Misc on KK's Blog (fromkk)

Kindle Paperwhite 5 Review

bebound@gmail.com (KK) — Fri, 09 Jan 2026 21:49:00 +0800

I bought a Kindle Paperwhite 1 in 2013, when I still in the university. I like it very much and I’ve read many programming books with it. It still works fine after 10 years, but I want to tries the new model with larger screen and faster fresh speed. So I bought a used Kindle Paperwhite 5 signature version for only 620 Yuan (about $90) recently. Here is my review.

Run Synology in QNAP NAS with PVE

bebound@gmail.com (KK) — Sun, 29 Jun 2025 20:53:00 +0800

Three years ago, I bought a QNAP TS-453Dmini NAS. Although it has a slow WEB UI and slow restart, it still fits my needs as all of the applications I need are running in Docker.

Recently, I want to move some files from my Mac to NAS to save space. I need a application behave like Dropbox, which can show all the files in the NAS and only download the files I need. I have tried the QSync, but it does not have thumbnails for cloud image and it does not have icons to show the file status. I also tried the Seafile, it’s a powerful application, which requires 4G RAM to run, and there is bug in the thumbnail. I used to have a Synology ARM NAS, the Synology Drive has all the features I need, so I want to run it on my QNAP NAS. After some research, I managed to run Synology and QNAP together on my NAS. Here is the guide.

Improve Git speed in WSL

bebound@gmail.com (KK) — Tue, 26 Dec 2023 11:16:00 +0800

The disk performance in WSL2 is poor, it takes a long time to run git status in a host’s repo. Moreover, if you set a fancy shell prompt, it will take a long time to show the prompt. This article will introduce how to speed up Git in WSL2.

How to speed up Git Command

The performance of file system in WSL2 is poor, it takes a long time to run git status in a host’s repo. The solution is to use git.exe in Windows folder. You can add this into your bashrc:

iPod Video Review

bebound@gmail.com (KK) — Tue, 26 Dec 2023 11:16:00 +0800

I bought a iPod Video 5.5th Gen 80G recently. It’s only 200 Yuan (about $30) and I’m satisfied with it.

Rockbox

The original firmware supports few audio format, it even can’t play FLAC. I install rockbox on it, which support FLAC and other format and I can transfer music without using iTunes or Finder. It also support theme and plugin, which makes it more powerful.

MacPod error

If you restore the iPod on macOS, it raises Warning: This is a MacPod, Rockbox only runs on WinPods. See http://www.rockbox.org/wiki/IpodConversionToFAT32 during installation. The easiest way to fix this is to restore it on Windows.

Line Ending in Git

bebound@gmail.com (KK) — Sat, 21 Oct 2023 15:40:00 +0800

When working on a project with multiple developers, the line ending can be troublesome. This article will explain how to configure line ending in Git.

Basic configuration

The line ending on Windows is CRLF, on Linux is LF. To prevent the line ending issue, we can set core.autocrlf to true on Windows to let git convert CRLF to LF when commit, and convert LF to CRLF when checkout. It is automatically configured if you install git on Windows.

How to copy files temporarily in Dockerfile

bebound@gmail.com (KK) — Thu, 24 Aug 2023 11:49:00 +0800

It’s very common to copy a local file into the container when build docker image. In general, we use COPY command. But it creates a new layer and increase the final image size. If this is a temporal file and we don’t want users waste their storage space, how can we remove it? Here are some approaches.

Download the File Dynamically

If the file can be download from URL or you can create a local HTTP server to share the file, you can download the file, use it and delete it in one RUN command. For example:

Emacs Chinese-related Settings

bebound@gmail.com (KK) — Thu, 17 Feb 2022 01:27:00 +0800

Auto Switch Input Method in Evil

This setting makes it possible to switch input method based on the context of cursor when entering insert mode.

sis

I’m using sis package with this configuration. You may need to install macism if you’re not using railwaycat/emacsmacport. More settings can be found in emacs-smart-input-source.

(sis-ism-lazyman-config
 "com.apple.keylayout.US"
 "com.apple.inputmethod.SCIM.ITABC")

(sis-global-cursor-color-mode t)
(sis-global-respect-mode t)
(sis-global-context-mode t)
(sis-global-inline-mode t)

fcitx

You can also install fcitx-remote for-osx and use cute-jumper/fcitx.el to do so. As homebrew no longer support some build options, you need to follow the install instructions in the GitHub repository to build fcitx.

QNAP TS-453Dmini Review

bebound@gmail.com (KK) — Wed, 19 Jan 2022 00:17:00 +0800

My first NAS is Synology DS120j, which is ARM based entry level product. It’s okay to use it for downloading and backup, but not power enough for running docker and virtual machine.

So I bought this NAS last month, and I’m satisfied with it. Here are the advantages and disadvantages.

Advantages

High performance.

It is equipped with J4125 quad-core 2.0 GHz processor, 8G RAM, two 2.5G Ports and 4 bays. Here is the spec. Although J4125 is not the fastest CPU in 2022(the newer model coming with N5105), it is still able to run several docker containers together, and I can even run Synology and Windows 10 inside build-in Virtualization Station.

Internet Account Keeps Coming Back after deletion on MacOS

bebound@gmail.com (KK) — Sat, 08 Jan 2022 00:09:00 +0800

Today I tried to delete an inactive Internet account on system preference. It was deleted successfully but come back again after 20 seconds. This drives me nuts.

I tried these methods, but none of them works.

Boot in safe mode, delete account.
Delete record in ZACCOUNT table in ~/Library/Accounts/Accounts4.sqlite.
Delete related items in Keychain Access app.

Later, RedHatDude’s answer gives me a clue, it looks like a iCloud sync problem. I tried to delete the account on my 3 MacBooks together. Thank goodness! It does not show up again.

Dynamic Allocate Executors when Executing Jobs in Spark

bebound@gmail.com (KK) — Sun, 18 Jul 2021 16:52:00 +0800

I wrote a Spark program to process logs. The number of logs always changes as time goes by. To ensure logs can be processed instantly, the number of executors is calculated by the maximum of logs per minutes. As a consequence, the CPU usage is low in executors. In order to decrease resource waste, I tried to find a way to schedule executors during the execution of program.

As shown below, the maximum number of logs per minutes can be a dozen times greater than the minimum number in one day.

Improve Kafka throughput

bebound@gmail.com (KK) — Fri, 28 May 2021 00:57:00 +0800

Kafka is a high-performance and scalable messaging system. Sometimes when handling big data. The default configuration may limit the maximum performance. In this article, I’ll explain how messages are generate and saved in Kafka, and how to improve performance by changing configuration.

Kafka Internals

How does Producer Send Messages?

In short, messages will assembled into batches (named RecordBatch) and send to broker.

The producer manages some internal queues, and each queue contains RecordBatch that will send to one broker. When calling send method, the producer will look into the internal queue and try to append this message to RecordBatch which is smaller than batch.size (default value is 16KB) or create new RecordBatch.

Fix Error: Cask 'java' is unavailable in Homebrew

bebound@gmail.com (KK) — Sun, 07 Mar 2021 00:10:00 +0800

After update brew to latest version, when calling cask related command, it always outputs Error: Cask 'java' is unavailable: No Cask with this name exists., such as brew list --cask. However, the brew command works.

After doing some research, I found Java has been moved to homebrew/core. This makes sense now. I installed java by cask, but it’s not available now and cask throw this error. If I uninstall java from cask, the error should disappear.

Timezone in JVM

bebound@gmail.com (KK) — Sun, 18 Oct 2020 23:49:00 +0800

I wrote a Scala code to get the current time. However, the output is different on the development server and docker.

import java.util.Calendar

println(Calendar.getInstance().getTime)

On my development server, it outputs Sun Oct 18 18:01:01 CST 2020, but in docker, it print a UTC time.

I guess it related to the timezone setting and do a research, here is the result.

How Did JVM Detect Timezone

All of the code can be found in this function: private static synchronized TimeZone setDefaultZone()

Retrieve Large Dataset in Elasticsearch

bebound@gmail.com (KK) — Sun, 21 Jun 2020 20:33:00 +0800

It’s easy to get small dataset from Elasticsearch by using size and from. However, it’s impossible to retrieve large dataset in the same way.

Deep Paging Problem

As we know it, Elasticsearch data is organised into indexes, which is a logical namespace, and the real data is stored into physical shards. Each shard is an instance of Lucene. There are two kind of shards, primary shards and replica shards. Replica shards is the copy of primary shards in case nodes or shards fail. By distributing documents in an index across multiple shards, and distributing those shards across multiple nodes, Elasticsearch can ensure redundancy and scalability. By default, Elasticsearch create 5 primary shards and one replica shard for each primary shards.

C-m, RET and Return Key in Emacs

bebound@gmail.com (KK) — Sat, 11 Apr 2020 21:23:00 +0800

I use Emacs to write blog. In the recent update, I found M-RET no longer behave as leader key in org mode, but behave as org-meta-return. And even more strange is that in other mode, it behave as leader key. And M-RET also works in terminal in org mode. In GUI, pressing C-M-m can trigger leader key.

SO I opened this issue, with the help of these friends, the issue has been fixed. Here is the cause of the bug.

Time boundary in InfluxDB Group by Time Statement

bebound@gmail.com (KK) — Sun, 29 Mar 2020 22:30:00 +0800

These days I use InfluxDB to save some time series data. I love these features it provides:

High Performance

According to to it’s hardware guide, a single node will support more than 750k point write per second, 100 moderate queries per second and 10M series cardinality.

Continuous Queries

Simple aggregation can be done by InfluxDB’s continuous queries.

Overwrite Duplicated Points

If you submit a new point with same measurements, tag set and timestamp, the new data will overwrite the old one.

Jaeger Code Structure

bebound@gmail.com (KK) — Sun, 22 Sep 2019 17:07:00 +0800

Here is the main logic for jaeger agent and jaeger collector. (Based on jaeger 1.13.1)

Jaeger Agent

Collect UDP packet from 6831 port, convert it to model.Span, send to collector by gRPC

Jaeger Collector

Process gRPC or process packet from Zipkin(port 9411).

Jaeger Query

Listen gRPC and HTTP request from 16686.

Build Your Own Tiny Tiny RSS Service

bebound@gmail.com (KK) — Mon, 10 Jun 2019 00:25:00 +0800

After Inoreader change the free plan, which limit the max subscription to 150, I begin to find an alternative. Finally, I found Tiny Tiny RSS. It has a nice website and has the fever API Plugin which was supported by most of the RSS reader app, so you can read RSS on all of you devices.

This post will tell you how to deploy it on your server.

Prerequisite

You need to install Docker and Docker Compose before using docker-compose.yml

Preview LaTeX in Org Mode with Emacs in MacOS

bebound@gmail.com (KK) — Sun, 12 May 2019 20:26:00 +0800

Using the right Emacs Version

I failed to preview LaTeX with emacs-plus. If you have installed d12frosted/emacs-plus, uninstall it and use emacs-mac.

brew tap railwaycat/emacsmacport
brew install emacs-mac

If you like the fancy spacemacs icon, install it with cask: brew cask install emacs-mac-spacemacs-icon

Install Tex

Download and install BasicTeX.pkg here.
Add /Library/TeX/texbin to PATH.
Install dvisvgm by sudo tlmgr update --self && sudo tlmgr install dvisvgm collection-fontsrecommended

Emacs settings

Add TeX related bin to path: (setenv "PATH" (concat (getenv "PATH") ":/Library/TeX/texbin"))
Tell Org Mode to create svg images: (setq org-latex-create-formula-image-program 'dvisvgm)

Now you can see the rendered LaTeX equation by calling org-preview-latex-fragment or using shortcut ,Tx.

Some Useful Shell Tools

bebound@gmail.com (KK) — Sun, 07 May 2017 15:34:00 +0800

Here are some shell tools I use, which can boost your productivity. Mordern-unix is a great repo that list lots of modern unix tools.

Prezto

A zsh configuration framework. Provides auto completion, prompt theme and lots of modules to work with other useful tools. I extremely love the agnoster theme.

Fasd

Help you to navigate between folders and launch application.

Here are the official usage example:

Start

bebound@gmail.com (KK) — Tue, 18 Apr 2017 15:46:00 +0800

Over the years, I have read so many programmers’ blogs, which has helped me a lot. Now I think it’s the time to start my own blog.

I hope this can enforce myself to review what I have learned, and it would even be better if someone can benefit from it.