Autoupdate policy implementation

Author: DavidePrincipi

porthos/root/srv/porthos/script/auth.php

@@ -78,7 +78,7 @@
 if($is_tier_request && $valid_credentials) {
     // Seeking a snapshot is a time-consuming op. Ensure we have valid
     // credentials before running it!
-    $snapshot = lookup_snapshot($uri['full_path'], $tier_id, $config['week_size']);
+    $snapshot = lookup_snapshot($uri['full_path'], $uri['version'], $tier_id);
 } else {
     $snapshot = 'head';
 }
@@ -108,4 +108,8 @@
 }
 
 header('Cache-Control: private');
-return_file('/' . $snapshot . $uri['full_path']);
+if($snapshot == 'empty') {
+    return_file('/empty/repodata/' . basename($uri['full_path']));
+} else {
+    return_file('/' . $snapshot . $uri['full_path']);
+}

porthos/root/srv/porthos/script/config-porthos.php

@@ -56,6 +56,18 @@
 //     the PHP timezone for this application
 $config['timezone'] = 'UTC';
 
+// autoupdate_policy (array)
+//     Decide the content returned for a given version/tier_id combination.
+//     Valid keys are, for instance "7.6.1810/2" "6.10/0" "7.7.1908/*" ...
+//     Valid values are "head" "empty" "d20191104" (a snapshot name). If the
+//     snapshot dir does not exist, "empty" is assumed.
+$config['autoupdate_policy'] = array();
+
+// snapshots_dir (string)
+//     Filesystem directory path where snapshot directories are stored with
+//     trailing slash.
+$config['snapshots_dir'] = '/srv/porthos/webroot/';
+
 // tier_seed (int)
 //     The system_id value is reduced to the integer range 0-9 plus the seed.
 //     The resulting value is mapped to a tier_id

porthos/root/srv/porthos/script/lib.php

@@ -79,8 +79,49 @@ function get_snapshot_timestamp($snapshot_name) {
     return mktime(0, 0, 0, $parts['month'], $parts['day'], $parts['year']);
 }
 
-function lookup_snapshot($path, $tier_id = 0, $week_size = 5) {
-    $root_path = "/srv/porthos/webroot/";
+function lookup_policy($version, $tier_id) {
+    global $config;
+
+    $policy_map = $config['autoupdate_policy'] ?: array();
+    $policy_key = $version . '/' . $tier_id;
+    $poldef_key = $version . '/*';
+
+    if(isset($policy_map[$policy_key])) {
+        $value = $policy_map[$policy_key];
+    } elseif(isset($policy_map[$poldef_key])) {
+        $value = $policy_map[$poldef_key];
+    } else {
+        $value = 'lookup_monday';
+    }
+
+    return $value;
+}
+
+function lookup_fixed($path, $snapshot_start) {
+    global $config;
+
+    $root_path = $config['snapshots_dir'] ?: "/srv/porthos/webroot/";
+    $snapshots = array_map('basename', glob($root_path . "d20*"));
+
+    $start_key = array_search($snapshot_start, $snapshots);
+    if( ! $start_key) {
+        // the fixed snapshot does not exist: fall back to the empty repository.
+        return 'empty';
+    }
+    $snapshots = array_slice($snapshots, $start_key);
+    foreach($snapshots as $snapshot) {
+        if(is_file($root_path . $snapshot . '/' . $path)) {
+            return $snapshot;
+        }
+    }
+    return 'head';
+}
+
+function lookup_monday($path, $tier_id) {
+    global $config;
+
+    $week_size = $config['week_size'] ?: 5;
+    $root_path = $config['snapshots_dir'] ?: "/srv/porthos/webroot/";
     $snapshots = array_reverse(array_map('basename', glob($root_path . "d20*")));
     $last_snapshot_day_id = date('w', get_snapshot_timestamp($snapshots[0]));
     // $monday_offset formula:
@@ -93,4 +134,19 @@ function lookup_snapshot($path, $tier_id = 0, $week_size = 5) {
         }
     }
     return $i < 0 ? 'head' : $snapshots[$i];
-}
+}
+
+function lookup_snapshot($path, $version, $tier_id) {
+    global $config;
+
+    $policy_name = lookup_policy($version, $tier_id);
+    if($policy_name == 'lookup_monday') {
+        return lookup_monday($path, $tier_id);
+    } elseif(substr($policy_name, 0, 6) == 'fixed-') {
+        return lookup_fixed($path, substr($policy_name, 6));
+    } elseif($policy_name == 'empty') {
+        return 'empty';
+    } else {
+        return 'head';
+    }
+}