Google Cloud Functions Java 11 (Beta) Runtime - Performance Issue

Question

I have created a new Cloud Function using Java 11 (Beta) Runtime to handle HTML form submission for my static site. It's a simple 3-field form (name, email, message). No file upload is involved. The function does 2 things primarily:

1. Creates a pull request with BitBucket
2. Sends email to me using SendGrid

NOTE: It also verifies recaptcha but I've disabled it for testing.

The function when ran on my local machine (base model 2019 Macbook Pro 13") takes about 3 secs. I'm based in SE Asia. The same function when deployed to Google Cloud us-central1 takes about 25 secs (8 times slower). I have almost the same code running in production as part of a Servlet on GAE Java 8 runtime also in US Central region for a few years. It takes about 2-3 secs including recaptcha verification and sending the email. I'm trying to port it over to Cloud Function, but the performance is about 10 times slower with Cloud Function even without recaptcha verification.

For comparison, the Cloud Function is running on 256MB / 400GHz instance, whereas my GAE Java 8 runtime runs on F1 (128MB / 600GHz) instance. The function is using only about 75MB of memory. The function is configured to accept unauthenticated requests.

I noticed that even basic String concatenation like: String c = a + b; takes a good 100ms on the Cloud Function. I have timed the calls and a simple string concatenation of about 15 strings into one takes about 1.5-2.0 seconds.

Moreover, writing a small message (~ 1KB) to the HTTPUrlConnection output stream and reading the response back takes about 10 seconds (yes seconds)!

/* Writing < 1KB to output stream takes about 4-5 secs */
wr = new OutputStreamWriter(con.getOutputStream());
wr.write(encodedParams);
wr.flush();
wr.close();

/* Reading response also take about 4-5 secs */
String responseMessage = con.getResponseMessage();

Similarly, the SendGrid code below takes another 10 secs to send the email. It takes about 1 sec on my local machine.

Email from = new Email(fromEmail, fromName);
Email to = new Email(toEmail, toName);
Email replyTo = new Email(replyToEmail, replyToName);
Content content = new Content("text/html", body);

Mail mail = new Mail(from, subject, to, content);
mail.setReplyTo(replyTo);
SendGrid sg = new SendGrid(SENDGRID_API_KEY);
Request sgRequest = new Request();
Response sgResponse = null;
try {
    sgRequest.setMethod(Method.POST);
    sgRequest.setEndpoint("mail/send");
    sgRequest.setBody(mail.build());
    sgResponse = sg.api(sgRequest);            
} catch (IOException ex) {
    throw ex;
}

Something is obviously wrong with the Cloud Function. Since my original code is running on GAE Java 8 runtime, it was very easy for me to port it over to the Cloud Function with minor changes. Otherwise I would have gone with NodeJS runtime. I'm also not seeing any of the performance issues when running this function on my local machine.

Can someone help me make sense of the slow performance issue?

Answer 1

What you're seeing is almost certainly due to the "cold start" cost associated with the creation of a new server instance to handle the request. This is an issue with all types of Cloud Functions, as described in the documentation:

Several of the recommendations in this document center around what is known as a cold start. Functions are stateless, and the execution environment is often initialized from scratch, which is called a cold start. Cold starts can take significant amounts of time to complete. It is best practice to avoid unnecessary cold starts, and to streamline the cold start process to whatever extent possible (for example, by avoiding unnecessary dependencies).

I would expect JVM languages to have an even longer cold start time due to the amount of time that it takes to initalize a JVM, in addition to the server instance itself.

Other than the advice above, there is very little one can due to effectively mitigate cold starts. Efforts to keep a function warm are not as effective as you might imagine. There is a lot of discussion about this on the internet if you wish to search.

Keep in mind that the Java runtime is also in beta, so you can expect improvements in the future. The same thing happened with the other runtimes.