Gall Data Types

This document describes the data types for Gall defined in lull.hoon.

`$bitt`

Incoming subscriptions.

+$  bitt  (map duct (pair ship path))

This is the structure Gall uses to keep track of incoming subscriptions for a Gall agent. The sup field of a $bowl contains the $bitt for our agent.

`$boat`

Outgoing subscriptions.

+$  boat  (map [=wire =ship =term] [acked=? =path])

This is the structure Gall uses to keep track of subscriptions our agent has initiated. The wex field of a $bowl contails the $boat for that agent.

The $wire field is the $wire which $sign:agents will come in on. The $ship and $term fields are the ship and the name of the agent to which our agent has subscribed.

The acked field is %.y if they have acknowledged our subscription request with a %watch-ack, and %.n if they have not. The $path field is the $path on the other agent to which our agent has subscribed.

`$boar`

Subscription nonces.

+$  boar  (map [=wire =ship =term] nonce=@)

Gall uses this to keep track of nonces for subscriptions.

`$fans`

Revisions for a remote scry file published at a particular path.

+$  fans  ((mop @ud (pair @da (each page @uvI))) lte)

The +mop is organized by file revision number. Each value includes the date-time of the entry, and then either the file as a $page or just the @uvI hash of the file if it has been tombstoned.

`$bowl`

Additional agent state.

+$  bowl                                              ::  standard app state
  $:  $:  our=ship                                    ::  host
          src=ship                                    ::  guest
          dap=term                                    ::  agent
          sap=path                                    ::  provenance
      ==                                              ::
      $:  wex=boat                                    ::  outgoing subs
          sup=bitt                                    ::  incoming subs
          sky=(map path fans)                         ::  scry bindings
      ==                                              ::
      $:  act=@ud                                     ::  change number
          eny=@uvJ                                    ::  entropy
          now=@da                                     ::  current time
          byk=beak                                    ::  load source
  ==  ==                                              ::

A $bowl is given to the agent core each time an event comes in. The fields are as follows:

our: Our ship.
src: The ship from which the current request originated.
dap: The name of our agent.
wex: Outgoing subscriptions. That is, subscriptions our agent has initiated. See the $boat section for details of the type.
sup: Incoming subscriptions. That is, subscriptions others have made to our agent. See the $bitt section for details of the type.
sky: Remote scry bindings. A map from binding paths to a $fans, an ordered map of files by revision number. Tombstoned files have an @uvI hash rather than $page.
act: The total number of $moves our agent has processed so far.
eny: 512 bits of entropy.
now: The current date-time.
byk: The ship, desk and $case in Clay from which this agent was loaded. The $case will be [%da @da] where the @da is the when the agent was loaded. A $beak is a triple of [ship desk case].

`$dude`

Agent name.

+$  dude  term

`$gill`

A general contact.

+$  gill  (pair ship term)

A pair of the ship and agent name.

`$load`

Loadout.

+$  load  (list [=dude =beak =agent])

The $dude is the agent name, the $beak is the ship/desk/case in which it resides, and the +agent is the built agent itself. Clay passes this to Gall when it builds or modifies the state of running agents.

`$scar`

Opaque duct - used internally.

+$  scar
  $:  p=@ud
      q=(map duct bone)
      r=(map bone duct)
  ==

`$suss`

Configuration report.

+$  suss  (trel dude @tas @da)

`$well`

Desk and agent.

+$  well  (pair desk term)

`$deal`

An agent task or raw poke.

+$  deal
  $%  [%raw-poke =mark =noun]
      task:agent
  ==

The additional %raw-poke is for pokes which haven't yet been converted to an ordinary %poke by molding the $noun with the specified .mark core. This structure is passed around on the kernel level, it would not be used in userspace.

`$unto`

An agent gift or a raw fact.

+$  unto
  $%  [%raw-fact =mark =noun]
      sign:agent
  ==

The additional %raw-fact is for facts which haven't yet been converted to an ordinary %fact by molding the $noun it with the specified .mark core. This structure is passed around on the kernel level, it would not be used in userspace.

`$verb`

Verbosity flags.

+$  verb  ?(%odd)

Flags to set Gall verbosity. Currently only %odd for unusual errors.

`$coop`

Verbosity flags.

+$  coop  spur

A security context for remote scries.

`+agent`

++  agent
  =<  form
  |%

Container for Gall agent types. The most significant arm is form:agent, which specifies the structure of the agent itself. There are also some additional structures defined here, mostly defining the kinds of messages agents can send. The different arms of the core in +agent are considered separately below.

`step:agent`

+$  step  (quip card form)

A cell of card:agents to be sent and a new agent state. This is the type returned by most arms of an agent. A (quip a b) is the same as [(list a) b], it's just a more convenient way to specify it.

`card:agent`

+$  card  (wind note gift)

An effect - typically a message to be sent to another agent or vane. A list of these are returned by most agent arms along with a new state in a step:agent. A +wind is the following:

++  wind
  |$  [a b]
  $%  [%pass p=path q=a]
      [%slip p=a]
      [%give p=b]
  ==

Gall will not allow a %slip, so in practice a $card will be one of:

[%pass path note]
[%give gift]

For %pass, .p specifies the $wire on which a response should be returned. See $note:agent and $gift:agent below for details of their types.

`note:agent`

+$  note
  $%  [%agent [=ship name=term] =task]
      [%arvo note-arvo]
      [%pyre =tang]
  ::
      [%grow =spur =page]
      [%tomb =case =spur]
      [%cull =case =spur]
  ==

The type for messages initiated by our agent. This is opposed to gift:agent, which is the type for responding to other agents or vanes, or for sending out updates to subscribers. The three cases are:

%agent: Poke another agent, subscribe to another agent, or cancel a subscription to another agent. The $ship and $name fields are the ship and agent to which the task should be sent. The task is the request itself, see $task:agent below for its possible types.

%arvo: Pass a task to a vane. The type of a $note-arvo is:

+$  note-arvo
  $~  [%b %wake ~]
  $%  [%a task:ames]
      [%b task:behn]
      [%c task:clay]
      [%d task:dill]
      [%e task:eyre]
      [%g task:gall]
      [%i task:iris]
      [%j task:jael]
      [%k task:khan]
      [%$ %whiz ~]
      [@tas %meta vase]
  ==

You can refer to the /sys/lull.hoon source code for all the possible vane tasks, or see each vane's API Reference section in the Arvo documentation

%pyre: This is for aborting side-effects initiated during agent installation. The $tang is an error message.
%grow/%tomb/%cull: These are used for publishing and managing data available for remote scries. For more information, see the remote scries guide.

A note:agent is always wrapped in a %pass $card:agent.

`task:agent`

The types of messages initiated by our agent and sent to another agent.

+$  task
  $%  [%watch =path]
      [%watch-as =mark =path]
      [%leave ~]
      [%poke =cage]
      [%poke-as =mark =cage]
  ==

This is in contrast to gift:agents, which are responses to incoming messages from agents or updates to agents already subscribed. The five kinds of task:agent are:

%watch: Subscribe to $path on the target ship and agent.
%watch-as: Same as %watch, except you ask the target's Gall to convert subscription updates to the $mark you specified rather than just giving you the $mark produced by the agent.
%leave: Cancel subscription. The particular subscription to cancel will be determined by the $wire given in the .p field of the containing %pass card:agent.
%poke: Poke the target ship and agent with the given $cage, which is a pair of [mark vase].
%poke-as: Same as %poke, except the $cage will be converted to the specified $mark before sending.

A task:agent is always wrapped in a %pass card:agent.

`gift:agent`

The types of messages our agent can either send in response to messages from other agents, or send to subscribed agents.

+$  gift
  $%  [%fact paths=(list path) =cage]
      [%kick paths=(list path) ship=(unit ship)]
      [%watch-ack p=(unit tang)]
      [%poke-ack p=(unit tang)]
  ==

This is in contrast to task:agents, which are messages to other agents our agent initiates rather than sends in response. The four kinds of gift:agent are:

%fact: An update to existing subscribers. The .paths field specifies which subscription paths the update should go out to. The $cage is the data, and is a [mark vase].
%kick: Kick subscriber, ending their subscription. The .paths field specifies which paths the subscriber should be kicked from, and the $ship field specifies the ship to kick. If the $ship field is null, all subscribers on the specified paths are kicked. Gall will automatically remove the subscription from our agent's $bitt (inbound subscription +map), and subscriber will no longer receive updates on the $paths in question.
%watch-ack: Acknowledge a subscription request. If .p is null, it's an ack (positive acknowledgement), and if .p is non-null, it's a nack (negative acknowledgement). Simply crashing will caused Gall to nack a subscription request, and not crashing but not explicitly producing a %watch-ack gift will cause Gall to ack a subscription request. Therefore, you'd typically only explicitly produce a %watch-ack gift if you wanted to nack a subscription request with a custom error in the $tang.
%poke-ack: Acknowledge a poke. If .p is null, it's an ack, and if .p is non-null, it's a nack. Simply crashing will cause Gall to nack a poke, and not crashing but not explicitly producing a %poke-ack gift will cause Gall to ack a poke. Therefore, you'd typically only explicitly produce a %poke-ack gift if you wanted to nack a poke with a custom error in the $tang.

A gift:agent is always wrapped in a %give card:agent.

`sign:agent`

A $sign is like a gift:agent but it's something that comes in to our agent from another agent rather than something we send out.

+$  sign
  $%  [%poke-ack p=(unit tang)]
      [%watch-ack p=(unit tang)]
      [%fact =cage]
      [%kick ~]
  ==

The possible types are:

%poke-ack: Another agent has acked (positively acknowledged) or nacked (negatively acknowledged) a %poke $task:agent we previously sent. It's an ack if .p is null and a nack if .p is non-null. The $tang contains an error or traceback if it's a nack.
%watch-ack: Another agent has acked or nacked a %watch $task:agent (subscription request) we previously sent. It's an ack if .p is null and a nack if .p is non-null. The $tang contains an error or traceback if it's a nack. If it's a nack, Gall will automatically remove the subscription from our agent's $boat (outbound subscription map).
%fact: An update from another agent to which we've previously subscribed with a %watch $task:agent (subscription request). The $cage contains the data, and is a [mark vase].
%kick: Our subscription to another agent has been ended, and we'll no longer receive updates. A %kick may be intentional, but it may also happen due to certain network conditions or other factors. As a result, it's best to try and resubscribe with another %watch $task:agent, and if they nack the %watch, we can conclude it was intentional and give up.

`form:agent`

This defines the structure of the agent itself.

++  form
  $_  ^|
  |_  bowl
  ++  on-init
    *(quip card _^|(..on-init))
  ::
  ++  on-save
    *vase
  ::
  ++  on-load
    |~  old-state=vase
    *(quip card _^|(..on-init))
  ::
  ++  on-poke
    |~  [mark vase]
    *(quip card _^|(..on-init))
  ::
  ++  on-watch
    |~  path
    *(quip card _^|(..on-init))
  ::
  ++  on-leave
    |~  path
    *(quip card _^|(..on-init))
  ::
  ++  on-peek
    |~  path
    *(unit (unit cage))
  ::
  ++  on-agent
    |~  [wire sign]
    *(quip card _^|(..on-init))
  ::
  ++  on-arvo
    |~  [wire sign-arvo]
    *(quip card _^|(..on-init))
  ::
  ++  on-fail
    |~  [term tang]
    *(quip card _^|(..on-init))
  --
--

The agent is a door with a $bowl as its sample and exactly ten arms. Below we'll describe each arm briefly.

`+on-init`

Accepts: Nothing.
Produces: $step:agent

This arm is called when the agent is initially installed.

`+on-poke`

Accepts: $cage
Produces: $step:agent

This arm is called when another agent pokes our agent.

`+on-watch`

Accepts: $path
Produces: $step:agent

This arm is called when another agent subscribes to our agent.

`+on-leave`

Accepts: $path
Produces: $step:agent

This arm is called when another agent unsubscribes from a subscription path on our agent.

`+on-peek`

Accepts: $path
Produces: (unit (unit cage))

This arm is called when a scry is performed on our agent.

`+on-agent`

Accepts: [wire sign:agent]
Produces: $step:agent

This arm is called when another agent give our agent a $sign:agent.

`+on-arvo`

Accepts: [wire sign-arvo]
Produces: $step:agent

This arm is called when a vane gives our agent a gift. A $sign-arvo is:

+$  sign-arvo
  $%  [%ames gift:ames]
      $:  %behn
          $%  gift:behn
              $>(%wris gift:clay)
              $>(%writ gift:clay)
              $>(%mere gift:clay)
              $>(%unto gift:gall)
          ==
      ==
      [%clay gift:clay]
      [%dill gift:dill]
      [%eyre gift:eyre]
      [%gall gift:gall]
      [%iris gift:iris]
      [%jael gift:jael]
      [%khan gift:khan]
  ==

You can refer to the /sys/lull.hoon source code, or the API Reference of each vane in the Arvo documentation.

`+on-fail`

Accepts: [term tang]
Produces: $step:agent

This arm is called if certain errors occur in Gall, such as if our agent tries to create a duplicate subscription.

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