Skip to main content

Goroutines

Goroutine is an abstraction of go runtime for parallelism and concurrency. Go on runtime has its scheduler, which distributes goroutines to OS threads. The scheduler is split for each native OS thread scheduler, and each scheduler can steal work from others.

I have done quite a lot of actor programming and know a little about different concurrency models. Go's goroutines can be compared to green threads or Erlang VM's processes, although the go community avoids making such comparisons.

The best part of go concurrency is that it is not based on relatively inefficient OS threads. Creating a thread and switching between them is an expensive operation both in CPU cycles and memory terms.

Goroutines should communicate with each other by messaging and not sharing memory. The Effective Go guide states that

 Do not communicate by sharing memory; instead, share memory by communicating. 

A Gouroutine can use a message channel to communicate with other goroutines. Similar to the actor model programming, it is a sort of a message box between one or more goroutines. Some write to it, some read from it.

In a project I am working on, we replaced a python script with a go program. It is part of a machine learning pipeline, so in essence, it is a glorified CSV writer. The python script was a real CPU and a memory hog, so we thought a go rewrite could reduce the resource usage.

What were the results?

We were IO-bound, so we did not get significant speed improvement, but we achieved some gains in reducing resource usage.
The python script took one core and 4G memory - everything it was given by Kubernetes - and then crashed.

 The go program took all the resources as well but did not crash.

 The bad part is that there is about 1.5 times code in the go program compared to the python script.

 Edit:
My presentation about the subject https://www.youtube.com/watch?v=t-N3ag2rLI4
Labels:

Comments

Post a Comment

Popular posts from this blog

RocksDB data recovery

I recently needed to do some maintenance on a RocksDB key-value store. The task was simple enough, just delete some keys as the db served as a cache and did not contain any permanent data. I used the RocksDB cli administration tool ldb to erase the keys. After running a key scan with it, I got this error Failed: Corruption: Snappy not supported or corrupted Snappy compressed block contents So a damaged database. Fortunately, there's a tool to fix it, and after running it, I had access to the db via the admin tool. All the data was lost though. Adding and removing keys worked fine but all the old keys were gone. It turned out that the corrupted data was all the data there was. The recovery tool made a backup folder, and I recovered the data by taking the files from the backup folder and manually changing the CURRENT file to point to the old MANIFEST file which is apparently how RocksDB knows which sst (table) files to use. I could not access the data with the admin tool, ...
Post a Comment
Read more

I'm not a passionate developer

A family friend of mine is an airlane pilot. A dream job for most, right? As a child, I certainly thought so. Now that I can have grown-up talks with him, I have discovered a more accurate description of his profession. He says that the truth about the job is that it is boring. To me, that is not that surprising. Airplanes are cool and all, but when you are in the middle of the Atlantic sitting next to the colleague you have been talking to past five years, how stimulating can that be? When he says the job is boring, it is not a bad kind of boring. It is a very specific boring. The "boring" you would want as a passenger. Uneventful.  Yet, he loves his job. According to him, an experienced pilot is most pleased when each and every tiny thing in the flight plan - goes according to plan. Passengers in the cabin of an expert pilot sit in the comfort of not even noticing who is flying. As someone employed in a field where being boring is not exactly in high demand, this sounds pro...
Post a Comment
Read more

Careful with externalTrafficPolicy

On a project I am working on is hosted in an EKS cluster with the NGINX ingress controller (the one maintained by Kubernetes). It is deployed using it's official official Helm chart, which I realized, after a lengthy debugging session, was a mistake. The initial setup I aimed to improve had several flaws. Firstly, we were using the AWS Classic Load Balancer in front of the nginx ingress in the cluster, which has been deprecated for some time (years?). Continuing to use it makes little sense to us. The second issue was that we were only running one(!) nginx pod, which is quite sketchy since the exposed web services had essentially no high availability.  I switched to the Network Load Balancer (NLB), which was straightforward - I just needed to change the ingress-nginx service annotation to specify the load balancer type as NLB: service.beta.kubernetes.io/aws-load-balancer-type: nlb However, increasing the replica count turned out to be tricky. When I bumped it up to two, I began to ...
Post a Comment
Read more