fix: Race conditions with multiple downloads on the same layer (#7422)

* fix: Race conditions with multiple downloads on the same layer

* Update format

* Fix lint

* Using uuid for download filename

Author: dkphm

samcli/local/layers/layer_downloader.py

@@ -3,6 +3,7 @@
 """
 
 import logging
+import uuid
 from pathlib import Path
 from typing import List
 
@@ -106,7 +107,7 @@ def download(self, layer: LayerVersion, force=False) -> LayerVersion:
             LOG.info("%s is already cached. Skipping download", layer.arn)
             return layer
 
-        layer_zip_path = layer.codeuri + ".zip"
+        layer_zip_path = f"{layer.codeuri}_{uuid.uuid4().hex}.zip"
         layer_zip_uri = self._fetch_layer_uri(layer)
         unzip_from_uri(
             layer_zip_uri,

tests/integration/local/start_api/test_start_api.py

@@ -3220,6 +3220,20 @@ def test_can_invoke_lambda_layer_successfully(self):
         self.assertEqual(response.content.decode("utf-8"), '"Layer1"')
 
 
+class TestWarmContainersMultipleRemoteLayersInvoke(WarmContainersWithRemoteLayersBase):
+    template_path = "/testdata/start_api/template-warm-containers-multi-layers.yaml"
+    container_mode = ContainersInitializationMode.EAGER.value
+    mode_env_variable = str(uuid.uuid4())
+    parameter_overrides = {"ModeEnvVariable": mode_env_variable}
+
+    @pytest.mark.flaky(reruns=3)
+    @pytest.mark.timeout(timeout=600, method="thread")
+    def test_can_invoke_lambda_layer_successfully(self):
+        response = requests.get(self.url + "/", timeout=300)
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.content.decode("utf-8"), '"Layer1"')
+
+
 class TestDisableAuthorizer(StartApiIntegBaseClass):
     # integration test for scenario: 'sam local start-api --disable-authorizer'
     template_path = "/testdata/start_api/lambda_authorizers/serverless-api-props.yaml"

tests/integration/testdata/start_api/template-warm-containers-multi-layers.yaml

@@ -0,0 +1,88 @@
+AWSTemplateFormatVersion : '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+
+Parameters:
+  ModeEnvVariable:
+    Type: String
+  LayerArn:
+    Default: arn:aws:lambda:us-west-2:111111111111:layer:layer:1
+    Type: String
+
+Resources:
+  ApiGatewayApi:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: prod
+      CacheClusterEnabled: true
+      CacheClusterSize: '0.5'
+      MethodSettings:
+        - ResourcePath: /
+          HttpMethod: GET
+          CachingEnabled: true
+          CacheTtlInSeconds: 300
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: main-layers.custom_layer_handler
+      Runtime: python3.9
+      FunctionName: customname
+      CodeUri: .
+      Timeout: 600
+      Environment:
+        Variables:
+          MODE: !Ref ModeEnvVariable
+      Layers:
+        # Test remote layers with warm containers.
+        - Ref: LayerArn
+      Events:
+        ApiEvent:
+          Type: Api
+          Properties:
+            Path: /
+            Method: get
+            RestApiId:
+              Ref: ApiGatewayApi
+  HelloWorldFunction2:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: main-layers.custom_layer_handler
+      Runtime: python3.9
+      FunctionName: customname
+      CodeUri: .
+      Timeout: 600
+      Environment:
+        Variables:
+          MODE: !Ref ModeEnvVariable
+      Layers:
+        # Test remote layers with warm containers.
+        - Ref: LayerArn
+      Events:
+        ApiEvent:
+          Type: Api
+          Properties:
+            Path: /
+            Method: get
+            RestApiId:
+              Ref: ApiGatewayApi   
+  HelloWorldFunction3:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: main-layers.custom_layer_handler
+      Runtime: python3.9
+      FunctionName: customname
+      CodeUri: .
+      Timeout: 600
+      Environment:
+        Variables:
+          MODE: !Ref ModeEnvVariable
+      Layers:
+        # Test remote layers with warm containers.
+        - Ref: LayerArn
+      Events:
+        ApiEvent:
+          Type: Api
+          Properties:
+            Path: /
+            Method: get
+            RestApiId:
+              Ref: ApiGatewayApi                          

tests/unit/local/layers/test_download_layers.py

@@ -98,6 +98,10 @@ def test_download_layer_that_was_template_defined(self, create_cache_patch, reso
     def test_download_layer(
         self, is_layer_cached_patch, create_cache_patch, fetch_layer_uri_patch, unzip_from_uri_patch
     ):
+        class AnyStringWith(str):
+            def __eq__(self, other):
+                return self in other
+
         is_layer_cached_patch.return_value = False
 
         download_layers = LayerDownloader("/home", ".", Mock())
@@ -118,7 +122,7 @@ def test_download_layer(
         fetch_layer_uri_patch.assert_called_once_with(layer_mock)
         unzip_from_uri_patch.assert_called_once_with(
             "layer/uri",
-            str(Path("/home/layer1.zip").resolve()),
+            AnyStringWith(str(Path("/home/layer1_"))),
             unzip_output_dir=str(Path("/home/layer1").resolve()),
             progressbar_label="Downloading arn:layer:layer1",
         )