It provides an implementation of the GRPC functions that Kubernetes relies upon. Kine is the component of k3s that allows it to use various RDBMS as an etcd replacement. Therefore, to use SQL database as a storage, we need to provide an etcd-to-SQL translation layer, which is called Kine. Cluster components (API server) expect an etcd-like interface to which they can write and from which they can read. If it works for k3s, why wouldn't it work for any other cluster? How?Īs was mentioned in the beginning, Kubernetes and etcd are tightly coupled. Due to this, critical bugs take a long time to fix.īesides, why not? Why shouldn't we use other storage backends with Kubernetes? Having more options is a good thing and there really are no downsides to running Kubernetes with RDBMS, whether it's PostgreSQL, MySQL or anything else you might be comfortable with.Īlso, running Kubernetes with RDBMS isn't such a novel idea either, k3s, a production-grade Kubernetes distribution can run with relational DB instead of etcd. Apart the user perspective, etcd has little usage outside of Kubernetes and has been in state of decline because no one wants to maintain it. If you're running your own Kubernetes cluster, then you know the pains of managing etcd. In this article we will explore how we could replace etcd with PostgreSQL database, as well as why and when it might make sense to do so. It's intertwined and tightly coupled with Kubernetes, and it might seem like an inseparable part of a cluster, or is it? In our database, the smartwatch has the production date ' 07:35:13' now it's ' 00:00:00', which is the first day of the month.Etcd is the brain of every Kubernetes cluster, the key-value storage keeping track of all the objects in a cluster. In this query, the function DATE_TRUNC() truncates the timestamp to month precision. You can also use it to get the first day of the month for a given date.įor each watch, let's get the name and production date to month precision – no grouping needed. Of course, you don't have to use the DATE_TRUNC() function just to group records. (In our example, this is D ATE_TRUNC( 'month', production_timestamp).) After the GROUP BY clause, you should place the columns or expressions used with the aggregate function in the SELECT statement.
If you group records using an aggregate function, you have to use the GROUP BY clause. (The COUNT() aggregate function counts the number of products).
In our example, the number of products is totaled for each month. Grouping records by month is very common in PostgreSQL. days, months) of the timestamp are replaced with ones.) The month-level precision causes the day to be displayed as '01' and the time to be filled with zeros. In our database, the smartwatch has the production date 07:35:13 after it's been truncated to month precision, it becomes 00:00:00. The function DATE_TRUNC() truncates the timestamp to the given precision (in this case, the month). (In our example, we use the column production_timestamp). The second argument is the timestamp value this can be an expression returning a timestamp value or the name of a timestamp column. Note that the specifier is a string and needs to be enclosed in quotes. First, we have the date part specifier (in our example, 'month'). (In our example, we used month precision.) Use the DATE_TRUNC() function if you want to retrieve a date or time with a specific precision from a PostgreSQL database. Here's the result of the query: production_to_month GROUP BY DATE_TRUNC('month',production_timestamp) You can use the DATE_TRUNC() function to group records in a table by month. Our database has a table named watch with data in the columns id, name, and production_timestamp. You'd like to group records by month in a PostgreSQL database.
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