NativeSessionStorage Failed start

This is happening for me now on 10.1 when indexing using search api:

RuntimeException while trying to render item entity:node/75890:en with view mode full for search index Search Site: Failed to start the session because headers have already been sent by "/var/www/html/web/core/modules/big_pipe/src/Render/BigPipe.php" at line 264. in Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 132 of /var/www/html/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php).

This is postponed because information is needed.

Sorry I missed the request for modules installed, is there something else you need?

Core Automated Cron (automated_cron) Enabled 10.1.0
Core BigPipe (big_pipe) Enabled 10.1.0
Core Block (block) Enabled 10.1.0
Core Block Content (block_content) Enabled 10.1.0
Core Breakpoint (breakpoint) Enabled 10.1.0
Core CKEditor 5 (ckeditor5) Enabled 10.1.0
Core Configuration Manager (config) Enabled 10.1.0
Core Contextual Links (contextual) Enabled 10.1.0
Field types Datetime (datetime) Enabled 10.1.0
Core Database Logging (dblog) Enabled 10.1.0
Core Internal Dynamic Page Cache Enabled 10.1.0
(dynamic_page_cache)
Core Text Editor (editor) Enabled 10.1.0
Core Field (field) Enabled 10.1.0
Core Field UI (field_ui) Enabled 10.1.0
Field types File (file) Enabled 10.1.0
Core Filter (filter) Enabled 10.1.0
Field types Image (image) Enabled 10.1.0
Field types Link (link) Enabled 10.1.0
Core Custom Menu Links (menu_link_content) Enabled 10.1.0
Core Menu UI (menu_ui) Enabled 10.1.0
Migration Migrate (migrate) Enabled 10.1.0
Core MySQL (mysql) Enabled 10.1.0
Core Node (node) Enabled 10.1.0
Field types Options (options) Enabled 10.1.0
Core Internal Page Cache (page_cache) Enabled 10.1.0
Core Path (path) Enabled 10.1.0
Core Path alias (path_alias) Enabled 10.1.0
Core Password Compatibility (phpass) Enabled 10.1.0
Web services Serialization (serialization) Enabled 10.1.0
Core System (system) Enabled 10.1.0
Core Taxonomy (taxonomy) Enabled 10.1.0
Field types Text (text) Enabled 10.1.0
Core Toolbar (toolbar) Enabled 10.1.0
Core Update Manager (update) Enabled 10.1.0
Core User (user) Enabled 10.1.0
Core Views (views) Enabled 10.1.0
Core Views UI (views_ui) Enabled 10.1.0
Administration Admin Toolbar (admin_toolbar) Enabled 3.3.0
Administration Admin Toolbar Extra Tools Enabled 3.3.0
(admin_toolbar_tools)
Views Better Exposed Filters Enabled 6.0.3
(better_exposed_filters)
Config Config Filter (config_filter) Enabled 8.x-1.10
Config Configuration Split (config_split) Enabled 8.x-1.9
Elasticsearch Elasticsearch Connector Enabled 8.x-7.0-alpha4
(elasticsearch_connector)
(elasticsearch_connector_views)
Search Elasticsearch - Search API Enabled
(elasticsearch_search_api)
Entity Entity Redirect (entity_redirect) Enabled 8.x-2.2
Search Facets (facets) Enabled 2.0.6
Search Facets Searchbox Widget Enabled 2.0.6
(facets_searchbox_widget)
Search Facets autocomplete Enabled 2.1.1
(facets_autocomplete)
Fields Inline Entity Form Enabled 8.x-1.0-rc14
(inline_entity_form)
jQuery UI jQuery UI (jquery_ui) Enabled 8.x-1.6
jQuery UI jQuery UI Datepicker Enabled 2.0.0
(jquery_ui_datepicker)
jQuery UI jQuery UI Slider (jquery_ui_slider) Enabled 2.0.0
jQuery UI jQuery UI Touch Punch Enabled 1.1.0
(jquery_ui_touch_punch)
Field types JSON Field (json_field) Enabled 8.x-1.2
Field types JSON Field Widget (json_field_widget) Enabled 8.x-1.2
Migration Migrate Plus (migrate_plus) Enabled 6.0.1
Migration Migrate Source CSV Enabled 8.x-3.5
(migrate_source_csv)
Migration Migrate Tools (migrate_tools) Enabled 6.0.1
Other Rabbit Hole taxonomy (rh_taxonomy) Enabled 8.x-1.0-beta11
Other Rabbit Hole (rabbit_hole) Enabled 8.x-1.0-beta11
Schema.org Schema.org Blueprints JSON-LD Enabled
Blueprints API (schemadotorg_jsonld)
Schema.org Schema.org Blueprints UI Enabled
Blueprints (schemadotorg_ui)
Schema.org Schema.org Blueprints (schemadotorg) Enabled
Blueprints
Search Search API (search_api) Enabled 8.x-1.29
Search Algolia Search (search_api_algolia) Enabled 3.0.0-beta7
Other Storage Entities (storage) Enabled 1.2.6
Other Token (token) Enabled 8.x-1.11
Administration Upgrade Status (upgrade_status) Enabled 4.0.0-alpha1
Views Views Aggregator Plus Enabled 2.0.1
(views_aggregator)
Core Claro (claro) Enabled 10.1.0
Core Stable 9 (stable9) Enabled 10.1.0

The question was about contributed modules. Anyway, what about comment #4?

I'll check for empty lines before <?php, it's going to take a bit of time.

I don't have any module printing before the session starts that I'm aware of.

Search api is trying to render the content so I can index the rendered content so maybe that is triggering the issue.

Related issue in search api

Ok I had a chance to check, I don't see any modules with empty space before the php tag.

I think in my case it's from trying to render items to index them. I posted the related issue.

Forgot to move this back to active after answering.

The OP did not reply so this should probably be closed.

Later comments about search API strongly point to the existing issue in #15 as the main discussion area.

Sorry, do you mean that Search api has a bug in how it's render for indexing functionality?
How can we be sure the issue is there and not with BigPipe?

Okipa may not have replied, but I've experienced the same issue and responded with the requested info.

What information is the maintainer still requesting that was not answered?

Two questions I see:
Do you have any modules that are printing output before the session is started?
Or perhaps some php files with blank lines before the opening <?php

I listed all modules for that project and checked for the extra space in my project.