Web & search stack internals

The web-serving half of BOA: how Provision turns an Ægir site node into an Nginx vhost + a settings.php, where the edge-map wall that fronts every request is declared, and how the Barracuda installer lays down the Solr search backends those vhosts talk to.

Two languages meet here — the vhost/settings generator is Drush 8 / PHP 5.6-floor PHP inside the Provision fork, the Solr installer is Barracuda-side bash inside boa-private — and a change on either side has to survive the other's assumptions.

If you touch server.tpl.php, a settings template, or solr.sh.inc, this is the wiring your change lands in.

The render pipeline in one pass

Every Nginx config file BOA writes goes through the same Provision_Config machinery, driven by the nginx service class (Provision_Service_http_nginx, http/Provision/Service/http/nginx.php:3). init_server() registers which config classes render at server vs site scope (nginx.php:23-25,39-40), and save_server()/verify_server_cmd() probe the running box — nginx -V feature flags, socket-vs-port PHP-FPM mode, the /data/conf/global.inc BOA-mode marker — and stash the results as server properties the templates read (nginx.php:44-160).

Each registered class is a Provision_Config subclass whose write() runs the fixed cycle in the base (Provision/Config.php:195):

1. process() populates $this->data.
2. load_template() resolves the .tpl.php (through the provision_config_load_templates[_alter] hooks, Config.php:117-160).
3. render_template() eval('?>' . $template)s it with $this and $data in scope (Config.php:169-186) before file_put_contents writes the file.
4. Then Provision_Config_Http::write() ->sync()s it to the target server (http/Provision/Config/Http.php:10-13).

The three server/site classes and what they emit:

The SSL variants (Nginx/Ssl/*, registered by nginx/ssl.php) render the quic-enabled listeners; the subdir feature adds Provision_Config_Nginx_Subdir

• _SubdirVhost only when provision_hosting_feature_enabled('subdirs') (nginx.php:37-41). All of them extend the same base, so the pipeline above is invariant — only the template and filename() change.

Both server-scope classes also splice in drush_command_invoke_all('provision_nginx_server_config', …) / _vhost_config output (Nginx/Server.php, Nginx/Site.php), the extension seam documented on the Ægir backend APIs topic — that is how a hosting_* module injects config without editing a template.

Where the four leaves sit

Aegir site node  ──(verify task)──▶  Provision http service
                                        │
   ┌────────────────────────────────────┼───────────────────────────────┐
   │ server.tpl.php  (once per server)   │ vhost.tpl.php / vhost_ssl      │  settings template
   │  http { ... maps + geo + zones }    │  (once per site)              │  (once per site)
   │  $is_banned, $is_cms_probe,         │  server { listen; server_name;│  settings.php:
   │  $is_ai_*, $cache_uid,              │    fastcgi_param db_* creds;  │   literal db creds,
   │  $boa_i18n_* ...                    │    include nginx_vhost_common }│   global.inc chain,
   │        ↓ [1 edge maps]              │        ↓ [2 vhost generator]  │   local.settings.php
   │  Inc/vhost_include.tpl.php          │                               │        ↓ [3 settings wiring]
   │   guard chain: if ($is_*) return 444│                               │
   └────────────────────────────────────┴───────────────────────────────┘
                                        │
                          php-fpm ──▶ Drupal ──▶ Search API / Solr
                                                      ↑ [4 Solr installer: solr.sh.inc]

• [1] Edge maps are declared in server.tpl.php (http scope, once per server) and enforced in vhost_include.tpl.php (per request, in every vhost). Splitting declaration from enforcement is deliberate: a map is a cheap constant-time lookup, so the guard chain is a flat list of if ($is_x) return 444; with no per-request regex.
• [2] The vhost generator is vhost.tpl.php / Ssl/vhost_ssl.tpl.php plus the Provision_Config_Nginx_* classes that render them — the per-site server block, the DB-cred fastcgi_param injection, and the include that pulls in the shared guard chain.
• [3] settings.php wiring is the Drupal-side companion: BOA writes the DB creds literally into settings.php (BOA turns Ægir's $_SERVER db-cloaking off — cloaked_db_creds() returns FALSE), plus the three-level global.inc → platform → local.settings.php include chain.
• [4] The Solr installer is Barracuda-side bash — solr.sh.inc lays down the Solr 4/7/9 backends and their JVM/service wiring that Search-API vhost traffic ultimately reaches.

Hold that picture; each leaf zooms into one box.

Adjacent developing topics

• Ægir backend APIs — the provision_nginx_server_config / provision_nginx_vhost_config / provision_drupal_config hooks these templates invoke, and the Provision template-alter chain a hosting_* extension uses to add config without patching a .tpl.php.
• Install & staged-setup internals — how the Provision codebase (and the Solr backends) get onto a box in the first place: the staged AegirSetup* engine and the /opt/tmp/make_local build tree.
• Monitor & abuse-guard internals (code) — the scan_nginx scorer that reads the access log these vhosts write and reacts to the 444s the guard chain and the $boa_i18n_anon cap emit; the ban decisions it makes land back in the $is_banned geo declared here.

Reference

• Variables and Commands — the consolidated _VAR and CLI tables, including the _SOLR_*/_JETTY_*/_XTRAS_LIST knobs the installer reads. The Nginx map variables ($is_banned, $is_cms_probe, $boa_i18n_*, $cache_uid, …) are deployed-vhost contract surface: add, never rename or remove.
• Discontinued features — retired search/web pieces (older Solr/Jetty generations, superseded template mechanics) land there; check it before documenting anything found only in old trees or logs.