Microservices Applications

🍹 Technologies: TypeScript, Node.JS, Express, React, Redux, Next.js, MongoDB, Mongoose, Event Driven, Pub-Sub, Docker, Kubernetes, CI/CD, Skaffold, Apache Kafka, NATS Streaming Server etc.

Author

Aditya Hajare (Linkedin).

Current Status

WIP (Work In Progress)!

License

Open-sourced software licensed under the MIT license.

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Notes

+ Why Database Per-Service

• We want each service to run independently of other services.
• Database schema/structure might change unexpectedly.
• Some services might function efficiently with different types of DB's (SQL vs. NoSQL).

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+ Communication Strategies Between Services

• Sync: Services communicate with each other using direct requests.
  • Conceptually easy to understand.
  • Service won't need a database.
  • Introduces a dependency between services.
  • If any inter-service request failes, the entire service fails.
  • The entire request is only as fast as the slowest request.
  • Can easily introduce webs of requests.
• Async (Event Based Communication): Services communicate with each other using events.
  • No inter-service dependency.
  • Service will be extremely fast since it has it's own data store.
  • Introduces data duplication. Paying for extra storage + extra DB.
  • Harder to understand.

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+ Event Bus

• Many different implementations. For e.g. RabbitMQ, Kafka, NATS etc..
• Receives events, publishes them to listeners.
• Many different subtle features that make async communication way easier or way harder.

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+ Kubernetes Basic Terminologies

• Cluster: A collection of nodes + a master to manage them.
• Node: A virtual machine that runs our containers.
• Pod: More or less a running container. Technically, a pod can run multiple containers.
• Deployment: Monitors a set of pods. Make sure they are running and restarts them if they crash.
• Service: Provides an easy-to-remember URL to access a running container.

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+ Kubernetes Config Files

• Tells Kubernetes about the different Deployments, Pods and Services (Referred to as Objects) that we want to create.
• Written in YAML syntax.
• Always store these files with our project source code - they are documentation!
• We can create Objects without config files - DO NOT DO THIS!. Config files provide a precise definition of what our cluster is running.

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+ Securely Create Secrets In Kubernetes

• Following command will create a secret called JWT_KEY:

kubectl create secret generic jwt-secret --from-literal=JWT_KEY=adityahajare

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