Ferricstore.Commands.Blocking (ferricstore v0.3.2)

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Parses and validates blocking list commands: BLPOP, BRPOP, BLMOVE, BLMPOP.

These commands are not dispatched through the normal Dispatcher because they require connection-level blocking (the connection process enters a receive block). Instead, Connection calls this module to parse args and then handles the blocking logic itself.

Blocking semantics

When the target list is non-empty, the command executes immediately (pop and return). When the list is empty, the connection process registers as a waiter in the Ferricstore.Waiters ETS table and enters a receive block with an after clause for the timeout. When another client pushes to the watched key, the waiter is notified via {:waiter_notify, key}. The BEAM runtime handles the timeout with zero polling.

Supported commands

  • BLPOP key [key ...] timeout -- block until left pop
  • BRPOP key [key ...] timeout -- block until right pop
  • BLMOVE source destination LEFT|RIGHT LEFT|RIGHT timeout -- blocking LMOVE
  • BLMPOP timeout numkeys key [key ...] LEFT|RIGHT [COUNT count] -- blocking LMPOP

Summary

Functions

handle(binary, args, store)
parse_blmove_args(arg1)

Parses BLMOVE arguments into {:ok, source, destination, from_dir, to_dir, timeout_ms}.

parse_blmpop_args(arg1)

Parses BLMPOP arguments.

parse_blpop_args(args)

Parses BLPOP/BRPOP arguments into {:ok, keys, timeout_ms} or {:error, msg}.

parse_brpoplpush_args(arg1)

Parses BRPOPLPUSH arguments into {:ok, source, destination, timeout_ms} or {:error, msg}.

Functions

handle(binary, args, store)

@spec handle(binary(), [binary()], map()) :: term()

parse_blmove_args(arg1)

@spec parse_blmove_args([binary()]) ::
  {:ok, binary(), binary(), :left | :right, :left | :right, non_neg_integer()}
  | {:error, binary()}

Parses BLMOVE arguments into {:ok, source, destination, from_dir, to_dir, timeout_ms}.

Parameters

  • args -- [source, destination, wherefrom, whereto, timeout]

Returns

  • {:ok, source, destination, from_dir, to_dir, timeout_ms}
  • {:error, reason}

parse_blmpop_args(arg1)

@spec parse_blmpop_args([binary()]) ::
  {:ok, [binary()], :left | :right, pos_integer(), non_neg_integer()}
  | {:error, binary()}

Parses BLMPOP arguments.

Format: timeout numkeys key [key ...] LEFT|RIGHT [COUNT count]

Returns

  • {:ok, keys, direction, count, timeout_ms}
  • {:error, reason}

parse_blpop_args(args)

@spec parse_blpop_args([binary()]) ::
  {:ok, [binary()], non_neg_integer()} | {:error, binary()}

Parses BLPOP/BRPOP arguments into {:ok, keys, timeout_ms} or {:error, msg}.

The last argument is the timeout in seconds (float or integer). All preceding arguments are keys.

Parameters

  • args -- list of string arguments

Returns

  • {:ok, keys, timeout_ms} -- parsed keys and timeout in milliseconds
  • {:error, reason} -- parse error

parse_brpoplpush_args(arg1)

@spec parse_brpoplpush_args([binary()]) ::
  {:ok, binary(), binary(), non_neg_integer()} | {:error, binary()}

Parses BRPOPLPUSH arguments into {:ok, source, destination, timeout_ms} or {:error, msg}.

Format: source destination timeout

Parameters

  • args -- list of string arguments: [source, destination, timeout]

Returns

  • {:ok, source, destination, timeout_ms} -- parsed arguments
  • {:error, reason} -- parse error