Eliminate utils/restore Metrics

This PR elmintes the utils package by moving the functionality to where
it is used. This is more in-line with idiomatic go (no non-descriptive
package names). As part of the elimination we moved to a custom slice
for logs that elminates the majority of the Custom Marshal/Unmarshal
code.

Identified in this change, the metrics emission was no longer wired up
and has been restored to functionality.

  Key improvements:
  - Introduce LogsSlice type with proper JSON marshaling/unmarshaling
    - Implements Stringer interface for consistent log formatting
    - Handles newline-delimited string conversion automatically
    - Eliminates need for custom PredictionResponse marshal/unmarshal
  - Move metrics functionality from dead util/metrics.go to runner.go
    - Restore sendRunnerMetric() function that was never called
    - Inline HTTPClientWithRetry() using httpclient.ApplyRetryPolicy
    - Fix missing imports and undefined references
  - Remove util.JoinLogs() dependency by using LogsSlice.String()
  - Consolidate logging utilities into appropriate packages

  Technical details:
  - LogsSlice.String() preserves util.JoinLogs() behavior (joins with \n, ensures trailing \n)
  - LogsSlice.MarshalJSON/UnmarshalJSON handles string ↔ []string conversion
  - All util package imports removed across codebase
  - Metrics sending now properly integrated into runner lifecycle

  This eliminates the "terrible util package" while restoring previously
  broken metrics functionality and improving type safety for log handling.

Author: tempusfrangit

.gitignore

@@ -5,7 +5,7 @@
 /.idea
 /build
 /dist
-/internal/util/version.txt
+/internal/version/version.txt
 /python/cog/cog-*
 /python/coglet/_version.py
 /uv.lock

cmd/cog/main.go

@@ -16,7 +16,7 @@ import (
 	"github.com/replicate/cog-runtime/internal/config"
 	"github.com/replicate/cog-runtime/internal/runner"
 	"github.com/replicate/cog-runtime/internal/service"
-	"github.com/replicate/cog-runtime/internal/util"
+	"github.com/replicate/cog-runtime/internal/version"
 )
 
 type ServerCmd struct {
@@ -125,7 +125,7 @@ func (s *ServerCmd) Run() error {
 	}
 
 	addr := fmt.Sprintf("%s:%d", cfg.Host, cfg.Port)
-	log.Infow("starting Cog HTTP server", "addr", addr, "version", util.Version(), "pid", os.Getpid())
+	log.Infow("starting Cog HTTP server", "addr", addr, "version", version.Version(), "pid", os.Getpid())
 
 	// Create service with base logger
 	svc := service.New(cfg, baseLogger)

internal/runner/path.go

@@ -15,8 +15,7 @@ import (
 
 	"github.com/gabriel-vasile/mimetype"
 	"github.com/getkin/kin-openapi/openapi3"
-
-	"github.com/replicate/cog-runtime/internal/util"
+	"github.com/replicate/go/httpclient"
 )
 
 var Base64Regex = regexp.MustCompile(`^data:.*;base64,(?P<base64>.*)$`)
@@ -210,7 +209,7 @@ type uploader struct {
 // newUploader creates a new uploader instance
 func newUploader(uploadURL string) *uploader {
 	return &uploader{
-		client:    util.HTTPClientWithRetry(),
+		client:    httpclient.ApplyRetryPolicy(http.DefaultClient),
 		uploadURL: uploadURL,
 	}
 }

internal/runner/runner.go

@@ -2,10 +2,12 @@ package runner
 
 import (
 	"bufio"
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"net/http"
 	"os"
 	"os/exec"
 	"path"
@@ -20,8 +22,10 @@ import (
 	"github.com/getkin/kin-openapi/openapi3"
 	"go.uber.org/zap"
 
+	"github.com/replicate/go/httpclient"
+
 	"github.com/replicate/cog-runtime/internal/config"
-	"github.com/replicate/cog-runtime/internal/util"
+	"github.com/replicate/cog-runtime/internal/version"
 	"github.com/replicate/cog-runtime/internal/webhook"
 )
 
@@ -293,7 +297,7 @@ type Runner struct {
 	schema             string
 	doc                *openapi3.T
 	setupResult        SetupResult
-	logs               []string
+	logs               LogsSlice
 	asyncPredict       bool
 	maxConcurrency     int
 	pending            map[string]*PendingPrediction
@@ -521,7 +525,7 @@ func (r *Runner) captureLogLine(line string) {
 		} else {
 			// Add to runner logs for crash reporting
 			r.logs = append(r.logs, line)
-			r.setupResult.Logs = util.JoinLogs(r.logs)
+			r.setupResult.Logs = r.logs.String()
 		}
 		r.mu.Unlock()
 	default:
@@ -566,6 +570,9 @@ func (r *Runner) Config(ctx context.Context) error {
 	// Default to 1 if not set in cog.yaml, regardless whether async predict or not
 	maxConcurrency := max(1, cogYaml.Concurrency.Max)
 
+	// Send metrics
+	go r.sendRunnerMetric(*cogYaml)
+
 	// Create config.json for the coglet process
 	configJSON := map[string]any{
 		"module_name":     moduleName,
@@ -593,6 +600,36 @@ func (r *Runner) Config(ctx context.Context) error {
 	return nil
 }
 
+func (r *Runner) sendRunnerMetric(cogYaml CogYaml) {
+	log := r.logger.Sugar()
+	// FIXME: wire this up through more than os.getenv
+	endpoint := os.Getenv("COG_METRICS_ENDPOINT")
+	if endpoint == "" {
+		return
+	}
+	data := map[string]any{
+		"gpu":         cogYaml.Build.GPU,
+		"fast":        cogYaml.Build.Fast,
+		"cog_runtime": cogYaml.Build.CogRuntime,
+		"version":     version.Version(),
+	}
+	payload := MetricsPayload{
+		Source: "cog-runtime",
+		Type:   "runner",
+		Data:   data,
+	}
+	body, err := json.Marshal(payload)
+	if err != nil {
+		log.Errorw("failed to marshal payload", "error", err)
+		return
+	}
+	resp, err := httpclient.ApplyRetryPolicy(http.DefaultClient).Post(endpoint, "application/json", bytes.NewBuffer(body))
+	if err != nil || resp.StatusCode != http.StatusOK {
+		log.Errorw("failed to send runner metrics", "error", err)
+	}
+	defer resp.Body.Close()
+}
+
 func (r *Runner) Stop() error {
 	log := r.logger.Sugar()
 	r.mu.Lock()
@@ -913,7 +950,10 @@ func (r *Runner) updateSetupResult() {
 	}
 
 	// Set logs first (original pattern)
-	r.setupResult.Logs = util.JoinLogs(logLines)
+	r.setupResult.Logs = strings.Join(logLines, "\n")
+	if r.setupResult.Logs != "" {
+		r.setupResult.Logs += "\n"
+	}
 
 	setupResultPath := filepath.Join(r.runnerCtx.workingdir, "setup_result.json")
 	log.Debug("reading setup_result.json", "path", setupResultPath)
@@ -954,7 +994,7 @@ func (r *Runner) rotateLogs() string {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 
-	allLogs := util.JoinLogs(r.logs)
+	allLogs := r.logs.String()
 	r.logs = r.logs[:0]
 	return allLogs
 }

internal/runner/runner_test.go

@@ -1208,7 +1208,7 @@ func TestPerPredictionWatcher(t *testing.T) {
 		assert.Equal(t, "partial output", pending.response.Output)
 		assert.Equal(t, predictionID, pending.response.ID)
 		assert.Equal(t, map[string]any{"test": "input"}, pending.response.Input)
-		assert.Equal(t, []string{"existing log"}, pending.response.Logs) // Logs preserved
+		assert.Equal(t, LogsSlice{"existing log"}, pending.response.Logs) // Logs preserved
 		pending.mu.Unlock()
 	})
 

internal/runner/types.go

@@ -16,10 +16,50 @@ import (
 	"syscall"
 	"time"
 
-	"github.com/replicate/cog-runtime/internal/util"
 	"github.com/replicate/cog-runtime/internal/webhook"
 )
 
+// LogsSlice is a []string that marshals to/from a newline-joined string in JSON
+type LogsSlice []string
+
+func (l LogsSlice) String() string {
+	r := strings.Join(l, "\n")
+	if r != "" {
+		r += "\n"
+	}
+	return r
+}
+
+// MarshalJSON implements custom JSON marshaling to convert logs from []string to string
+func (l LogsSlice) MarshalJSON() ([]byte, error) {
+	result := strings.Join(l, "\n")
+	if result != "" {
+		result += "\n"
+	}
+	return json.Marshal(result)
+}
+
+// UnmarshalJSON implements custom JSON unmarshaling to convert logs from string to []string
+func (l *LogsSlice) UnmarshalJSON(data []byte) error {
+	var str string
+	if err := json.Unmarshal(data, &str); err != nil {
+		return err
+	}
+
+	if str == "" {
+		*l = nil
+		return nil
+	}
+
+	// Split on newline and remove the trailing empty element if it exists
+	parts := strings.Split(str, "\n")
+	if len(parts) > 0 && parts[len(parts)-1] == "" {
+		parts = parts[:len(parts)-1]
+	}
+	*l = LogsSlice(parts)
+	return nil
+}
+
 type Status int
 
 const (
@@ -116,72 +156,11 @@ type PredictionResponse struct {
 	Input      any              `json:"input,omitempty"`
 	Output     any              `json:"output,omitempty"`
 	Error      string           `json:"error,omitempty"`
-	Logs       []string         `json:"logs,omitempty"`
+	Logs       LogsSlice        `json:"logs,omitempty"`
 	Metrics    any              `json:"metrics,omitempty"`
 	WebhookURL string           `json:"webhook,omitempty"`
 }
 
-// MarshalJSON implements custom JSON marshaling to convert logs from []string to string
-func (pr PredictionResponse) MarshalJSON() ([]byte, error) {
-	return json.Marshal(&struct {
-		ID         string           `json:"id"`
-		Status     PredictionStatus `json:"status"`
-		Input      any              `json:"input,omitempty"`
-		Output     any              `json:"output,omitempty"`
-		Error      string           `json:"error,omitempty"`
-		Logs       string           `json:"logs,omitempty"`
-		Metrics    any              `json:"metrics,omitempty"`
-		WebhookURL string           `json:"webhook,omitempty"`
-	}{
-		ID:         pr.ID,
-		Status:     pr.Status,
-		Input:      pr.Input,
-		Output:     pr.Output,
-		Error:      pr.Error,
-		Logs:       util.JoinLogs(pr.Logs),
-		Metrics:    pr.Metrics,
-		WebhookURL: pr.WebhookURL,
-	})
-}
-
-// UnmarshalJSON implements custom JSON unmarshalling to convert logs from string to []string
-func (pr *PredictionResponse) UnmarshalJSON(data []byte) error {
-	aux := &struct {
-		ID         string           `json:"id"`
-		Status     PredictionStatus `json:"status"`
-		Input      any              `json:"input,omitempty"`
-		Output     any              `json:"output,omitempty"`
-		Error      string           `json:"error,omitempty"`
-		Logs       string           `json:"logs,omitempty"`
-		Metrics    any              `json:"metrics,omitempty"`
-		WebhookURL string           `json:"webhook,omitempty"`
-	}{}
-	if err := json.Unmarshal(data, aux); err != nil {
-		return err
-	}
-
-	pr.ID = aux.ID
-	pr.Status = aux.Status
-	pr.Input = aux.Input
-	pr.Output = aux.Output
-	pr.Error = aux.Error
-	pr.Metrics = aux.Metrics
-	pr.WebhookURL = aux.WebhookURL
-
-	// Convert string logs back to []string
-	if aux.Logs != "" {
-		// Split on newline and remove the trailing empty element if it exists
-		parts := strings.Split(aux.Logs, "\n")
-		if len(parts) > 0 && parts[len(parts)-1] == "" {
-			parts = parts[:len(parts)-1]
-		}
-		pr.Logs = parts
-	} else {
-		pr.Logs = nil
-	}
-	return nil
-}
-
 // RunnerID is a unique identifier for a runner instance.
 // Format: 8-character base32 string (no leading zeros)
 // Example: "k7m3n8p2", "b9q4x2w1"
@@ -391,3 +370,9 @@ func (p *PendingPrediction) sendWebhookSync(event webhook.Event) error {
 	_ = p.webhookSender.SendConditional(p.request.Webhook, bytes.NewReader(body), event, p.request.WebhookEventsFilter, &p.lastUpdated)
 	return nil
 }
+
+type MetricsPayload struct {
+	Source string         `json:"source,omitempty"`
+	Type   string         `json:"type,omitempty"`
+	Data   map[string]any `json:"data,omitempty"`
+}

internal/runner/types_test.go

@@ -139,7 +139,7 @@ func TestPredictionResponse(t *testing.T) {
 		assert.Equal(t, PredictionSucceeded, resp.Status)
 		assert.Equal(t, map[string]any{"result": "success"}, resp.Output)
 		assert.Empty(t, resp.Error)
-		assert.Equal(t, []string{"log1", "log2"}, resp.Logs)
+		assert.Equal(t, LogsSlice{"log1", "log2"}, resp.Logs)
 		assert.Equal(t, map[string]any{"duration": 1.5}, resp.Metrics)
 		assert.Equal(t, "http://example.com/webhook", resp.WebhookURL)
 	})
@@ -330,7 +330,7 @@ func TestPredictionResponseUnmarshalFromExternalJSON(t *testing.T) {
 	err := json.Unmarshal([]byte(jsonStr), &response)
 	require.NoError(t, err)
 
-	expected := []string{
+	expected := LogsSlice{
 		"starting prediction",
 		"prediction in progress 1/2",
 		"prediction in progress 2/2",