Entry Registry

Query and modify registered entries. Access metadata, snapshots, and version history.

Loading

local registry = require("registry")

Entry Structure

{
    id = "app.lib:assert",     -- string: "namespace:name"
    kind = "function.lua",     -- string: entry type
    meta = {type = "test"},    -- table: searchable metadata
    data = {...}               -- any: entry payload
}

Entries read back from registry.get, registry.find, snap:entries(), snap:get(), snap:namespace() and snap:find() carry only these four author-facing fields.

dependency_root is a write-side field accepted by changes:create() and changes:update(). It is a boolean that marks an ns.dependency entry as a deployment root. It is never returned by the entry APIs; registry-owned state is read through snap:state().

Get Entry

local entry, err = registry.get("app.lib:assert")

Permission: registry.get on entry ID

Find Entries

local entries, err = registry.find({[".kind"] = "function.lua"})
local entries, err = registry.find({[".kind"] = "http.endpoint", [".ns"] = "app.api"})

Keys prefixed with . match entry fields (.kind, .ns, .name, .id) and accept * globs. Keys prefixed with meta. match entry metadata; a leading ~, *, ^ or $ on a meta. key selects regex, contains, prefix or suffix matching. Keys with neither prefix are ignored.

Parse ID

local id = registry.parse_id("app.lib:assert")
-- id.ns = "app.lib", id.name = "assert"

Snapshots

Point-in-time view of the registry:

local snap, err = registry.snapshot()           -- current state
local snap, err = registry.snapshot_at(5)       -- at version 5

Snapshot Methods

Snapshot State

snap:state() returns the entry state together with the module graph selected for the snapshot version. Registry-owned provenance is carried on each entry rather than merged into meta, so it cannot be confused with authored metadata.

local snap, err = registry.snapshot()
local state, err = snap:state()

for _, entry in ipairs(state.entries) do
    print(entry.id, entry.registry.owner, entry.registry.root)
end

if state.resolution then
    print(state.resolution.digest, state.resolution.input_digest)
    for _, module in ipairs(state.resolution.modules) do
        print(module.name, module.version)
    end
end

Each entry in state.entries has the four author-facing fields plus:

• registry.owner - deployment source that supplied the entry
• registry.root - true when the entry is a dependency declaration selected by the deployment

state.resolution describes the module graph of a registry.snapshot() view. It is absent on snapshots that carry no graph of their own, including registry.snapshot_at() and overlay snapshots:

roots and references entries have id, component and version. modules entries have name and version, plus version_id, source, digest, size_bytes and protected when set.

Versions

local version, err = registry.current_version()
local versions, err = registry.versions()

print(version:id())       -- numeric ID
print(version:string())   -- display string
local prev = version:previous()  -- previous version or nil
local next = version:next()      -- next version or nil

History

local hist, err = registry.history()
local versions, err = hist:versions()
local version, err = hist:get_version(5)
local snap, err = hist:snapshot_at(version)

Changesets

Build and apply modifications:

local snap, err = registry.snapshot()
local changes = snap:changes()

changes:create({
    id = "test:new_entry",
    kind = "test.kind",
    meta = {type = "test"},
    data = {config = "value"}
})

changes:update({
    id = "test:existing",
    kind = "test.kind",
    meta = {updated = true},
    data = {new_value = true}
})

changes:delete("test:old_entry")

local new_version, err = changes:apply()

Permission: registry.apply for changes:apply()

Deleting Entries

changes:delete() accepts an ID string, a table with an id string, a table with ns and name strings, or an array of any of those. Arrays may nest, and duplicate IDs collapse into a single delete operation.

changes:delete("test:old_entry")
changes:delete({id = "test:old_entry"})
changes:delete({ns = "test", name = "old_entry"})
changes:delete({"test:a", {ns = "test", name = "b"}, {"test:c"}})

An empty list, a table that references itself, and a value that is neither a string nor a table are rejected with errors.INVALID.

Changes Methods

Apply Version

Roll back or forward to a specific version:

local prev = current_version:previous()
local ok, err = registry.apply_version(prev)

Permission: registry.apply_version

Build Delta

Compute operations to transition between states:

local from = {{id = "test:a", kind = "test", meta = {}, data = {}}}
local to = {{id = "test:b", kind = "test", meta = {}, data = {}}}

local ops, err = registry.build_delta(from, to)
for _, op in ipairs(ops) do
    print(op.kind, op.entry.id)  -- "entry.create", "entry.update", "entry.delete"
end

Overlays

An overlay is a process-local set of registry entries owned by a logical identity. Overlay entries take part in ordinary topology and handler transitions, so services start and stop for them exactly as for durable entries, but they never advance registry history and never appear in a version. They exist only in the running process and are empty after a cold boot, so the owning control service reconciles them on startup.

local snap, err = registry.overlay("data-sources:crm")

Returns: Snapshot, error

The snapshot exposes the owner's overlay entries through the usual methods and reports the current registry version from snap:version(). It also captures the overlay generation at the moment it is opened, which is what makes writes safe.

local snap, err = registry.overlay("data-sources:crm")
if err then return nil, err end

local changes = snap:changes()
changes:create({
    id = "data.crm:connection",
    kind = "registry.entry",
    meta = {},
    data = {endpoint = "https://crm.internal"}
})

local version, err = changes:apply()

changes:apply() on an overlay snapshot writes the overlay and returns the current registry version. No history version is created, so the returned version is unchanged unless a durable change happened concurrently.

Concurrency

Each overlay carries a generation counter that increases on every successful apply. changes:apply() succeeds only if the generation still matches the one captured when the snapshot was opened. A concurrent apply to the same overlay fails with errors.CONFLICT marked retryable: reopen the overlay and rebuild the changeset.

local last_err
for _ = 1, 3 do
    local snap, err = registry.overlay("data-sources:crm")
    if err then return nil, err end

    local _, apply_err = snap:changes():delete("data.crm:connection"):apply()
    if not apply_err then return true end
    if not apply_err:retryable() then return nil, apply_err end
    last_err = apply_err
end
return nil, last_err

Restrictions

• The owner string is required and must not be blank.
• A changeset must be non-empty and must not name the same entry twice.
• create fails when the ID already exists in durable state or in any overlay.
• update and delete only work on entries this owner created; any other ID fails with errors.NOT_FOUND.
• Overlay entries cannot set dependency_root or any other registry-owned metadata.
• Overlay entries cannot use kinds owned by a registry directive, such as ns.dependency.
• A delete that removes an entry a surviving entry depends on is rejected.
• Dependencies cannot cross overlay owner boundaries, and durable entries cannot depend on overlay entries.

The rest surface as errors.CONFLICT or errors.INVALID, and none are retryable: only the generation mismatch above is.

Permissions: registry.overlay.get on the owner to open and read, registry.overlay.apply on the owner to write, and registry.overlay.<create|update|delete>.<kind> on each entry ID in the changeset.

Permissions

Errors

See Error Handling for working with errors.