Baby.Connection.Idle (Baby v0.38.0)

The idle-timeout state of a single Baby.Connection.

A connection is considered idle when nothing has been sent or received for some number of outbox intervals (spins). Any real activity -- sending a packet or processing an inbound message -- resets the counter, so the budget measures consecutive silence rather than wall-clock time on a busy link.

The budget is three-tiered, shrinking as the connection earns trust:

before a valid HELLO has been exchanged (short_peer is unset) the tight handshake_spins budget applies, so an anonymous flood that never completes a handshake is dropped quickly and cannot pin the listener's connection slots.
while the initial replication sync has not completed (synced: false) the generous bootstrap_spins budget applies. A peer may legitimately take a while to compute its WANT list, but a peer that stalls entirely must not be allowed to hang forever -- its registry entry would block every later cryout to that host.
once sync completes the tighter max_spins budget applies, so a caught up connection is dropped (and later re-established by the next cryout) rather than held open indefinitely.

The whole unit is kept in the connection's state (conn_info.idle) so the live value can be inspected directly, e.g. :sys.get_state(pid).idle.

Summary

Types

t()

Functions

describe(idle, handshaken?)

A human readable summary for logging.

expired?(idle, arg2)

The connection has been idle for longer than its budget.

new(opts \\ [])

Create a fresh idle timer.

poke(idle)

Record progress. Any sent or received message resets the idle counter while leaving the sync state untouched.

synced(idle)

Mark the initial replication sync as complete and restart the clock.

tick(idle)

One idle interval has passed without any activity.

Types

t()

@type t() :: %Baby.Connection.Idle{
  bootstrap_spins: non_neg_integer(),
  handshake_spins: non_neg_integer(),
  max_spins: non_neg_integer(),
  spins: non_neg_integer(),
  synced: boolean()
}

Functions

describe(idle, handshaken?)

@spec describe(t(), boolean()) :: String.t()

A human readable summary for logging.

expired?(idle, arg2)

@spec expired?(t(), boolean()) :: boolean()

The connection has been idle for longer than its budget.

handshaken? indicates whether a valid HELLO has been received, which selects between the pre-handshake and mid-bootstrap budgets for a connection whose initial sync has not yet completed.

This budget selection is mirrored by the idle-disconnect clauses in Baby.Connection; keep the two in step when adding tiers.

new(opts \\ [])

@spec new(keyword()) :: t()

Create a fresh idle timer.

All budgets are measured in outbox intervals (i.e. spins); multiply by the connection's outrate for wall-clock time. By default each is a random prime near a nominal value, giving jitter so that many connections do not drop in lockstep.

Consumers may pin them via Application config, which is read as the source of truth:

config :baby, max_spins: 1000, bootstrap_spins: 5000

or per-connection, which takes precedence over the Application config:

:handshake_spins - budget before a valid HELLO has been received. Defaults to a random prime near 375 (~30s at the default outrate).
:max_spins - budget once the initial sync has completed. Defaults to a random prime near 1200.
:bootstrap_spins - budget while the initial sync is still in progress. Defaults to a random prime near 3000.

Example: Idle.new(max_spins: 1000, bootstrap_spins: 5000)

poke(idle)

@spec poke(t()) :: t()

Record progress. Any sent or received message resets the idle counter while leaving the sync state untouched.

synced(idle)

@spec synced(t()) :: t()

Mark the initial replication sync as complete and restart the clock.

tick(idle)

@spec tick(t()) :: t()

One idle interval has passed without any activity.