feat: separate flow service from config service with explicit queue
lifecycle management
The flow service is now an independent service that owns the lifecycle
of flow and blueprint queues. System services own their own queues.
Consumers never create queues.
Flow service separation:
- New service at trustgraph-flow/trustgraph/flow/service/
- Uses async ConfigClient (RequestResponse pattern) to talk to config
service
- Config service stripped of all flow handling
Queue lifecycle management:
- PubSubBackend protocol gains create_queue, delete_queue,
queue_exists, ensure_queue — all async
- RabbitMQ: implements via pika with asyncio.to_thread internally
- Pulsar: stubs for future admin REST API implementation
- Consumer _connect() no longer creates queues (passive=True for named
queues)
- System services call ensure_queue on startup
- Flow service creates queues on flow start, deletes on flow stop
- Flow service ensures queues for pre-existing flows on startup
Two-phase flow stop:
- Phase 1: set flow status to "stopping", delete processor config
entries
- Phase 2: retry queue deletion, then delete flow record
Config restructure:
- active-flow config replaced with processor:{name} types
- Each processor has its own config type, each flow variant is a key
- Flow start/stop use batch put/delete — single config push per
operation
- FlowProcessor subscribes to its own type only
Blueprint format:
- Processor entries split into topics and parameters dicts
- Flow interfaces use {"flow": "topic"} instead of bare strings
- Specs (ConsumerSpec, ProducerSpec, etc.) read from
definition["topics"]
Tests updated
Derive consumer behaviour from queue class, remove
consumer_type parameter
The queue class prefix (flow, request, response, notify) now
fully determines consumer behaviour in both RabbitMQ and Pulsar
backends. Added 'notify' class for ephemeral broadcast (config
push notifications). Response and notify classes always create
per-subscriber auto-delete queues, eliminating orphaned queues
that accumulated on service restarts.
Change init-trustgraph to set up the 'notify' namespace in
Pulsar instead of old hangover 'state'.
Fixes 'stuck backlog' on RabbitMQ config notification queue.
Replace the config push mechanism that broadcast the full config
blob on a 'state' class pub/sub queue with a lightweight notify
signal containing only the version number and affected config
types. Processors fetch the full config via request/response from
the config service when notified.
This eliminates the need for the pub/sub 'state' queue class and
stateful pub/sub services entirely. The config push queue moves
from 'state' to 'flow' class — a simple transient signal rather
than a retained message. This solves the RabbitMQ
late-subscriber problem where restarting processes never received
the current config because their fresh queue had no historical
messages.
Key changes:
- ConfigPush schema: config dict replaced with types list
- Subscribe-then-fetch startup with retry: processors subscribe
to notify queue, fetch config via request/response, then
process buffered notifies with version comparison to avoid race
conditions
- register_config_handler() accepts optional types parameter so
handlers only fire when their config types change
- Short-lived config request/response clients to avoid subscriber
contention on non-persistent response topics
- Config service passes affected types through put/delete/flow
operations
- Gateway ConfigReceiver rewritten with same notify pattern and
retry loop
Tests updated
New tests:
- register_config_handler: without types, with types, multiple
types, multiple handlers
- on_config_notify: old/same version skipped, irrelevant types
skipped (version still updated), relevant type triggers fetch,
handler without types always called, mixed handler filtering,
empty types invokes all, fetch failure handled gracefully
- fetch_config: returns config+version, raises on error response,
stops client even on exception
- fetch_and_apply_config: applies to all handlers on startup,
retries on failure
