Tag: english

Down the __extmap rabbit hole

December 15, 2020
valeblog
0 Comment

Was trying to figure out what defrecord does in the impl of ILookup it generates and I absolutely do not understand that magic. Essentially it amounts to (get __extmap key)  and I can’t even figure out how this magical __extmap gets into scope (a global or some special runtime thing?) and this isn’t even used. Confused

zerusski on Clojurians Slack

This post on Clojurians sent me down the rabbit hole looking for where this “mysterious” __extmap comes from. It really isn’t obvious at first, but when I found it, it was “wow” times “duh”.

Read More

Beyond burger

December 14, 2020
valeblog
0 Comment

Pretty much starved and three more hours to go until my flight out of Dubai, I was looking for food. Something filling. Tokyo destroyed my plan of eating something before taking off there since there was literally not a single shop open in Narita airport. Luckily Dubai wasn’t dead like that so I had plenty to choose from.

Read More

Mount Eggplant!

December 5, 2020
valeblog
0 Comment

One of the 100 famous Japanese mountains in reach for a day hike from Tokyo is Mt Nasu (which in Japanese is a homophone with “eggplant”) in Tochigi. It’s easy (though not particularly cheap) to get there by (bullet) train and bus. This time I went for a quick hike to the Chausu peak (which is a much shorter climb than the highest Sanbon-yari). The weather wasn’t exactly great, cloudy and extremely windy, but at least it wasn’t dumping on me.

Read More

QUIC and quicker

December 4, 2020
valeblog
0 Comment

The past week or so I’ve been working on implementing the QUIC protocol in Clojure. Currently there is no Java implementation to use either (that I know of), and I just found out the other day that netty decided to use the Cloudflare’s Rust library quiche under the hood instead of rolling their own. The protocol is currently a IETF draft at version 32, expected to turn into an RFC soon.

Read More

GitOps with Argo

December 1, 2020
valeblog
0 Comment

It’s been a year since I wrote about bootstrapping a cluster with Argo and using Argo Rollouts for canary deploys based on Prometheus metrics. Since then many things have changed. I moved from Digital Ocean to Linode (mostly because Linode has a Tokyo region) and from a single-node k3s “cluster” to a 4-node one. But most of how I use Argo CD for GitOps hasn’t changed.

orange and brown tree branch
Read More

Clojure and Java functional interfaces

November 23, 2020
valeblog
1 Comment

Java 8 came out in 2014 and brought along functional interfaces. Functional in general just means that you can treat functions (or methods) as “things” instead of having no proper way to talk about them. In this sense Javascript for example is functional: you can pass around functions all you want. Java’s had Runnable and Callable that are pretty similar in concept.

Then came Java 8 and with it the “mighty arrows.” For some reason Ruby, Javascript and Java all opted to use the same bit of syntax to talk about lambdas (anonymous functions): ->. In Ruby it’s ->(foo) { foo }, in Javascript it’s (foo) -> foo, and surprisingly in Java it’s the same. Run a few rounds with futures and/or streaming stuff and you’ll definitely want to pass such a lambda to forEach for example.

Read More

Clojure proxy

November 22, 2020
valeblog
0 Comment

Next up in the series complaining about Clojure’s Java interop is proxy. While vararg method calls are inconvenient at worst, there are some (I’d say common) things that simply cannot be achieved with proxy.

Once again this is something I ran into while working with Netty. In one of the HTTP/2 examples, they have one implementation extending AbstractHttp2ConnectionHandlerBuilder<T, B> (have I mentioned I find these extremely long Java class names just hilarious?). The Java implementation is pretty straightforward: implement the abstract method of the class and be done with it.

Read More

Greenbelly Meal2Go

October 30, 2020
valeblog
0 Comment

I heard about the Greenbelly trail food from a thru-hiker’s video and since I was looking for some alternative to my protein bars, I gave it a try. I figured ordering the 30-pack box will last me a while.

They’re pretty big granola-bar like blocks of stuff. The packet they come in can be re-sealed too if you can’t eat one in one go (which is a possibility actually).

Read More

How does Kubernetes select labels?

October 7, 2020
valeblog
1 Comment

kubectl has the feature to select objects by filtering on labels using the -l flag. Labels are key-value pairs attached to objects as metadata and they don’t have to be unique. I’ve most often seen them used to identify what project or app an individual resource belongs to. Helm uses labels to mark resources with the app, chart and revision they belong to.

But wait, if they’re not unique and there is a way to select multiple values with set operators, how does that work? The database backing Kubernetes by default, etcd is a key-value store. While it can natively select multiple records by prefix matching, it’d be hard to imagine labels working like that. There are many of them and the selectors are complex.

So I dove into Kubernetes’s source code to figure out how it works.

Read More

Partition of integer into exactly the given number of distinct parts

October 5, 2020
valeblog
0 Comment

Ran into this issue in a programming challenge on HackerRank and I was surprised there weren’t any “simple” solutions online. The math related is mostly focused on finding the number of possible partitions of an integer, instead of generating even just one such partition.

A very naive approach might be to enumerate all partitions and then filter them down to those with exactly the wanted number of summands and then filter further to those with distinct parts and pick the first that fulfills the conditions.

But when the subject integer can be 1018 then that simply isn’t realistic. Insert sophisticated simile involving the heat death of the universe.

Read More