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glm-5.2 cc470a363a docs: port architecture specs + 45 ADRs from alknet, renumbered

Port the call + channels architecture documentation from the alknet
mono-repo into docs/architecture/, renumbered as alkcall ADR-001..045.

Renumbering map (alknet -> alkcall):
  Core:        001,002,004,006,007,011,065,070,092,014,050,091 -> 001-012
  Call:        005,064,012,023,015,022,024,016,049,017,028,029,030,032,066,069,067,068 -> 013-030
  Shared:      003,009,013 -> 031-033
  Channels:    071,093,072,073,074,075,076,094,079,080,081,089 -> 034-045

3 superseded/reversed ADRs kept for historical trail:
  - ADR-013 (irpc foundation, superseded by ADR-014)
  - ADR-023 (peer-scoped filtering, superseded by ADR-024)
  - ADR-077 (TTY inside channels, reversed by ADR-035 — not ported, TTY-only)

Ported docs (11 spec files + README + open-questions):
  - call-README.md, call-protocol.md, operation-registry.md, client-and-adapters.md
  - channels-README.md, channels-overview.md, channels-wire.md, channels-connection.md, channels-adapter.md, channel-operations.md, channel-client.md
  - README.md (index with doc table, ADR table grouped by category, key principles)
  - open-questions.md (lean — 30 OQs, renumbered OQ-01..030; includes new OQ-22 for the pub/sub gap)

Cross-reference rewriting:
  - All ADR-NNN references rewritten single-pass (no chaining bug)
  - Markdown link paths fixed
  - Title lines aligned with filenames
  - Non-ported ADR refs (052, 082, 086, etc.) left as-is with README note

The open-questions.md includes OQ-22 (new): the call protocol pub/sub
gap — subscribe exists but pub does not, needed for channels
channel/resources/subscribe fan-out. This is the next ADR to write
(alkcall ADR-046).

2026-08-12 07:06:57 +00:00

4.2 KiB

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ADR-015: Call Protocol Stream Model

Status

Accepted

Context

The call protocol (alknet-call) operates on a QUIC connection with ALPN alknet/call. Within that connection, QUIC provides bidirectional streams. The question is how the call protocol uses those streams and how it correlates requests with responses — especially when both sides can initiate calls.

The reference implementation used EventEnvelope framing with a PendingRequestMap that correlates call.requested events to call.responded events by request ID, regardless of which stream carries them. This works well but the relationship between streams and operations was underspecified.

OQ-07 asked: "What is the scope of the call protocol within a connection? Should operations be multiplexed within a single stream, or should each operation get its own stream?"

Decision

The call protocol uses bidirectional QUIC streams with EventEnvelope framing and ID-based correlation. The protocol does not prescribe a stream usage pattern — it works with any arrangement:

EventEnvelope on every stream — every bidirectional stream opened on the alknet/call connection carries length-prefixed JSON EventEnvelope messages. The five event types (call.requested, call.responded, call.completed, call.aborted, call.error) are the protocol primitives.
PendingRequestMap correlates by ID, not by stream — the id field in EventEnvelope correlates requests with responses. A response on stream 5 can fulfill a request sent on stream 3. The PendingRequestMap is keyed by request ID.
Protocol is symmetric — both sides of the connection can open_bi() to initiate calls and accept_bi() to receive them. The server calling a client operation uses the same EventEnvelope format and the same correlation mechanism.
Top-level protocol operations — the call protocol defines four operations that map to EventEnvelope event patterns:
- call: call.requested → call.responded (one response) or call.error
- subscribe: call.requested → one or more call.responded → call.completed or call.aborted
- batch: multiple call.requested events (with correlated IDs) → multiple call.responded events
- schema: call.requested (name /services/list or /services/schema) → call.responded
Stream usage is the client's choice — a client may open one stream per operation, one stream for all operations, or any mix. The protocol is stream-agnostic. The server accepts streams and processes EventEnvelopes regardless of which stream they arrive on.

This resolves OQ-07: the call protocol's scope within a connection is the full operation registry. One alknet/call connection gives access to all operations (call, subscribe, batch, schema). QUIC's built-in stream multiplexing handles concurrency — the protocol doesn't need to impose additional multiplexing.

Consequences

Positive:

Simple mental model: one connection, full access, stream-agnostic correlation
The protocol works the same way regardless of stream usage — no "right" way to use streams
Bidirectional calls are natural — either side can open a stream and send call.requested
PendingRequestMap from the reference implementation carries forward without modification
QUIC's stream multiplexing provides natural flow control and head-of-line blocking avoidance
The top-level operations (call, subscribe, batch, schema) are protocol primitives, not separate ALPNs

Negative:

Clients that multiplex many operations on one stream must manage request IDs carefully — but this is standard RPC practice
The PendingRequestMap requires timeout-based cleanup to prevent memory leaks from abandoned requests — but this is already implemented and tested in the reference
No built-in stream-level backpressure per operation when multiple operations share a stream — but QUIC provides connection-level and stream-level flow control

References

ADR-013: irpc as call protocol foundation
ADR-004: ALPN string convention and connection model
ADR-005: BiStream type definition
OQ-07: Call protocol scope within a connection (resolved by this ADR)
Reference implementation: /workspace/@alkdev/alknet-main/crates/alknet-core/src/call/

4.2 KiB Raw Blame History