Docker Compose Networks

Docker Compose Default Network

graph LR
    subgraph "Project: myapp"
        subgraph "Default Bridge Network
(myapp_default)"
            web[Service: web]
            api[Service: api]
            db[Service: db]
        end
    end

    web <--> api
    api <--> db
    web <--> db

    style web fill:#f9f,stroke:#333,stroke-width:2px
    style api fill:#9cf,stroke:#333,stroke-width:2px
    style db fill:#ccf,stroke:#333,stroke-width:2px

Custom Networks for Segmentation

graph TD
    subgraph "Application"
        subgraph "Frontend Network"
            web[Service: web]
        end

        subgraph "Backend Network"
            db[Service: db]
        end

        %% Define the shared API service outside the network subgraphs
        api[Service: api]

        %% Define the connections
        web <--> api
        api <--> db
    end

    %% Apply styles to match the original image
    style web fill:#f9f,stroke:#333,stroke-width:2px
    style db fill:#ccf,stroke:#333,stroke-width:2px
    style api fill:#9cf,stroke:#333,stroke-width:2px

Service Discovery via Docker's DNS

sequenceDiagram
    participant web as Service A (web)
    participant dns as Docker DNS Resolver
    participant db as Service B (db)

    web->>dns: Who is the service 'db'? (DNS Query)
    activate dns
    %% Changed to a dashed arrow for a reply message
    dns-->>web: The service 'db' is at IP 172.18.0.5
    deactivate dns

    web->>db: Connect to 172.18.0.5
    activate db
    db-->>web: Connection established
    deactivate db

Overview of Docker Network Drivers

graph TD
    A[Docker Network Drivers] --> B[Single-Host];
    A --> C[Multi-Host];

    B --> B1["bridge (default)
Creates a private, isolated
network on the host"];
    B --> B2["host
Removes network isolation,
shares host's network"];
    B --> B3["macvlan
Assigns a MAC address,
container appears as a
physical device"];
    B --> B4["none
Disables all networking for
a container"];

    C --> C1["overlay
Creates a distributed
network spanning multiple
hosts (for Swarm)"];