“Microservices and common parts"

14 Aug 2016 - Tags: distributed_system

Changing my glossary and replacing the concept of application with service could be a buzzword but this takes me to built a new approach to my work.

Nowadays many products require more services than before to work: perhaps they could be modules, libraries directly integrate in one or more services or applications that communicate and provide a feature, it doesn’t matter cause in any case the product’ll have some dependences.

If you start to follow this path, a lot of redundant concepts will show up in your product:

  • Monitoring
  • Logging
  • Authentication
  • Scaling
  • High availability
  • Distribution
  • Testing (unit, functional, integration..)
  • And others

Some of them, like monitoring or logs, require architecture and tools selection: you can use some B2B tools or host something in house. It’s not only a problem of tooling, the other face of this “redundant money” is how your services can communicate logs, metrics with outside in a clean and reusable way.

In this post I will try to share the common part of a microservices ecosystem and some possible approach to solve this issues.

Logging

All applications require a good and strong log system. There are few libraries able to help you in managing this section but the minimum requirement, in my opinion, includes:

  • Support for multiple stream: usually, I use stdout or file and I move them in a database with a separate pipeline, but a lot of good libraries allow you to manage your logs in different collectors.
  • Different layers like: INFO, DEBUG, WARNING, FATAL.
  • Provide a way to change this layer runtime, for example with a RPC call.

The third point is really important: if your application start to have a big traffic, the amount of logs you must manage will be relevant; so, changing this level runtime allows you to manage the amount of logs that you store and, for example, allows DEBUG information only if you need to do some specific debugging in production. This strategy save storage and money.

There are a lot of services and open source tools able to manage and storage this data. The real issue is decide which street follow.

Are you interested to manage your logs or it’s a big effort for your company? You can move all to log entries and forgot about elastic search and kibana and similar in this case. Think about your environment and catch the best solution. Remember that it could be just a temporary solution. When you start a business you have different thoughts, start slim and easy.

Monitoring

Several services require several time and energy to be monitored and to be maintained alive.

The best way to do that is with a time series database like prometheus, InfluxDB or other as a service solution like NewRelic or AppDynamics.

The real problem is how your application can provide metrics readable and usable from external systems. You can find a very good solution to this problem in Docker: they provide different streams and events to grab this kind of informations.

If you take a lot on how it manage this part you can implement a good system in your application. A stream of events is also a good API to allow other services to enjoy features provided from your service.

Heahtcheck

Understand with a single request if your application has all what it needs to work is really important.

The microservices ecosystem contains a lot of micro applications that change and have dependencies to work. How can you understand if all your system is up and runs without spend a lot of time?

You can create for each service the call /heath that return 200 if all it’s fine and 500 if there is something that it’s not working properly.

During a release you can use this endpoint in order to understand if your service is ready to be attached into the production pool.

In practice, if you have one service called Users that depends from MySQL and from another service like Emailer, the health entrypoint for Users’s service will check whether it can connect to the MySql and also you can call /health for Emailer in order to check if the service is up.

Your orchestration and deploy framework can check after each deploy if the health is up and running and manage your release, it can revert or it doesn’t include your new release into the production pool.

Authentication

Your microservice is not public, sometime you have a set of firewall’s rules or a strong network settings to manage the security of your environment but for other services the authentication layer is a requirement and usually there are few services that need to know which is the identity of the user that is persisting an action.

Think about a To Do service, it need to know the identity of the user in order to fetch the correct items.

For this reason this layer could be common between your services and it’s also a critical section of your architecture because usually from it depends the security of your application and users.

Oauth2 is a framework to manage authentication, I recommend it because it has a documentation already done, it’s a standard. You don’t reivent anything, there are a lot of libraries and use cases about it that make it solid, flexible and reusable.

Automation and Deploy

A good layer of automation is important in every ecosystem to make your work less bored but also to decrease chance for a human to make a mistake during a repetitive task.

If you are thinking about a microservices ecosystem all this problems are multiplied for a big number of applications.

Without a good layer of automation and a good deploy’s flow you will spend all your day to put line of code in production without have time to stay focused on new features or other business’s requests.

Documentation

  • Describe the topology of your ecosystem,
  • how match microservices you have?
  • where they are and how they are distributed across your datacenters
  • Make it extensible and easy to read and update.
  • How a single service works?
  • Which APIs it expose
  • how another service can communicate with it.
  • Single dependencies for each microservices is also important to know.

All common part like, logs, auth, metrics help you to have a common documentation easy to maintain, read and implement but for each service you must provide a specific documentation because all it’s clear today but between few months when you worked on ten other services the situation could be really different.

One of the goal about microservices is the possibility to add and integrate them easily. Documentation is one of the goal to make this possible and efficient.

Communication Layer

A lot of companies have one communication layer in the environment, JSON and REST. It’s a good choice, easy to implement and there are also a lot of tools to test, document and create client libraries.

But HTTP/REST is not the unique way to expose features out of your service, this is really important to know.

There are other efficient and less expensive solution, binary protocol is one of them.

For all this topics we can stay here to speech for years for this reason I have in plan other posts to analyze some points better.

Please let me know if in your experience there are other common part between your services.