objectNullMessage extends AutoReceivedMessage with Product with Serializable
This message is sent directly after the Supervise system message in order
to form a barrier wrt. the first real message sent by the child, so that e.g.
Failed() cannot overtake Supervise(). Processing this does nothing.
Detailed explanation:
The race happens because Supervise and Failed may be queued between the
parent's check for system messages and dequeue(). Thus, if the parent
processes the NullMessage first (by way of that tiny race window), it is
guaranteed to then find the Supervise system message in its mailbox prior
to turning its attention to the next real message.
Linear Supertypes
Product, Equals, AutoReceivedMessage, Serializable, Serializable, AnyRef, Any
This message is sent directly after the Supervise system message in order to form a barrier wrt. the first real message sent by the child, so that e.g. Failed() cannot overtake Supervise(). Processing this does nothing.
Detailed explanation:
The race happens because Supervise and Failed may be queued between the parent's check for system messages and dequeue(). Thus, if the parent processes the NullMessage first (by way of that tiny race window), it is guaranteed to then find the Supervise system message in its mailbox prior to turning its attention to the next real message.