delete(StoreId, PathPattern, Options) -> Ret when StoreId :: khepri:store_id(), PathPattern :: khepri_path:pattern(), Options :: khepri:command_options() | khepri:tree_options(), Ret :: khepri_machine:common_ret() | khepri_machine:async_ret(). %% @doc Deletes all tree nodes matching the path pattern. %% %% @param StoreId the name of the Ra cluster. %% @param PathPattern the path (or path pattern) to the nodes to delete. %% @param Options command options such as the command type. %% %% @returns in the case of a synchronous delete, an `{ok, NodePropsMap}' tuple %% with a map with zero, one or more entries, or an `{error, Reason}' tuple; %% in the case of an asynchronous put, always `ok' (the actual return value %% may be sent by a message if a correlation ID was specified). delete(StoreId, PathPattern, Options) when ?IS_KHEPRI_STORE_ID(StoreId) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), {CommandOptions, TreeOptions} = split_command_options(Options), %% TODO: Ensure `PutOptions' are not set this map. Command = #delete{path = PathPattern1, options = TreeOptions}, process_command(StoreId, Command, CommandOptions). -spec transaction(StoreId, FunOrPath, Args, ReadWrite, Options) -> Ret when StoreId :: khepri:store_id(), FunOrPath :: Fun | PathPattern, Fun :: khepri_tx:tx_fun(), PathPattern :: khepri_path:pattern(), Args :: list(), ReadWrite :: ro | rw | auto, Options :: khepri:command_options() | khepri:query_options(), Ret :: khepri_machine:tx_ret() | khepri_machine:async_ret(). %% @doc Runs a transaction and returns the result. %% %% @param StoreId the name of the Ra cluster. %% @param FunOrPath an arbitrary anonymous function or a path pattern pointing %% to a stored procedure. %% @param Args a list of arguments to pass to `FunOrPath'. %% @param ReadWrite the read/write or read-only nature of the transaction. %% @param Options command options such as the command type. %% %% @returns in the case of a synchronous transaction, `{ok, Result}' where %% `Result' is the return value of `FunOrPath', or `{error, Reason}' if the %% anonymous function was aborted; in the case of an asynchronous transaction, %% always `ok' (the actual return value may be sent by a message if a %% correlation ID was specified). transaction(StoreId, Fun, Args, auto = ReadWrite, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_list(Args) andalso is_function(Fun, length(Args)) andalso is_map(Options) -> case khepri_tx_adv:to_standalone_fun(Fun, ReadWrite) of StandaloneFun when ?IS_HORUS_STANDALONE_FUN(StandaloneFun) -> readwrite_transaction(StoreId, StandaloneFun, Args, Options); _ -> readonly_transaction(StoreId, Fun, Args, Options) end; transaction(StoreId, PathPattern, Args, auto, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso ?IS_KHEPRI_PATH_PATTERN(PathPattern) andalso is_list(Args) andalso is_map(Options) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), readwrite_transaction(StoreId, PathPattern1, Args, Options); transaction(StoreId, Fun, Args, rw = ReadWrite, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_list(Args) andalso is_function(Fun, length(Args)) andalso is_map(Options) -> StandaloneFun = khepri_tx_adv:to_standalone_fun(Fun, ReadWrite), readwrite_transaction(StoreId, StandaloneFun, Args, Options); transaction(StoreId, PathPattern, Args, rw, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso ?IS_KHEPRI_PATH_PATTERN(PathPattern) andalso is_list(Args) andalso is_map(Options) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), readwrite_transaction(StoreId, PathPattern1, Args, Options); transaction(StoreId, Fun, Args, ro, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_list(Args) andalso is_function(Fun, length(Args)) andalso is_map(Options) -> readonly_transaction(StoreId, Fun, Args, Options); transaction(StoreId, PathPattern, Args, ro, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso ?IS_KHEPRI_PATH_PATTERN(PathPattern) andalso is_list(Args) andalso is_map(Options) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), readonly_transaction(StoreId, PathPattern1, Args, Options); transaction(StoreId, Fun, Args, ReadWrite, Options) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_function(Fun) andalso is_list(Args) andalso is_atom(ReadWrite) andalso is_map(Options) -> {arity, Arity} = erlang:fun_info(Fun, arity), ?khepri_misuse( denied_tx_fun_with_invalid_args, #{'fun' => Fun, arity => Arity, args => Args}). -spec readonly_transaction(StoreId, FunOrPath, Args, Options) -> Ret when StoreId :: khepri:store_id(), FunOrPath :: Fun | PathPattern, Fun :: khepri_tx:tx_fun(), PathPattern :: khepri_path:pattern(), Args :: list(), Options :: khepri:query_options(), Ret :: khepri_machine:tx_ret(). readonly_transaction(StoreId, Fun, Args, Options) when is_list(Args) andalso is_function(Fun, length(Args)) -> Query = fun(State) -> %% It is a read-only transaction, therefore we assert that %% the state is unchanged and that there are no side %% effects. {State, Ret, []} = khepri_tx_adv:run( State, Fun, Args, false), Ret end, case process_query(StoreId, Query, Options) of {exception, _, _, _} = Exception -> handle_tx_exception(Exception); Ret -> {ok, Ret} end; readonly_transaction(StoreId, PathPattern, Args, Options) when ?IS_KHEPRI_PATH_PATTERN(PathPattern) andalso is_list(Args) -> Query = fun(State) -> %% It is a read-only transaction, therefore we assert that %% the state is unchanged and that there are no side %% effects. {State, Ret, []} = locate_sproc_and_execute_tx( State, PathPattern, Args, false), Ret end, case process_query(StoreId, Query, Options) of {exception, _, _, _} = Exception -> handle_tx_exception(Exception); Ret -> {ok, Ret} end. -spec readwrite_transaction(StoreId, FunOrPath, Args, Options) -> Ret when StoreId :: khepri:store_id(), FunOrPath :: Fun | PathPattern, Fun :: horus:horus_fun(), PathPattern :: khepri_path:pattern(), Args :: list(), Options :: khepri:command_options(), Ret :: khepri_machine:tx_ret() | khepri_machine:async_ret(). readwrite_transaction( StoreId, Fun, Args, Options) when is_list(Args) andalso (is_function(Fun, length(Args)) orelse ?IS_HORUS_STANDALONE_FUN(Fun, length(Args))) -> readwrite_transaction1(StoreId, Fun, Args, Options); readwrite_transaction( StoreId, PathPattern, Args, Options) when ?IS_KHEPRI_PATH_PATTERN(PathPattern) andalso is_list(Args) -> PathPattern1 = khepri_path:from_string(PathPattern), khepri_path:ensure_is_valid(PathPattern1), readwrite_transaction1(StoreId, PathPattern1, Args, Options). readwrite_transaction1(StoreId, StandaloneFunOrPath, Args, Options) -> Command = #tx{'fun' = StandaloneFunOrPath, args = Args}, case process_command(StoreId, Command, Options) of {exception, _, _, _} = Exception -> handle_tx_exception(Exception); ok = Ret -> CommandType = select_command_type(Options), case CommandType of sync -> {ok, Ret}; {async, _, _} -> Ret end; Ret -> {ok, Ret} end. handle_tx_exception( {exception, _, ?TX_ABORT(Reason), _}) -> {error, Reason}; handle_tx_exception( {exception, error, ?khepri_exception(_, _) = Reason, _Stacktrace}) -> %% If the exception is a programming misuse of Khepri, we %% re-throw a new exception instead of using `erlang:raise()'. %% %% The reason is that the default stacktrace is limited to 8 frames by %% default (see `erlang:system_flag(backtrace_depth, Depth)' to reconfigure %% it). Most if not all of those 8 frames might be taken by Khepri's %% internal calls, making the stacktrace uninformative to the caller. %% %% By throwing a new exception, we increase the chance that there %% is a frame pointing to the transaction function. ?khepri_misuse(Reason); handle_tx_exception( {exception, Class, Reason, Stacktrace}) -> erlang:raise(Class, Reason, Stacktrace). -spec register_trigger( StoreId, TriggerId, EventFilter, StoredProcPath, Options) -> Ret when StoreId :: khepri:store_id(), TriggerId :: khepri:trigger_id(), EventFilter :: khepri_evf:event_filter() | khepri_path:pattern(), StoredProcPath :: khepri_path:path(), Options :: khepri:command_options(), Ret :: ok | khepri:error(). %% @doc Registers a trigger. %% %% @param StoreId the name of the Ra cluster. %% @param TriggerId the name of the trigger. %% @param EventFilter the event filter used to associate an event with a %% stored procedure. %% @param StoredProcPath the path to the stored procedure to execute when the %% corresponding event occurs. %% %% @returns `ok' if the trigger was registered, an `{error, Reason}' tuple %% otherwise. register_trigger(StoreId, TriggerId, EventFilter, StoredProcPath, Options) when ?IS_KHEPRI_STORE_ID(StoreId) -> EventFilter1 = khepri_evf:wrap(EventFilter), StoredProcPath1 = khepri_path:from_string(StoredProcPath), khepri_path:ensure_is_valid(StoredProcPath1), Command = #register_trigger{id = TriggerId, sproc = StoredProcPath1, event_filter = EventFilter1}, process_command(StoreId, Command, Options). -spec register_projection(StoreId, PathPattern, Projection, Options) -> Ret when StoreId :: khepri:store_id(), PathPattern :: khepri_path:pattern(), Projection :: khepri_projection:projection(), Options :: khepri:command_options(), Ret :: ok | khepri:error(). %% @doc Registers a projection. %% %% @param StoreId the name of the Ra cluster. %% @param PathPattern the pattern of tree nodes which should be projected. %% @param Projection the projection record created with {@link %% khepri_projection:new/3}. %% @param Options command options such as the command type. %% %% @returns `ok' if the projection was registered, an `{error, Reason}' tuple %% otherwise. register_projection( StoreId, PathPattern0, #khepri_projection{name = Name, projection_fun = ProjectionFun, ets_options = EtsOptions} = Projection, Options0) when is_atom(Name) andalso is_list(EtsOptions) andalso (?IS_HORUS_STANDALONE_FUN(ProjectionFun) orelse ProjectionFun =:= copy) -> Options = Options0#{reply_from => local}, PathPattern = khepri_path:from_string(PathPattern0), khepri_path:ensure_is_valid(PathPattern), Command = #register_projection{pattern = PathPattern, projection = Projection}, process_command(StoreId, Command, Options). -spec unregister_projection(StoreId, ProjectionName, Options) -> Ret when StoreId :: khepri:store_id(), ProjectionName :: atom(), Options :: khepri:command_options(), Ret :: ok | khepri:error(). %% @doc Unregisters a projection by name. %% %% @param StoreId the name of the Ra cluster. %% @param ProjectionName the name of the projection to unregister. %% @param Options command options such as the command type. %% %% @returns `ok' if the projection existed and was unregistered, an `{error, %% Reason}' tuple otherwise. unregister_projection(StoreId, ProjectionName, Options0) when ?IS_KHEPRI_STORE_ID(StoreId) andalso is_atom(ProjectionName) -> Options = Options0#{reply_from => local}, Command = #unregister_projection{name = ProjectionName}, process_command(StoreId, Command, Options). -spec ack_triggers_execution(StoreId, TriggeredStoredProcs) -> Ret when StoreId :: khepri:store_id(), TriggeredStoredProcs :: [triggered()], Ret :: ok | khepri:error(). %% @doc Acknowledges the execution of a trigger. %% %% This is part of a mechanism to ensure that a trigger is executed at least %% once. %% %% @private ack_triggers_execution(StoreId, TriggeredStoredProcs) when ?IS_KHEPRI_STORE_ID(StoreId) -> Command = #ack_triggered{triggered = TriggeredStoredProcs}, process_command(StoreId, Command, #{async => true}). -spec get_keep_while_conds_state(StoreId, Options) -> Ret when StoreId :: khepri:store_id(), Options :: khepri:query_options(), Ret :: khepri:ok(khepri_tree:keep_while_conds_map()) | khepri:error(). %% @doc Returns the `keep_while' conditions internal state. %% %% The returned state consists of all the `keep_while' condition set so far. %% However, it doesn't include the reverse index. %% %% @param StoreId the name of the Ra cluster. %% %% @returns the `keep_while' conditions internal state. %% %% @private get_keep_while_conds_state(StoreId, Options) when ?IS_KHEPRI_STORE_ID(StoreId) -> Query = fun(#?MODULE{tree = #tree{keep_while_conds = KeepWhileConds}}) -> {ok, KeepWhileConds} end, process_query(StoreId, Query, Options). -spec get_projections_state(StoreId, Options) -> Ret when StoreId :: khepri:store_id(), Options :: khepri:query_options(), Ret :: khepri:ok(ProjectionState) | khepri:error(), ProjectionState :: khepri_pattern_tree:tree(Projection), Projection :: khepri_projection:projection(). %% @doc Returns the `projections' internal state. %% %% The returned state is a pattern tree containing the projections registered %% in the store. (See {@link khepri_pattern_tree:tree()} and {@link %% khepri_projection:projection()}.) %% %% @see khepri_pattern_tree. %% @see khepri_projection. %% %% @private get_projections_state(StoreId, Options) when ?IS_KHEPRI_STORE_ID(StoreId) -> Query = fun(#?MODULE{projections = Projections}) -> {ok, Projections} end, process_query(StoreId, Query, Options). -spec split_query_options(Options) -> {QueryOptions, TreeOptions} when Options :: QueryOptions | TreeOptions, QueryOptions :: khepri:query_options(), TreeOptions :: khepri:tree_options(). %% @private split_query_options(Options) -> Options1 = set_default_options(Options), maps:fold( fun (Option, Value, {Q, T}) when Option =:= timeout orelse Option =:= favor -> Q1 = Q#{Option => Value}, {Q1, T}; (props_to_return, [], {Q, T}) -> {Q, T}; (Option, Value, {Q, T}) when Option =:= expect_specific_node orelse Option =:= props_to_return orelse Option =:= include_root_props -> T1 = T#{Option => Value}, {Q, T1} end, {#{}, #{}}, Options1). -spec split_command_options(Options) -> {CommandOptions, TreeAndPutOptions} when Options :: CommandOptions | TreeAndPutOptions, CommandOptions :: khepri:command_options(), TreeAndPutOptions :: khepri:tree_options() | khepri:put_options(). %% @private split_command_options(Options) -> Options1 = set_default_options(Options), maps:fold( fun (Option, Value, {C, TP}) when Option =:= reply_from orelse Option =:= timeout orelse Option =:= async -> C1 = C#{Option => Value}, {C1, TP}; (props_to_return, [], Acc) -> Acc; (Option, Value, {C, TP}) when Option =:= expect_specific_node orelse Option =:= props_to_return orelse Option =:= include_root_props -> TP1 = TP#{Option => Value}, {C, TP1}; (keep_while, KeepWhile, {C, TP}) -> %% `keep_while' is kept in `TreeAndPutOptions' here. The state %% machine will extract it in `apply()'. KeepWhile1 = khepri_condition:ensure_native_keep_while( KeepWhile), TP1 = TP#{keep_while => KeepWhile1}, {C, TP1} end, {#{}, #{}}, Options1). -spec split_put_options(TreeAndPutOptions) -> {TreeOptions, PutOptions} when TreeAndPutOptions :: TreeOptions | PutOptions, TreeOptions :: khepri:tree_options(), PutOptions :: khepri:put_options(). %% @private split_put_options(TreeAndPutOptions) -> maps:fold( fun (keep_while, KeepWhile, {T, P}) -> P1 = P#{keep_while => KeepWhile}, {T, P1}; (Option, Value, {T, P}) -> T1 = T#{Option => Value}, {T1, P} end, {#{}, #{}}, TreeAndPutOptions). set_default_options(Options) -> %% By default, return payload-related properties. The caller can set %% `props_to_return' to an empty map to get a minimal return value. Options1 = case Options of #{props_to_return := _} -> Options; _ -> Options#{props_to_return => ?DEFAULT_PROPS_TO_RETURN} end, Options1. -spec process_command(StoreId, Command, Options) -> Ret when StoreId :: khepri:store_id(), Command :: command(), Options :: khepri:command_options(), Ret :: any(). %% @doc Processes a command which is appended to the Ra log and processed by %% this state machine code. %% %% `Command' may modify the state of the machine. %% %% The command associated code is executed in the context of the state machine %% process on each Ra members. %% %% @param StoreId the name of the Ra cluster. %% %% @returns the result of the command or an "error" tuple. %% %% @private process_command(StoreId, Command, Options) -> CommandType = select_command_type(Options), case CommandType of sync -> process_sync_command(StoreId, Command, Options); {async, Correlation, Priority} -> process_async_command( StoreId, Command, Correlation, Priority) end. process_sync_command(StoreId, Command, Options) -> Timeout = get_timeout(Options), ReplyFrom = maps:get(reply_from, Options, leader), CommandOptions = #{timeout => Timeout, reply_from => ReplyFrom}, T0 = khepri_utils:start_timeout_window(Timeout), LeaderId = khepri_cluster:get_cached_leader(StoreId), RaServer = use_leader_or_local_ra_server(StoreId, LeaderId), case ra:process_command(RaServer, Command, CommandOptions) of {ok, Ret, NewLeaderId} -> khepri_cluster:cache_leader_if_changed( StoreId, LeaderId, NewLeaderId), just_did_consistent_call(StoreId), ?raise_exception_if_any(Ret); {timeout, _} = TimedOut -> {error, TimedOut}; {error, Reason} when LeaderId =/= undefined andalso ?HAS_TIME_LEFT(Timeout) andalso (Reason == noproc orelse Reason == nodedown orelse Reason == shutdown) -> %% The cached leader is no more. We simply clear the cache %% entry and retry. khepri_cluster:clear_cached_leader(StoreId), NewTimeout = khepri_utils:end_timeout_window(Timeout, T0), Options1 = Options#{timeout => NewTimeout}, process_sync_command(StoreId, Command, Options1); {error, Reason} = Error when LeaderId =:= undefined andalso ?HAS_TIME_LEFT(Timeout) andalso (Reason == noproc orelse Reason == nodedown orelse Reason == shutdown) -> case khepri_utils:is_ra_server_alive(RaServer) of true -> %% The follower doesn't know about the new leader yet. %% Retry again after waiting a bit. NewTimeout0 = khepri_utils:end_timeout_window(Timeout, T0), NewTimeout = khepri_utils:sleep( ?NOPROC_RETRY_INTERVAL, NewTimeout0), Options1 = Options#{timeout => NewTimeout}, process_sync_command(StoreId, Command, Options1); false -> Error end; {error, _} = Error -> Error end. process_async_command(StoreId, Command, Correlation, Priority) -> LeaderId = khepri_cluster:get_cached_leader(StoreId), RaServer = use_leader_or_local_ra_server(StoreId, LeaderId), ra:pipeline_command(RaServer, Command, Correlation, Priority). -spec select_command_type(Options) -> CommandType when Options :: khepri:command_options(), CommandType :: sync | {async, Correlation, Priority}, Correlation :: ra_server:command_correlation(), Priority :: ra_server:command_priority(). %% @doc Selects the command type depending on what the caller wants. %% %% @private -define(DEFAULT_RA_COMMAND_CORRELATION, no_correlation). -define(DEFAULT_RA_COMMAND_PRIORITY, low). -define(IS_RA_COMMAND_CORRELATION(Correlation), (is_integer(Correlation) orelse is_reference(Correlation))). -define(IS_RA_COMMAND_PRIORITY(Priority), (Priority =:= normal orelse Priority =:= low)). select_command_type(Options) when not is_map_key(async, Options) -> sync; select_command_type(#{async := false}) -> sync; select_command_type(#{async := true}) -> {async, ?DEFAULT_RA_COMMAND_CORRELATION, ?DEFAULT_RA_COMMAND_PRIORITY}; select_command_type(#{async := Correlation}) when ?IS_RA_COMMAND_CORRELATION(Correlation) -> {async, Correlation, ?DEFAULT_RA_COMMAND_PRIORITY}; select_command_type(#{async := Priority}) when ?IS_RA_COMMAND_PRIORITY(Priority) -> {async, ?DEFAULT_RA_COMMAND_CORRELATION, Priority}; select_command_type(#{async := {Correlation, Priority}}) when ?IS_RA_COMMAND_CORRELATION(Correlation) andalso ?IS_RA_COMMAND_PRIORITY(Priority) -> {async, Correlation, Priority}. -spec process_query(StoreId, QueryFun, Options) -> Ret when StoreId :: khepri:store_id(), QueryFun :: query_fun(), Options :: khepri:query_options(), Ret :: any(). %% @doc Processes a query which is by the Ra leader. %% %% The `QueryFun' function takes the machine state as an argument and can %% return anything. However, the machine state is never modified. The query %% does not go through the Ra log and is not replicated. %% %% The `QueryFun' function is executed from a process on the leader Ra member. %% %% @param StoreId the name of the Ra cluster. %% %% @returns the result of the query or an "error" tuple. %% %% @private process_query(StoreId, QueryFun, Options) -> QueryType = select_query_type(StoreId, Options), Timeout = get_timeout(Options), case QueryType of local -> process_local_query(StoreId, QueryFun, Timeout); _ -> process_non_local_query(StoreId, QueryFun, QueryType, Timeout) end. -spec process_local_query(StoreId, QueryFun, Timeout) -> Ret when StoreId :: khepri:store_id(), QueryFun :: query_fun(), Timeout :: timeout(), Ret :: any(). process_local_query(StoreId, QueryFun, Timeout) -> LocalServerId = {StoreId, node()}, Ret = ra:local_query(LocalServerId, QueryFun, Timeout), process_query_response( StoreId, LocalServerId, false, QueryFun, local, Timeout, Ret). -spec process_non_local_query(StoreId, QueryFun, QueryType, Timeout) -> Ret when StoreId :: khepri:store_id(), QueryFun :: query_fun(), QueryType :: leader | consistent, Timeout :: timeout(), Ret :: any(). process_non_local_query(StoreId, QueryFun, QueryType, Timeout) when QueryType =:= leader orelse QueryType =:= consistent -> T0 = khepri_utils:start_timeout_window(Timeout), LeaderId = khepri_cluster:get_cached_leader(StoreId), RaServer = use_leader_or_local_ra_server(StoreId, LeaderId), Ret = case QueryType of leader -> ra:leader_query(RaServer, QueryFun, Timeout); consistent -> ra:consistent_query(RaServer, QueryFun, Timeout) end, NewTimeout = khepri_utils:end_timeout_window(Timeout, T0), %% TODO: If the consistent query times out in the context of %% `QueryType=compromise`, should we retry with a local query to %% never block the query and let the caller continue? process_query_response( StoreId, RaServer, LeaderId =/= undefined, QueryFun, QueryType, NewTimeout, Ret). -spec process_query_response( StoreId, RaServer, IsLeader, QueryFun, QueryType, Timeout, Response) -> Ret when StoreId :: khepri:store_id(), RaServer :: ra:server_id(), IsLeader :: boolean(), QueryFun :: query_fun(), QueryType :: local | leader | consistent, Timeout :: timeout(), Response :: {ok, {RaIndex, any()}, NewLeaderId} | {ok, any(), NewLeaderId} | {error, any()} | {timeout, ra:server_id()}, RaIndex :: ra:index(), NewLeaderId :: ra:server_id(), Ret :: any(). process_query_response( StoreId, RaServer, IsLeader, _QueryFun, consistent, _Timeout, {ok, Ret, NewLeaderId}) -> case IsLeader of true -> khepri_cluster:cache_leader_if_changed( StoreId, RaServer, NewLeaderId); false -> khepri_cluster:cache_leader(StoreId, NewLeaderId) end, just_did_consistent_call(StoreId), ?raise_exception_if_any(Ret); process_query_response( StoreId, RaServer, IsLeader, _QueryFun, _QueryType, _Timeout, {ok, {_RaIndex, Ret}, NewLeaderId}) -> case IsLeader of true -> khepri_cluster:cache_leader_if_changed( StoreId, RaServer, NewLeaderId); false -> khepri_cluster:cache_leader(StoreId, NewLeaderId) end, ?raise_exception_if_any(Ret); process_query_response( _StoreId, _RaServer, _IsLeader, _QueryFun, _QueryType, _Timeout, {timeout, _} = TimedOut) -> {error, TimedOut}; process_query_response( StoreId, _RaServer, true = _IsLeader, QueryFun, QueryType, Timeout, {error, Reason}) when QueryType =/= local andalso ?HAS_TIME_LEFT(Timeout) andalso (Reason == noproc orelse Reason == nodedown orelse Reason == shutdown) -> %% The cached leader is no more. We simply clear the cache %% entry and retry. It may time out eventually. khepri_cluster:clear_cached_leader(StoreId), process_non_local_query(StoreId, QueryFun, QueryType, Timeout); process_query_response( StoreId, RaServer, false = _IsLeader, QueryFun, QueryType, Timeout, {error, Reason} = Error) when QueryType =/= local andalso ?HAS_TIME_LEFT(Timeout) andalso (Reason == noproc orelse Reason == nodedown orelse Reason == shutdown) -> case khepri_utils:is_ra_server_alive(RaServer) of true -> %% The follower doesn't know about the new leader yet. Retry again %% after waiting a bit. NewTimeout = khepri_utils:sleep(?NOPROC_RETRY_INTERVAL, Timeout), process_non_local_query(StoreId, QueryFun, QueryType, NewTimeout); false -> Error end; process_query_response( _StoreId, _RaServer, _IsLeader, _QueryFun, _QueryType, _Timeout, {error, _} = Error) -> Error. -spec select_query_type(StoreId, Options) -> QueryType when StoreId :: khepri:store_id(), Options :: khepri:query_options(), QueryType :: local | leader | consistent. %% @doc Selects the query type depending on what the caller favors. %% %% @private select_query_type(StoreId, #{favor := Favor}) -> do_select_query_type(StoreId, Favor); select_query_type(StoreId, _Options) -> do_select_query_type(StoreId, compromise). -define( LAST_CONSISTENT_CALL_TS_REF(StoreId), {khepri, last_consistent_call_ts_ref, StoreId}). do_select_query_type(StoreId, compromise) -> Key = ?LAST_CONSISTENT_CALL_TS_REF(StoreId), Idx = 1, case persistent_term:get(Key, undefined) of AtomicsRef when AtomicsRef =/= undefined -> %% We verify when was the last time we did a command or a %% consistent query (i.e. we made sure there was an active leader %% in a cluster with a quorum of active members). %% %% If the last one was more than 10 seconds ago, we force a %% consistent query to verify the cluster health at the same time. %% Otherwise, we select a leader query which is a good balance %% between freshness and latency. Last = atomics:get(AtomicsRef, Idx), Now = erlang:monotonic_time(), Elapsed = erlang:convert_time_unit(Now - Last, native, second), ConsistentAgainAfter = application:get_env( khepri, consistent_query_interval_in_compromise, 10), if Elapsed < ConsistentAgainAfter -> leader; true -> consistent end; undefined -> consistent end; do_select_query_type(_StoreId, consistency) -> consistent; do_select_query_type(_StoreId, low_latency) -> local. just_did_consistent_call(StoreId) -> %% We record the timestamp of the successful command or consistent query %% which just returned. This timestamp is used in the `compromise' query %% strategy to perform a consistent query from time to time, and leader %% queries the rest of the time. %% %% We store the system time as seconds in an `atomics' structure. The %% reference of that structure is stored in a persistent term. We don't %% store the timestamp directly in a persistent term because it is not %% suited for frequent writes. This way, we store the `atomics' reference %% once and update the `atomics' afterwards. Idx = 1, AtomicsRef = case get_last_consistent_call_atomics(StoreId) of Ref when Ref =/= undefined -> Ref; undefined -> Key = ?LAST_CONSISTENT_CALL_TS_REF(StoreId), Ref = atomics:new(1, []), persistent_term:put(Key, Ref), Ref end, Now = erlang:monotonic_time(), ok = atomics:put(AtomicsRef, Idx, Now), ok. get_last_consistent_call_atomics(StoreId) -> Key = ?LAST_CONSISTENT_CALL_TS_REF(StoreId), persistent_term:get(Key, undefined). -spec get_timeout(Options) -> Timeout when Options :: khepri:command_options() | khepri:query_options(), Timeout :: timeout(). %% @private get_timeout(#{timeout := Timeout}) -> Timeout; get_timeout(_) -> khepri_app:get_default_timeout(). use_leader_or_local_ra_server(_StoreId, LeaderId) when LeaderId =/= undefined -> LeaderId; use_leader_or_local_ra_server(StoreId, undefined) -> ThisNode = node(), khepri_cluster:node_to_member(StoreId, ThisNode). -spec clear_cache(StoreId) -> ok when StoreId :: khepri:store_id(). %% @doc Clears the cached data for the given `StoreId'. %% %% @private clear_cache(StoreId) -> _ = persistent_term:erase(?LAST_CONSISTENT_CALL_TS_REF(StoreId)), ok. %% ------------------------------------------------------------------- %% ra_machine callbacks. %% ------------------------------------------------------------------- -spec init(Params) -> State when Params :: machine_init_args(), State :: state(). %% @private init(#{store_id := StoreId, member := Member} = Params) -> Config = case Params of #{snapshot_interval := SnapshotInterval} -> #config{store_id = StoreId, member = Member, snapshot_interval = SnapshotInterval}; _ -> #config{store_id = StoreId, member = Member} end, State = #?MODULE{config = Config}, %% Create initial "schema" if provided. Commands = maps:get(commands, Params, []), State3 = lists:foldl( fun(Command, State1) -> Meta = #{index => 0, term => 0, system_time => 0}, {S, _, _} = apply(Meta, Command, State1), S end, State, Commands), reset_applied_command_count(State3). -spec init_aux(StoreId :: khepri:store_id()) -> aux_state(). %% @private init_aux(StoreId) -> #khepri_machine_aux{store_id = StoreId}. -spec handle_aux(RaState, Type, Command, AuxState, LogState, MachineState) -> {no_reply, AuxState, LogState} when RaState :: ra_server:ra_state(), Type :: {call, ra:from()} | cast, Command :: term(), AuxState :: aux_state(), LogState :: ra_log:state(), MachineState :: state(). %% @private handle_aux( _RaState, cast, #trigger_projection{path = Path, old_props = OldProps, new_props = NewProps, projection = Projection}, AuxState, LogState, _MachineState) -> khepri_projection:trigger(Projection, Path, OldProps, NewProps), {no_reply, AuxState, LogState}; handle_aux( _RaState, cast, restore_projections, AuxState, LogState, #?MODULE{tree = Tree, projections = ProjectionTree}) -> khepri_pattern_tree:foreach( ProjectionTree, fun(PathPattern, Projections) -> [restore_projection(Projection, Tree, PathPattern) || Projection <- Projections] end), {no_reply, AuxState, LogState}; handle_aux(_RaState, _Type, _Command, AuxState, LogState, _MachineState) -> {no_reply, AuxState, LogState}. restore_projection(Projection, Tree, PathPattern) -> _ = khepri_projection:init(Projection), TreeOptions = #{props_to_return => ?PROJECTION_PROPS_TO_RETURN, include_root_props => true}, case khepri_tree:find_matching_nodes(Tree, PathPattern, TreeOptions) of {ok, MatchingNodes} -> maps:foreach(fun(Path, Props) -> khepri_projection:trigger( Projection, Path, #{}, Props) end, MatchingNodes); Error -> ?LOG_DEBUG( "Failed to recover projection ~s due to an error: ~p", khepri_projection:name(Projection), Error), ok end. -spec apply(Meta, Command, State) -> {State, Ret, SideEffects} when Meta :: ra_machine:command_meta_data(), Command :: command(), State :: state(), Ret :: any(), SideEffects :: ra_machine:effects(). %% @private %% TODO: Handle unknown/invalid commands. apply( Meta, #put{path = PathPattern, payload = Payload, options = TreeAndPutOptions}, State) -> {TreeOptions, PutOptions} = split_put_options(TreeAndPutOptions), Ret = insert_or_update_node( State, PathPattern, Payload, PutOptions, TreeOptions), bump_applied_command_count(Ret, Meta); apply( Meta, #delete{path = PathPattern, options = TreeOptions}, State) -> Ret = delete_matching_nodes(State, PathPattern, TreeOptions), bump_applied_command_count(Ret, Meta); apply( Meta, #tx{'fun' = StandaloneFun, args = Args}, State) when ?IS_HORUS_FUN(StandaloneFun) -> Ret = khepri_tx_adv:run(State, StandaloneFun, Args, true), bump_applied_command_count(Ret, Meta); apply( Meta, #tx{'fun' = PathPattern, args = Args}, State) when ?IS_KHEPRI_PATH_PATTERN(PathPattern) -> Ret = locate_sproc_and_execute_tx(State, PathPattern, Args, true), bump_applied_command_count(Ret, Meta); apply( Meta, #register_trigger{id = TriggerId, sproc = StoredProcPath, event_filter = EventFilter}, #?MODULE{triggers = Triggers} = State) -> StoredProcPath1 = khepri_path:realpath(StoredProcPath), EventFilter1 = case EventFilter of #evf_tree{path = Path} -> Path1 = khepri_path:realpath(Path), EventFilter#evf_tree{path = Path1} end, Triggers1 = Triggers#{TriggerId => #{sproc => StoredProcPath1, event_filter => EventFilter1}}, State1 = State#?MODULE{triggers = Triggers1}, Ret = {State1, ok}, bump_applied_command_count(Ret, Meta); apply( Meta, #ack_triggered{triggered = ProcessedTriggers}, #?MODULE{emitted_triggers = EmittedTriggers} = State) -> EmittedTriggers1 = EmittedTriggers -- ProcessedTriggers, State1 = State#?MODULE{emitted_triggers = EmittedTriggers1}, Ret = {State1, ok}, bump_applied_command_count(Ret, Meta); apply( Meta, #register_projection{pattern = PathPattern, projection = Projection}, #?MODULE{tree = Tree, projections = ProjectionTree} = State) -> Reply = khepri_projection:init(Projection), State1 = case Reply of ok -> restore_projection(Projection, Tree, PathPattern), ProjectionTree1 = khepri_pattern_tree:update( ProjectionTree, PathPattern, fun (?NO_PAYLOAD) -> [Projection]; (Projections) -> [Projection | Projections] end), erase(compiled_projection_tree), State#?MODULE{projections = ProjectionTree1}; _ -> State end, Ret = {State1, Reply}, bump_applied_command_count(Ret, Meta); apply( Meta, #unregister_projection{name = ProjectionName}, #?MODULE{projections = ProjectionTree} = State) -> ProjectionTree1 = khepri_pattern_tree:filtermap( ProjectionTree, fun (PathPattern, Projections) -> Projections1 = lists:filter( fun (#khepri_projection{name = Name} = Projection) when Name =:= ProjectionName -> khepri_projection:delete(Projection), false; (_OtherProjection) -> true end, Projections), case Projections1 of [] -> false; _ -> {PathPattern, Projections1} end end), Reply = case ProjectionTree1 of ProjectionTree -> Info = #{name => ProjectionName}, Reason = ?khepri_error(projection_not_found, Info), {error, Reason}; _ -> erase(compiled_projection_tree), ok end, State1 = State#?MODULE{projections = ProjectionTree1}, Ret = {State1, Reply}, bump_applied_command_count(Ret, Meta). -spec bump_applied_command_count(ApplyRet, Meta) -> {State, Ret, SideEffects} when ApplyRet :: {State, Ret} | {State, Ret, SideEffects}, State :: state(), Ret :: any(), Meta :: ra_machine:command_meta_data(), SideEffects :: ra_machine:effects(). %% @private bump_applied_command_count({State, Result}, Meta) -> bump_applied_command_count({State, Result, []}, Meta); bump_applied_command_count( {#?MODULE{config = #config{snapshot_interval = SnapshotInterval}, metrics = Metrics} = State, Result, SideEffects}, #{index := RaftIndex}) -> AppliedCmdCount0 = maps:get(applied_command_count, Metrics, 0), AppliedCmdCount = AppliedCmdCount0 + 1, case AppliedCmdCount < SnapshotInterval of true -> Metrics1 = Metrics#{applied_command_count => AppliedCmdCount}, State1 = State#?MODULE{metrics = Metrics1}, {State1, Result, SideEffects}; false -> ?LOG_DEBUG( "Move release cursor after ~b commands applied " "(>= ~b commands)", [AppliedCmdCount, SnapshotInterval], #{domain => [khepri, ra_machine]}), State1 = reset_applied_command_count(State), ReleaseCursor = {release_cursor, RaftIndex, State1}, SideEffects1 = [ReleaseCursor | SideEffects], {State1, Result, SideEffects1} end. reset_applied_command_count(#?MODULE{metrics = Metrics} = State) -> Metrics1 = maps:remove(applied_command_count, Metrics), State#?MODULE{metrics = Metrics1}. %% @private state_enter(leader, State) -> SideEffects1 = emitted_triggers_to_side_effects(State), SideEffects1; state_enter(recovered, _State) -> SideEffect = {aux, restore_projections}, [SideEffect]; state_enter(_StateName, _State) -> []. %% @private emitted_triggers_to_side_effects( #?MODULE{config = #config{store_id = StoreId}, emitted_triggers = [_ | _] = EmittedTriggers}) -> SideEffect = {mod_call, khepri_event_handler, handle_triggered_sprocs, [StoreId, EmittedTriggers]}, [SideEffect]; emitted_triggers_to_side_effects(_State) -> []. %% @private overview(#?MODULE{config = #config{store_id = StoreId}, tree = #tree{keep_while_conds = KeepWhileConds} = Tree, triggers = Triggers}) -> TreeOptions = #{props_to_return => [payload, payload_version, child_list_version, child_list_length], include_root_props => true}, {ok, NodePropsMap} = khepri_tree:find_matching_nodes( Tree, [?KHEPRI_WILDCARD_STAR_STAR], TreeOptions), MapFun = fun (#{sproc := Sproc} = Props) -> Props#{sproc => horus:to_fun(Sproc)}; (Props) -> Props end, NodeTree = khepri_utils:flat_struct_to_tree(NodePropsMap, MapFun), #{store_id => StoreId, tree => NodeTree, triggers => Triggers, keep_while_conds => KeepWhileConds}. version() -> 0. %% ------------------------------------------------------------------- %% Internal functions. %% ------------------------------------------------------------------- locate_sproc_and_execute_tx( #?MODULE{tree = Tree} = State, PathPattern, Args, AllowUpdates) -> TreeOptions = #{expect_specific_node => true, props_to_return => [raw_payload]}, {StandaloneFun, Args1} = case khepri_tree:find_matching_nodes(Tree, PathPattern, TreeOptions) of {ok, Result} -> case maps:values(Result) of [#{raw_payload := #p_sproc{ sproc = StoredProc, is_valid_as_tx_fun = ReadWrite}}] when AllowUpdates andalso (ReadWrite =:= ro orelse ReadWrite =:= rw) -> {StoredProc, Args}; [#{raw_payload := #p_sproc{ sproc = StoredProc, is_valid_as_tx_fun = ro}}] when not AllowUpdates -> {StoredProc, Args}; [#{raw_payload := #p_sproc{}}] -> Reason = ?khepri_error( sproc_invalid_as_tx_fun, #{path => PathPattern}), {fun failed_to_locate_sproc/1, [Reason]}; _ -> Reason = ?khepri_error( no_sproc_at_given_path, #{path => PathPattern}), {fun failed_to_locate_sproc/1, [Reason]} end; {error, Reason} -> {fun failed_to_locate_sproc/1, [Reason]} end, khepri_tx_adv:run(State, StandaloneFun, Args1, AllowUpdates). -spec failed_to_locate_sproc(Reason) -> no_return() when Reason :: any(). %% @private failed_to_locate_sproc(Reason) -> khepri_tx:abort(Reason). -spec insert_or_update_node( State, PathPattern, Payload, PutOptions, TreeOptions) -> Ret when State :: state(), PathPattern :: khepri_path:native_pattern(), Payload :: khepri_payload:payload(), PutOptions :: khepri:put_options(), TreeOptions :: khepri:tree_options(), Ret :: {State, Result} | {State, Result, ra_machine:effects()}, Result :: khepri_machine:common_ret(). %% @private insert_or_update_node( #?MODULE{tree = Tree} = State, PathPattern, Payload, PutOptions, TreeOptions) -> Ret1 = khepri_tree:insert_or_update_node( Tree, PathPattern, Payload, PutOptions, TreeOptions), case Ret1 of {ok, Tree1, AppliedChanges, Ret2} -> State1 = State#?MODULE{tree = Tree1}, {State2, SideEffects} = create_tree_change_side_effects( State, State1, Ret2, AppliedChanges), {State2, {ok, Ret2}, SideEffects}; Error -> {State, Error} end. -spec delete_matching_nodes(State, PathPattern, TreeOptions) -> Ret when State :: state(), PathPattern :: khepri_path:native_pattern(), TreeOptions :: khepri:tree_options(), Ret :: {State, Result} | {State, Result, ra_machine:effects()}, Result :: khepri_machine:common_ret(). %% @private delete_matching_nodes( #?MODULE{tree = Tree} = State, PathPattern, TreeOptions) -> Ret = khepri_tree:delete_matching_nodes( Tree, PathPattern, #{}, TreeOptions), case Ret of {ok, Tree1, AppliedChanges, Ret2} -> State1 = State#?MODULE{tree = Tree1}, {State2, SideEffects} = create_tree_change_side_effects( State, State1, Ret2, AppliedChanges), {State2, {ok, Ret2}, SideEffects}; Error -> {State, Error} end. create_tree_change_side_effects( InitialState, NewState, Ret, KeepWhileAftermath) -> %% We make a map where for each affected tree node, we indicate the type %% of change. Changes0 = maps:merge(Ret, KeepWhileAftermath), Changes = maps:map( fun (_, NodeProps) when NodeProps =:= #{} -> create; (_, #{} = _NodeProps) -> update; (_, delete) -> delete end, Changes0), ProjectionEffects = create_projection_side_effects( InitialState, NewState, Changes), {NewState1, TriggerEffects} = create_trigger_side_effects( InitialState, NewState, Changes), {NewState1, ProjectionEffects ++ TriggerEffects}. create_projection_side_effects( #?MODULE{tree = InitialTree} = _InitialState, #?MODULE{tree = NewTree, projections = ProjectionTree0} = _NewState, Changes) -> ProjectionTree = get_compiled_projection_tree(ProjectionTree0), maps:fold( fun(Path, Change, Effects) -> create_projection_side_effects1( InitialTree, NewTree, ProjectionTree, Path, Change, Effects) end, [], Changes). create_projection_side_effects1( InitialTree, NewTree, ProjectionTree, Path, delete = Change, Effects) -> %% Deletion changes recursively delete the subtree below the deleted tree %% node. Find any children in the tree that were also deleted by this %% change and trigger any necessary projections for those children. ChildrenFindOptions = #{props_to_return => ?PROJECTION_PROPS_TO_RETURN, expect_specific_node => false}, ChildrenPattern = Path ++ [?KHEPRI_WILDCARD_STAR_STAR], EffectsForChildrenFun = fun(ChildPath, _NodeProps, EffectAcc) -> create_projection_side_effects2( InitialTree, NewTree, ProjectionTree, ChildPath, Change, EffectAcc) end, {ok, Effects1} = khepri_tree:fold( InitialTree, ChildrenPattern, EffectsForChildrenFun, Effects, ChildrenFindOptions), %% Also trigger a change for the deleted path itself. create_projection_side_effects2( InitialTree, NewTree, ProjectionTree, Path, Change, Effects1); create_projection_side_effects1( InitialTree, NewTree, ProjectionTree, Path, Change, Effects) -> create_projection_side_effects2( InitialTree, NewTree, ProjectionTree, Path, Change, Effects). create_projection_side_effects2( InitialTree, NewTree, ProjectionTree, Path, Change, Effects) -> PatternMatchingTree = case Change of create -> NewTree; update -> NewTree; delete -> InitialTree end, khepri_pattern_tree:fold( ProjectionTree, PatternMatchingTree, Path, fun(_PathPattern, Projections, Effects1) -> lists:foldl( fun(Projection, Effects2) -> evaluate_projection( InitialTree, NewTree, Path, Projection, Effects2) end, Effects1, Projections) end, Effects). -spec evaluate_projection(InitialTree, NewTree, Path, Projection, Effects) -> Ret when InitialTree :: khepri_tree:tree(), NewTree :: khepri_tree:tree(), Path :: khepri_path:native_path(), Projection :: khepri_projection:projection(), Effects :: ra_machine:effects(), Ret :: ra_machine:effects(). %% @private evaluate_projection( InitialTree, NewTree, Path, Projection, Effects) -> FindOptions = #{props_to_return => ?PROJECTION_PROPS_TO_RETURN, expect_specific_node => true}, InitialRet = khepri_tree:find_matching_nodes( InitialTree, Path, FindOptions), InitialProps = case InitialRet of {ok, #{Path := InitialProps0}} -> InitialProps0; _ -> #{} end, NewRet = khepri_tree:find_matching_nodes( NewTree, Path, FindOptions), NewProps = case NewRet of {ok, #{Path := NewProps0}} -> NewProps0; _ -> #{} end, Trigger = #trigger_projection{path = Path, old_props = InitialProps, new_props = NewProps, projection = Projection}, Effect = {aux, Trigger}, [Effect | Effects]. create_trigger_side_effects( #?MODULE{triggers = Triggers} = _InitialState, NewState, _Changes) when Triggers =:= #{} -> {NewState, []}; create_trigger_side_effects( %% We want to consider the new state (with the updated tree), but we want %% to use triggers from the initial state, in case they were updated too. %% In other words, we want to evaluate triggers in the state they were at %% the time the change to the tree was requested. #?MODULE{triggers = Triggers, emitted_triggers = EmittedTriggers} = _InitialState, #?MODULE{config = #config{store_id = StoreId}, tree = Tree} = NewState, Changes) -> TriggeredStoredProcs = list_triggered_sprocs(Tree, Changes, Triggers), %% We record the list of triggered stored procedures in the state %% machine's state. This is used to guaranty at-least-once execution of %% the trigger: the event handler process is supposed to ack when it %% executed the triggered stored procedure. If the Ra cluster changes %% leader in between, we know that we need to retry the execution. %% %% This could lead to multiple execution of the same trigger, therefore %% the stored procedure must be idempotent. NewState1 = NewState#?MODULE{ emitted_triggers = EmittedTriggers ++ TriggeredStoredProcs}, %% We still emit a `mod_call' effect to wake up the event handler process %% so it doesn't have to poll the internal list. SideEffect = {mod_call, khepri_event_handler, handle_triggered_sprocs, [StoreId, TriggeredStoredProcs]}, {NewState1, [SideEffect]}. list_triggered_sprocs(Tree, Changes, Triggers) -> TriggeredStoredProcs = maps:fold( fun(Path, Change, TSP) -> % For each change, we evaluate each trigger. maps:fold( fun(TriggerId, TriggerProps, TSP1) -> evaluate_trigger( Tree, Path, Change, TriggerId, TriggerProps, TSP1) end, TSP, Triggers) end, [], Changes), sort_triggered_sprocs(TriggeredStoredProcs). evaluate_trigger( Tree, Path, Change, TriggerId, #{sproc := StoredProcPath, event_filter := #evf_tree{path = PathPattern, props = EventFilterProps} = EventFilter}, TriggeredStoredProcs) -> %% For each trigger based on a tree event: %% 1. we verify the path of the changed tree node matches the monitored %% path pattern in the event filter. %% 2. we verify the type of change matches the change filter in the %% event filter. PathMatches = khepri_tree:does_path_match(Path, PathPattern, Tree), DefaultWatchedChanges = [create, update, delete], WatchedChanges = case EventFilterProps of #{on_actions := []} -> DefaultWatchedChanges; #{on_actions := OnActions} when is_list(OnActions) -> OnActions; _ -> DefaultWatchedChanges end, ChangeMatches = lists:member(Change, WatchedChanges), case PathMatches andalso ChangeMatches of true -> %% We then locate the stored procedure. If the path doesn't point %% to an existing tree node, or if this tree node is not a stored %% procedure, the trigger is ignored. %% %% TODO: Should we return an error or at least log something? This %% could be considered noise if the trigger exists regardless of %% the presence of the stored procedure on purpose (for instance %% the caller code is being updated). case find_stored_proc(Tree, StoredProcPath) of undefined -> TriggeredStoredProcs; StoredProc -> %% TODO: Use a record to format %% stored procedure arguments? EventProps = #{path => Path, on_action => Change}, Triggered = #triggered{ id = TriggerId, event_filter = EventFilter, sproc = StoredProc, props = EventProps}, [Triggered | TriggeredStoredProcs] end; false -> TriggeredStoredProcs end; evaluate_trigger( _Root, _Path, _Change, _TriggerId, _TriggerProps, TriggeredStoredProcs) -> TriggeredStoredProcs. find_stored_proc(Tree, StoredProcPath) -> TreeOptions = #{expect_specific_node => true, props_to_return => [payload, payload_version, child_list_version, child_list_length]}, Ret = khepri_tree:find_matching_nodes( Tree, StoredProcPath, TreeOptions), %% Non-existing nodes and nodes which are not stored procedures are %% ignored. case Ret of {ok, #{StoredProcPath := #{sproc := StoredProc}}} -> StoredProc; _ -> undefined end. sort_triggered_sprocs(TriggeredStoredProcs) -> %% We first sort by priority, then by triggered ID if priorities are equal. %% The priority can be any integer (even negative integers). The default %% priority is 0. %% %% A higher priority (a greater integer) means that the triggered stored %% procedure will be executed before another one with lower priority %% (smaller integer). %% %% If the priorities are equal, a trigger with an ID earlier in %% alphabetical order will be executed before another one with an ID later %% in alphabetical order. lists:sort( fun(#triggered{id = IdA, event_filter = EventFilterA}, #triggered{id = IdB, event_filter = EventFilterB}) -> PrioA = khepri_evf:get_priority(EventFilterA), PrioB = khepri_evf:get_priority(EventFilterB), if PrioA =:= PrioB -> IdA =< IdB; true -> PrioA > PrioB end end, TriggeredStoredProcs). -spec get_compiled_projection_tree(ProjectionTree) -> CompiledProjectionTree when ProjectionTree :: khepri_machine:projection_tree(), CompiledProjectionTree :: khepri_machine:projection_tree(). %% @doc Gets the compiled version of the projection pattern tree. %% %% The pattern tree for projections must be compiled before it can be queried %% into for changes to the store via {@link khepri_pattern_tree:fold/5}. %% %% This compiled pattern tree is cached in the process dictionary for the Ra %% server process. If the cached value does not exist, `SourceProjectionTree' %% is compiled with {@link khepri_pattern_tree:compile/1} and stored for %% future lookups. %% %% @private get_compiled_projection_tree(SourceProjectionTree) -> case get(compiled_projection_tree) of undefined -> CompiledProjectionTree = khepri_pattern_tree:compile( SourceProjectionTree), put(compiled_projection_tree, CompiledProjectionTree), CompiledProjectionTree; CompiledProjectionTree -> CompiledProjectionTree end. -ifdef(TEST). get_tree(#?MODULE{tree = Tree}) -> Tree. get_root(#?MODULE{tree = #tree{root = Root}}) -> Root. get_keep_while_conds( #?MODULE{tree = #tree{keep_while_conds = KeepWhileConds}}) -> KeepWhileConds. get_keep_while_conds_revidx( #?MODULE{tree = #tree{keep_while_conds_revidx = KeepWhileCondsRevIdx}}) -> KeepWhileCondsRevIdx. -endif.