add options to build requirements as a lambda layer

Author: david-mkl

README.md

@@ -146,6 +146,38 @@ custom:
 ```
 This will remove all folders within the installed requirements that match
 the names in `slimPatterns`
+
+### Lamba Layer
+Another method for dealing with large dependencies is to put them into a
+[Lambda Layer](https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html).
+Simply add the `layer` option to the configuration.
+```yaml
+custom:
+  pythonRequirements:
+    layer: true
+```
+The requirements will be zipped up and a layer will be created automatically.
+Now just add the reference to the functions that will use the layer.
+```yaml
+functions:
+  hello:
+    handler: handler.hello
+    layers:
+      - {Ref: PythonRequirementsLambdaLayer}
+```
+If the layer requires additional or custom configuration, add them onto the `layer` option.
+```yaml
+custom:
+  pythonRequirements:
+    layer:
+      name: ${self:provider.stage}-layerName
+      description: Python requirements lamba layer
+      compatibleRuntimes:
+        - python3.7
+      licenseInfo: GPLv3
+      allowedAccounts:
+        - '*'
+```
 ## Omitting Packages
 You can omit a package from deployment with the `noDeploy` option. Note that
 dependencies of omitted packages must explicitly be omitted too. By default,

index.js

@@ -10,6 +10,7 @@ const {
   packRequirements
 } = require('./lib/zip');
 const { injectAllRequirements } = require('./lib/inject');
+const { layerRequirements } = require('./lib/layer');
 const { installAllRequirements } = require('./lib/pip');
 const { pipfileToRequirements } = require('./lib/pipenv');
 const { cleanup, cleanupCache } = require('./lib/clean');
@@ -31,6 +32,8 @@ class ServerlessPythonRequirements {
         slimPatterns: false,
         slimPatternsAppendDefaults: true,
         zip: false,
+        inject: true,
+        layer: false,
         cleanupZipHelper: true,
         invalidateCaches: false,
         fileName: 'requirements.txt',
@@ -94,6 +97,14 @@ class ServerlessPythonRequirements {
       }`;
       options.dockerImage = options.dockerImage || defaultImage;
     }
+    if (options.layer) {
+      // If layers are being used, dependencies should not be injected.
+      options.inject = false;
+      // If layer was set as a boolean, set it to an empty object to use the layer defaults.
+      if (options.layer === true) {
+        options.layer = {};
+      }
+    }
     return options;
   }
 
@@ -167,6 +178,7 @@ class ServerlessPythonRequirements {
       }
       return BbPromise.bind(this)
         .then(removeVendorHelper)
+        .then(layerRequirements)
         .then(() =>
           injectAllRequirements.bind(this)(
             arguments[1].functionObj &&

lib/inject.js

@@ -72,6 +72,10 @@ function moveModuleUp(source, target, module) {
  * @return {Promise} the combined promise for requirements injection.
  */
 function injectAllRequirements(funcArtifact) {
+  if (!this.options.inject) {
+    return BbPromise.resolve();
+  }
+
   this.serverless.cli.log('Injecting required Python packages to package...');
 
   if (this.serverless.service.package.individually) {

lib/layer.js

@@ -0,0 +1,49 @@
+const BbPromise = require('bluebird');
+const fse = require('fs-extra');
+const path = require('path');
+const JSZip = require('jszip');
+const { writeZip, addTree } = require('./zipTree');
+
+BbPromise.promisifyAll(fse);
+
+/**
+ * Zip up requirements to be used as layer package.
+ * @return {Promise} the JSZip object constructed.
+ */
+function zipRequirements() {
+    return addTree(new JSZip(), path.join('.serverless', 'requirements')).then(zip =>
+      writeZip(zip, path.join('.serverless', 'pythonRequirements.zip'))
+    );
+}
+
+/**
+ * Creates a layer on the serverless service for the requirements zip.
+ * @return {Promise}
+ */
+function createLayers() {
+  this.serverless.service.layers['pythonRequirements'] = Object.assign({
+      artifact: path.join('.serverless', 'pythonRequirements.zip'),
+      name: `${this.serverless.service.stage}-python-requirements`,
+      description: 'Python requirements generated by serverless-python-requirements.',
+  }, this.options.layer);
+
+  return BbPromise.resolve();
+}
+
+/**
+ * Creates a layer from the installed requirements.
+ * @return {Promise} the combined promise for requirements layer.
+ */
+function layerRequirements() {
+  if (!this.options.layer) {
+    return BbPromise.resolve()
+  }
+
+  this.serverless.cli.log('Packaging Python Requirements Lambda Layer...');
+
+  return BbPromise.bind(this)
+    .then(zipRequirements)
+    .then(createLayers)
+}
+
+module.exports = { layerRequirements };