Web Server
Usage：receive & process request, load balance problem. Listen to http request with some opening port. Maybe 1k request concurrent, but 10k for each second.
Framework: Nginx, OpenResty, Tomcat, Django
API Gateway
Usgae: An API gateway takes all API calls from clients, then routes them to the appropriate microservice with request routing, composition, and protocol translation. Typically it handles a request by invoking multiple microservices and aggregating the results, to determine the best path. It can translate between web protocols and web‑unfriendly protocols that are used internally.
Framework: Tyk, Kong, Zuul, Orange.
Cache
Usage: distributed cache is a system that pools together the random-access memory (RAM) of multiple networked computers into a single in-memory data store used as a data cache to provide fast access to data. While most caches are traditionally in one physical server or hardware component, a distributed cache can grow beyond the memory limits of a single computer by linking together multiple computers–referred to as a distributed architecture or a distributed cluster–for larger capacity and increased processing power.
Application acceleration; Storing web session data; Decreasing network usage/costs; Reducing the impact of interruptions; Extreme scaling. here
Framework: Redis, Memcached …
RPC Framework
Usage: Remote procedure call, RPC. A remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (local) procedure call, without the programmer explicitly coding the details for the remote interaction.
Framework: Tars, Dubbo, gRPC, Thrift …
Database Sharding
Usage: Database sharding is the process of making partitions of data in a database or search engine, such that the data is divided into various smaller distinct chunks, or shards.
Framework: Sharding jdbc.
Logs
Usage: fetch logs & analyze the logs. ELK B.
Framework: Elasticsearch, Logstash, Kibana, Beats.
Configuere Server
Usage: Store all configures & update.
Framework: Apollo, Zookeeper.
All service in one -> 随着需求增大，很难维护。当里面有个业务模块负载过高时，并不能够单独扩展该服务，必须扩展整个应用程序（就是这么霸道），这可能导致额外的资源浪费。
Micro-service：微服务是由以单一应用程序构成的小服务，自己拥有自己的行程与轻量化处理，服务依业务功能设计，以全自动的方式部署，与其他服务使用 HTTP API 通信。同时服务会使用最小的规模的集中管理 (例如 Docker) 能力，服务可以用不同的编程语言与数据库等组件实现 。
Advantage：技术异构性，可以使用不同的micro-service；isolation；scalable；easy deploy；easy to optimization。
Disadvantage: 服务注册和发现；服务容错；服务监控；服务安全。
Virtualization
虚拟化，是指通过虚拟化技术将一台计算机虚拟为多台逻辑计算机。
OpenStack 管理 VM（Virtual Machine）虚拟机（KVM，Xen，OpenVZ）的工具；Kubernetes 简称 K8s ，是管理 container 容器（Docker）的工具。
Ref: here