README.md

optvar

This library implements "optional variable": a synchronization primitive similar to condition variable. Optional variables can be set, unset and read.

When a variable is unset, any process that tries to read it gets blocked until the variable is set. Once another process sets the variable, all readers immediately get unblocked and get the value. If the variable is already set, read function returns the value immediately.

This library has been optimized for very large numbers of readers and variables; it uses ets table for storing the variables, and handles different variables in parallel, so it shouldn't become a bottleneck.

API

Assign value Value to a variable Var:

set(Var, Value) -> ok.

Clear the value of variable Var:

unset(Var) -> ok

Wait until the variable Var is set, and return the value:

read(Var) -> Value

Read the value of a variable with timeout:

read(Var, Timeout) -> {ok, Value} | timeout

Return the value of a variable immediately if it's set, or undefined if it's unset:

peek(Var) -> {ok, Value} | undefined

Check if the variable is set:

is_set(Var) -> boolean()

Warning

optvar library has been designed under an assumption that any variable that is read eventually will be set. When some process tries to read an unset variable, it spawns a special notifier process, which doesn't exit until the variable is set, or until optvar application is stopped. Please keep this in mind when using read/2 API with timeout: it leaves the notifier process running even after the timeout.