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Software Architecture Guide

UML Deployment Diagram

Explanation

Section titled “Explanation”

A deployment diagram describes the execution architecture of a system. It assigns software artifacts to system elements. An artifact is a piece of software that gets deployed.

How it looks

  • Nodes are drawn as boxes.
  • Artifacts allocated to a node appear as rectangles inside its box.
  • Nodes can be nested. A subnode appears as a box inside another box.
  • One node can stand for several physical nodes at once.

Use in architecture documentation

arc42 recommends UML deployment diagrams for the deployment view. For more complex infrastructure, it suggests nested diagrams. The article Deployment View covers that view in detail.

Systems often run in several environments. Examples are development, test, and production. Each environment may need its own deployment documentation.

Example

Section titled “Example”

An online shop runs on three boxes: a web server, an application server, and a database server. Each box holds a rectangle for the software placed on it. A fourth box group, labeled “test environment”, could repeat this layout for testing. A box labeled “application server” might stand for several identical machines.

Trade-offs

Section titled “Trade-offs”

Nesting keeps complex infrastructure readable, because each diagram shows one level of detail. The cost is more diagrams to maintain. Separate documentation per environment adds the same cost. A node that stands for several physical machines keeps the picture simple, but it hides how many machines exist.

Generic deployment diagram: artifacts inside nested nodes.

Diagram source 
@startuml
node "Web Server" {
  artifact "site files"
}
node "Application Server" {
  artifact "shop program"
}
node "Database Server" {
  artifact "database"
}
@enduml

Checks

Section titled “Checks”
  • Artifacts are drawn as rectangles inside the box of the node they are allocated to.
  • Complex infrastructure is documented with nested diagrams or nested nodes.
  • Each environment that needs it (development, test, production) has its own deployment documentation.
Section titled “Related”

Sources

Section titled “Sources”