`%gall`

%gall manages our userspace applications.

It allows applications and vanes to send messages to applications and subscribe to data streams. This requires %gall to be a sort of a hypervisor. Messages coming into %gall are routed to the intended application, and the response comes back along the same route. If the intended target is on another ship, %gall will behind-the-scenes route it through ames to the other ship to run. This provides an abstraction where all apps on all ships are communicated with over the same interface.

%gall neither accepts events from unix nor produces effects. It exists entirely for the benefit of other vanes and, in particular, applications. Eyre exposes %gall's interface over http, and ames does the same over the ames network. %gall uses ford to compile and run the applications.

Cards

%gall accepts the following cards. The first three are the most commonly used, while the others are primarily used internally.

`%mess`

Sends a message to an app. This will result in a call to the app's ++poke arm. The response is exactly one of a %nice if the action succeeded or a %mean if not.

`%show`

Subscribes to a stream from an app. This will result in a call to the app's either ++peek or ++peer arm. The first response will always be either a %nice or a %mean, indicating whether or not the subscription was successful. After the first response, there will be zero or more responses of either %rush or %rust, which communicate either a differntial or full update to the data stream. There may be a %mean, which indicates that the subscription has been canceled and no more responses will be received along this stream.

`%nuke`

Unsubscribes the current duct from its stream. This receives a response of either a %nice or a %mean. Note that a response of %nice does not imply that the current duct was in fact subscribed to any stream.

`%init`

Initializes a ship's apps. This should be called exactly once for each ship on the pier. This produces no moves in response.

`%sire`

Instantiates a child app. The app will be at path [p parent-path], and it will be an instance of the q app. The only response will be %gone when the child dies.

`%rote`

Signifies a remote request from ames. r should be of type rook. This how an app on a foreign ship may send a %mess, %show, or %nuke card. Note that %gall automatically converts %mess, %show, and %nuke into ames messages behind the scenes, so the only entity that should use %rote and %roth is ames. Formally, the response is either a %nice or a %mean, which ames uses to give a positive or negative ack. A logical response comes by passing a %roth card.

`%roth`

Gives the response received from a remote request. r should be of type roon. This is how an app responds to a foreign request with a %rush, %rust, %nice, or %mean. The response is either a %nice or a %mean. Even though we, as the proverb goes, "never ack an ack", we do need to acknowledge these responses since they're really independent one-way messages.

`%wipe`

Wipes the given app from memory. This is generally considered a hack, but it is sometimes useful during development to wipe the state of an app. We don't guarantee that this actually completely wipes the app. Generally, you want to use a %cide card if you actually want to kill an app. This gives no response.

`%cide`

Kills an app and all its children. Even though it's not technically a part of %gall's interface since it's not in ++kiss and can't be called from the outside, it's worth mentioning %cide, which may be called from within %gall apps. It should call ++part to allow the app any last words. This gives no response.