[6.x] Lock the Comb index file across each read-modify-write

src/Search/Comb/Index.php

@@ -2,6 +2,8 @@
 
 namespace Statamic\Search\Comb;
 
+use Closure;
+use Illuminate\Support\Facades\Cache;
 use Statamic\Facades\File;
 use Statamic\Search\Comb\Exceptions\NoQuery;
 use Statamic\Search\Comb\Exceptions\NoResultsFound;
@@ -88,32 +90,36 @@ public function path()
 
     public function delete($document)
     {
-        try {
-            $data = $this->data();
-        } catch (IndexNotFoundException $e) {
-            return;
-        }
+        $this->locked(function () use ($document) {
+            try {
+                $data = $this->data();
+            } catch (IndexNotFoundException $e) {
+                return;
+            }
 
-        $ref = $document->getSearchReference();
+            $ref = $document->getSearchReference();
 
-        if (! $data->has($ref)) {
-            return;
-        }
+            if (! $data->has($ref)) {
+                return;
+            }
 
-        $data->forget($ref);
+            $data->forget($ref);
 
-        $this->save($data);
+            $this->save($data);
+        });
     }
 
     public function insertDocuments(Documents $documents)
     {
-        try {
-            $data = $this->data();
-        } catch (IndexNotFoundException $e) {
-            $data = collect();
-        }
-
-        $this->save($documents->union($data));
+        $this->locked(function () use ($documents) {
+            try {
+                $data = $this->data();
+            } catch (IndexNotFoundException $e) {
+                $data = collect();
+            }
+
+            $this->save($documents->union($data));
+        });
     }
 
     public function deleteIndex()
@@ -128,6 +134,11 @@ protected function save($documents)
         app('files')->put($this->path(), $documents->toJson(), lock: true);
     }
 
+    private function locked(Closure $callback)
+    {
+        return Cache::lock('search-index-'.$this->name, 60)->block(30, $callback);
+    }
+
     public function extraAugmentedResultData(Result $result)
     {
         return [

tests/Search/CombIndexTest.php

@@ -2,11 +2,14 @@
 
 namespace Tests\Search;
 
+use Illuminate\Contracts\Cache\Lock;
 use Illuminate\Contracts\Filesystem\Filesystem;
+use Illuminate\Support\Facades\Cache;
 use Mockery;
 use PHPUnit\Framework\Attributes\Test;
 use Statamic\Contracts\Search\Searchable;
 use Statamic\Search\Comb\Index;
+use Statamic\Search\Documents;
 use Tests\TestCase;
 
 class CombIndexTest extends TestCase
@@ -114,6 +117,59 @@ public function delete_rewrites_the_index_when_the_reference_is_present()
         );
     }
 
+    #[Test]
+    public function inserting_holds_the_index_lock_across_the_read_and_the_write()
+    {
+        $path = $this->createIndexFile(['entry::a' => ['title' => 'Foo']]);
+        $this->expectIndexLock(
+            acquired: fn () => $this->assertSame(['entry::a' => ['title' => 'Foo']], json_decode(file_get_contents($path), true)),
+            released: fn () => $this->assertSame(['entry::b' => ['title' => 'Bar'], 'entry::a' => ['title' => 'Foo']], json_decode(file_get_contents($path), true)),
+        );
+
+        $index = $this->getIndex('test', ['path' => $this->tmpDir], null);
+
+        $index->insertDocuments(new Documents(['entry::b' => ['title' => 'Bar']]));
+    }
+
+    #[Test]
+    public function deleting_holds_the_index_lock_across_the_read_and_the_write()
+    {
+        $path = $this->createIndexFile(['entry::a' => ['title' => 'Foo'], 'entry::b' => ['title' => 'Bar']]);
+        $this->expectIndexLock(
+            acquired: fn () => $this->assertCount(2, json_decode(file_get_contents($path), true)),
+            released: fn () => $this->assertSame(['entry::b' => ['title' => 'Bar']], json_decode(file_get_contents($path), true)),
+        );
+
+        $index = $this->getIndex('test', ['path' => $this->tmpDir], null);
+
+        $document = Mockery::mock(Searchable::class);
+        $document->shouldReceive('getSearchReference')->andReturn('entry::a');
+
+        $index->delete($document);
+    }
+
+    private function expectIndexLock(?\Closure $acquired = null, ?\Closure $released = null)
+    {
+        $lock = Mockery::mock(Lock::class);
+        $lock->shouldReceive('block')->withArgs(fn ($seconds, $callback) => $callback instanceof \Closure)->once()->andReturnUsing(function ($seconds, $callback) use ($acquired, $released) {
+            if ($acquired) {
+                $acquired();
+            }
+
+            $result = $callback();
+
+            if ($released) {
+                $released();
+            }
+
+            return $result;
+        });
+
+        Cache::shouldReceive('lock')->with('search-index-test', 60)->once()->andReturn($lock);
+
+        return $lock;
+    }
+
     private function createIndexFile(array $data): string
     {
         $this->tmpDir = sys_get_temp_dir().'/statamic_comb_test_'.uniqid();