bugfix: dispatch missing load balance strategies in Select (#1073) by paultanay · Pull Request #1196 · apache/incubator-seata-go

paultanay · 2026-09-22T08:30:30Z

What this PR does:

Updates loadbalance.Select to explicitly handle and dispatch ConsistentHashLoadBalance and
LeastActiveLoadBalance strategies. Previously, these values fell through to the default branch
and incorrectly routed to the random load balancing strategy. This PR also introduces a
comprehensive dispatcher-level regression test suite in pkg/remoting/loadbalance/loadbalance_test. go to ensure correctness across all load balancing configurations.

Which issue(s) this PR fixes:

Fixes #1073

Special notes for your reviewer:

The implementations for ConsistentHashLoadBalance and LeastActiveLoadBalance were already
present in the codebase but lacked the necessary routing logic in the central Select function.
The 7 newly added tests verify proper routing for all 5 strategies, confirm the fallback behavior,
validate empty/closed session handling, and cover concurrent dispatch execution. All 27 tests in
the package pass locally.

Does this PR introduce a user-facing change?:

NONE

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Review effort: Lite
Findings: 1 · 1 · 3

Open (5)

Calling assert.NotNil(t, ...) from multiple goroutines is not safe because it writes to the… · New
These tests only assert that Select(...) returns non-nil, which would still pass even if Select… · New
There are blank lines containing trailing whitespace (tabs/spaces). Please remove trailing… · New
There are blank lines containing trailing whitespace (tabs/spaces). Please remove trailing… · New
There are blank lines containing trailing whitespace (tabs/spaces). Please remove trailing… · New

What changed in this PR

Fixes loadbalance.Select dispatch so ConsistentHashLoadBalance and LeastActiveLoadBalance no longer fall back to random, and adds regression tests for strategy selection behavior.

Changes:

Add missing Select switch cases for consistent-hash and least-active load balancing.
Introduce a new dispatcher-focused test suite covering strategy selection, fallback, empty/closed sessions, and concurrent dispatch.

File	Description
pkg/remoting/loadbalance/loadbalance.go	Adds explicit dispatch branches for consistent-hash and least-active strategies.
pkg/remoting/loadbalance/loadbalance_test.go	Adds new tests intended to validate dispatcher behavior across strategies and concurrency.

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+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func(idx int) {
+			defer wg.Done()
+			strategy := strategies[idx%len(strategies)]
+			conn := Select(strategy, sessions, "test_xid")
+			assert.NotNil(t, conn)
+		}(i)
+	}


+func TestSelect_ConsistentHashLoadBalance(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := setupSessions(ctrl, 3, false)
+	conn := Select(consistentHashLoadBalance, sessions, "test_xid")
+	assert.NotNil(t, conn)
+}


+func TestSelect_ConcurrentDispatch(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := setupSessions(ctrl, 10, false)
+


+		consistentHashLoadBalance,
+		leastActiveLoadBalance,
+	}
+


+			assert.NotNil(t, conn)
+		}(i)
+	}
+


codecov-commenter · 2026-09-23T03:33:53Z

Codecov Report

❌ Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.60%. Comparing base (7c162b6) to head (9abe001).
⚠️ Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
...emoting/loadbalance/consistent_hash_loadbalance.go	40.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1196      +/-   ##
==========================================
+ Coverage   61.52%   61.60%   +0.07%     
==========================================
  Files         309      309              
  Lines       22625    22633       +8     
==========================================
+ Hits        13920    13943      +23     
+ Misses       7420     7408      -12     
+ Partials     1285     1282       -3

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Ethan-Xingyue · 2026-09-23T03:41:24Z

plz fix ci

Ethan-Xingyue

The dispatch change itself is correct, but this isn't ready to merge: CI is red, the new tests pass without the fix, and both newly reachable balancers carry pre-existing bugs that should be fixed first. Before merge:

Fix formatting so golang ci lint passes (sh goimports.sh).
Make the new tests fail when the two new case lines are removed.
Fix the constant load-balance key (pre-existing), here or in a PR that lands first; otherwise ConsistentHashLoadBalance pins every request to one TC.
Read the rpc.Status counters atomically (pre-existing data race, now reachable via LeastActiveLoadBalance).
Add changes/dev.md and changes/dev_zh.md entries and a release note, since configured ConsistentHashLoadBalance/LeastActiveLoadBalance no longer fall back to random.

Ethan-Xingyue · 2026-09-23T08:56:54Z

+func TestSelect_ConcurrentDispatch(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	sessions := setupSessions(ctrl, 10, false)
+


CI golang ci lint fails here: lines 95, 104 and 114 contain only a tab, which gofmt -s rejects. Running sh goimports.sh (or goimports -local seata.apache.org/seata-go/v2 -w) fixes them and also moves the seata.apache.org/seata-go/v2/pkg/remoting/mock import on line 26 into its own group.

Ethan-Xingyue · 2026-09-23T08:56:54Z

+	ctrl := gomock.NewController(t)
+	sessions := setupSessions(ctrl, 3, false)
+	conn := Select(consistentHashLoadBalance, sessions, "test_xid")
+	assert.NotNil(t, conn)


These tests still pass with the two new case lines removed: every mock returns the same RemoteAddr() (line 34), NotNil holds for any strategy, and without resetConsistentHashForTest() the ring can be empty and fall back to random. Please give each mock a distinct address and assert strategy-specific results, e.g. mark all but one address busy with rpc.BeginCount and expect that one from leastActiveLoadBalance (line 71), and after resetConsistentHashForTest() expect repeated Select(consistentHashLoadBalance, ...) calls with the same xid to return the same connection (use an xid that doesn't hash past the last virtual node; see the wrap-around note on loadbalance.go).

Ethan-Xingyue · 2026-09-23T08:56:54Z

 	case roundRobinLoadBalance:
 		return RoundRobinLoadBalance(sessions, xid)
+	case consistentHashLoadBalance:
+		return ConsistentHashLoadBalance(sessions, xid)


Pre-existing, but this case makes it user-visible: xid is a constant here in production. SendSync/SendAsync pass the whole message.RpcMessage to selectSession/selectChannel (getty_remoting.go:53,71, grpc_remoting.go:52,71), so getXid returns "<invalid Value>" (getty) or "" (gRPC) for every message, and ConsistentHashLoadBalance sends every request, branch commit/rollback responses included, to the same TC. Please pass msg.Body there and, like the Java client, fall back to a random key when no xid is found, either here or in a PR that lands first.

Ethan-Xingyue · 2026-09-23T08:56:54Z

+	case consistentHashLoadBalance:
+		return ConsistentHashLoadBalance(sessions, xid)
+	case leastActiveLoadBalance:
+		return LeastActiveLoadBalance(sessions, xid)


Pre-existing, but only reachable through this case: LeastActiveLoadBalance calls rpc.GetStatus(addr).GetActive(), which reads Status.Active without synchronization while SendSync/SendAsync update it with atomic.AddInt32, so concurrent requests race on it. Please switch GetActive/GetTotal in pkg/remoting/rpc/rpc_status.go to atomic.LoadInt32.

Ethan-Xingyue · 2026-09-23T08:56:54Z

 		return XidLoadBalance(sessions, xid)
 	case roundRobinLoadBalance:
 		return RoundRobinLoadBalance(sessions, xid)
+	case consistentHashLoadBalance:


Not blocking, pre-existing: ConsistentHashLoadBalance builds its ring once via a package-level sync.Once and rebuilds it only when a picked connection is closed, while both managers pass a fresh snapshot on every call. So if the first call sees no sessions, the ring stays empty and every pick falls back to random; TC nodes that join or reconnect later stay out of the ring until some ringed connection closes. Suggested follow-up: rebuild the ring whenever the snapshot's membership changes, as the Java ConsistentHashSelectorWrapper does.

Ethan-Xingyue · 2026-09-23T08:56:54Z

 		return XidLoadBalance(sessions, xid)
 	case roundRobinLoadBalance:
 		return RoundRobinLoadBalance(sessions, xid)
+	case consistentHashLoadBalance:


Not blocking, pre-existing: when the key hashes past the last virtual node, pick returns RandomLoadBalance(...) instead of wrapping to sortedHashNodes[0], so those xids may go to a different TC on each call. Suggested follow-up: wrap around like the Java selector (tailMap.isEmpty() ? firstKey() : tailMap.firstKey()).

Ethan-Xingyue · 2026-09-23T08:56:55Z

+			defer wg.Done()
+			strategy := strategies[idx%len(strategies)]
+			conn := Select(strategy, sessions, "test_xid")
+			assert.NotNil(t, conn)


Not blocking: assert.NotNil from these goroutines is fine (assert reports through t.Errorf, which is goroutine-safe), but nothing here calls rpc.BeginCount/EndCount while LeastActiveLoadBalance runs, which is the concurrency SendSync produces. Adding such a goroutine would cover the GetActive race under -race.

thunguo · 2026-10-24T10:15:14Z

Plz resolve the conflicts.

paultanay · 2026-11-05T15:08:25Z

Since #1205 has been merged and resolves #1073, this PR is superseded. I’m closing this PR to avoid duplicating the fix.

bugfix: dispatch missing load balance strategies in Select (apache#1073)

40a0289

paultanay marked this pull request as ready for review September 22, 2026 08:30

paultanay mentioned this pull request Sep 22, 2026

loadbalance.Select does not dispatch ConsistentHashLoadBalance or LeastActiveLoadBalance #1073

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github-actions Bot added coding remoting bug Something isn't working module/at labels Sep 22, 2026

thunguo requested a lite review from Copilot September 22, 2026 13:41

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Merge branch 'master' into fix-issue-1073

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Copilot started reviewing on behalf of thunguo September 22, 2026 14:32

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Merge branch 'master' into fix-issue-1073

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Merge branch 'master' into fix-issue-1073

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Ethan-Xingyue reviewed Sep 23, 2026

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paultanay force-pushed the fix-issue-1073 branch from fd1322b to 0f7b446 Compare September 24, 2026 16:58

github-actions Bot added documentation Improvements or additions to documentation milestone labels Sep 24, 2026

fix: address PR feedback for load balance dispatch issue

9abe001

paultanay force-pushed the fix-issue-1073 branch from 0f7b446 to 9abe001 Compare September 24, 2026 17:18

paultanay requested a review from Ethan-Xingyue September 28, 2026 06:00

Ethan-Xingyue mentioned this pull request Sep 28, 2026

bugfix: dispatch ConsistentHashLoadBalance and LeastActiveLoadBalance #1205

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Merge upstream/master into fix-issue-1073

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paultanay closed this Nov 5, 2026

github-actions Bot removed the milestone label Nov 5, 2026

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