perf(indexers): offload sync embed_text to thread across background workers

Connector kb_sync_services (gmail, onedrive, google_calendar, jira),
streaming indexers (discord, luma, teams) and the file-processor save
path all called embed_text inside async coroutines, blocking the
background worker's event loop for the duration of the embed. Wrap each
call site in asyncio.to_thread so concurrent indexing tasks stop
serialising on the embed.

surfsense_backend/app/services/gmail/kb_sync_service.py

@@ -1,3 +1,4 @@
+import asyncio
 import logging
 from datetime import datetime
 
@@ -100,7 +101,9 @@ class GmailKBSyncService:
             else:
                 logger.warning("No LLM configured -- using fallback summary")
                 summary_content = f"Gmail Message: {subject}\n\n{indexable_content}"
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(indexable_content)
             now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")

surfsense_backend/app/services/google_calendar/kb_sync_service.py

@@ -116,7 +116,9 @@ class GoogleCalendarKBSyncService:
                 summary_content = (
                     f"Google Calendar Event: {event_summary}\n\n{indexable_content}"
                 )
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(indexable_content)
             now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
@@ -295,7 +297,9 @@ class GoogleCalendarKBSyncService:
                 summary_content = (
                     f"Google Calendar Event: {event_summary}\n\n{indexable_content}"
                 )
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(indexable_content)
             now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")

surfsense_backend/app/services/jira/kb_sync_service.py

@@ -98,7 +98,9 @@ class JiraKBSyncService:
                 summary_content = (
                     f"Jira Issue {issue_identifier}: {issue_title}\n\n{issue_content}"
                 )
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(issue_content)
             now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
@@ -212,7 +214,9 @@ class JiraKBSyncService:
                 summary_content = (
                     f"Jira Issue {issue_identifier}: {issue_title}\n\n{issue_content}"
                 )
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(issue_content)
 

surfsense_backend/app/services/onedrive/kb_sync_service.py

@@ -1,3 +1,4 @@
+import asyncio
 import logging
 from datetime import datetime
 
@@ -95,7 +96,9 @@ class OneDriveKBSyncService:
             else:
                 logger.warning("No LLM configured — using fallback summary")
                 summary_content = f"OneDrive File: {file_name}\n\n{indexable_content}"
-                summary_embedding = embed_text(summary_content)
+                summary_embedding = await asyncio.to_thread(
+                    embed_text, summary_content
+                )
 
             chunks = await create_document_chunks(indexable_content)
             now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")

surfsense_backend/app/tasks/connector_indexers/discord_indexer.py

@@ -670,7 +670,9 @@ async def index_discord_messages(
 
                 # Heavy processing (embeddings, chunks)
                 chunks = await create_document_chunks(item["combined_document_string"])
-                doc_embedding = embed_text(item["combined_document_string"])
+                doc_embedding = await asyncio.to_thread(
+                    embed_text, item["combined_document_string"]
+                )
 
                 # Update document to READY with actual content
                 document.title = f"{item['guild_name']}#{item['channel_name']}"

surfsense_backend/app/tasks/connector_indexers/luma_indexer.py

@@ -6,6 +6,7 @@ Implements 2-phase document status updates for real-time UI feedback:
 - Phase 2: Process each event: pending → processing → ready/failed
 """
 
+import asyncio
 import time
 from collections.abc import Awaitable, Callable
 from datetime import datetime, timedelta
@@ -465,7 +466,9 @@ async def index_luma_events(
                     summary_content = (
                         f"Luma Event: {item['event_name']}\n\n{item['event_markdown']}"
                     )
-                    summary_embedding = embed_text(summary_content)
+                    summary_embedding = await asyncio.to_thread(
+                        embed_text, summary_content
+                    )
 
                 chunks = await create_document_chunks(item["event_markdown"])
 

surfsense_backend/app/tasks/connector_indexers/teams_indexer.py

@@ -9,6 +9,7 @@ Uses 2-phase document status updates for real-time UI feedback:
 - Phase 2: Process each document: pending → processing → ready/failed
 """
 
+import asyncio
 import time
 from collections.abc import Awaitable, Callable
 from datetime import UTC, datetime
@@ -581,7 +582,9 @@ async def index_teams_messages(
 
                 # Heavy processing (embeddings, chunks)
                 chunks = await create_document_chunks(item["combined_document_string"])
-                doc_embedding = embed_text(item["combined_document_string"])
+                doc_embedding = await asyncio.to_thread(
+                    embed_text, item["combined_document_string"]
+                )
 
                 # Update document to READY with actual content
                 document.title = f"{item['team_name']} - {item['channel_name']}"

surfsense_backend/app/tasks/document_processors/_save.py

@@ -2,6 +2,7 @@
 Unified document save/update logic for file processors.
 """
 
+import asyncio
 import logging
 
 from sqlalchemy.exc import SQLAlchemyError
@@ -43,7 +44,7 @@ async def _generate_summary(
     """
     if not enable_summary:
         summary = f"File: {file_name}\n\n{markdown_content[:4000]}"
-        return summary, embed_text(summary)
+        return summary, await asyncio.to_thread(embed_text, summary)
 
     if etl_service == "DOCLING":
         from app.services.docling_service import create_docling_service
@@ -65,7 +66,7 @@ async def _generate_summary(
                 parts.append(f"**{formatted_key}:** {value}")
 
         enhanced = "\n".join(parts) + "\n\n# DOCUMENT SUMMARY\n\n" + summary_text
-        return enhanced, embed_text(enhanced)
+        return enhanced, await asyncio.to_thread(embed_text, enhanced)
 
     # Standard summary (Unstructured / LlamaCloud / others)
     meta = {