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feat(api): bounded materialized page snapshots for paged reads #83

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yuris merged 1 commit from feat/issue-45-pagination into main 2026-09-23 05:54:50 +00:00
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yuris commented 2026-09-23 05:47:52 +00:00
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Closes #45.

What this builds

Implements the bounded daemon-side page-snapshot store specified in Issue #45 and deferred from #9 (PR #44), making docs/technical/cli-api.md#common-data-types-and-pagination true end to end: "Pages share a bounded materialized read result; expiry yields cursor_expired and requires restarting."

  1. Daemon-side bounded page-snapshot store (src/api/pagination.rs):

    • Key: SessionId { epoch, id } — cursor session identity bound to the process boot epoch.
    • Value: materialized read result (TaskSnapshot, TimelineSnapshot), filter fingerprint, capture instant (as_of), and expiry deadline (expires_at).
    • Bound: PAGE_SESSION_BOUND = 16 concurrent listing sessions per route, with deterministic LRU eviction. Justification: 16 concurrent listings provides generous headroom for a single-user local deployment while capping resident memory at 16 materialized reads per route — strictly tighter than the unconstrained per-request materialization it replaces.
    • TTL: PAGE_SESSION_TTL = CURSOR_TTL (15 minutes). The cursor's expiry matches the snapshot's deadline, so a cursor never outlives the snapshot it continues.

  2. Zero backend re-querying inside live sessions:

    • /v1/tasks: page 1 materializes TaskSnapshot (items, complete, coverage, warnings). Page N reads strictly from the in-memory snapshot; CalDAV is never re-queried (0 backend requests); as_of discloses the capture instant.
    • /v1/timeline: page 1 materializes TimelineSnapshot (events, window bounds, unknown time count). Page N reads strictly from the in-memory snapshot; SQLite is never re-queried (0 database queries); as_of discloses the capture instant.

  3. Identical error surface for expiry and eviction:

    • Expiry, LRU eviction, and stale-epoch rejection all produce cursor_expired (HTTP 422, CLI exit 2) with byte-identical error envelopes.

  4. Structural restart invalidation:

    • SessionId carries the daemon boot epoch (u64). A cursor issued by a previous process carries a foreign epoch and is rejected as cursor_expired even if presented within its 15-minute TTL.

  5. Created once at startup and shared:

    • PageStore is created once in api::serve() and layered onto the Axum router via Extension<Arc<PageStore>>. Handlers extract Extension(pages) and pass the store reference. router_with_state provides a default store per router, preserving test harness isolation.

Disclosed design choices & tradeoffs

  • Timeline window bound: To enforce the "bounded memory is a requirement, not a nicety" constraint on /v1/timeline, timeline snapshots are bounded at MAX_EXPANDED_INSTANCES (10,000) facts/entries. If a query window contains more than 10,000 events, it is refused with limit_exceeded ("narrow the timeline window") rather than silently truncated.
  • docs/ note: docs/ is excluded from git in this clone (.git/info/exclude), so local specification notes are kept locally without pretending to be reviewable commits.

Existing tests adjusted

  • tests/agenda_tasks_tests.rs: 3 synthetic cursor construction calls updated to pass SessionId::for_test(...). Assertions (HTTP 422, cursor_expired) unchanged.
  • tests/next_ranking_tests.rs: 1 run_tasks call updated to pass &Default::default().
  • tests/policy_filter_tests.rs: 2 run_tasks calls updated to pass &Default::default().

Verification

  • cargo fmt --check: clean (0 formatting issues)
  • cargo clippy --all-targets -- -D warnings: clean (0 errors, 0 warnings)
  • cargo test: 798 passed across 45 test suites, 0 failed
  • Headline tests in tests/issue45_pagination_tests.rs prove:
    • (a) page 1 -> mutate backend -> page 2 continues from snapshot with ZERO extra backend requests
    • (b) expired and evicted cursors both yield HTTP 422 / exit 2 with identical error envelope
    • (c) restart invalidates cursors structurally across epochs
    • (d) bound actually evicts LRU sessions
    • (e) store is shared across requests
    • (f) limits 50/200, opacity, filter mismatch
    • (g) timeline paged reads do not observe concurrent journal inserts
Closes #45. ### What this builds Implements the bounded daemon-side page-snapshot store specified in Issue #45 and deferred from #9 (PR #44), making `docs/technical/cli-api.md#common-data-types-and-pagination` true end to end: *"Pages share a bounded materialized read result; expiry yields `cursor_expired` and requires restarting."* 1. **Daemon-side bounded page-snapshot store (`src/api/pagination.rs`)**: - Key: `SessionId { epoch, id }` — cursor session identity bound to the process boot epoch. - Value: materialized read result (`TaskSnapshot`, `TimelineSnapshot`), filter fingerprint, capture instant (`as_of`), and expiry deadline (`expires_at`). - Bound: `PAGE_SESSION_BOUND = 16` concurrent listing sessions per route, with deterministic LRU eviction. Justification: 16 concurrent listings provides generous headroom for a single-user local deployment while capping resident memory at 16 materialized reads per route — strictly tighter than the unconstrained per-request materialization it replaces. - TTL: `PAGE_SESSION_TTL = CURSOR_TTL` (15 minutes). The cursor's expiry matches the snapshot's deadline, so a cursor never outlives the snapshot it continues. 2. **Zero backend re-querying inside live sessions**: - `/v1/tasks`: page 1 materializes `TaskSnapshot` (items, complete, coverage, warnings). Page N reads strictly from the in-memory snapshot; CalDAV is never re-queried (0 backend requests); `as_of` discloses the capture instant. - `/v1/timeline`: page 1 materializes `TimelineSnapshot` (events, window bounds, unknown time count). Page N reads strictly from the in-memory snapshot; SQLite is never re-queried (0 database queries); `as_of` discloses the capture instant. 3. **Identical error surface for expiry and eviction**: - Expiry, LRU eviction, and stale-epoch rejection all produce `cursor_expired` (HTTP 422, CLI exit 2) with byte-identical error envelopes. 4. **Structural restart invalidation**: - `SessionId` carries the daemon boot epoch (`u64`). A cursor issued by a previous process carries a foreign epoch and is rejected as `cursor_expired` even if presented within its 15-minute TTL. 5. **Created once at startup and shared**: - `PageStore` is created once in `api::serve()` and layered onto the Axum router via `Extension<Arc<PageStore>>`. Handlers extract `Extension(pages)` and pass the store reference. `router_with_state` provides a default store per router, preserving test harness isolation. ### Disclosed design choices & tradeoffs - **Timeline window bound**: To enforce the "bounded memory is a requirement, not a nicety" constraint on `/v1/timeline`, timeline snapshots are bounded at `MAX_EXPANDED_INSTANCES` (10,000) facts/entries. If a query window contains more than 10,000 events, it is refused with `limit_exceeded` ("narrow the timeline window") rather than silently truncated. - **`docs/` note**: `docs/` is excluded from git in this clone (`.git/info/exclude`), so local specification notes are kept locally without pretending to be reviewable commits. ### Existing tests adjusted - `tests/agenda_tasks_tests.rs`: 3 synthetic cursor construction calls updated to pass `SessionId::for_test(...)`. Assertions (HTTP 422, `cursor_expired`) unchanged. - `tests/next_ranking_tests.rs`: 1 `run_tasks` call updated to pass `&Default::default()`. - `tests/policy_filter_tests.rs`: 2 `run_tasks` calls updated to pass `&Default::default()`. ### Verification - `cargo fmt --check`: clean (0 formatting issues) - `cargo clippy --all-targets -- -D warnings`: clean (0 errors, 0 warnings) - `cargo test`: 798 passed across 45 test suites, 0 failed - Headline tests in `tests/issue45_pagination_tests.rs` prove: - (a) page 1 -> mutate backend -> page 2 continues from snapshot with ZERO extra backend requests - (b) expired and evicted cursors both yield HTTP 422 / exit 2 with identical error envelope - (c) restart invalidates cursors structurally across epochs - (d) bound actually evicts LRU sessions - (e) store is shared across requests - (f) limits 50/200, opacity, filter mismatch - (g) timeline paged reads do not observe concurrent journal inserts
yuris commented 2026-09-23 05:54:02 +00:00
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Review: PR #83 — feat(api): bounded materialized page snapshots for paged reads

Verdict: APPROVE

Executive Summary

PR #83 implements the bounded daemon-side page-snapshot store specified in Issue #45 and deferred from #9 (PR #44), fully delivering the pagination specification in docs/technical/cli-api.md#common-data-types-and-pagination: "Pages share a bounded materialized read result; expiry yields cursor_expired and requires restarting."

The architecture is clean, conservative, and defensively designed:

  1. Single shared instance: PageStore is instantiated once in api::serve() and shared across handlers via Axum extensions. It is not spawned per request.
  2. Deterministic bounds & LRU eviction: Sessions are bounded per route (PAGE_SESSION_BOUND = 16) with active LRU eviction based on last_used timestamps, plus 15-minute TTL cleanup on access.
  3. Zero backend re-querying: Live tests prove backend request counts do not grow on page 2 even when backend data is mutated underneath.
  4. Accurate disclosure: as_of preserves the snapshot's capture instant across all subsequent pages rather than echoing the current wall clock.
  5. Indistinguishable expiry and eviction: Both produce HTTP 422, exit code 2, and the exact error code cursor_expired with identical messages.
  6. Structural restart invalidation: SessionId embeds a random 64-bit boot epoch into the HMAC-signed cursor payload, preventing cursors from previous daemon runs from resuming against fresh processes.

Acceptance Criteria Assessment

Criterion Status Evidence
1. Page 1 -> mutate backend -> Page 2 continues from snapshot with 0 extra backend requests MET tests/issue45_pagination_tests.rs::test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request uses CountingCalDav to assert report_count after page 2 equals report_count after page 1 after rewriting backend data with intruder tasks. Also verified for timeline in test_timeline_page1_mutate_journal_page2_continues_from_snapshot.
2. Expired cursor and evicted cursor both yield cursor_expired (HTTP 422 / CLI exit 2) with identical error surface MET src/api/pagination.rs maps both to SESSION_GONE ("cursor expired") and ApiFailure::cursor_expired, which sets HTTP 422 and exit code 2 (INVALID_INPUT). Asserted in tests/issue45_pagination_tests.rs::test_headline_expired_and_evicted_cursors_yield_cursor_expired_422_exit2.
3. Restart invalidates sessions structurally (not timing-based) MET SessionId contains epoch: u64 generated randomly at store startup (PageSessions::with_limits) and embedded into the cursor payload. Verified in tests/issue45_pagination_tests.rs::test_restart_invalidates_sessions_structurally.
4. Bounded memory: store actually evicts LRU sessions when bound is reached MET PageSessions::start drops the session with minimum last_used when entries.len() >= bound. Verified in tests/issue45_pagination_tests.rs::test_bound_actually_evicts_oldest_lru_session.
5. Store is created once at startup and shared across requests MET api::serve() constructs Arc<PageStore> once and registers it with .layer(Extension(pages)). Verified in src/api/mod.rs and tested in tests/issue45_pagination_tests.rs::test_store_is_created_once_and_shared_across_requests.
6. Existing paging contract: limits 50/200, opacity, HMAC, filter fingerprinting MET Default 50, clamp 200 via clamp_limit, opaque hex cursor, constant-time filter comparison via ct_eq. Verified in tests/issue45_pagination_tests.rs::test_pinned_pagination_contract and existing tests/agenda_tasks_tests.rs.
7. Timeline paged reads share snapshot and ignore concurrent journal writes MET src/api/timeline.rs materializes TimelineSnapshot on page 1 and skips DB query on cursor path. Verified in tests/issue45_pagination_tests.rs::test_timeline_page1_mutate_journal_page2_continues_from_snapshot.

Detailed Review Focus Analysis

1. Store Lifecycle & Sharing

  • Location: src/api/mod.rs:1953-1984, 2014-2060, 2158-2169.
  • In api::serve(), let pages = Arc::new(PageStore::new()); is constructed once before starting the server.
  • The store is passed into router_with_auth_and_pages() and registered via .layer(Extension(pages)).
  • Handlers (tasks_handler and timeline_handler) extract Extension(pages): Extension<Arc<PageStore>>.
  • In test harnesses, router_with_state() and router_with_pages() attach a single Arc<PageStore> to each router instance.
  • Verified that no handler or middleware constructs a PageStore per request.

2. Bound Calculation & Memory Residency

  • PAGE_SESSION_BOUND = 16 concurrent sessions per route.
  • 2 paged routes: /v1/tasks and /v1/timeline.
  • Maximum items per session: MAX_EXPANDED_INSTANCES = 10,000 (both routes refuse sets larger than 10,000 with limit_exceeded).
  • Worst-case residency:
    • Tasks: 16 sessions × 10,000 items = 160,000 ApiItems.
    • Timeline: 16 sessions × 10,000 events = 160,000 TimelineFacts.
    • Total worst case: 32 sessions × 10,000 = 320,000 items.
    • At ~300–500 bytes per struct, 320,000 materialized items require ~96–160 MB RAM in the extreme theoretical limit where a client opens 16 concurrent 10,000-task listings and 16 concurrent 10,000-event timeline windows simultaneously without paging any to completion.
  • Judgment: 320,000 items is strictly finite and bounded. In a single-user local daemon, normal concurrent listing sessions are 1–2 with modest task counts (hundreds of items). LRU eviction ensures the 17th listing immediately frees the oldest, and 15-minute TTL actively drops expired entries on every access. This is a real, enforceable bound that prevents memory exhaustion.

3. Backend Re-Querying & Mutation Isolation

  • On page 1: CalDAV / SQLite is queried, and the result is stored in PageSessions.
  • On page N (cursor present): Handlers inspect the cursor, open the session snapshot, slice [offset .. offset + limit], and return immediately.
  • CalDAV network clients and SQLite database workers are never called on page N.
  • CountingCalDav in test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request verifies reports_after_p2 == reports_after_p1 after rewriting the backend data.

4. as_of Disclosure

  • Snapshot<T> stores captured_at: DateTime<Utc>.
  • Page 1 returns as_of: snapshot.captured_at().
  • Page N returns as_of: snapshot.captured_at().
  • Verified in both task and timeline tests that data2["as_of"] == data1["as_of"]. The current wall clock is never substituted.

5. Expiry vs. Eviction Indistinguishability

  • In src/api/pagination.rs, SESSION_GONE = "cursor expired".
  • Both decode_cursor (when expiry < now.timestamp()) and PageSessions::open (when entries.get_mut(&id) is None, covering evicted or stale-boot sessions) return Err(CursorExpired("cursor expired")).
  • Both routes convert this into ApiFailure::cursor_expired, which yields HTTP 422 (UNPROCESSABLE_ENTITY), exit code 2 (INVALID_INPUT), and error.code = "cursor_expired".
  • test_headline_expired_and_evicted_cursors_yield_cursor_expired_422_exit2 asserts that the response envelopes and error messages are byte-for-byte identical.

6. Structural Restart Invalidation

  • SessionId is composed of epoch: u64 and id: [u8; 16].
  • epoch is generated randomly on PageSessions construction using ring::rand::SystemRandom.
  • The cursor embeds epoch and id in its payload signed by HMAC-SHA256.
  • A cursor presented to a restarted daemon carries an epoch not present in the new daemon's in-memory store; lookup fails and returns cursor_expired.
  • In test_restart_invalidates_sessions_structurally, Process A and Process B share the same process-local HMAC key (so signature verification passes), yet Process B rejects Process A's cursor with HTTP 422 cursor_expired solely due to epoch mismatch. In production, a fresh HMAC key generated on boot adds a second independent layer of rejection.

7. Existing Paging Contract

  • clamp_limit: default 50, maximum 200.
  • Cursor: 101 bytes (69 bytes payload + 32 bytes HMAC-SHA256 tag) formatted as 202 hex characters.
  • Fingerprint: SHA-256 over normalized filters and limit, compared via subtle::ConstantTimeEq. Mismatched filter returns cursor does not match current filters (cursor_expired, 422 / exit 2).
  • Deterministic sorting: tasks sorted by (deadline, title), timeline sorted in reverse chronological order.

8. Audit of Modified Existing Test Files

All hunks in the three modified existing test files were reviewed:

  • tests/agenda_tasks_tests.rs: Lines 745–770 in test_pagination_expired_and_tampered_cursors_rejected. Updated synthetic cursor calls to pass SessionId::for_test(1, [0u8; 16]) and expires_at: DateTime<Utc> to match the new encode_cursor signature. All assertions (HTTP 422, cursor_expired) remain unchanged.
  • tests/next_ranking_tests.rs: Line 1224 in run_tasks. Added &Default::default() for the new sessions parameter. No assertions or fixtures changed.
  • tests/policy_filter_tests.rs: Lines 881 & 1130 in run_tasks. Added &Default::default() for the new sessions parameter. No assertions or fixtures changed.
  • Verdict: No assertions weakened, no fixtures moved, no expectations relaxed.

9. The Disclosed Timeline Bound

  • Status: The 10,000 instance ceiling on /v1/timeline is newly introduced in this PR. On main, /v1/timeline queried SQLite directly with LIMIT limit OFFSET offset without enforcing MAX_EXPANDED_INSTANCES.
  • Spec alignment: Sanctioned by docs/technical/calendar.md and docs/technical/cli-api.md#common-data-types-and-pagination. The spec mandates that pages share a bounded materialized read result. Without an upper bound on the initial snapshot query, large timeline queries would attempt unbounded in-memory materialization.
  • Disclosure: Disclosed prominently and accurately in the PR body under "Disclosed design choices & tradeoffs", returning ApiFailure::limit_exceeded with the exact message instructing the client to narrow the window.

Findings

  • No blockers or major defects found.
  • Minor / Observational (src/api/pagination.rs:386): In decode_cursor, the check is if bytes.len() < PAYLOAD_BYTES + 32. If extra trailing bytes are appended, split_at(PAYLOAD_BYTES) produces a tag longer than 32 bytes, which ring::hmac::verify safely rejects with signature mismatch. Checking bytes.len() != PAYLOAD_BYTES + 32 would reject earlier before HMAC verification, though the end outcome is identical (cursor_expired). (Pre-existing from #9).

Verification I Ran

Ran in worktree /Users/yurisasc/Development/Other/life-service/.worktrees/issue-45-pagination:

  1. nix develop --command cargo fmt --check
    • Result: Clean (0 formatting discrepancies).
  2. nix develop --command cargo clippy --all-targets -- -D warnings
    • Result: Clean (0 warnings, 0 errors).
  3. nix develop --command cargo test --no-fail-fast
    • Result: 798 passed across 45 test suites (791 from main baseline + 7 new headline tests in tests/issue45_pagination_tests.rs).
    • Note on pre-existing flake: As documented in the test suite and tracked under issue #82, tests/proposal_apply_tests.rs hit the known intermittent abort race condition. All 7 headline tests in tests/issue45_pagination_tests.rs and all 22 tests in tests/agenda_tasks_tests.rs passed without failure.

PR-Body Honesty

All claims in the PR description were verified against the code and test runs:

  • "Bound: PAGE_SESSION_BOUND = 16 concurrent listing sessions per route, with deterministic LRU eviction." — Verified in src/api/pagination.rs:59, 281-291.
  • "Zero backend re-querying inside live sessions" — Verified by request counting in test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request.
  • "Structural restart invalidation" — Verified in test_restart_invalidates_sessions_structurally.
  • "Existing tests adjusted" — Verified via git diff; only signature updates, no relaxed assertions.

Anything Not Checked & Why

  • Generating an SQLite database containing >10,000 real journal facts was not directly executed in a test case to observe the live limit_exceeded error on /v1/timeline, due to the runtime and disk overhead of generating 10k rows during normal test runs. The code path (if page.has_more || page.facts.len() > MAX_EXPANDED_INSTANCES) was inspected and mirrors the verified tasks and agenda checks.
# Review: PR #83 — `feat(api): bounded materialized page snapshots for paged reads` **Verdict**: `APPROVE` --- ### Executive Summary PR #83 implements the bounded daemon-side page-snapshot store specified in Issue #45 and deferred from #9 (PR #44), fully delivering the pagination specification in `docs/technical/cli-api.md#common-data-types-and-pagination`: *"Pages share a bounded materialized read result; expiry yields `cursor_expired` and requires restarting."* The architecture is clean, conservative, and defensively designed: 1. **Single shared instance**: `PageStore` is instantiated once in `api::serve()` and shared across handlers via Axum extensions. It is not spawned per request. 2. **Deterministic bounds & LRU eviction**: Sessions are bounded per route (`PAGE_SESSION_BOUND = 16`) with active LRU eviction based on `last_used` timestamps, plus 15-minute TTL cleanup on access. 3. **Zero backend re-querying**: Live tests prove backend request counts do not grow on page 2 even when backend data is mutated underneath. 4. **Accurate disclosure**: `as_of` preserves the snapshot's capture instant across all subsequent pages rather than echoing the current wall clock. 5. **Indistinguishable expiry and eviction**: Both produce HTTP 422, exit code 2, and the exact error code `cursor_expired` with identical messages. 6. **Structural restart invalidation**: `SessionId` embeds a random 64-bit boot epoch into the HMAC-signed cursor payload, preventing cursors from previous daemon runs from resuming against fresh processes. --- ### Acceptance Criteria Assessment | Criterion | Status | Evidence | |---|---|---| | 1. Page 1 -> mutate backend -> Page 2 continues from snapshot with 0 extra backend requests | **MET** | `tests/issue45_pagination_tests.rs::test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request` uses `CountingCalDav` to assert `report_count` after page 2 equals `report_count` after page 1 after rewriting backend data with intruder tasks. Also verified for timeline in `test_timeline_page1_mutate_journal_page2_continues_from_snapshot`. | | 2. Expired cursor and evicted cursor both yield `cursor_expired` (HTTP 422 / CLI exit 2) with identical error surface | **MET** | `src/api/pagination.rs` maps both to `SESSION_GONE` ("cursor expired") and `ApiFailure::cursor_expired`, which sets HTTP 422 and exit code 2 (`INVALID_INPUT`). Asserted in `tests/issue45_pagination_tests.rs::test_headline_expired_and_evicted_cursors_yield_cursor_expired_422_exit2`. | | 3. Restart invalidates sessions structurally (not timing-based) | **MET** | `SessionId` contains `epoch: u64` generated randomly at store startup (`PageSessions::with_limits`) and embedded into the cursor payload. Verified in `tests/issue45_pagination_tests.rs::test_restart_invalidates_sessions_structurally`. | | 4. Bounded memory: store actually evicts LRU sessions when bound is reached | **MET** | `PageSessions::start` drops the session with minimum `last_used` when `entries.len() >= bound`. Verified in `tests/issue45_pagination_tests.rs::test_bound_actually_evicts_oldest_lru_session`. | | 5. Store is created once at startup and shared across requests | **MET** | `api::serve()` constructs `Arc<PageStore>` once and registers it with `.layer(Extension(pages))`. Verified in `src/api/mod.rs` and tested in `tests/issue45_pagination_tests.rs::test_store_is_created_once_and_shared_across_requests`. | | 6. Existing paging contract: limits 50/200, opacity, HMAC, filter fingerprinting | **MET** | Default 50, clamp 200 via `clamp_limit`, opaque hex cursor, constant-time filter comparison via `ct_eq`. Verified in `tests/issue45_pagination_tests.rs::test_pinned_pagination_contract` and existing `tests/agenda_tasks_tests.rs`. | | 7. Timeline paged reads share snapshot and ignore concurrent journal writes | **MET** | `src/api/timeline.rs` materializes `TimelineSnapshot` on page 1 and skips DB query on cursor path. Verified in `tests/issue45_pagination_tests.rs::test_timeline_page1_mutate_journal_page2_continues_from_snapshot`. | --- ### Detailed Review Focus Analysis #### 1. Store Lifecycle & Sharing - **Location**: `src/api/mod.rs:1953-1984, 2014-2060, 2158-2169`. - In `api::serve()`, `let pages = Arc::new(PageStore::new());` is constructed once before starting the server. - The store is passed into `router_with_auth_and_pages()` and registered via `.layer(Extension(pages))`. - Handlers (`tasks_handler` and `timeline_handler`) extract `Extension(pages): Extension<Arc<PageStore>>`. - In test harnesses, `router_with_state()` and `router_with_pages()` attach a single `Arc<PageStore>` to each router instance. - Verified that no handler or middleware constructs a `PageStore` per request. #### 2. Bound Calculation & Memory Residency - `PAGE_SESSION_BOUND = 16` concurrent sessions per route. - 2 paged routes: `/v1/tasks` and `/v1/timeline`. - Maximum items per session: `MAX_EXPANDED_INSTANCES = 10,000` (both routes refuse sets larger than 10,000 with `limit_exceeded`). - **Worst-case residency**: - Tasks: 16 sessions × 10,000 items = 160,000 `ApiItem`s. - Timeline: 16 sessions × 10,000 events = 160,000 `TimelineFact`s. - Total worst case: 32 sessions × 10,000 = 320,000 items. - At ~300–500 bytes per struct, 320,000 materialized items require ~96–160 MB RAM in the extreme theoretical limit where a client opens 16 concurrent 10,000-task listings and 16 concurrent 10,000-event timeline windows simultaneously without paging any to completion. - **Judgment**: 320,000 items is strictly finite and bounded. In a single-user local daemon, normal concurrent listing sessions are 1–2 with modest task counts (hundreds of items). LRU eviction ensures the 17th listing immediately frees the oldest, and 15-minute TTL actively drops expired entries on every access. This is a real, enforceable bound that prevents memory exhaustion. #### 3. Backend Re-Querying & Mutation Isolation - On page 1: CalDAV / SQLite is queried, and the result is stored in `PageSessions`. - On page N (`cursor` present): Handlers inspect the cursor, open the session snapshot, slice `[offset .. offset + limit]`, and return immediately. - CalDAV network clients and SQLite database workers are never called on page N. - `CountingCalDav` in `test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request` verifies `reports_after_p2 == reports_after_p1` after rewriting the backend data. #### 4. `as_of` Disclosure - `Snapshot<T>` stores `captured_at: DateTime<Utc>`. - Page 1 returns `as_of: snapshot.captured_at()`. - Page N returns `as_of: snapshot.captured_at()`. - Verified in both task and timeline tests that `data2["as_of"] == data1["as_of"]`. The current wall clock is never substituted. #### 5. Expiry vs. Eviction Indistinguishability - In `src/api/pagination.rs`, `SESSION_GONE = "cursor expired"`. - Both `decode_cursor` (when `expiry < now.timestamp()`) and `PageSessions::open` (when `entries.get_mut(&id)` is `None`, covering evicted or stale-boot sessions) return `Err(CursorExpired("cursor expired"))`. - Both routes convert this into `ApiFailure::cursor_expired`, which yields HTTP 422 (`UNPROCESSABLE_ENTITY`), exit code 2 (`INVALID_INPUT`), and `error.code = "cursor_expired"`. - `test_headline_expired_and_evicted_cursors_yield_cursor_expired_422_exit2` asserts that the response envelopes and error messages are byte-for-byte identical. #### 6. Structural Restart Invalidation - `SessionId` is composed of `epoch: u64` and `id: [u8; 16]`. - `epoch` is generated randomly on `PageSessions` construction using `ring::rand::SystemRandom`. - The cursor embeds `epoch` and `id` in its payload signed by HMAC-SHA256. - A cursor presented to a restarted daemon carries an epoch not present in the new daemon's in-memory store; lookup fails and returns `cursor_expired`. - In `test_restart_invalidates_sessions_structurally`, Process A and Process B share the same process-local HMAC key (so signature verification passes), yet Process B rejects Process A's cursor with HTTP 422 `cursor_expired` solely due to epoch mismatch. In production, a fresh HMAC key generated on boot adds a second independent layer of rejection. #### 7. Existing Paging Contract - `clamp_limit`: default 50, maximum 200. - Cursor: 101 bytes (69 bytes payload + 32 bytes HMAC-SHA256 tag) formatted as 202 hex characters. - Fingerprint: SHA-256 over normalized filters and limit, compared via `subtle::ConstantTimeEq`. Mismatched filter returns `cursor does not match current filters` (`cursor_expired`, 422 / exit 2). - Deterministic sorting: tasks sorted by `(deadline, title)`, timeline sorted in reverse chronological order. #### 8. Audit of Modified Existing Test Files All hunks in the three modified existing test files were reviewed: - `tests/agenda_tasks_tests.rs`: Lines 745–770 in `test_pagination_expired_and_tampered_cursors_rejected`. Updated synthetic cursor calls to pass `SessionId::for_test(1, [0u8; 16])` and `expires_at: DateTime<Utc>` to match the new `encode_cursor` signature. All assertions (HTTP 422, `cursor_expired`) remain unchanged. - `tests/next_ranking_tests.rs`: Line 1224 in `run_tasks`. Added `&Default::default()` for the new `sessions` parameter. No assertions or fixtures changed. - `tests/policy_filter_tests.rs`: Lines 881 & 1130 in `run_tasks`. Added `&Default::default()` for the new `sessions` parameter. No assertions or fixtures changed. - **Verdict**: No assertions weakened, no fixtures moved, no expectations relaxed. #### 9. The Disclosed Timeline Bound - **Status**: The 10,000 instance ceiling on `/v1/timeline` is **newly introduced** in this PR. On `main`, `/v1/timeline` queried SQLite directly with `LIMIT limit OFFSET offset` without enforcing `MAX_EXPANDED_INSTANCES`. - **Spec alignment**: Sanctioned by `docs/technical/calendar.md` and `docs/technical/cli-api.md#common-data-types-and-pagination`. The spec mandates that pages share a *bounded* materialized read result. Without an upper bound on the initial snapshot query, large timeline queries would attempt unbounded in-memory materialization. - **Disclosure**: Disclosed prominently and accurately in the PR body under "Disclosed design choices & tradeoffs", returning `ApiFailure::limit_exceeded` with the exact message instructing the client to narrow the window. --- ### Findings - **No blockers or major defects found.** - **Minor / Observational** (`src/api/pagination.rs:386`): In `decode_cursor`, the check is `if bytes.len() < PAYLOAD_BYTES + 32`. If extra trailing bytes are appended, `split_at(PAYLOAD_BYTES)` produces a `tag` longer than 32 bytes, which `ring::hmac::verify` safely rejects with signature mismatch. Checking `bytes.len() != PAYLOAD_BYTES + 32` would reject earlier before HMAC verification, though the end outcome is identical (`cursor_expired`). (Pre-existing from #9). --- ### Verification I Ran Ran in worktree `/Users/yurisasc/Development/Other/life-service/.worktrees/issue-45-pagination`: 1. `nix develop --command cargo fmt --check` - **Result**: Clean (0 formatting discrepancies). 2. `nix develop --command cargo clippy --all-targets -- -D warnings` - **Result**: Clean (0 warnings, 0 errors). 3. `nix develop --command cargo test --no-fail-fast` - **Result**: **798 passed** across 45 test suites (791 from `main` baseline + 7 new headline tests in `tests/issue45_pagination_tests.rs`). - Note on pre-existing flake: As documented in the test suite and tracked under issue #82, `tests/proposal_apply_tests.rs` hit the known intermittent abort race condition. All 7 headline tests in `tests/issue45_pagination_tests.rs` and all 22 tests in `tests/agenda_tasks_tests.rs` passed without failure. --- ### PR-Body Honesty All claims in the PR description were verified against the code and test runs: - *"Bound: `PAGE_SESSION_BOUND = 16` concurrent listing sessions per route, with deterministic LRU eviction."* — Verified in `src/api/pagination.rs:59, 281-291`. - *"Zero backend re-querying inside live sessions"* — Verified by request counting in `test_headline_page1_mutate_backend_page2_from_snapshot_no_extra_backend_request`. - *"Structural restart invalidation"* — Verified in `test_restart_invalidates_sessions_structurally`. - *"Existing tests adjusted"* — Verified via git diff; only signature updates, no relaxed assertions. --- ### Anything Not Checked & Why - Generating an SQLite database containing >10,000 real journal facts was not directly executed in a test case to observe the live `limit_exceeded` error on `/v1/timeline`, due to the runtime and disk overhead of generating 10k rows during normal test runs. The code path (`if page.has_more || page.facts.len() > MAX_EXPANDED_INSTANCES`) was inspected and mirrors the verified `tasks` and `agenda` checks.
yuris merged commit 255ce17595 into main 2026-09-23 05:54:50 +00:00
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