71 lines
4.9 KiB
Markdown
71 lines
4.9 KiB
Markdown
# device-pool Specification
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## Purpose
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TBD - created by archiving change cloud-runtime. Update Purpose after archive.
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## Requirements
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### Requirement: Host registration and heartbeat sync
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The system SHALL provide a `DevicePool` that tracks a `HostRegistration` (host id, address, last-seen timestamp) for each host process that registers itself, and SHALL update a host's last-seen timestamp whenever that host pushes a device snapshot via `sync_host_devices(host_id, snapshot)`.
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#### Scenario: New host registers and syncs devices
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- **WHEN** a previously-unknown `host_id` calls `sync_host_devices` with a list of devices
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- **THEN** the pool creates a new `HostRegistration` for that host, records the current time as its last-seen timestamp, and stores each synced device as a `PooledDevice` owned by that host
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#### Scenario: Known host re-syncs
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- **WHEN** an already-registered `host_id` calls `sync_host_devices` again with an updated device snapshot
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- **THEN** the pool updates that host's last-seen timestamp and replaces its previously-stored `PooledDevice` records with the new snapshot, without duplicating or losing devices from other hosts
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### Requirement: Aggregated device listing across hosts
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The system SHALL provide a way to list all `PooledDevice` records across every registered host, including each device's owning `host_id`, `driver_type`, status, and capability tags.
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#### Scenario: Listing devices across multiple hosts
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- **WHEN** two hosts have each synced a non-empty device snapshot
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- **THEN** a caller listing pool devices sees devices from both hosts in one combined result, each tagged with its correct `host_id`
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#### Scenario: No hosts registered
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- **WHEN** a caller lists pool devices before any host has ever synced
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- **THEN** the pool returns an empty list rather than raising an error
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### Requirement: Stale host devices degrade to unreachable
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The system SHALL mark all `PooledDevice`s belonging to a host `unreachable` once that host's last-seen timestamp exceeds a configured staleness threshold, computed at read time, without requiring any background process and without raising an error for the stale host's absence.
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#### Scenario: Host misses its sync interval
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- **WHEN** a host's last-seen timestamp is older than `config.stale_after_seconds` at the time of a `list_devices()`/`get_device()` call
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- **THEN** every `PooledDevice` owned by that host is reported with status `unreachable`, regardless of the status value in its last-synced snapshot
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#### Scenario: Host resumes syncing after being stale
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- **WHEN** a host previously marked stale calls `sync_host_devices` again
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- **THEN** its devices immediately stop being reported `unreachable` and reflect the statuses in the new snapshot
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### Requirement: Device lookup by id across the pool
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The system SHALL allow looking up a single `PooledDevice` by `device_id` regardless of which host owns it, returning a clear not-found result when no host has ever reported that device id.
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#### Scenario: Lookup finds device on any host
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- **WHEN** a caller requests a device by id that exists in some host's synced snapshot
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- **THEN** the pool returns that `PooledDevice` including its owning `host_id`
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#### Scenario: Lookup for unknown device id
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- **WHEN** a caller requests a device by id that no host has ever synced
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- **THEN** the pool returns a not-found result (e.g. `None`) rather than raising an unhandled exception
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### Requirement: Authenticated network synchronization feeds the device pool
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The system SHALL expose an authenticated Host Agent operation that validates a host device snapshot and delegates it to the existing device-pool synchronization behavior.
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#### Scenario: Valid remote snapshot
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- **WHEN** an authenticated Host Agent submits a valid complete snapshot for its bound host id
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- **THEN** the device pool refreshes that host and its devices with the same replacement and staleness semantics as an in-process synchronization call
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#### Scenario: Invalid snapshot is rejected atomically
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- **WHEN** a Host Agent snapshot contains invalid device identifiers, driver types, statuses, or capability tags
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- **THEN** the control plane rejects the snapshot without partially replacing the host's previously stored devices
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### Requirement: Device identity ownership conflicts are explicit
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The device pool SHALL reject a snapshot that claims a `device_id` actively owned by a different non-stale host, rather than silently transferring ownership.
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#### Scenario: Two live hosts report the same device id
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- **WHEN** host B reports a device id currently owned by non-stale host A
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- **THEN** host B's conflicting snapshot is rejected with an ownership-conflict response and host A retains ownership
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#### Scenario: Previous owner is stale
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- **WHEN** a configured ownership-recovery policy permits takeover and the prior owning host is stale beyond the recovery threshold
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- **THEN** the new host may claim the device id and the ownership transition is recorded
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