西维蜀黍

【Database】Cassandra

Cassandra

Cassandra is a free and open-source, distributed, wide-column store, NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassandra offers support for clusters spanning multiple datacenters, with asynchronous masterless replication allowing low latency operations for all clients.

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【OpenVPN】Ubuntu Setup OpenVPN Server

Server Installation

To install openvpn in a terminal enter:

$ sudo apt install openvpn easy-rsa
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【Golang】Go Memory Model

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【Design Pattern】Microservices - Application Metrics Pattern

Context

You have applied the Microservice architecture pattern.

Problem

How to understand the behavior of an application and troubleshoot problems?

Forces

  • Any solution should have minimal runtime overhead
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【Design Pattern】Microservices - Service Template Pattern

Context

When you start the development of an application you often spend a significant amount of time putting in place the mechanisms to handle cross-cutting concerns. Examples of cross-cutting concern include:

As well as these generic cross-cutting concerns, there are also cross-cutting concerns that are specific to the technologies that an application uses. Applications that use infrastructure services such as databases or a message brokers require boilerplate configuration in order to do that. For example, applications that use a relational database must be configured with a connection pool. Web applications that process HTTP requests also need boilerplate configuration.

It is common to spend one or two days, sometimes even longer, setting up these mechanisms. If you going to spend months or years developing a monolithic application then the upfront investment in handling cross-cutting concerns is insignificant. The situation is very different, however, if you are developing an application that has the microservice architecture. There are tens or hundreds of services. You will frequently create new services, each of which will only take days or weeks to develop. You cannot afford to spend a few days configuring the mechanisms to handle cross-cutting concerns. What is even worse is that in a microservice architecture there are additional cross-cutting concerns that you have to deal with including service registration and discovery, and circuit breakers for reliably handling partial failure.

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