Encodes a %Dragonfly.Parent{} struct into string.

Gets the %Dragonfly.Parent{} struct from the system environment.

Returns nil if no parent is set.

When booting a Dragonfly node, the Dragonfly.Backend is required to export the DRAGONFLY_PARENT environment variable for the provisioned instance. This value holds required information about the parent node and can be set using the Dragonfly.Parent.encode/3 function.

Returns a new %Dragonfly.Parent{} struct.

The pid is the parent node's Dragonfly.Runner process started by the Dragonfly.Pool.