I put a bit of a honeypot in place (in the form of a 'query' callback) to get stack traces, and I found many instances of the following:
[2024-11-21 22:12:55] shutdown_action_hook, do_action('shutdown'), WP_Hook->do_action, WP_Hook->apply_filters, S2_Upgrade->upgrade, S2_Upgrade->upgrade6_4, S2_Multisite->namechange_subscribe2_widget, wpdb->get_col, wpdb->query, apply_filters('query'), WP_Hook->apply_filters, {closure}
[2024-11-21 22:12:57] shutdown_action_hook, do_action('shutdown'), WP_Hook->do_action, WP_Hook->apply_filters, S2_Upgrade->upgrade, S2_Upgrade->upgrade6_4, S2_Multisite->namechange_subscribe2_widget, wpdb->get_col, wpdb->query, apply_filters('query'), WP_Hook->apply_filters, WP_CLI\Runner->{closure}
[2024-11-21 22:13:11] shutdown_action_hook, do_action('shutdown'), WP_Hook->do_action, WP_Hook->apply_filters, S2_Upgrade->upgrade, S2_Upgrade->upgrade6_4, S2_Multisite->namechange_subscribe2_widget, wpdb->get_col, wpdb->query, apply_filters('query'), WP_Hook->apply_filters, {closure}
[2024-11-21 22:13:48] shutdown_action_hook, do_action('shutdown'), WP_Hook->do_action, WP_Hook->apply_filters, S2_Upgrade->upgrade, S2_Upgrade->upgrade6_4, S2_Multisite->namechange_subscribe2_widget, wpdb->get_col, wpdb->query, apply_filters('query'), WP_Hook->apply_filters, {closure}
What the subscribe2 plugin is trying to do here is kinda dumb, and the fact that they run it on a shutdown hook that indiscriminately runs across the network is very bad. I've put a fix in place that prevents this particular part of the plugin upgrade routine from running: https://github.com/cuny-academic-commons/cac/commit/17f727212d34ede4c67aed2c4ab78c367d82515c This has been deployed immediately, in the chances that it's related to recent outages.