Advanced Docker Scenarios: Scaling u0026 Production Deployments Quiz Quiz

Explore advanced Docker scenarios focused on efficient container scaling and robust production deployments. Assess your understanding of clustering, orchestration, persistent storage, networking strategies, and best practices for high-availability containers.

1. Scaling Docker Applications

   When scaling a Dockerized web service for traffic spikes, which approach ensures containers are evenly distributed and easily replaced during failures?

   1. Storing persistent data inside the running container
   2. Increasing the CPU allocation for existing containers
   3. Using a container orchestrator to manage replicas
   4. Manually running multiple containers on a single host

   Explanation: Container orchestrators efficiently manage and distribute multiple replicas of containers across nodes, ensuring high availability and automatic recovery from failures. Manually running containers doesn't provide automated balancing or failover. Just increasing CPU won't handle traffic spikes if more instances are needed. Storing persistent data inside containers is risky for failure recovery and doesn't address distribution or scaling.

2. Load Balancing in Production

   In a production environment utilizing Docker Swarm clusters, how is incoming network traffic typically distributed across multiple container instances?

   1. Layer 7 reverse proxy with service discovery
   2. Manual adjustment of port mappings per container
   3. Only direct IP address routing to containers
   4. Static DNS entries pointing to container IDs

   Explanation: A Layer 7 reverse proxy with service discovery intelligently routes incoming requests to available container instances and is dynamic in adapting to scaling. Direct IP routing is fragile and breaks with scaling. Manual port mapping quickly becomes unmanageable at scale. Static DNS pointing to container IDs is unreliable due to changing instance lifecycles and lacks true load balancing.

3. Persistent Storage Choices

   Which practice allows Docker containers to persist application data safely across scaling events and restarts in a multi-host environment?

   1. Relying on the writable container layer
   2. Mounting external network volumes to containers
   3. Backing up data from container logs
   4. Saving files only in a temporary directory

   Explanation: Mounting external network volumes ensures data is accessible and persistent regardless of container or host lifecycle, making it suitable for scaling scenarios. Using the writable container layer risks data loss on recreation or migration. Temporary directories are erased with container restarts. Logs do not provide reliable or consistent data persistence for application state.

4. Rolling Updates Strategy

   During a rolling update of a Docker service, which method prevents downtime while new versions are deployed across containers?

   1. Only updating containers on idle hosts
   2. Running both old and new versions indefinitely
   3. Gradually replacing containers one by one while keeping the service available
   4. Stopping all containers before updating

   Explanation: Rolling updates replace containers sequentially to maintain service availability, which reduces or eliminates downtime. Stopping all containers interrupts service and should be avoided. Running both versions indefinitely can cause version drift and instability. Only updating idle hosts might not update active containers or might leave old versions running.

5. Network Isolation for Multi-Tier Apps

   For a Dockerized multi-tier application, what is the recommended method to enforce secure communication between tiers, such as from web servers to databases?

   1. Relying solely on container port numbers for separation
   2. Allowing all containers on the same host to communicate freely
   3. Exposing database ports on the public network interface
   4. Using custom Docker networks with restricted access controls

   Explanation: Custom Docker networks with access restrictions enable secure, controlled communication between only appropriate tiers, enhancing overall security. Allowing all containers free communication risks unauthorized access. Port numbers alone do not prevent connections between containers. Exposing databases to public networks poses significant security risks and is not recommended.