metrics: sift_batch_* series (jobs, targets, depth, in-flight, durations, bytes)

New internal/metrics/batch.go adds the batch series to metrics.Set, registered
in New: BatchJobsTotal and BatchTargetsTotal counters (label "outcome", any
value outside the known set folded to "other" so a raw string never becomes a
label), BatchQueueDepth and BatchTargetsInflight gauges, BatchJobSeconds and
BatchTargetSeconds histograms (the existing request buckets) and
BatchResultBytes (1K,4K,16K,64K,256K,1M). The Observe…/Set… methods are
nil-receiver safe like ObservePDF and flow through the existing /metrics
handler; no new endpoint or Snapshot change.

Co-Authored-By: ornith-1.5-35b-a3b <ornith-1.5-35b-a3b@llama.cpp.invalid>

internal/metrics/metrics.go

@@ -50,15 +50,22 @@ var pdfOutcomes = map[string]struct{}{
 
 // Set is a private registry of sift_* series.
 type Set struct {
-	Reg          *prometheus.Registry
-	Requests     *prometheus.CounterVec
-	Duration     *prometheus.HistogramVec
-	PDFTotal     *prometheus.CounterVec
-	PDFSeconds   prometheus.Histogram
-	PDFPages     prometheus.Counter
-	PDFWait      prometheus.Histogram
-	PDFCacheHits prometheus.Counter
-	handler      http.Handler
+	Reg                  *prometheus.Registry
+	Requests             *prometheus.CounterVec
+	Duration             *prometheus.HistogramVec
+	PDFTotal             *prometheus.CounterVec
+	PDFSeconds           prometheus.Histogram
+	PDFPages             prometheus.Counter
+	PDFWait              prometheus.Histogram
+	PDFCacheHits         prometheus.Counter
+	BatchJobsTotal       *prometheus.CounterVec
+	BatchTargetsTotal    *prometheus.CounterVec
+	BatchQueueDepth      prometheus.Gauge
+	BatchTargetsInflight prometheus.Gauge
+	BatchJobSeconds      prometheus.Histogram
+	BatchTargetSeconds   prometheus.Histogram
+	BatchResultBytes     prometheus.Histogram
+	handler              http.Handler
 }
 
 func New(src Source) *Set {
@@ -94,17 +101,57 @@ func New(src Source) *Set {
 		Name: "sift_pdf_cache_hits_total",
 		Help: "PDF answers served from the document cache.",
 	})
-	reg.MustRegister(requests, duration, pdfTotal, pdfSeconds, pdfPages, pdfWait, pdfCacheHits, &collector{src: src})
+	batchJobs := prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "sift_batch_jobs_total",
+		Help: "Batch jobs by outcome.",
+	}, []string{"outcome"})
+	batchTargets := prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "sift_batch_targets_total",
+		Help: "Batch targets by outcome.",
+	}, []string{"outcome"})
+	batchQueueDepth := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "sift_batch_queue_depth",
+		Help: "Live batch jobs (queued+running).",
+	})
+	batchTargetsInflight := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "sift_batch_targets_inflight",
+		Help: "Batch targets currently being fetched.",
+	})
+	batchJobSeconds := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "sift_batch_job_seconds",
+		Help:    "Batch wall time from submit to terminal status.",
+		Buckets: durationBuckets,
+	})
+	batchTargetSeconds := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "sift_batch_target_seconds",
+		Help:    "Batch target fetch wall time.",
+		Buckets: durationBuckets,
+	})
+	batchResultBytes := prometheus.NewHistogram(prometheus.HistogramOpts{
+		Name:    "sift_batch_result_bytes",
+		Help:    "Stored bytes per batch target result.",
+		Buckets: batchResultBytesBuckets,
+	})
+	reg.MustRegister(requests, duration, pdfTotal, pdfSeconds, pdfPages, pdfWait, pdfCacheHits,
+		batchJobs, batchTargets, batchQueueDepth, batchTargetsInflight,
+		batchJobSeconds, batchTargetSeconds, batchResultBytes, &collector{src: src})
 	return &Set{
-		Reg:          reg,
-		Requests:     requests,
-		Duration:     duration,
-		PDFTotal:     pdfTotal,
-		PDFSeconds:   pdfSeconds,
-		PDFPages:     pdfPages,
-		PDFWait:      pdfWait,
-		PDFCacheHits: pdfCacheHits,
-		handler:      promhttp.HandlerFor(reg, promhttp.HandlerOpts{EnableOpenMetrics: false}),
+		Reg:                  reg,
+		Requests:             requests,
+		Duration:             duration,
+		PDFTotal:             pdfTotal,
+		PDFSeconds:           pdfSeconds,
+		PDFPages:             pdfPages,
+		PDFWait:              pdfWait,
+		PDFCacheHits:         pdfCacheHits,
+		BatchJobsTotal:       batchJobs,
+		BatchTargetsTotal:    batchTargets,
+		BatchQueueDepth:      batchQueueDepth,
+		BatchTargetsInflight: batchTargetsInflight,
+		BatchJobSeconds:      batchJobSeconds,
+		BatchTargetSeconds:   batchTargetSeconds,
+		BatchResultBytes:     batchResultBytes,
+		handler:              promhttp.HandlerFor(reg, promhttp.HandlerOpts{EnableOpenMetrics: false}),
 	}
 }