Hands-On Software Engineering with Golang

Implementing an in-memory graph store

The in-memory graph implementation will serve as a gentle introduction to writing a complete graph store implementation. By virtue of maintaining the graph in memory, this implementation is simple, self-contained, and safe for concurrent access. This makes it an ideal candidate for writing unit tests that require access to the link graph component.

Let's take a look at its implementation, starting with the definition of the InMemoryGraph type:

type edgeList []uuid.UUID

type InMemoryGraph struct {
    mu sync.RWMutex

    links map[uuid.UUID]*graph.Link
    edges map[uuid.UUID]*graph.Edge

    linkURLIndex map[string]*graph.Link
    linkEdgeMap  map[uuid.UUID]edgeList
}

The InMemoryGraph struct defines two maps (links and