feat(conflict): add Analyzer extension and wire it into the batch controller

Makefile

@@ -274,7 +274,7 @@ local-stovepipe-stop: ## Stop Stovepipe service
 
 mocks: ## Generate mock files using mockgen
 	@echo "Generating mocks..."
-	@$(BAZEL) run @rules_go//go -- generate ./extension/storage/... ./extension/changestore/... ./extension/counter/... ./extension/queue/... ./extension/mergechecker/... ./extension/scorer/... ./core/consumer/...
+	@$(BAZEL) run @rules_go//go -- generate ./extension/storage/... ./extension/changestore/... ./extension/counter/... ./extension/queue/... ./extension/mergechecker/... ./extension/pusher/... ./extension/scorer/... ./extension/conflict/... ./core/consumer/...
 	@echo "Mocks generated successfully!"
 
 proto: ## Generate protobuf files from .proto definitions

example/server/orchestrator/BUILD.bazel

@@ -18,6 +18,7 @@ go_library(
         "//extension/changeprovider/github",
         "//extension/changestore",
         "//extension/changestore/mysql",
+        "//extension/conflict/all",
         "//extension/counter",
         "//extension/counter/mysql",
         "//extension/mergechecker",

example/server/orchestrator/main.go

@@ -37,6 +37,7 @@ import (
 	githubprovider "github.com/uber/submitqueue/extension/changeprovider/github"
 	"github.com/uber/submitqueue/extension/changestore"
 	mysqlchangestore "github.com/uber/submitqueue/extension/changestore/mysql"
+	"github.com/uber/submitqueue/extension/conflict/all"
 	"github.com/uber/submitqueue/extension/counter"
 	mysqlcounter "github.com/uber/submitqueue/extension/counter/mysql"
 	"github.com/uber/submitqueue/extension/mergechecker"
@@ -436,6 +437,9 @@ func registerControllers(c consumer.Consumer, logger *zap.SugaredLogger, scope t
 		registry,
 		cnt,
 		store,
+		// TODO: replace with a real conflict analyzer (e.g. one backed by
+		// Tango target analysis). The "all" stub serializes the queue.
+		all.New(),
 		consumer.TopicKeyBatch,
 		"orchestrator-batch",
 	)

extension/conflict/BUILD.bazel

@@ -0,0 +1,9 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "conflict",
+    srcs = ["conflict.go"],
+    importpath = "github.com/uber/submitqueue/extension/conflict",
+    visibility = ["//visibility:public"],
+    deps = ["//entity"],
+)

extension/conflict/README.md

@@ -0,0 +1,46 @@
+# Conflict
+
+Vendor-agnostic interface for detecting conflicts between a candidate batch
+and the batches already in flight.
+
+## Interface
+
+`Analyzer` exposes a single `Analyze` method that takes the candidate batch
+and the list of in-flight batches it might conflict with. It returns the
+subset of in-flight batches that conflict with the candidate, each paired
+with a `ConflictType` describing the kind of conflict. An empty result means
+the candidate is free to advance independently.
+
+Callers are responsible for filtering out the candidate itself and any
+terminal batches from the in-flight list before invoking the analyzer. The
+analyzer itself stays free of lifecycle knowledge. A non-nil error reports
+an infrastructure failure of the analysis and should be treated as
+retryable by the caller.
+
+The analyzer is intentionally pure with respect to batch state: it does not
+mutate inputs, does not read storage, and may be called concurrently. Real
+implementations are expected to resolve the batch contents (e.g. changed
+build targets, modified files) via whichever upstream system they depend
+on, and to return as much classification detail as that system supports.
+
+## Implementations
+
+- [`all/`](all/) — pessimistic stub: reports every in-flight batch as a
+  `ConflictTypeConservative` conflict. Useful as a worst-case baseline and
+  for wiring tests where speculation must serialize.
+- [`none/`](none/) — optimistic stub: reports no conflicts. Useful as a
+  best-case baseline and for wiring tests where speculation should run all
+  batches in parallel.
+
+## Adding a new backend
+
+1. Create `extension/conflict/{backend}/` with an `Analyzer` implementation.
+2. Resolve each `entity.Batch` into whatever signal the backend needs
+   (e.g. changed build targets, files touched, dependency graphs).
+3. Emit one `Conflict` per (in-flight batch, detected conflict type). Pick
+   the most specific `ConflictType` your backend can determine; use
+   `ConflictTypeConservative` only when the backend cannot prove the absence
+   of a conflict and falls back to a pessimistic default. Introduce a new
+   `ConflictType` constant when you can classify the conflict more precisely.
+4. Return a plain error for transient infrastructure failures so callers
+   can classify and retry.

extension/conflict/all/BUILD.bazel

@@ -0,0 +1,24 @@
+load("@rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "all",
+    srcs = ["all.go"],
+    importpath = "github.com/uber/submitqueue/extension/conflict/all",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//entity",
+        "//extension/conflict",
+    ],
+)
+
+go_test(
+    name = "all_test",
+    srcs = ["all_test.go"],
+    embed = [":all"],
+    deps = [
+        "//entity",
+        "//extension/conflict",
+        "@com_github_stretchr_testify//assert",
+        "@com_github_stretchr_testify//require",
+    ],
+)

extension/conflict/all/all.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package all provides a conflict.Analyzer that pessimistically reports a
+// conflict against every in-flight batch. It is intended as a stub for
+// wiring tests and as a worst-case baseline for speculation behavior.
+package all
+
+import (
+	"context"
+
+	"github.com/uber/submitqueue/entity"
+	"github.com/uber/submitqueue/extension/conflict"
+)
+
+// analyzer is a conflict.Analyzer that reports every in-flight batch as a
+// conflict, classified as ConflictTypeConservative.
+type analyzer struct{}
+
+// New returns a conflict.Analyzer that reports a conflict against every
+// in-flight batch.
+func New() conflict.Analyzer {
+	return analyzer{}
+}
+
+// Analyze returns one ConflictTypeConservative Conflict per in-flight batch,
+// preserving the input order. Returns an empty slice when inFlight is empty.
+func (analyzer) Analyze(_ context.Context, _ entity.Batch, inFlight []entity.Batch) ([]conflict.Conflict, error) {
+	if len(inFlight) == 0 {
+		return nil, nil
+	}
+	conflicts := make([]conflict.Conflict, len(inFlight))
+	for i, b := range inFlight {
+		conflicts[i] = conflict.Conflict{
+			BatchID: b.ID,
+			Type:    conflict.ConflictTypeConservative,
+		}
+	}
+	return conflicts, nil
+}

extension/conflict/all/all_test.go

@@ -0,0 +1,68 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package all
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/uber/submitqueue/entity"
+	"github.com/uber/submitqueue/extension/conflict"
+)
+
+func TestAnalyze(t *testing.T) {
+	batch := entity.Batch{ID: "queueA/batch/10"}
+
+	tests := []struct {
+		name     string
+		inFlight []entity.Batch
+		want     []conflict.Conflict
+	}{
+		{
+			name:     "no in-flight batches yields no conflicts",
+			inFlight: nil,
+			want:     nil,
+		},
+		{
+			name:     "empty in-flight slice yields no conflicts",
+			inFlight: []entity.Batch{},
+			want:     nil,
+		},
+		{
+			name: "every in-flight batch is reported in input order",
+			inFlight: []entity.Batch{
+				{ID: "queueA/batch/1"},
+				{ID: "queueA/batch/2"},
+				{ID: "queueA/batch/3"},
+			},
+			want: []conflict.Conflict{
+				{BatchID: "queueA/batch/1", Type: conflict.ConflictTypeConservative},
+				{BatchID: "queueA/batch/2", Type: conflict.ConflictTypeConservative},
+				{BatchID: "queueA/batch/3", Type: conflict.ConflictTypeConservative},
+			},
+		},
+	}
+
+	a := New()
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := a.Analyze(context.Background(), batch, tt.inFlight)
+			require.NoError(t, err)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}

extension/conflict/conflict.go

@@ -0,0 +1,68 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package conflict
+
+//go:generate mockgen -source=conflict.go -destination=mock/conflict_mock.go -package=mock
+
+import (
+	"context"
+
+	"github.com/uber/submitqueue/entity"
+)
+
+// ConflictType classifies why two batches are considered to conflict.
+// New values may be added as more sophisticated analyzers are introduced.
+type ConflictType string
+
+const (
+	// ConflictTypeUnknown is the unreachable zero value, set by default when
+	// the structure is initialized. It should never be seen in the system.
+	ConflictTypeUnknown ConflictType = ""
+	// ConflictTypeConservative means the analyzer treated the batches as
+	// conflicting because it could not prove otherwise, without identifying a
+	// specific reason. Used by conservative analyzers that serialize
+	// everything by default.
+	ConflictTypeConservative ConflictType = "conservative"
+	// ConflictTypeTargetOverlap means the two batches modify one or more of
+	// the same build targets and may therefore interfere with each other.
+	ConflictTypeTargetOverlap ConflictType = "target_overlap"
+)
+
+// Conflict reports a single conflict between the analyzed batch and one of
+// the in-flight batches.
+type Conflict struct {
+	// BatchID is the ID of the in-flight batch that conflicts with the
+	// analyzed batch.
+	BatchID string
+	// Type classifies the conflict. A single (analyzed, in-flight) pair may
+	// be reported with multiple Conflict entries when different conflict
+	// types apply.
+	Type ConflictType
+}
+
+// Analyzer detects conflicts between a candidate batch and the batches
+// already in flight, so the speculation layer can decide which batches can
+// safely advance in parallel.
+type Analyzer interface {
+	// Analyze returns the subset of inFlight batches that conflict with
+	// batch, each paired with the type of conflict detected. An empty
+	// result means batch does not conflict with any in-flight batch.
+	//
+	// Callers should not include batch itself in inFlight; terminal batches
+	// should be filtered out before calling. A non-nil error indicates the
+	// analysis itself failed (infrastructure issue) and should be treated as
+	// retryable by the caller.
+	Analyze(ctx context.Context, batch entity.Batch, inFlight []entity.Batch) ([]Conflict, error)
+}

extension/conflict/mock/BUILD.bazel

@@ -0,0 +1,13 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "mock",
+    srcs = ["conflict_mock.go"],
+    importpath = "github.com/uber/submitqueue/extension/conflict/mock",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//entity",
+        "//extension/conflict",
+        "@org_uber_go_mock//gomock",
+    ],
+)