API Reference

Agent Notes

A note is a request to a vane or agent which you initiate. A note is one of:

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

A note is always wrapped in a %pass card, like so:

[%pass p=wire q=note]

The wire is just a path like /foo/bar/baz. You use it as a tag to identify responses.

The possible cases of an %agent note are documented separately below.

We'll look at the remaining cases here.

%arvo

Pass a vane task to a vane (kernel module).

[%arvo note-arvo]

A note-arvo is defined as the following:

+$  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]
  ==

The first part is vane letter (%g for Gall, %i for Iris, etc). The second part is a task belonging to that vane.

%pyre

Abort event.

[%pyre =tang]

This note tells Gall to crash with the given tang in the stack trace. You'd use it in ++on-load or ++on-init when you wanted the upgrade/installation to fail under some condition.

%grow

Publish remote scry file.

[%grow =spur =page]

The spur is the path the file should be published at. The revision number will be determined implicitly. As an example, if the spur was /foo, the agent %bar, and it was the first revision, the resulting remote scry path would be /g/x/0/bar//foo

The page is the file, a pair of [p=mark q=noun].

%tomb

Delete remote scry file.

[%tomb =case =spur]

The case is the file revision, for example [%ud 3]. The spur is the path it's bound to, for example /foo.

The file at the specified spur and specific case will be deleted and replaced by a simple hash.

%cull

Delete remote scry file up to the given revision.

[%cull =case =spur]

All revisions of the remote scry file published at the path in spur up to and including the revision specified in case will be deleted. For example, if the case is [%ud 2], then revisions 0, 1, and 2 will all be deleted.

Agent Tasks

A task is a request to an agent you initiate, as opposed to a gift, which is a response.

Passing an agent task looks like so:

[%pass p=wire q=[%agent [=ship name=term] =task]]

• wire: this is just a path like /foo/bar/baz. You use it as a tag to identify any gift that come back in response.
• ship: is the ship to pass the task to.
• name: is the name of the agent on the specified ship that should receive the task.
• task: the task itself, as described below.

%watch

Subscribe to a path on an agent for updates.

[%watch =path]

The path is a subscription path like /foo/bar/baz which the receiving agent publishes updates on. The publisher's Gall will automatically respond with a %watch-ack. The %watch-ack will be positive (an "ack") if the agent did not crash processing the %watch, and will be negative (a "nack") if it crashed.

Assuming the subscription request was successful (and therefore the %watch-ack was positive), the publisher will begin sending updates as %fact gifts to the subscriber. The publisher will continue sending updates until the subscriber %leaves or the publisher %kicks them.

%watch-as

Subscribe to a path on an agent for updates, asking for the updates to have a specified mark.

[%watch-as =mark =path]

The path is a subscription path like /foo/bar/baz which the receiving agent publishes updates on. The mark is the mark you want the publisher to use for the data it gives you in the updates.

This behaves the same as an ordinary %watch request, except the publisher's Gall will try to convert from the mark of the %facts the agent produced to the mark you specified before sending it off. If the publisher's Gall is unable to perform the mark conversion, you'll get %kicked from the subscription, and they'll send themselves a %leave on your behalf.

%leave

Unsubscribe from a subscription path on an agent.

[%leave ~]

The subscription to end is determined by the wire, ship and agent name in the %pass card this is wrapped in. That is, if you originally subscribed to subscription path /foo/bar/baz in agent %foo on ship ~zod using wire /x/y/z, you'd unsubscribe by specifying /x/y/z, ~zod and %foo.

Once sent, you'll stop receiving %facts from the publisher for the subscription in question.

%poke

A one-off request/datagram to an agent.

[%poke =cage]

A %poke task is a one-off, unsolicited delivery of some data. This is in contrast to a %fact gift, the other basic method of passing data between agents, which is ultimately a solicited response to a past %watch request for subscription updates. Unlike a %watch request, the recipient of the %poke cannot directly send data back to the %poke-er (though they could conceivably send a new, separate %poke back). The only response you get to a %poke is a %poke-ack, indicating a simple success/failure result.

The data of the %poke is contained in the cage, which is a pair of [p=mark q=vase]. It's the basic way to pass around dynamically typed data.

%poke-as

A one-off request/datagram to an agent, asking the recipient's Gall to convert the data to the specified mark before delivering it to the agent.

[%poke-as =mark =cage]

This behaves the same as an ordinary %poke but with additional mark conversion to the mark you specify by the recipient's Gall.

The mark is the mark you want the cage converted to before delivery to the agent. The cage is the data itself, a pair of [p=mark q=vase]. The mark conversion will be performed by the recipient's Gall, not the sender's.

If the mark conversion fails, the sender will be sent a negative %poke-ack (nack). Otherwise, the recipient will receive a %poke with the target mark specified.

Agent Gifts

An agent gift is ultimately a response to an agent task. Sometimes it's an immediate, direct response, and other times it happens down the line, or there's an ongoing series of gifts, as in the case of subscriptions. They do all ultimately arise from an original task, though, be it a a %watch subscription request or a %poke. A gift cannot be sent out unsolicited to other agents. Where they are routed to, whether another local agent, an agent on a remote ship, or even to vanes or a browser-based front-end in some cases, is determined by the original task.

Giving a gift takes the general form of:

[%give p=gift]

Each possible gift is detailed below.

%fact

Produce a subscription update.

[%fact paths=(list path) =cage]

A %fact is a piece of data given to all subscribers on one or more subscription paths.

The fields are:

• paths: a list of subscription paths to send the update on. In +on-watch alone, if no path is given, then the update is given exclusively to the source of the %watch request. This is useful for giving initial state to new subscribers. In other contexts, one or more subscription paths should be provided.
• cage: the data. A cage is a pair of [p=mark q=vase].

%kick

Close subscription.

[%kick paths=(list path) ship=(unit ship)]

If ship is null, all subscribers will be kicked from the specified subscription paths and will stop receiving updates. If ship is non-null, only the specified ship will be kicked from the given paths.

It should be noted that %kick gifts are not only emitted intentionally by the publishing agent. Gall itself will %kick remote subscribers if too many undelivered outbound %facts queue up due to network connectivity problems. On the subscriber side, their Gall will %kick themselves if they crash while processing an incoming %fact. It should therefore not be assumed the %kick was intentional. Typically agents will be designed to resubscribe on %kick with a new %watch, only giving up on negative %watch-ack. You should be careful with automatic resubscribe logic, though, because you can inadvertently create a network loop of infinite resubscribes and kicks if, for example, a crash on %fact is repeatable.

%watch-ack

Acknowledge a subscription request.

[%watch-ack p=(unit tang)]

A %watch-ack is automatically given by Gall in response to a %watch task. A %watch-ack is either positive (an "ack") or negative (a "nack"). It's an ack when p is null, and a nack when p is non-null, instead containing a stack trace.

A %watch-ack is given automatically and implicitly by Gall itself, it is unnecessary for an agent to emit one explicitly. An ack will be given as long as ++on-watch doesn't crash. A nack will be given if it does crash, with a trace of the crash in p. Your agent should therefore be designed to accept or reject a subscription request by crashing or not crashing, respectively.

%poke-ack

Acknowledge a poke.

[%poke-ack p=(unit tang)]

A %poke-ack is automatically given by Gall in response to a %poke task. A %poke-ack is either positive (an "ack") or negative (a "nack"). It's an ack when p is null, and a nack when p is non-null, instead containing a stack trace.

A %poke-ack is given automatically and implicitly by Gall itself, it is unnecessary for an agent to emit one explicitly. An ack will be given as long as ++on-poke doesn't crash. A nack will be given if it does crash, with a trace of the crash in p. Your agent should therefore be designed to accept or reject a poke by crashing or not crashing, respectively.

Vane Tasks

These are the Vane tasks that can be %passed to Gall itself in an %arvo note. Most of these are only used internally by the kernel, though some app management tasks might be of use in userspace.

%deal

Full transmission.

[%deal p=sock q=term r=deal]

Gall translates agent task:agents emitted by agents into %deal tasks, as well as requests from over the network. This task is kernel-level only, it cannot be used directly from userspace.

Its fields are:

• p: A sock, a (pair ship ship), the sending and receiving ships.
• q: The source agent.
• r: A deal is either a task:agent or a %raw-poke. This is the request itself.

Returns

Gall returns no gift in response to a %deal.

%sear

Clear pending queues.

[%sear =ship]

This task clears blocked inbound moves from the given ship. Moves get blocked and queued when sent to an agent that isn't currently running.

Returns

Gall returns no gift in response to a %sear.

%jolt

Restart agent (deprecated).

[%jolt =desk =dude]

Restart agent dude on desk desk. This task is deprecated and now a no-op.

Returns

Gall returns no gift in response to a %jolt.

%idle

Suspend agent.

[%idle =dude]

The agent specified in dude will be suspended. Note it is usually better to suspend agents with a %rein task to Clay rather than an %idle task to Gall.

Returns

Gall returns no gift in response to an %idle.

%load

Load agents.

[%load =load]

This task is given to Gall by Clay. It contains the compiled agents to be installed or updated. This task would not be used from userspace.

See the load entry in the type reference for more details of the datastructure in this task.

Returns

Gall returns no gift in response to a %load.

%nuke

Delete agent.

[%nuke =dude]

The agent in dude will be stopped and its state discarded.

Returns

Gall returns no gift in response to a %nuke.

%doff

Kill old-style subscriptions.

[%doff dude=(unit dude) ship=(unit ship)]

Kills nonceless outgoing subscriptions. If dude is non-null, it only applies to the specified agent. If the ship is non-null, it only applies to subscriptions to the specified ship. Otherwise, it applies to all subscriptions.

You're unlikely to use this task from userspace.

Returns

Gall returns no gift in response to a %doff.

%rake

Reclaim old subscriptions.

[%rake dude=(unit dude) all=?]

This sends an Ames %cork on any old subscription ducts. If dude is null, it applies to all agents, otherwise to the specified one. The all flag should only be set if you want the ship to try and kill an old subscription at sub-nonce zero.

You are unlikely to use this task.

Returns

Gall returns no gift in response to a %rake.

%spew

Set verbosity.

[%spew veb=(list verb)]

This sets verbosity flags for Gall. Currently there's only one verb, %odd, which prints messages for unusual error cases. This overwrites the existing verbosity settings: an empty list will turn all verbosity flags off.

Returns

Gall returns no gift in response to a %spew.

%sift

Filter verbose debug printing to certain agents.

[%sift dudes=(list dude)]

The dudes are the agents you want verbose debug printing for. An empty list enables it for all agents. See %spew for setting verbosity.

Returns

Gall returns no gift in response to a %sift.