A health check for the parts of the framework that can fall behind silently: the database, the outbox and the projections.

DDD.Health.check()
# => %{
#      status: :ok,
#      checks: %{
#        database: %{status: :ok},
#        outbox: %{status: :ok, pending: 0, in_flight: 0, dead_letters: 0,
#                  oldest_pending_age_ms: 0},
#        projections: %{"MyApp.Projections.ListSummary" => %{status: :ok, pending: 0, ...}}
#      }
#    }

The overall :status is the worst of the checks:

• :unhealthy - the database does not answer
• :degraded - the outbox has unresolved dead letters, or its oldest pending event (or a projection's oldest unprocessed event) has waited longer than the threshold
• :ok

The result is JSON-encodable, so serve it from a Plug route, a Phoenix controller, or the MCP server (DDD.Health.Query). mix vic.health prints it and exits non-zero unless :ok.

Options

Each falls back to config :vicander, :health, ..., then to the default:

• :repo - default: the configured repo (config :vicander, repo: MyApp.Repo)
• :projections - the projection modules to check (default [])
• :max_outbox_age_ms - default 60_000
• :max_dead_letters - default 0
• :max_projection_lag_ms - default 60_000
• :emit - also emit the DDD.Telemetry gauges (default true)