feat: Provide environment variable to customize varnishd startup parameters and increase

Author: das-peter

README.md

@@ -65,9 +65,23 @@ Make sure to commit the `.ddev/.env.varnish` file to version control.
 
 All customization options (use with caution):
 
-| Variable | Flag | Default |
-| -------- | ---- | ------- |
-| `VARNISH_DOCKER_IMAGE` | `--varnish-docker-image` | `varnish:6.0` |
+| Variable                  | Flag                        | Default                                                                                                            |
+|---------------------------|-----------------------------|--------------------------------------------------------------------------------------------------------------------|
+| `VARNISH_DOCKER_IMAGE`    | `--varnish-docker-image`    | `varnish:6.0`                                                                                                      |
+| `VARNISH_VARNISHD_PARAMS` | `--varnish-varnishd-params` | `-p http_max_hdr=1000 -p http_resp_hdr_len=1M -p http_resp_size=2M -p workspace_backend=3M -p workspace_client=3M` |
+
+### VARNISH_VARNISHD_PARAMS
+
+Allows modifying the varnish [startup parameters](https://varnish-cache.org/docs/6.0/reference/varnishd.html).
+
+The provided defaults are set deliberately higher than what varnish usually defines.
+The reason for this is that in development environments it is not uncommon to
+have larger payloads either in HTML or HTTP-Headers. E.g. Drupals theme debugging
+or cache tag handling.
+Without increasing these limits, one might encounter hard to isolate errors like the following form nginx:
+```
+2025/07/15 09:01:01 [info] 1549#1549: *259 writev() failed (32: Broken pipe) while sending to client, client: 172.20.0.6, server: , request: "GET /en HTTP/1.1", upstream: "fastcgi://unix:/run/php-fpm.sock:", host: "myproject.ddev.site"
+```
 
 ## Credits
 

docker-compose.varnish.yaml

@@ -28,4 +28,4 @@ services:
     expose:
       - "8025"
     entrypoint:
-      /usr/local/bin/docker-varnish-entrypoint -a 0.0.0.0:8025
+      /usr/local/bin/docker-varnish-entrypoint -a 0.0.0.0:8025 ${VARNISH_VARNISHD_PARAMS:--p http_max_hdr=1000 -p http_resp_hdr_len=1M -p http_resp_size=2M -p workspace_backend=3M -p workspace_client=3M}

tests/test.bats

@@ -41,6 +41,7 @@ setup() {
 
   run ddev start -y
   assert_success
+  export CUSTOM_VARNISH_VARNISHD_PARAMS=false
 }
 
 health_checks() {
@@ -61,6 +62,36 @@ health_checks() {
   curl -sfI "http://${PROJNAME}.ddev.site:${MAILPIT_HTTP_PORT}/" | grep -i "http://novarnish.${PROJNAME}.ddev.site:${MAILPIT_HTTP_PORT}/" >/dev/null || (echo "# http://${PROJNAME}.ddev.site:${MAILPIT_HTTP_PORT} did not redirect" >&3 && exit 1);
   echo "# test https://${PROJNAME}.ddev.site:${MAILPIT_HTTPS_PORT}/ for https novarnish redirect" >&3
   curl -sfI "https://${PROJNAME}.ddev.site:${MAILPIT_HTTPS_PORT}/" | grep -i "https://novarnish.${PROJNAME}.ddev.site:${MAILPIT_HTTPS_PORT}/" >/dev/null || (echo "# https://${PROJNAME}.ddev.site:${MAILPIT_HTTPS_PORT} did not redirect" >&3 && exit 1);
+ 
+  if [ "${CUSTOM_VARNISH_VARNISHD_PARAMS}" = "true" ]; then
+    run ddev varnishadm param.show http_max_hdr
+    assert_success
+    assert_output --partial 'Value is: 123 [header lines]'
+
+    run ddev varnishadm param.show http_resp_hdr_len
+    assert_success
+    assert_output --partial 'Value is: 16k [bytes]'
+  else
+    run ddev varnishadm param.show http_max_hdr
+    assert_success
+    assert_output --partial 'Value is: 1000 [header lines]'
+
+    run ddev varnishadm param.show http_resp_hdr_len
+    assert_success
+    assert_output --partial 'Value is: 1M [bytes]'
+
+    run ddev varnishadm param.show http_resp_size
+    assert_success
+    assert_output --partial 'Value is: 2M [bytes]'
+
+    run ddev varnishadm param.show workspace_backend
+    assert_success
+    assert_output --partial 'Value is: 3M [bytes]'
+
+    run ddev varnishadm param.show workspace_client
+    assert_success
+    assert_output --partial 'Value is: 3M [bytes]'
+  fi
 }
 
 teardown() {
@@ -104,3 +135,23 @@ teardown() {
   export ROUTER_HTTP_PORT=8080 ROUTER_HTTPS_PORT=8443 MAILPIT_HTTP_PORT=18025 MAILPIT_HTTPS_PORT=18026
   health_checks
 }
+
+@test "customize varnishd startup parameters" {
+  set -eu -o pipefail
+  echo "# ddev add-on get ${DIR} with project ${PROJNAME} in $(pwd)" >&3
+  run ddev add-on get "${DIR}"
+  assert_success
+  run ddev dotenv set .ddev/.env.varnish --varnish-varnishd-params='-p http_max_hdr=123 -p http_resp_hdr_len=16k'
+  assert_success
+  run cat .ddev/.env.varnish
+  assert_success
+  assert_output 'VARNISH_VARNISHD_PARAMS="-p http_max_hdr=123 -p http_resp_hdr_len=16k"'
+  run ddev restart -y
+  assert_success
+  export ROUTER_HTTP_PORT=80 ROUTER_HTTPS_PORT=443 MAILPIT_HTTP_PORT=8025 MAILPIT_HTTPS_PORT=8026 
+  export CUSTOM_VARNISH_VARNISHD_PARAMS=false
+  health_checks
+  run ddev varnishadm param.show http_max_hdr
+  assert_output --partial 'Value is: 123 [header lines]'
+  assert_success
+}