fix(workflows): dont delete signal rows (#965)

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## Changes

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Author: MasterPtato

docs/libraries/workflow/GLOSSARY.md

@@ -39,6 +39,32 @@ Examples include:
 
 Operations are not required; all of their functionality can be put into an activity instead.
 
+## Tags
+
+Tags are JSON blobs associated with either workflows or signals. Tags are not meant to be very abstract; i.e.
+they should be unique.
+
+## Signal
+
+A payload sent to a specific workflow from anywhere else in the codebase. The workflow must be listening for
+this signal for it to be picked up, otherwise it will stay in the database indefinitely until consumed by a
+workflow. Signals do not have a response; another signal must be sent back from the workflow and listened to
+by the sender.
+
+## Tagged Signal
+
+Same as a signal except it is sent with a JSON blob as its "tags" instead of to a specific workflow. Any
+workflow with tags that are a superset of the signals tags will consume the signal. Note that tagged signals
+are consumed on a first-come-first-serve basis, meaning if there are two workflows that both have a superset
+of the signal's tags, only one will receive the signal.
+
+See [the signals document](./SIGNALS.md).
+
+## Join Signal
+
+A "one of" for signal listening. Allows for listening to multiple signals at once and receiving the first one
+that gets sent.
+
 ## Workflow Event
 
 An action that gets executed in a workflow. An event can be a:

docs/libraries/workflow/SIGNALS.md

@@ -0,0 +1,7 @@
+# Signals
+
+## Tagged signals
+
+Tagged signals are consumed on a first-come-first-serve basis because a single signal being consumed by more
+than one workflow is not a supported design pattern. To work around this, consume the signal by a workflow
+then publish multiple signals from that workflow.

lib/chirp-workflow/core/src/compat.rs

@@ -158,7 +158,7 @@ pub async fn signal<I: Signal + Serialize, B: Debug + Clone>(
 	}
 
 	let signal_id = Uuid::new_v4();
-	
+
 	tracing::info!(name=%I::NAME, %workflow_id, %signal_id, "dispatching signal");
 
 	// Serialize input
@@ -185,7 +185,7 @@ pub async fn tagged_signal<I: Signal + Serialize, B: Debug + Clone>(
 	}
 
 	let signal_id = Uuid::new_v4();
-	
+
 	tracing::info!(name=%I::NAME, ?tags, %signal_id, "dispatching tagged signal");
 
 	// Serialize input

lib/chirp-workflow/core/src/ctx/api.rs

@@ -183,7 +183,7 @@ impl ApiCtx {
 		input: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::info!(name=%T::NAME, %workflow_id, %signal_id, "dispatching signal");
 
 		// Serialize input
@@ -205,7 +205,7 @@ impl ApiCtx {
 		input: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::info!(name=%T::NAME, ?tags, %signal_id, "dispatching tagged signal");
 
 		// Serialize input

lib/chirp-workflow/core/src/ctx/test.rs

@@ -187,7 +187,7 @@ impl TestCtx {
 		input: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::info!(name=%T::NAME, %workflow_id, %signal_id, "dispatching signal");
 
 		// Serialize input
@@ -209,7 +209,7 @@ impl TestCtx {
 		input: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::info!(name=%T::NAME, ?tags, %signal_id, "dispatching tagged signal");
 
 		// Serialize input

lib/chirp-workflow/core/src/ctx/workflow.rs

@@ -669,7 +669,7 @@ impl WorkflowCtx {
 		body: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::info!(name=%T::NAME, %workflow_id, %signal_id, "dispatching signal");
 
 		// Serialize input
@@ -692,7 +692,7 @@ impl WorkflowCtx {
 		body: T,
 	) -> GlobalResult<Uuid> {
 		let signal_id = Uuid::new_v4();
-		
+
 		tracing::debug!(name=%T::NAME, ?tags, %signal_id, "dispatching tagged signal");
 
 		// Serialize input

lib/chirp-workflow/core/src/db/postgres.rs

@@ -132,7 +132,8 @@ impl Database for DatabasePostgres {
 								FROM db_workflow.signals AS s
 								WHERE
 									s.workflow_id = w.workflow_id AND
-									s.signal_name = ANY(w.wake_signals)
+									s.signal_name = ANY(w.wake_signals) AND
+									s.ack_ts IS NULL
 								LIMIT 1
 							) OR
 							-- Tagged signal exists
@@ -141,7 +142,8 @@ impl Database for DatabasePostgres {
 								FROM db_workflow.tagged_signals AS s
 								WHERE
 									s.signal_name = ANY(w.wake_signals) AND
-									s.tags <@ w.tags
+									s.tags <@ w.tags AND
+									s.ack_ts IS NULL
 								LIMIT 1
 							) OR
 							-- Sub workflow completed
@@ -456,27 +458,31 @@ impl Database for DatabasePostgres {
 					FROM db_workflow.signals
 					WHERE
 						workflow_id = $1 AND
-						signal_name = ANY($2)
+						signal_name = ANY($2) AND
+						ack_ts IS NULL
 					UNION ALL
 					SELECT true AS tagged, signal_id, create_ts, signal_name, body
 					FROM db_workflow.tagged_signals
 					WHERE
 						signal_name = ANY($2) AND
-						tags <@ (SELECT tags FROM db_workflow.workflows WHERE workflow_id = $1)
+						tags <@ (SELECT tags FROM db_workflow.workflows WHERE workflow_id = $1) AND
+						ack_ts IS NULL
 					ORDER BY create_ts ASC
 					LIMIT 1
 				),
-				-- If the next signal is not tagged, delete it with this statement
-				delete_signal AS (
-					DELETE FROM db_workflow.signals
+				-- If the next signal is not tagged, acknowledge it with this statement
+				ack_signal AS (
+					UPDATE db_workflow.signals
+					SET ack_ts = $4
 					WHERE signal_id = (
 						SELECT signal_id FROM next_signal WHERE tagged = false
 					)
 					RETURNING 1
 				),
-				-- If the next signal is tagged, delete it with this statement
-				delete_tagged_signal AS (
-					DELETE FROM db_workflow.tagged_signals
+				-- If the next signal is tagged, acknowledge it with this statement
+				ack_tagged_signal AS (
+					UPDATE db_workflow.tagged_signals
+					SET ack_ts = $4
 					WHERE signal_id = (
 						SELECT signal_id FROM next_signal WHERE tagged = true
 					)

svc/Cargo.lock

@@ -14,13 +14,20 @@ CREATE TABLE tagged_signals (
   signal_name TEXT NOT NULL,
 
   create_ts INT NOT NULL,
+  ack_ts INT,
   ray_id UUID NOT NULL,
 
-  body JSONB NOT NULL,
-
-  INDEX (signal_name)
+  body JSONB NOT NULL
 );
 
 CREATE INDEX gin_tagged_signals_tags
 ON tagged_signals
-USING GIN (tags);
+USING GIN (tags)
+WHERE ack_ts IS NULL;
+
+-- Fix signal indexes
+ALTER TABLE signals
+  ADD COLUMN ack_ts INT;
+
+DROP INDEX signals@signals_signal_name_idx;
+DROP INDEX signals@signals_workflow_id_idx;