HTTP 503 errors after Upgrading vom 4.6.1 to 4.7.3

Silverstripe Version: 4.7.3


After upgrading from 4.6.1 to 4.7.3 via composer some of my sites only show the following message:

HTTP 503

Service Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Accessing the admin panel is possible for a few page loads, but after, say 2 or 3 clicks, I also get the HTTP 503 error there (I can “reset” that, by manually clearing the silverstripe-cache-directory).

SS_ENVIRONMENT_TYPE is set to dev, php_error_log is activated, but I am unable to get information from either of them. Neither does the php log contain anything at all, nor am I able to get information out of Silverstripe beyond the 503 display at all.

I am currently at a loss as to how to proceed any further to find this error…

Here is my composer.json from the working 4.6.1 installation:

    "name": "silverstripe/installer",
    "type": "silverstripe-recipe",
    "description": "The SilverStripe Framework Installer",
    "require": {
        "php": ">=7.4.0",
        "silverstripe/recipe-plugin": "^1.2",
        "silverstripe/recipe-cms": "4.6.1@stable",
        "undefinedoffset/sortablegridfield": "^2.0",
        "undefinedoffset/silverstripe-nocaptcha": "^2.1",
        "silverstripe/spamprotection": "^3.0",
        "tractorcow/silverstripe-fluent": "^5.0",
        "silverstripe/googlesitemaps": "dev-main"
    "require-dev": {
        "phpunit/phpunit": "^5.7"
    "extra": {
        "project-files-installed": [
        "public-files-installed": [
    "config": {
        "process-timeout": 600
    "prefer-stable": true,
    "minimum-stability": "dev"

To upgrade, I changed the silverstripe-cms to "silverstripe/recipe-cms": "4.7.3@stable",.
Versions between 4.7.0 and 4.7.3 produce an error when talking to MariaDB ("Error in statement USE "<databasename>"), that’s why I am jumping directly to 4.7.3.

I hope some of you have ideas how I can pin point this error :confused:

Thanks for your time and help!

You may get more information by running ./vendor/bin/sake / to try to render the home page on the command line.

Thanks for your suggestion. In the meantime I could figure out which part of the update exactly causes the problem (for me) and how to work around it: [SS 4.7.2 -> 4.7.3] HTTP 503 errors after upgrading symfony/cache from v3.4.47 to v4.4.31 · Issue #10115 · silverstripe/silverstripe-framework · GitHub

I just tried your suggestion (even altered the sake script to use different PHP versions, since my hoster provides multiple), but unfortunately(?) when calling the page with sake I get HTML output as expected. Seems to be some interworkings with the Webserver and PHP-FPM or something … :confused: