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DOCKER ORCHESTRATION

What it is:

  • Automated management of containerized application lifecycle across multiple hosts
  • Handles deployment, scaling, networking, availability
  • Ensures actual state matches desired state

Problem it solves:

  • Manually managing containers across multiple hosts is error-prone and doesn't scale
  • Need automatic restart when containers crash at 3am
  • Need automatic scaling when traffic spikes
  • Need zero-downtime deployments
  • Orchestration automates all of this

When You Need Orchestration​

Use for:

  • Production deployments requiring high availability
  • Multi-host container environments
  • Automatic scaling based on load
  • Rolling updates with zero downtime
  • Self-healing systems that recover from failures

Skip for:

  • Single-host deployments (use docker_compose instead)
  • Simple applications with no scaling needs
  • Development environments (adds complexity)
  • Learning Docker basics (start simple, add orchestration later)

Core Capabilities​

Declarative deployment​

  • Describe desired state (5 replicas of web service, 2 replicas of API)
  • Orchestrator makes it happen and maintains it

Self-healing​

  • Containers crash → orchestrator restarts them
  • Nodes fail → orchestrator reschedules containers to healthy nodes
  • Uses docker_healthcheck to detect failures

Scaling​

  • Horizontal scaling adds/removes container replicas based on CPU, memory, or custom metrics
  • Can be automatic (autoscaling) or manual

Rolling updates​

  • Deploy new versions gradually with no downtime
  • Automatic rollback if problems detected

Service discovery and load balancing​

  • Containers find each other by name via internal DNS
  • Traffic automatically distributed across replicas with health-based routing

Platform Comparison​

Docker Swarm​

  • Simpler, Docker-native, smaller ecosystem
  • Good for straightforward clustering needs without complexity overhead

Kubernetes​

  • More powerful, massive ecosystem, steeper learning curve
  • Industry standard for enterprise and multi-cloud deployments
  • De facto choice at scale

Cloud-specific​

  • AWS ECS, Azure Container Instances, Google Cloud Run
  • Tightly integrated with cloud provider services
  • Easier if all-in on one cloud

Pattern: Swarm for simpler needs, Kubernetes for enterprise scale, cloud-specific for cloud-native architectures.

Orchestration vs Compose​

Comparison:

  • docker_compose: Single-host, development-focused, simple
  • Orchestration: Multi-host, production-grade, complex
  • Compose defines services, orchestration manages clusters
  • Start with Compose, graduate to orchestration when you need multi-host deployment

Common Pitfalls​

WARNING

Over-engineering: Don't use orchestration if you don't need it. Single-host docker_compose setup is simpler, faster to debug, and sufficient for many applications.

DANGER

Treating it like a VM platform: Orchestrators are designed for stateless, disposable containers. Stateful services (databases) need special handling with persistent docker_volumes and StatefulSets. Don't assume database clustering works the same as stateless app scaling.

References​