Thread by @RaeKnowler

The last speaker of #DevOpsDays Geneva is @RonYishai, talking about bottlenecks in serverless applications.

I love @RonYishai’s shirt. :) #DevOpsDays

What is serverless? Can be seen as part of an ongoing evolution of tech: more focus on business logic, less concern about stack implementation (also less control over it). #devopsdays @RonYishai

Serverless usually lets you pay for only the load you use; out of the box auto-scaling, including down to zero. Less cost, less ops (‘LowOps’), so higher dev velocity. #DevOpsDays @RonYishai

But... you get limited running time (15 mins on OpenFaaS), limited memory, cold starts 🥶, and your functions are all stateless. All you have are the data that the function was triggered with. Can make monitoring tough! #DevOpsDays @RonYishai

Serverless means microservices, highly distributed and event-driven. We utilise many different services via managed APIs. Look at all the services in this example from HSBC! This is already happening. #devopsdays @RonYishai

Bottlenecks in a simple non-serverless example could be the servers’ limitations in CPU, RAM, storage. We also have software-logic bottlenecks: in-memory queues for example. We need to monitor where these show up. #DevOpsDays @RonYishai

Here’s a serverless application using Kinesis and Lambda services. It looks very simple but can also have bottlenecks. We can see this by watching the age of iterators entering Lambda rising and peaking (and we get that graph automatically). #devopsday @RonYishai

Kinesis could be the bottleneck. It uses multiple shards to process data: use shard-level metrics to check that, and increase number of shards if not enough. #devopsdays @RonYishai

Lambda can also timeout. You might need to adjust its memory limit, or adjust the batch size from Kinesis. Past a certain CPU limit, there’s no more return in processing speed, so you should tune it carefully. #devopsdays @RonYishai

Tips:
- use at least 512 MB of memory when doing HTTPS
- use >1.8 GB to unlock another core and get more done!
#devopsdays @RonYishai

Final potential bottleneck in our example: the DynamoDB read/write limit. You can easily use autoscaling here, but set a min *and* max limit. (If it scales down too small, it will take too long to scale up when needed again.) #devopsdays @RonYishai

People tend to worry about cold starts, but it’s really not a big deal for serverless apps. (Unless you really *always* need very fast response times.) Do be aware of concurrency limits. But the biggest bottleneck cause is using unscalable resources. #devopsdays @RonYishai

In conclusion: know what you’re putting into your serverless application! Find out what the limitations of services are, which ones can scale, etc. Choose an event-driven flow. Set good limits! #DevOpsDays @RonYishai

Monitoring: distributed tracing is important, and so is cost monitoring. Load test the system before things break in production! #devopsdays @RonYishai

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