Turn the otel-app sink into a fake backend for sketches and raw fragments

otel-app/README.md

@@ -119,3 +119,27 @@ cumulative export; `raw-buffer` keeps every event as its own data point
 | `config-countsketch.yaml` | CountSketch |
 | `config-countminsketch.yaml` | CountMinSketch |
 | `config-baseline.yaml` | none (raw Sum/LastValue) |
+
+## Fake backend sink (`sink/`)
+
+`sink` stands in for the backend while it cannot ingest the Collector's
+output. It only receives: it counts what arrives, discards it, and prints
+totals on SIGINT/SIGTERM (and every `-stats-every` if set).
+
+```bash
+go run ./sink -grpc :4317 -http :10908 [-dump-dir /path] [-stats-every 30s]
+```
+
+- **OTLP/gRPC** (`-grpc`): point an OTLP exporter (the edge Collector or
+  otel-app `-target`) here. Sketch metrics are counted per sketch kind and
+  data-point encoding (`*Delta` encodings are deltas, the rest full state):
+  `SINK_SKETCH kind= encoding= mode= msgs= bytes=`. Plain points keep the
+  `SINK_STATS reqs= datapoints= bytes=` line.
+- **HTTP `POST /ingest/gorilla`** (`-http`): point `cold.ship_endpoint` here.
+  The gzipped ASAPFRG1 fragment frame is decoded to count
+  `SINK_RAW reqs= gzip_bytes= bytes= fragments= series= samples=`.
+- `-dump-dir`: write each request body to
+  `<receive-unix-ns>-<otlp|gorilla>-<seq>.bin` for offline comparison of
+  sketch answers with exact answers from the raw samples. Gorilla bodies are
+  stored as received (gzipped); OTLP bodies are the
+  `ExportMetricsServiceRequest` protobuf.

otel-app/go.mod

@@ -3,43 +3,112 @@ module github.com/approx-telemetry/otel-app
 go 1.25.0
 
 require (
+	github.com/ProjectASAP/asap-gorilla-go v0.0.0-00010101000000-000000000000
 	github.com/ProjectASAP/asap-precompute-go v0.0.0-00010101000000-000000000000
 	github.com/ProjectASAP/asap-precompute-go/monitor/grpcclient v0.0.0-00010101000000-000000000000
+	github.com/ProjectASAP/sketchlib-go v0.0.0-20260903015955-4b0919d3d653
+	go.opentelemetry.io/collector/pdata v1.42.0
 	go.opentelemetry.io/otel v1.43.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc v1.41.0
 	go.opentelemetry.io/otel/metric v1.43.0
 	go.opentelemetry.io/otel/sdk v1.41.0
 	go.opentelemetry.io/otel/sdk/metric v1.41.0
-	go.opentelemetry.io/proto/otlp v1.9.0
 	go.yaml.in/yaml/v2 v2.4.3
 	google.golang.org/grpc v1.79.1
-	google.golang.org/protobuf v1.36.11
 )
 
 replace (
+	github.com/ProjectASAP/asap-gorilla-go => ../asap-gorilla-go
 	github.com/ProjectASAP/asap-precompute-go => ../asap-precompute-go
 	github.com/ProjectASAP/asap-precompute-go/monitor/grpcclient => ../asap-precompute-go/monitor/grpcclient
 )
 
 require (
-	github.com/ProjectASAP/sketchlib-go v0.0.0-20260903015955-4b0919d3d653 // indirect
+	cloud.google.com/go/auth v0.16.5 // indirect
+	cloud.google.com/go/auth/oauth2adapt v0.2.8 // indirect
+	cloud.google.com/go/compute/metadata v0.9.0 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/azcore v1.19.1 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.12.0 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/internal v1.11.2 // indirect
+	github.com/AzureAD/microsoft-authentication-library-for-go v1.5.0 // indirect
+	github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b // indirect
+	github.com/aws/aws-sdk-go-v2 v1.41.7 // indirect
+	github.com/aws/aws-sdk-go-v2/config v1.31.12 // indirect
+	github.com/aws/aws-sdk-go-v2/credentials v1.18.16 // indirect
+	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.18.9 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.23 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.23 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/ini v1.8.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.13.9 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.13.23 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sso v1.29.6 // indirect
+	github.com/aws/aws-sdk-go-v2/service/ssooidc v1.35.1 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sts v1.38.6 // indirect
+	github.com/aws/smithy-go v1.25.1 // indirect
+	github.com/bboreham/go-loser v0.0.0-20230920113527-fcc2c21820a3 // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cenkalti/backoff/v5 v5.0.3 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/colega/zeropool v0.0.0-20230505084239-6fb4a4f75381 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/dennwc/varint v1.0.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/golang-jwt/jwt/v5 v5.3.0 // indirect
+	github.com/golang/snappy v1.0.0 // indirect
+	github.com/google/go-cmp v0.7.0 // indirect
+	github.com/google/s2a-go v0.1.9 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/googleapis/enterprise-certificate-proxy v0.3.6 // indirect
+	github.com/googleapis/gax-go/v2 v2.15.0 // indirect
 	github.com/grafana/regexp v0.0.0-20250905093917-f7b3be9d1853 // indirect
+	github.com/hashicorp/go-version v1.7.0 // indirect
+	github.com/jpillora/backoff v1.0.0 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.18.0 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.10 // indirect
+	github.com/kylelemons/godebug v1.1.0 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
+	github.com/oklog/ulid/v2 v2.1.1 // indirect
+	github.com/pkg/browser v0.0.0-20240102092130-5ac0b6a4141c // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
+	github.com/prometheus/client_golang v1.23.2 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
-	github.com/prometheus/common v0.66.1 // indirect
-	github.com/prometheus/prometheus v0.307.1 // indirect
+	github.com/prometheus/common v0.67.1 // indirect
+	github.com/prometheus/otlptranslator v1.0.0 // indirect
+	github.com/prometheus/procfs v0.16.1 // indirect
+	github.com/prometheus/prometheus v0.307.3 // indirect
+	github.com/prometheus/sigv4 v0.2.1 // indirect
+	github.com/stretchr/testify v1.11.1 // indirect
 	github.com/zeebo/xxh3 v1.1.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/collector/featuregate v1.47.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0 // indirect
 	go.opentelemetry.io/otel/trace v1.43.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.9.0 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	go.uber.org/goleak v1.3.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	golang.org/x/crypto v0.48.0 // indirect
+	golang.org/x/exp v0.0.0-20250808145144-a408d31f581a // indirect
 	golang.org/x/net v0.50.0 // indirect
+	golang.org/x/oauth2 v0.34.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/text v0.34.0 // indirect
+	golang.org/x/time v0.13.0 // indirect
+	google.golang.org/api v0.250.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260209200024-4cfbd4190f57 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	k8s.io/apimachinery v0.34.1 // indirect
+	k8s.io/client-go v0.34.1 // indirect
+	k8s.io/klog/v2 v2.130.1 // indirect
+	k8s.io/utils v0.0.0-20250604170112-4c0f3b243397 // indirect
 )
 
 // The `opentelemetry-go` submodule is kept in the repo with
@@ -55,6 +124,10 @@ require (
 // is `../../sketchlib-go` — matching the path opentelemetry-app used.
 replace (
 	github.com/ProjectASAP/sketchlib-go => ../../sketchlib-go
+	// The sink decodes OTLP with the patched pdata (the same module the
+	// asapedgeprocessor encodes with), which carries the SumAgg variant
+	// the patched proto bindings above do not.
+	go.opentelemetry.io/collector/pdata => ../opentelemetry-collector/pdata
 	go.opentelemetry.io/otel => ../opentelemetry-go
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc => ../opentelemetry-go/exporters/otlp/otlpmetric/otlpmetricgrpc
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp => ../opentelemetry-go/exporters/otlp/otlpmetric/otlpmetrichttp