Varnish CSP - Header too long

### Preconditions
1. Magento version 2.4.7 - No sample data
2. Live Search modules is installed
3. PHP 8.3 (magento/magento-cloud-docker-php:8.3-cli-1.3.7)
4. MySQL 10.6 (mariadb:10.6)
5. Varnish 6.6 (magento/magento-cloud-docker-varnish:6.6-1.3.7)
6. Nginx 1.24 (magento/magento-cloud-docker-nginx:1.24-1.3.7)
7. Opensearch 2.4 (magento/magento-cloud-docker-opensearch:2.4-1.3.7)
8. Fpm (magento/magento-cloud-docker-php:8.3-fpm-1.3.7)
9. Redis 7.2 (redis:7.2)

### Steps to reproduce
Use this docker-compose that are generated by ece-docker
```
# ./vendor/bin/ece-docker 'build:compose' --with-cron --with-xdebug --db='10.6' --php='8.3' --mode=developer --host='magento2.local' --no-es
version: '2.1'
services:
db:
hostname: db.magento2.local
image: 'mariadb:10.6'
shm_size: 2gb
environment:
- MYSQL_ROOT_PASSWORD=magento2
- MYSQL_DATABASE=magento2
- MYSQL_USER=magento2
- MYSQL_PASSWORD=magento2
ports:
- '3306:3306'
volumes:
- '.:/app:delegated'
- 'mymagento-magento-db:/var/lib/mysql'
healthcheck:
test: 'mysqladmin ping -h localhost -pmagento2'
interval: 30s
timeout: 30s
retries: 3
networks:
magento:
aliases:
- db.magento2.local
redis:
hostname: redis.magento2.local
image: 'redis:7.2'
volumes:
- '.:/app:delegated'
ports:
- '6379:6379'
sysctls:
net.core.somaxconn: 1024
ulimits:
nproc: 65535
nofile:
soft: 20000
hard: 40000
healthcheck:
test: 'redis-cli ping || exit 1'
interval: 30s
timeout: 30s
retries: 3
networks:
magento:
aliases:
- redis.magento2.local
opensearch:
hostname: opensearch.magento2.local
image: 'magento/magento-cloud-docker-opensearch:2.4-1.3.7'
ulimits:
memlock:
soft: -1
hard: -1
environment:
- cluster.name=docker-cluster
- discovery.type=single-node
- discovery.seed_hosts=opensearch
- bootstrap.memory_lock=true
- DISABLE_SECURITY_PLUGIN=true
networks:
magento:
aliases:
- opensearch.magento2.local
fpm:
hostname: fpm.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-fpm-1.3.7'
extends: generic
volumes:
- '.:/app:delegated'
networks:
magento:
aliases:
- fpm.magento2.local
depends_on:
db:
condition: service_healthy
web:
hostname: web.magento2.local
image: 'magento/magento-cloud-docker-nginx:1.24-1.3.7'
extends: generic
volumes:
- '.:/app:delegated'
environment:
- WITH_XDEBUG=1
- NGINX_WORKER_PROCESSES=1
- NGINX_WORKER_CONNECTIONS=1024
networks:
magento:
aliases:
- web.magento2.local
depends_on:
fpm:
condition: service_started
varnish:
hostname: varnish.magento2.local
image: 'magento/magento-cloud-docker-varnish:6.6-1.3.7'
networks:
magento:
aliases:
- varnish.magento2.local
depends_on:
web:
condition: service_started
tls:
hostname: tls.magento2.local
image: 'magento/magento-cloud-docker-nginx:1.24-1.3.7'
extends: generic
networks:
magento:
aliases:
- magento2.local
environment:
- NGINX_WORKER_PROCESSES=1
- NGINX_WORKER_CONNECTIONS=1024
- UPSTREAM_HOST=varnish
- UPSTREAM_PORT=80
ports:
- '80:80'
- '443:443'
depends_on:
varnish:
condition: service_started
fpm_xdebug:
hostname: fpm_xdebug.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-fpm-1.3.7'
extends: generic
volumes:
- '.:/app:delegated'
environment:
- 'PHP_EXTENSIONS=bcmath bz2 calendar exif gd gettext intl mysqli pcntl pdo_mysql soap sockets sysvmsg sysvsem sysvshm opcache zip xsl sodium xdebug'
networks:
magento:
aliases:
- fpm_xdebug.magento2.local
depends_on:
db:
condition: service_started
generic:
hostname: generic.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-cli-1.3.7'
env_file: ./.docker/config.env
environment:
- MAGENTO_RUN_MODE=developer
- 'PHP_EXTENSIONS=bcmath bz2 calendar exif gd gettext intl mysqli pcntl pdo_mysql soap sockets sysvmsg sysvsem sysvshm opcache zip xsl sodium'
- 'SENDMAIL_PATH=/usr/local/bin/mhsendmail --smtp-addr=mailhog:1025'
build:
hostname: build.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-cli-1.3.7'
extends: generic
volumes:
- '.:/app:delegated'
networks:
magento:
aliases:
- build.magento2.local
depends_on:
db:
condition: service_healthy
redis:
condition: service_healthy
opensearch:
condition: service_healthy
deploy:
hostname: deploy.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-cli-1.3.7'
extends: generic
volumes:
- '.:/app:delegated'
networks:
magento:
aliases:
- deploy.magento2.local
depends_on:
db:
condition: service_healthy
redis:
condition: service_healthy
opensearch:
condition: service_healthy
mailhog:
hostname: mailhog.magento2.local
image: 'magento/magento-cloud-docker-mailhog:1.0-1.3.7'
ports:
- '1025:1025'
- '8025:8025'
networks:
magento:
aliases:
- mailhog.magento2.local
cron:
hostname: cron.magento2.local
image: 'magento/magento-cloud-docker-php:8.3-cli-1.3.7'
extends: generic
command: run-cron
environment:
CRONTAB: '* * * * * root cd /app && /usr/local/bin/php bin/magento cron:run >> /app/var/log/cron.log'
volumes:
- '.:/app:delegated'
networks:
magento:
aliases:
- cron.magento2.local
depends_on:
db:
condition: service_healthy
redis:
condition: service_healthy
opensearch:
condition: service_healthy
volumes:
mymagento-magento-db: { }
networks:
magento:
driver: bridge
```
1. Install local docker machine
2. Install plain Magento without sample data
3. Install Live Search full bundle modules (with Popover, Search terms, etc...)
4. bin/magento s:d:c
4. bin/magento set:up

### Expected result
1. The frontend with Luma theme is showing and work correctly

### Actual result
1. Error 503 Backend fetch failed - Varnish Cache Server
2. Error in Varnish container `Header too long: Content-Security-Policy`

### Solution
1. Change default varnish VCL by updating this three parameters to desider value.
- http_max_hdr
- http_req_hdr_len
- http_resp_hdr_len

Start by reproducing the 503 response with the provided Docker Compose setup and inspect the Varnish container error for the Content-Security-Policy header. Locate the default Varnish VCL and review the http_max_hdr, http_req_hdr_len, and http_resp_hdr_len settings. Done means the frontend loads through Varnish without the “Header too long” error.

Written by the indexing model from the issue text.