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.

In Django, when edit field in admin page or post data to forms, the leading and tailing whitespace in CharField and TextField are removed.

The reason is strip=True parameter in forms.CharField, which is added in Djagno 1.9. You can see the discussion in django tiket #4960 and here is source code. models.CharField and models.TextField use formfield() to create form to interact with user, then both of them eventually create a forms.CharField

In Django 3.1, Django support save python data into database as JSON encoded data and it is also possible to make query based on field value in JSONField. The detailed usage can be found here. If you are using older version and want to try this feature. Though there are many packages ported this function, I recommend django-jsonfield-backport.

django-jsonfield-backport

This package save data as JSON in database and also support JSON query. If your database meet the requirements (MySQL > 5.7, PG > 9.5, MariaDB > 10.2 or SQLite > 3.9 with JSON1 extension), you can use JSONField like Django’s native implementation.

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.

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.

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.