From b4c3101b291f2b6ef620bbe1c62708682f6ed26c Mon Sep 17 00:00:00 2001
From: Andras Bacsai <5845193+andrasbacsai@users.noreply.github.com>
Date: Mon, 19 Oct 2026 21:08:06 +0200
Subject: [PATCH] fix(compose): reject scale and replicas greater than one
 (#12213)

---
 bootstrap/helpers/parsers.php             | 22 ++++++++
 tests/Feature/ComposeServiceScaleTest.php | 67 +++++++++++++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 tests/Feature/ComposeServiceScaleTest.php

diff --git a/bootstrap/helpers/parsers.php b/bootstrap/helpers/parsers.php
index aa9639f737..21f0d7326d 100644
--- a/bootstrap/helpers/parsers.php
+++ b/bootstrap/helpers/parsers.php
@@ -200,6 +200,26 @@ function forgetComposeBindStorage(Application|ServiceApplication|ServiceDatabase
  *
  * @throws Exception If the source is missing or contains shell metacharacters
  */
+/**
+ * Coolify sets container_name on every Compose service, and Docker Compose does not start more
+ * than one container of a service that has a fixed container_name.
+ *
+ * @throws Exception If the service sets scale or deploy.replicas to more than 1
+ */
+function validateComposeServiceScale(string $serviceName, mixed $service): void
+{
+    foreach (['scale', 'deploy.replicas'] as $key) {
+        $value = data_get($service, $key);
+        if (is_numeric($value) && (int) $value > 1) {
+            throw new Exception(
+                "Service \"{$serviceName}\" sets {$key} to {$value}. Coolify sets a container_name for each service, ".
+                'and Docker Compose cannot run more than one container with the same container_name. '.
+                "Remove {$key}, or define each instance as a separate service."
+            );
+        }
+    }
+}
+
 function validateComposeContentVolumeSource(array $volume): void
 {
     if (! array_key_exists('content', $volume) || ($volume['type'] ?? null) !== 'bind') {
@@ -1139,6 +1159,7 @@ function applicationParser(Application $resource, int $pull_request_id = 0, ?int
                 ' Service names must not contain shell metacharacters.'
             );
         }
+        validateComposeServiceScale((string) $serviceName, $service);
 
         $magicEnvironments = collect([]);
         $image = data_get_str($service, 'image');
@@ -2379,6 +2400,7 @@ function serviceParser(Service $resource): Collection
                 ' Service names must not contain shell metacharacters.'
             );
         }
+        validateComposeServiceScale((string) $serviceName, $service);
 
         $image = data_get_str($service, 'image');
 
diff --git a/tests/Feature/ComposeServiceScaleTest.php b/tests/Feature/ComposeServiceScaleTest.php
new file mode 100644
index 0000000000..ffa582e232
--- /dev/null
+++ b/tests/Feature/ComposeServiceScaleTest.php
@@ -0,0 +1,67 @@
+<?php
+
+use App\Models\Application;
+use App\Models\Environment;
+use App\Models\Project;
+use App\Models\Server;
+use App\Models\Service;
+use App\Models\StandaloneDocker;
+use App\Models\Team;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\Bus;
+
+uses(RefreshDatabase::class);
+
+beforeEach(function () {
+    Bus::fake();
+
+    $team = Team::factory()->create();
+    $server = Server::factory()->create(['team_id' => $team->id]);
+    $this->destination = StandaloneDocker::where('server_id', $server->id)->firstOrFail();
+    $project = Project::factory()->create(['team_id' => $team->id]);
+    $this->environment = Environment::factory()->create(['project_id' => $project->id]);
+});
+
+function scaleTestApplication(string $compose): Application
+{
+    return Application::factory()->create([
+        'build_pack' => 'dockercompose',
+        'docker_compose_raw' => $compose,
+        'environment_id' => test()->environment->id,
+        'destination_id' => test()->destination->id,
+        'destination_type' => test()->destination->getMorphClass(),
+    ])->fresh();
+}
+
+function scaleTestService(string $compose): Service
+{
+    return Service::factory()->create([
+        'docker_compose_raw' => $compose,
+        'environment_id' => test()->environment->id,
+        'server_id' => test()->destination->server_id,
+        'destination_id' => test()->destination->id,
+        'destination_type' => test()->destination->getMorphClass(),
+    ]);
+}
+
+it('rejects a compose application service with more than one replica', function (string $compose, string $setting) {
+    expect(fn () => applicationParser(scaleTestApplication($compose)))
+        ->toThrow(Exception::class, "Service \"celery\" sets {$setting} to 2. Coolify sets a container_name for each service");
+})->with([
+    'scale' => ["services:\n  celery:\n    image: alpine\n    scale: 2\n", 'scale'],
+    'deploy.replicas' => ["services:\n  celery:\n    image: alpine\n    deploy:\n      replicas: 2\n", 'deploy.replicas'],
+]);
+
+it('rejects a service stack service with more than one replica', function () {
+    expect(fn () => serviceParser(scaleTestService("services:\n  celery:\n    image: alpine\n    scale: '2'\n")))
+        ->toThrow(Exception::class, 'Service "celery" sets scale to 2.');
+});
+
+it('accepts one replica and a scale set from a variable', function () {
+    $compose = applicationParser(scaleTestApplication(
+        "services:\n  web:\n    image: alpine\n    scale: 1\n  worker:\n    image: alpine\n    deploy:\n      replicas: \${REPLICAS:-1}\n"
+    ));
+
+    expect(data_get($compose, 'services.web.scale'))->toBe(1)
+        ->and(data_get($compose, 'services.worker.container_name'))->not->toBeEmpty();
+});