Concurrency option for warming up X instances of of a lambda.

README.md

@@ -129,6 +129,7 @@ functions:
 * **enabled** (default `false`)
 * **source** (default `{ "source": "serverless-plugin-warmup" }`)
 * **sourceRaw** (default `false`)
+* **concurrency** (default `1`)
 
 ```yml
 custom:
@@ -146,7 +147,8 @@ custom:
     timeout: 20
     prewarm: true // Run WarmUp immediately after a deploymentlambda
     source: '{ "source": "my-custom-payload" }'
-    sourceRaw: true // Won't JSON.stringify() the source, may be necessary for Go/AppSync deployments   
+    sourceRaw: true // Won't JSON.stringify() the source, may be necessary for Go/AppSync deployments
+    concurrency: 5 // Warm up 5 concurrent instances
 ```
 
 **Options should be tweaked depending on:**
@@ -285,8 +287,20 @@ if(context.custom.source === 'serverless-plugin-warmup'){
 
 ...
 ```
+If you're using the `concurrency` option you might consider adding a slight delay before returning when warming up to ensure your function doesn't return before all concurrent requests have been started:
 
+```javascript
+module.exports.lambdaToWarm = function(event, context, callback) {
+  if (event.source === 'serverless-plugin-warmup') {
+    /** Slightly delayed (25ms) response for WarmUP plugin to ensure concurrent invocation */
+    await new Promise(r => setTimeout(r, 25))
+    console.log('WarmUP - Lambda is warm!')
+    return
+  }
 
+  ... add lambda logic after
+}
+```
 ## Deployment
 
 Once everything is configured WarmUP will run on SLS `deploy`.

src/index.js

@@ -135,7 +135,8 @@ class WarmUP {
         : defaultOpts.enabled,
       source: (typeof possibleConfig.source !== 'undefined')
         ? (possibleConfig.sourceRaw ? possibleConfig.source : JSON.stringify(possibleConfig.source))
-        : (defaultOpts.sourceRaw ? defaultOpts.source : JSON.stringify(defaultOpts.source))
+        : (defaultOpts.sourceRaw ? defaultOpts.source : JSON.stringify(defaultOpts.source)),
+      concurrency: (typeof possibleConfig.concurrency === 'number') ? possibleConfig.concurrency : defaultOpts.concurrency
     }
   }
 
@@ -157,7 +158,8 @@ class WarmUP {
 
     const functionDefaultOpts = {
       enabled: false,
-      source: JSON.stringify({ source: 'serverless-plugin-warmup' })
+      source: JSON.stringify({ source: 'serverless-plugin-warmup' }),
+      concurrency: 1
     }
 
     const customConfig = (this.custom && typeof this.custom.warmup !== 'undefined')
@@ -246,9 +248,13 @@ const aws = require("aws-sdk");
 aws.config.region = "${this.options.region}";
 const lambda = new aws.Lambda();
 const functions = ${JSON.stringify(functions)};
+
 module.exports.warmUp = async (event, context, callback) => {
   console.log("Warm Up Start");
+
   const invokes = await Promise.all(functions.map(async (func) => {
+    console.log(\`Warming up function: \${func.name} with concurrency: \${func.config.concurrency}\`);
+
     const params = {
       ClientContext: Buffer.from(\`{"custom":\${func.config.source}}\`).toString('base64'),
       FunctionName: func.name,
@@ -257,13 +263,14 @@ module.exports.warmUp = async (event, context, callback) => {
       Qualifier: process.env.SERVERLESS_ALIAS || "$LATEST",
       Payload: func.config.source
     };
-
+    
     try {
-      const data = await lambda.invoke(params).promise();
-      console.log(\`Warm Up Invoke Success: \${functionName}\`, data);
+      await Promise.all(Array(func.config.concurrency).fill(0)
+        .map(async _ => await lambda.invoke(params).promise()))
+      console.log(\`Warm Up Invoke Success: \${func.name}\`);
       return true;
     } catch (e) {
-      console.log(\`Warm Up Invoke Error: \${functionName}\`, e);
+      console.log(\`Warm Up Invoke Error: \${func.name}\`, e);
       return false;
     }
   }));