Support custom build script

README.md

@@ -71,6 +71,7 @@ function name unique per region, for example by setting
 | attach\_dead\_letter\_config | Set this to true if using the dead_letter_config variable | string | `"false"` | no |
 | attach\_policy | Set this to true if using the policy variable | string | `"false"` | no |
 | attach\_vpc\_config | Set this to true if using the vpc_config variable | string | `"false"` | no |
+| build\_script | The path to a custom build script for creating the Lambda package zip file (defaults to the included build.py) | string | `""` | no |
 | dead\_letter\_config | Dead letter configuration for the Lambda function | map | `<map>` | no |
 | description | Description of what your Lambda function does | string | `"Managed by Terraform"` | no |
 | enable\_cloudwatch\_logs | Set this to false to disable logging your Lambda output to CloudWatch Logs | string | `"true"` | no |

archive.tf

@@ -4,8 +4,9 @@ data "external" "archive" {
   program = ["${path.module}/hash.py"]
 
   query = {
-    runtime     = "${var.runtime}"
-    source_path = "${var.source_path}"
+    runtime      = "${var.runtime}"
+    source_path  = "${var.source_path}"
+    build_script = "${coalesce(var.build_script, "${path.module}/build.py")}"
   }
 }
 

hash.py

@@ -120,22 +120,24 @@ def update_hash(hash_obj, file_root, file_path):
     query = {
         'runtime': 'python3.6',
         'source_path': os.path.join(current_dir, 'tests', 'python3-pip', 'lambda'),
+        'build_script': os.path.join(current_dir, 'build.py'),
     }
 else:
     query = json.load(sys.stdin)
 runtime = query['runtime']
 source_path = query['source_path']
+build_script = query['build_script']
 
 # Validate the query.
 if not source_path:
     abort('source_path must be set.')
 
 # Generate a hash based on file names and content. Also use the
-# runtime value and content of build.py because they can have an
+# runtime value and content of the build script because they can have an
 # effect on the resulting archive.
 content_hash = generate_content_hash(source_path)
 content_hash.update(runtime.encode())
-with open(os.path.join(current_dir, 'build.py'), 'rb') as build_script_file:
+with open(build_script, 'rb') as build_script_file:
     content_hash.update(build_script_file.read())
 
 # Generate a unique filename based on the hash.
@@ -146,7 +148,7 @@ def update_hash(hash_obj, file_root, file_path):
 
 # Determine the command to run if Terraform wants to build a new archive.
 build_command = "{build_script} {build_data}".format(
-    build_script=os.path.join(current_dir, 'build.py'),
+    build_script=build_script,
     build_data=bytes.decode(base64.b64encode(str.encode(
         json.dumps({
             'filename': filename,

tests/build-script/lambda/build.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+# 
+# Compiles a Python package into a zip deployable on AWS Lambda.
+#
+# - Builds Python dependencies into the package, using a Docker image to
+#   correctly build native extensions
+# - Able to be used with the terraform-aws-lambda module
+#
+# Dependencies:
+#
+# - Docker
+# - base64
+# - jq
+#
+# Usage:
+#
+# $ ./build.sh "$(echo { \"filename\": \"out.zip\", \"runtime\": \"python3.7\", \"source_path\": \".\" \} | jq . | base64)"
+#
+# - Arguments to be provided as JSON, then Base64 encoded
+
+set -euo pipefail
+
+# Extract variables from the JSON-formatted, Base64 encoded input argument.
+# This is to conform to arguments as passed in by hash.py
+eval "$(echo $1 | base64 --decode | jq -r '@sh "FILENAME=\(.filename) RUNTIME=\(.runtime) SOURCE_PATH=\(.source_path)"')"
+
+# Convert to absolute paths
+SOURCE_DIR=$(cd "$SOURCE_PATH" && pwd)
+ZIP_DIR=$(cd "$(dirname "$FILENAME")" && pwd)
+ZIP_NAME=$(basename "$FILENAME")
+
+# Install dependencies, using a Docker image to correctly build native extensions
+docker run --rm -t -v "$SOURCE_DIR:/src" -v "$ZIP_DIR:/out" lambci/lambda:build-$RUNTIME sh -c "
+    cp -r /src /build &&
+    cd /build &&
+    pip install -r requirements.txt -t . &&
+    chmod -R 755 . &&
+    zip -r /out/$ZIP_NAME * &&
+    chown \$(stat -c '%u:%g' /out) /out/$ZIP_NAME
+"
+
+echo "Created $FILENAME from $SOURCE_PATH"

tests/build-script/lambda/src/main.py

@@ -0,0 +1,6 @@
+def lambda_handler(event, context):
+    print('importing numpy package')
+    import numpy as np  
+    print('checking numpy works correctly')
+    assert np.array_equal(np.array([1, 2]) + 3, np.array([4, 5]))
+    return 'test passed'

tests/build-script/lambda/src/requirements.txt

@@ -0,0 +1,3 @@
+# numpy has native extensions, needs a custom build script to 
+# install correctly if your host OS differs to Lambda OS
+numpy

tests/build-script/main.tf

@@ -0,0 +1,21 @@
+terraform {
+  backend "local" {
+    path = "terraform.tfstate"
+  }
+}
+
+provider "aws" {
+  region = "eu-west-1"
+}
+
+module "lambda" {
+  source = "../../"
+
+  function_name = "terraform-aws-lambda-test-build-script"
+  description   = "Test custom build script functionality in terraform-aws-lambda"
+  handler       = "main.lambda_handler"
+  runtime       = "python3.7"
+
+  source_path  = "${path.module}/lambda/src"
+  build_script = "${path.module}/lambda/build.sh"
+}

variables.tf

@@ -36,6 +36,12 @@ variable "source_path" {
   type        = "string"
 }
 
+variable "build_script" {
+  description = "The path to a custom build script for creating the Lambda package zip file (defaults to the included build.py)"
+  type        = "string"
+  default     = ""
+}
+
 variable "description" {
   description = "Description of what your Lambda function does"
   type        = "string"