feat(metrics): instrument extension implementations with core/metrics (#112)

## Summary
- Add `metrics.Begin`/`Complete` lifecycle tracking to all
uninstrumented extension implementations: `counter/mysql`,
`storage/mysql` (all 6 stores), `scorer/heuristic`, and
`scorer/composite`
- Each constructor now accepts a `tally.Scope` and every interface
method emits called/succeeded/failed counters plus latency timers with
error classification tags
- Update all call sites (gateway, orchestrator, integration tests, unit
tests) to pass the scope parameter

## Test plan
- [x] All unit tests pass (`make test` — 24/24 passing)
- [x] Full build succeeds (`make build`)
- [x] `make gazelle` confirms BUILD files are in sync
- [x] Integration tests pass with `tally.NoopScope` (Docker-based, run
in CI)

Author: behinddwalls

example/server/gateway/main.go

@@ -102,7 +102,7 @@ func run() error {
 	defer appDB.Close()
 
 	// Initialize counter from shared app database connection
-	cnt := mysqlcounter.NewCounter(appDB)
+	cnt := mysqlcounter.NewCounter(appDB, scope.SubScope("counter"))
 
 	// Open queue database connection
 	queueDSN := os.Getenv("QUEUE_MYSQL_DSN")

example/server/orchestrator/main.go

@@ -112,9 +112,9 @@ func run() error {
 	}
 	defer appDB.Close()
 
-	cnt := mysqlcounter.NewCounter(appDB)
+	cnt := mysqlcounter.NewCounter(appDB, scope.SubScope("counter"))
 
-	store, err := mysqlstorage.NewStorage(appDB)
+	store, err := mysqlstorage.NewStorage(appDB, scope.SubScope("storage"))
 	if err != nil {
 		return fmt.Errorf("failed to create storage: %w", err)
 	}

extension/counter/mysql/BUILD.bazel

@@ -6,6 +6,8 @@ go_library(
     importpath = "github.com/uber/submitqueue/extension/counter/mysql",
     visibility = ["//visibility:public"],
     deps = [
+        "//core/metrics",
         "//extension/counter",
+        "@com_github_uber_go_tally_v4//:tally",
     ],
 )

extension/counter/mysql/counter.go

@@ -5,21 +5,26 @@ import (
 	"database/sql"
 	"fmt"
 
+	"github.com/uber-go/tally/v4"
+	"github.com/uber/submitqueue/core/metrics"
 	"github.com/uber/submitqueue/extension/counter"
 )
 
 type mysqlCounter struct {
-	db *sql.DB
+	db    *sql.DB
+	scope tally.Scope
 }
 
 // NewCounter creates a new MySQL-backed Counter.
-func NewCounter(db *sql.DB) counter.Counter {
-	return &mysqlCounter{db: db}
+func NewCounter(db *sql.DB, scope tally.Scope) counter.Counter {
+	return &mysqlCounter{db: db, scope: scope}
 }
 
 // Next atomically increments the counter for the given domain and returns the new value.
 // Uses MySQL's LAST_INSERT_ID() to set the value atomically and read the incremented value.
-func (c *mysqlCounter) Next(ctx context.Context, domain string) (int64, error) {
+func (c *mysqlCounter) Next(ctx context.Context, domain string) (ret int64, retErr error) {
+	op := metrics.Begin(c.scope, "next")
+	defer func() { op.Complete(retErr) }()
 	result, err := c.db.ExecContext(ctx,
 		"INSERT INTO counter (domain, value) VALUES (?, LAST_INSERT_ID(1)) ON DUPLICATE KEY UPDATE value = LAST_INSERT_ID(value + 1)",
 		domain,

extension/scorer/composite/BUILD.bazel

@@ -6,8 +6,10 @@ go_library(
     importpath = "github.com/uber/submitqueue/extension/scorer/composite",
     visibility = ["//visibility:public"],
     deps = [
+        "//core/metrics",
         "//entity",
         "//extension/scorer",
+        "@com_github_uber_go_tally_v4//:tally",
     ],
 )
 
@@ -20,5 +22,6 @@ go_test(
         "//extension/scorer",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
+        "@com_github_uber_go_tally_v4//:tally",
     ],
 )

extension/scorer/composite/scorer.go

@@ -3,6 +3,8 @@ package composite
 import (
 	"context"
 
+	"github.com/uber-go/tally/v4"
+	"github.com/uber/submitqueue/core/metrics"
 	"github.com/uber/submitqueue/entity"
 	"github.com/uber/submitqueue/extension/scorer"
 )
@@ -51,12 +53,14 @@ type compositeScorer struct {
 	scorers map[string]scorer.Scorer
 	// reduce combines named scores into a single value.
 	reduce ReduceFunc
+	// scope is the tally scope for emitting metrics.
+	scope tally.Scope
 }
 
 // New creates a composite Scorer that evaluates all named child scorers and combines
 // their results using the given reduce function.
 // Panics if scorers is empty or reduce is nil.
-func New(scorers map[string]scorer.Scorer, reduce ReduceFunc) scorer.Scorer {
+func New(scorers map[string]scorer.Scorer, reduce ReduceFunc, scope tally.Scope) scorer.Scorer {
 	if len(scorers) == 0 {
 		panic("composite.New: scorers must not be empty")
 	}
@@ -66,12 +70,16 @@ func New(scorers map[string]scorer.Scorer, reduce ReduceFunc) scorer.Scorer {
 	return &compositeScorer{
 		scorers: scorers,
 		reduce:  reduce,
+		scope:   scope,
 	}
 }
 
 // Score evaluates all child scorers and combines their results using the reduce function.
 // If any child scorer returns an error, that error is returned immediately.
-func (c *compositeScorer) Score(ctx context.Context, change entity.Change) (float64, error) {
+func (c *compositeScorer) Score(ctx context.Context, change entity.Change) (ret float64, retErr error) {
+	op := metrics.Begin(c.scope, "score")
+	defer func() { op.Complete(retErr) }()
+
 	scores := make(map[string]float64, len(c.scorers))
 	for name, s := range c.scorers {
 		score, err := s.Score(ctx, change)

extension/scorer/composite/scorer_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/uber-go/tally/v4"
 	"github.com/uber/submitqueue/entity"
 	"github.com/uber/submitqueue/extension/scorer"
 )
@@ -83,7 +84,7 @@ func TestScorer_Score(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			s := New(tt.scorers, tt.reduce)
+			s := New(tt.scorers, tt.reduce, tally.NoopScope)
 			got, err := s.Score(context.Background(), entity.Change{})
 			require.NoError(t, err)
 			assert.InDelta(t, tt.want, got, 1e-9)
@@ -95,20 +96,20 @@ func TestScorer_Score_ChildError(t *testing.T) {
 	s := New(map[string]scorer.Scorer{
 		"error": &errorScorer{},
 		"files": &fixedScorer{0.9},
-	}, Min)
+	}, Min, tally.NoopScope)
 	_, err := s.Score(context.Background(), entity.Change{})
 	require.Error(t, err)
 }
 
 func TestNew_EmptyScorers(t *testing.T) {
 	assert.Panics(t, func() {
-		New(map[string]scorer.Scorer{}, Min)
+		New(map[string]scorer.Scorer{}, Min, tally.NoopScope)
 	})
 }
 
 func TestNew_NilReduce(t *testing.T) {
 	assert.Panics(t, func() {
-		New(map[string]scorer.Scorer{"files": &fixedScorer{0.9}}, nil)
+		New(map[string]scorer.Scorer{"files": &fixedScorer{0.9}}, nil, tally.NoopScope)
 	})
 }
 
@@ -124,7 +125,7 @@ func TestReduceFunc_ReceivesNames(t *testing.T) {
 	s := New(map[string]scorer.Scorer{
 		"files": &fixedScorer{0.9},
 		"deps":  &fixedScorer{0.95},
-	}, custom)
+	}, custom, tally.NoopScope)
 	got, err := s.Score(context.Background(), entity.Change{})
 	require.NoError(t, err)
 	assert.Equal(t, 0.9, got)

extension/scorer/heuristic/BUILD.bazel

@@ -6,8 +6,10 @@ go_library(
     importpath = "github.com/uber/submitqueue/extension/scorer/heuristic",
     visibility = ["//visibility:public"],
     deps = [
+        "//core/metrics",
         "//entity",
         "//extension/scorer",
+        "@com_github_uber_go_tally_v4//:tally",
     ],
 )
 
@@ -19,5 +21,6 @@ go_test(
         "//entity",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
+        "@com_github_uber_go_tally_v4//:tally",
     ],
 )

extension/scorer/heuristic/scorer.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/uber-go/tally/v4"
+	"github.com/uber/submitqueue/core/metrics"
 	"github.com/uber/submitqueue/entity"
 	"github.com/uber/submitqueue/extension/scorer"
 )
@@ -28,23 +30,28 @@ type heuristicScorer struct {
 	buckets []Bucket
 	// valueFunc extracts the numeric value from a Change.
 	valueFunc ValueFunc
+	// scope is the tally scope for emitting metrics.
+	scope tally.Scope
 }
 
 // New creates a new heuristic Scorer with the given buckets and value function.
 // Panics if valueFunc is nil.
-func New(buckets []Bucket, valueFunc ValueFunc) scorer.Scorer {
+func New(buckets []Bucket, valueFunc ValueFunc, scope tally.Scope) scorer.Scorer {
 	if valueFunc == nil {
 		panic("heuristic.New: valueFunc must not be nil")
 	}
 	return &heuristicScorer{
 		buckets:   buckets,
 		valueFunc: valueFunc,
+		scope:     scope,
 	}
 }
 
 // Score extracts the value from the change, then returns the probability score for the first
 // bucket whose range [Min, Max] contains the value. Returns an error if no bucket matches.
-func (s *heuristicScorer) Score(ctx context.Context, change entity.Change) (float64, error) {
+func (s *heuristicScorer) Score(ctx context.Context, change entity.Change) (ret float64, retErr error) {
+	op := metrics.Begin(s.scope, "score")
+	defer func() { op.Complete(retErr) }()
 	value, err := s.valueFunc(ctx, change)
 	if err != nil {
 		return 0, err

extension/scorer/heuristic/scorer_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"github.com/uber-go/tally/v4"
 	"github.com/uber/submitqueue/entity"
 )
 
@@ -91,7 +92,7 @@ func TestScorer_Score(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			s := New(tt.buckets, tt.valueFunc)
+			s := New(tt.buckets, tt.valueFunc, tally.NoopScope)
 			got, err := s.Score(context.Background(), entity.Change{})
 			if tt.wantErr {
 				require.Error(t, err)
@@ -107,13 +108,13 @@ func TestScorer_Score_ValueFuncError(t *testing.T) {
 	failing := func(_ context.Context, _ entity.Change) (int, error) {
 		return 0, assert.AnError
 	}
-	s := New([]Bucket{{Min: 0, Max: 10, Score: 0.9}}, failing)
+	s := New([]Bucket{{Min: 0, Max: 10, Score: 0.9}}, failing, tally.NoopScope)
 	_, err := s.Score(context.Background(), entity.Change{})
 	require.Error(t, err)
 }
 
 func TestNew_NilValueFunc(t *testing.T) {
 	assert.Panics(t, func() {
-		New([]Bucket{{Min: 0, Max: 10, Score: 0.85}}, nil)
+		New([]Bucket{{Min: 0, Max: 10, Score: 0.85}}, nil, tally.NoopScope)
 	})
 }