Internal Details

Deno and Linux analogy

Linux	Deno
Processes	Web Workers
Syscalls	Ops
File descriptors (fd)	Resource ids (rid)
Scheduler	Tokio
Userland: libc++ / glib / boost	https://deno.land/std/
/proc/$$/stat	Deno.metrics()
man pages	deno types

Resources

Resources (AKA rid) are Deno’s version of file descriptors. They are integer values used to refer to open files, sockets, and other concepts. For testing it would be good to be able to query the system for how many open resources there are.

console.log(Deno.resources());
// { 0: "stdin", 1: "stdout", 2: "stderr" }
Deno.close(0);
console.log(Deno.resources());
// { 1: "stdout", 2: "stderr" }

Metrics

Metrics is Deno’s internal counter for various statistics.

> console.table(Deno.metrics())
┌─────────────────────────┬───────────┐
│          (idx)          │  Values   │
├─────────────────────────┼───────────┤
│      opsDispatched      │    9      │
│    opsDispatchedSync    │    0      │
│   opsDispatchedAsync    │    0      │
│ opsDispatchedAsyncUnref │    0      │
│      opsCompleted       │    9      │
│    opsCompletedSync     │    0      │
│    opsCompletedAsync    │    0      │
│ opsCompletedAsyncUnref  │    0      │
│    bytesSentControl     │   504     │
│      bytesSentData      │    0      │
│      bytesReceived      │   856     │
└─────────────────────────┴───────────┘

Schematic diagram

architectural schematic

Conference

Ryan Dahl. (May 27, 2020). An interesting case with Deno. Deno Israel.
Bartek Iwańczuk. (Oct 6, 2020). Deno internals - how modern JS/TS runtime is built. Paris Deno.