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Services

Long-running, side-effecting subsystems. Each service owns one concern, runs under its own supervisor, and communicates with the rest of LiveDebugger via LiveDebugger.Bus.

File / folder structure

Each service lives in its own directory and follows the same skeleton:

services/<service_name>/
├── supervisor.ex         # registered in the app supervision tree
├── events.ex             # event structs this service publishes (Bus payloads)
├── gen_servers/          # processes owned by this service
│   └── *.ex
├── actions/              # side-effect-performing functions (write to ETS, broadcast, …)
├── queries/              # read-only functions (lookups, aggregations)
└── README.md             # one-paragraph overview of the service

Not every service has every directory — they are added when more files are needed.

Communication between services

Services should not call each other. Cross-service communication goes through LiveDebugger.Bus (built on Phoenix.PubSub):

  • lvdbg/* — general events
  • lvdbg/traces/* — trace data
  • lvdbg/states/* — LiveView state snapshots

The wildcard segment is usually a pid (debugged process or debugger LV) so subscribers can scope to a single target.

List of services

CallbackTracer

Sets up :dbg.tracer, monitors and manages it, parses raw traces, and broadcasts them on the bus. Reacts to module recompilations by re-applying trace patterns. GenServers: TracingManager (lifecycle), TraceHandler (parse + persist + broadcast).

ClientCommunicator

Owns the Phoenix channel used by the debugged app's browser-side client.js. Forwards messages between the debugger and the client (highlight node, inspect element, redirect). GenServer: ClientCommunicator.

GarbageCollector

Periodically trims ETS tables (traces, states) to stay within configured size limits and deletes tables for processes nobody is watching. GenServers: GarbageCollector (scheduler), TableWatcher (per-table observer).

ProcessMonitor

Watches the BEAM for LiveView process births and deaths and emits LiveViewBorn / LiveViewDied events. GenServers: DebuggedProcessesMonitor, DebuggerProcessesMonitor.

SuccessorDiscoverer

When a LiveView dies (e.g. page reload) a new one usually replaces it almost immediately. This service finds the successor in the same browser window so the debugger can switch to it without the user noticing the gap. GenServer: SuccessorDiscoverer.

TelemetryHandler

Attaches to :telemetry events emitted by Phoenix/LiveView and republishes the relevant ones on the bus. GenServer: TelemetryHandler.

Adding a new service

  • Create services/<name>/ with supervisor.ex.
  • Put processes in gen_servers/, side effects in actions/, lookups in queries/.
  • Add the supervisor to the application tree (lib/live_debugger/services.ex).
  • Subscribe to the bus from inside your GenServer if you need to react to other services' events.
  • Define event structs in events.ex if you emit something.
  • Add a README.md summarizing what the service does and why.