*: handle transaction protocol compatibility in request plans by zyguan · Pull Request #570 · tikv/client-rust

zyguan · 2026-10-10T10:27:19Z

Ref: tikv/tikv#20085

Summary

Declare per-client request origins and transaction protocol versions through a compatibility plan around dispatch. Select a version for each destination store, treating missing capability metadata as legacy [0, 0].

Recover eligible upper-version admission rejections with one immediate resend using the server-returned range, without refreshing or modifying cached metadata. Preserve undetermined and incompatible errors through shard aggregation and cleanup; retain resend allowances across routing retries and renew them for new cleanup pages.

Coordinate conditional store metadata refreshes with concurrent-fetch suppression, cooldown, timeout, and publication ordering. Retain the last valid range when PD returns invalid bounds. Include metrics and concise API documentation.

The client defaults to protocol version 1 and supports selecting 0. Shared-lock version 2 remains unsupported.

Validation

All 200+ unit tests passed.
All-target Clippy with integration-test features, formatting, and diff checks passed.

Summary by CodeRabbit

New Features
- Added configurable transaction protocol compatibility, with detailed rejection information and controlled retries when store capabilities change.
- Expanded protocol support for V3 keyspace identities across keyspace, metadata, and service requests.
- Added namespace management, keyspace lookup, and streaming garbage-collection state updates.
- Added scan-priority and batch-task scheduling options, shared-lock error details, and expanded resource and read-pool metrics.
Bug Fixes
- Improved transaction error prioritization and handling of uncertain commit outcomes.
- Strengthened store metadata refresh to preserve newer cached information and handle stale compatibility data.

coderabbitai · 2026-10-10T10:27:35Z

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Walkthrough

The PR adds transaction protocol compatibility contracts and Rust request handling, including store metadata reloads and retry rules. It also adds V3 keyspace identity and namespace schemas, GC-state watch APIs, coprocessor batch-task controls, and execution and resource metadata fields.

Changes: Transaction protocol compatibility

Layer / File(s)	Summary
Protocol contracts and policy `proto/errorpb.proto`, `proto/kvrpcpb.proto`, `proto/metapb.proto`, `src/config.rs`, `src/common/errors.rs`, `src/lib.rs`	Schemas define protocol versions, store version ranges, and structured incompatibility errors. Client configuration exposes request origin and protocol version. Errors receive priority classifications.
Store metadata and reload coordination `src/store/mod.rs`, `src/pd/client.rs`, `src/mock.rs`, `src/region_cache.rs`	Store mappings retain metadata. RegionCache timestamps store snapshots, coordinates reloads, and applies publication rules to stale or invalid protocol ranges.
Protocol-aware dispatch and error handling `src/store/request.rs`, `src/store/errors.rs`, `src/raw/requests.rs`, `src/request/*`	Request plans select protocol metadata, reload store data when needed, and constrain incompatible-request resends. Error handling prioritizes undetermined and incompatible outcomes.
Transaction, lock, and scan integration `src/transaction/*`	Transaction clients, lock operations, and scan pages carry request policy. Retry allowances persist across routing retries, and error priorities apply to shard aggregation and partial-lock cleanup.

V3 keyspace identity and namespace APIs

Layer / File(s)	Summary
Keyspace identity across RPC schemas `proto/apipb.proto`, `proto/autoid.proto`, `proto/disaggregated.proto`, `proto/kvrpcpb.proto`, `proto/mpp.proto`, `proto/pdpb.proto`, `proto/resource_manager.proto`, `proto/tsopb.proto`	Schemas add KeyspaceIdentity and use it alongside legacy numeric keyspace IDs in supported requests and metadata.
Namespace and keyspace management APIs `proto/keyspacepb.proto`	The schema adds namespace RPCs and metadata. Keyspace lookup, loading, state updates, and pagination support namespace references or V3 identity fields.
Keyspace metadata conversion `src/request/keyspace.rs`, `src/raw/client.rs`	The Rust client converts metadata through Keyspace::from_metadata, which accepts legacy IDs, defaults missing IDs to zero, and rejects V3 identity metadata.

Additional RPC and execution metadata

Layer / File(s)	Summary
GC state retrieval and watch `proto/pdpb.proto`	GetGCState can include global barriers. WatchGCStates streams state upserts and removals and supports skipping initial state loading.
Coprocessor batch-task controls `proto/coprocessor.proto`	Requests can negotiate merged task data and serial task execution independently. Task responses identify data merged into the enclosing response.
Scheduling and execution metadata `proto/cdcpb.proto`, `proto/kvrpcpb.proto`, `proto/pdpb.proto`, `proto/resource_usage_agent.proto`	Schemas add CDC scan priority, read-pool execution details, noisy-group feedback, IA-tier region-size metadata, and RocksDB block-read counts.
Physical-key semantics and vendoring `proto/pdpb.proto`, `proto/schedulingpb.proto`, `proto/VERSION`	Comments identify region and split keys as physical key bytes. The recorded kvproto revision and re-vendoring instructions are updated.

Estimated code review effort: 5 (Critical) | ~90 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant PlanBuilder
  participant TxnProtocolCompatibility
  participant KvRequest
  participant PdRpcClient
  participant RegionCache
  PlanBuilder->>TxnProtocolCompatibility: wrap request with policy
  TxnProtocolCompatibility->>KvRequest: set origin and protocol version
  TxnProtocolCompatibility->>KvRequest: dispatch request
  KvRequest-->>TxnProtocolCompatibility: return incompatible-request error
  TxnProtocolCompatibility->>PdRpcClient: reload store metadata when required
  PdRpcClient->>RegionCache: reload store by ID
  RegionCache-->>PdRpcClient: return refreshed store metadata
  TxnProtocolCompatibility->>KvRequest: resend when rejection permits replacement

Possibly related PRs

tikv/client-rust#573: Both PRs depend on the ExtractError contract for handling response-originated key errors.

Merge Risk: Minimal · previous review b1e8d

Transaction requests now negotiate protocol versions. No concrete merge-blocking regression was established.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 28.77% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title "*: handle transaction protocol compatibility in request plans" matches the main change. The changeset adds TxnProtocolCompatibility to request plans, selects per-store protocol versions, an…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title ": handle transaction protocol compatibility in request plans" matches the main change. The changeset adds TxnProtocolCompatibility to request plans, selects per-store protocol versions, and resends on version-out-of-range rejections. The title uses a bare "" scope prefix, which is a minor style issue and does not affect whether it describes the change.

Full details: Docstring Coverage

Explanation

Docstring coverage is 28.77% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 73 functions across 23 files.

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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coderabbitai

🧹 Nitpick comments (1)

src/config.rs (1)
10-19: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Mark the public RequestOrigin enum #[non_exhaustive].

RequestOrigin is exported from the crate root. The proto comments say that more origins will be added later. Without #[non_exhaustive], any user who writes an exhaustive match on this enum breaks when a new variant is added. Add the attribute now, before the enum is released. After release, adding the attribute is itself a breaking change.
♻️ Proposed change
 /// Identifies the process issuing transaction RPCs for compatibility auditing.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+#[non_exhaustive]
 pub enum RequestOrigin {
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Review comment at @src/config.rs around lines 10 - 19:
Add the #[non_exhaustive] attribute to the public RequestOrigin enum so
downstream users must allow for future variants in exhaustive matches.

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Nitpick comments:
Review comments at @src/config.rs:
- Around line 10-19: Add the #[non_exhaustive] attribute to the public
RequestOrigin enum so downstream users must allow for future variants in
exhaustive matches.

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📥 Commits

Reviewing files that changed from the base of the PR and between ab4be1c and 275e453.

⛔ Files ignored due to path filters (3)

src/generated/errorpb.rs is excluded by !**/generated/**
src/generated/kvrpcpb.rs is excluded by !**/generated/**
src/generated/metapb.rs is excluded by !**/generated/**

📒 Files selected for processing (25)

proto/VERSION
proto/errorpb.proto
proto/kvrpcpb.proto
proto/metapb.proto
src/common/errors.rs
src/common/mod.rs
src/config.rs
src/lib.rs
src/mock.rs
src/pd/client.rs
src/raw/requests.rs
src/region_cache.rs
src/request/mod.rs
src/request/plan.rs
src/request/plan_builder.rs
src/request/shard.rs
src/store/errors.rs
src/store/mod.rs
src/store/request.rs
src/transaction/client.rs
src/transaction/lock.rs
src/transaction/mod.rs
src/transaction/requests.rs
src/transaction/transaction.rs
src/transaction/transaction/scanner.rs

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zyguan · 2026-10-12T02:14:20Z

/retest

Declare per-client request origins and transaction protocol versions, select compatible versions per destination, and handle admission rejections with a bounded resend. Preserve protocol errors through retries and cleanup. Update kvproto, coordinate store metadata refreshes, reject invalid ranges, and add metrics, documentation, and regression coverage. Signed-off-by: zyguan <zhongyangguan@gmail.com>

ti-chi-bot · 2026-11-04T17:51:07Z

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coderabbitai

Actionable comments posted: 1

Fix comments: Fix CodeRabbit comments on this PR

Prompt to fix all issues

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @src/request/plan.rs:
- Around line 216-228: Update TxnProtocolCompatibility::execute to return
undetermined responses to the retry layer instead of converting them to
Error::RegionError. Remove the special early error return while preserving
compatibility handling, so RetryableMultiRegion can apply
terminal_on_undetermined only for the existing commit-specific plans.

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Files ignored due to path filters: 16

`src/generated/apipb.rs` is excluded by `!/generated/`

`src/generated/autoid.rs` is excluded by `!/generated/`

`src/generated/cdcpb.rs` is excluded by `!/generated/`

`src/generated/coprocessor.rs` is excluded by `!/generated/`

`src/generated/disaggregated.rs` is excluded by `!/generated/`

`src/generated/errorpb.rs` is excluded by `!/generated/`

`src/generated/keyspacepb.rs` is excluded by `!/generated/`

`src/generated/kvrpcpb.rs` is excluded by `!/generated/`

`src/generated/metapb.rs` is excluded by `!/generated/`

`src/generated/mod.rs` is excluded by `!/generated/`

`src/generated/mpp.rs` is excluded by `!/generated/`

`src/generated/pdpb.rs` is excluded by `!/generated/`

`src/generated/resource_manager.rs` is excluded by `!/generated/`

`src/generated/resource_usage_agent.rs` is excluded by `!/generated/`

`src/generated/schedulingpb.rs` is excluded by `!/generated/`

`src/generated/tsopb.rs` is excluded by `!/generated/`

Files selected for processing: 38

`proto/VERSION`

`proto/apipb.proto`

`proto/autoid.proto`

`proto/cdcpb.proto`

`proto/coprocessor.proto`

`proto/disaggregated.proto`

`proto/errorpb.proto`

`proto/keyspacepb.proto`

`proto/kvrpcpb.proto`

`proto/mpp.proto`

`proto/pdpb.proto`

`proto/resource_manager.proto`

`proto/resource_usage_agent.proto`

`proto/schedulingpb.proto`

`proto/tsopb.proto`

`src/common/errors.rs`

`src/common/mod.rs`

`src/config.rs`

`src/lib.rs`

`src/mock.rs`

`src/pd/client.rs`

`src/raw/client.rs`

`src/raw/requests.rs`

`src/region_cache.rs`

`src/request/keyspace.rs`

`src/request/mod.rs`

`src/request/plan.rs`

`src/request/plan_builder.rs`

`src/request/shard.rs`

`src/stats.rs`

`src/store/errors.rs`

`src/store/mod.rs`

`src/store/request.rs`

`src/transaction/client.rs`

`src/transaction/lock.rs`

`src/transaction/requests.rs`

`src/transaction/transaction.rs`

`src/transaction/transaction/scanner.rs`

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Signed-off-by: zyguan <zhongyangguan@gmail.com>

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zyguan · 2026-11-04T23:01:49Z

/retest

wfxr

Two questions about retry behavior in lock cleanup.

wfxr · 2026-11-05T03:00:23Z

+        if let Some(index) = selected {
+            let region_count = region_errors.as_ref().map_or(0, Vec::len);
+            return Err(if index < region_count {
+                region_errors.as_mut().unwrap().remove(index)
+            } else {
+                key_errors.as_mut().unwrap().remove(index - region_count)
+            });


Should we preserve the existing retry behavior for UndeterminedResult in both ResolveLock paths?

This branch now returns a bare Error::RegionError, but resolve_lock_with_retry and CleanupLocks::execute only route MultipleRegionErrors through their region-error retry handling. Consequently, a transient undetermined response aborts ordinary lock resolution or batch cleanup immediately, even with retries remaining.

I verified both paths with tests returning UndeterminedResult once, then success: they pass on the base commit but fail on this head. Should we update these callers to handle the new error shape while retaining their retry policy?

Agreed, this was a regression. Fixed in 2e764bf: both callers now handle bare Error::RegionError through their existing region-error retry paths. Added tests for recovery after an undetermined response and for backoff exhaustion, preserving the original error and marking regions cleaned only after success.

wfxr · 2026-11-05T03:00:23Z

        let plan = crate::request::PlanBuilder::new(pd_client.clone(), keyspace, request)
+            .txn_protocol_compatibility(self.request_policy)
            .single_region_with_store(store.clone())


Should we retain this resend allowance across outer cleanup routing retries?

Calling txn_protocol_compatibility here creates a fresh allowance whenever the batch is rebuilt. If version 1 is rejected and the version 0 resend returns RegionNotFound, outer cleanup retries the same page and transaction batch with another allowance.

A targeted test produces ResolveLock versions [1, 0, 1, 0], with identical scan start keys and transaction IDs. Should the second version-1 rejection be terminal here, since the batch already spent its resend allowance and cleanup has not advanced to a new page?

I checked client-go: its allowance belongs to sendReqState, which is recreated for each SendReq invocation. An outer cleanup retry starts a new send, so [1, 0, 1, 0] is permitted even for the same batch.

I’m keeping this behavior for parity. Relocation may select a different store, making negotiation necessary again; the outer backoff bounds repeated attempts. Added tests in 622f2ed covering recovery with this sequence and retry-budget exhaustion.

Signed-off-by: zyguan <zhongyangguan@gmail.com>

ti-chi-bot Bot added dco-signoff: yes Indicates the PR's author has signed the dco. size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. labels Oct 10, 2026

zyguan force-pushed the dev/txn-rpc-protection branch from 2e7c7b4 to 275e453 Compare October 10, 2026 10:28

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zyguan mentioned this pull request Oct 15, 2026

Enhance transactional RPC compatibility protection tikv/tikv#20085

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zyguan requested review from cfzjywxk, lcwangchao and wfxr November 3, 2026 09:36

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cfzjywxk requested a review from ekexium November 3, 2026 11:08

zyguan force-pushed the dev/txn-rpc-protection branch from 332057e to 46623fa Compare November 4, 2026 17:51

zyguan changed the title *: protect transaction RPC compatibility *: handle transaction protocol compatibility in request plans Nov 4, 2026

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Comment thread src/request/plan.rs Resolved

request: preserve retry policy for undetermined transaction responses

2800315

Signed-off-by: zyguan <zhongyangguan@gmail.com>

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request: preserve explicit transaction request origins

b1e8dd7

Signed-off-by: zyguan <zhongyangguan@gmail.com>

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zyguan added 2 commits November 5, 2026 03:30

transaction: retry undetermined lock resolution results

2e764bf

Signed-off-by: zyguan <zhongyangguan@gmail.com>

request: cover cleanup batch resend allowance boundaries

622f2ed

Signed-off-by: zyguan <zhongyangguan@gmail.com>

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