khepri_machine: Add where trigger option

src/khepri.erl

@@ -414,6 +414,23 @@
 %% khepri_machine:split_command_options/2} and {@link
 %% khepri_machine:split_put_options/2} must be adapted.
 
+-type trigger_options() :: #{where =>
+                             khepri_event_handler:trigger_exec_loc() | local}.
+%% Options specific to trigger registrations.
+%%
+%% <ul>
+%% <li>`where' allows to indicate on which member(s) of the cluster a
+%% triggered action should be executed. With `{member, MemberNode}', if the
+%% target member is not part of the cluster at the time the action is
+%% triggered, the trigger is executed on the leader. The special value `local'
+%% means that the node running `khepri_machine:register_trigger/5' will
+%% execute the trigger (if it is a member of the cluster at the time the
+%% action is triggered).</li>
+%% </ul>
+%%
+%% NOTE: When this list of trigger options is modified, {@link
+%% khepri_machine:split_command_options/2} must be adapted.
+
 -type fold_fun() :: fun((khepri_path:native_path(),
                          khepri:node_props(),
                          khepri:fold_acc()) -> khepri:fold_acc()).
@@ -524,6 +541,7 @@
               query_options/0,
               tree_options/0,
               put_options/0,
+              trigger_options/0,
 
               fold_fun/0,
               fold_acc/0,
@@ -2848,7 +2866,7 @@ register_trigger(TriggerId, EventFilter, StoredProcPath) ->
       TriggerId :: trigger_id(),
       EventFilter :: khepri_evf:event_filter_or_compat(),
       StoredProcPath :: khepri_path:path(),
-      Options :: command_options(),
+      Options :: command_options() | khepri:trigger_options(),
       Ret :: ok | error().
 %% @doc Registers a trigger.
 %%
@@ -2881,7 +2899,7 @@ register_trigger(TriggerId, EventFilter, StoredProcPath, Options)
       TriggerId :: trigger_id(),
       EventFilter :: khepri_evf:event_filter_or_compat(),
       StoredProcPath :: khepri_path:path(),
-      Options :: command_options(),
+      Options :: command_options() | khepri:trigger_options(),
       Ret :: ok | error().
 %% @doc Registers a trigger.
 %%

src/khepri_event_handler.erl

@@ -42,13 +42,17 @@
 %% It is the stored procedure pointed to by the path in the triggered action's
 %% arguments.
 
--type trigger_exec_loc() :: leader.
+-type trigger_exec_loc() :: leader | {member, node()} | all_members.
 %% Where to execute the triggered action.
 %%
 %% It supports the following locations:
 %% <ul>
 %% <li>`leader': the action is executed on the leader node at the time the
 %% action is triggered.</li>
+%% <li>`{member, Member}': the action is executed on the given node if it is a
+%% member of the cluster, or the leader otherwise.</li>
+%% <li>`all_members': the action is executed on all members of the
+%% cluster.</li>
 %% </ul>
 
 -type trigger_descriptor() :: #khepri_trigger{}.