Add remote write 2 receivers complicance tests

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>

Author: roidelapluie

remotewrite/receiver/.gitignore

@@ -0,0 +1,2 @@
+results.json
+prometheus.yml

remotewrite/receiver/README.md

@@ -1 +1,102 @@
-We currently do not have a test suite. We plan to introduce one and make it mandatory.
+# Prometheus Remote Write v2 Receiver Compliance Test Suite
+
+This repository contains a compliance test suite for Prometheus Remote Write Protocol v2.0 receivers. It validates that remote write endpoints properly implement the Remote Write v2 specification according to the [official protocol requirements](https://prometheus.io/docs/specs/prw/remote_write_spec_2_0/).
+
+## Overview
+
+The test suite sends various Remote Write v2 requests to configured endpoints and validates responses against the protocol specification. It tests proper handling of:
+
+- Sample data ingestion
+- Histogram data (including native histograms)
+- Exemplar data
+- Protocol headers and response codes
+- Error conditions and edge cases
+- Content-Type validation
+- Response header validation (`X-Prometheus-Remote-Write-*-Written`)
+
+## Features
+
+- **Protocol Compliance**: Tests MUST and SHOULD requirements from the Remote Write v2 specification
+- **Multi-Endpoint Testing**: Runs tests against multiple remote write configurations
+- **Comprehensive Coverage**: Tests samples, histograms, exemplars, and error conditions
+- **Response Validation**: Validates HTTP status codes, headers, and response bodies
+- **Native Histogram Support**: Full support for Prometheus native histogram format
+
+## Limitations
+
+- No reading of the data.
+- Some requests might be accepted by some backends and rejected by others. There is some tolerance w.r.t 200 vs 400 return codes as the receiver is responsible for the validation of the data.
+
+## Prerequisites
+
+- Go 1.25.0 or later
+- A Prometheus server with Remote Write Receiver enabled, as baseline:
+  ```bash
+  prometheus --web.enable-remote-write-receiver --enable-feature=native-histograms
+  ```
+- Any other Remote Write Receiver.
+
+## Configuration
+
+Create a `prometheus.yml` file in the root directory with your remote write configurations:
+
+```yaml
+remote_write:
+  - name: local-prometheus
+    url: http://127.0.0.1:9090/api/v1/write
+  - name: remote-endpoint
+    url: https://your-remote-write-endpoint.com/api/v1/write
+    basic_auth:
+      username: user
+      password: pass
+```
+
+If no `prometheus.yml` exists, the test suite will fall back to `prometheus_example.yml`.
+
+Alternatively, a configuration file can be provided with the `PROMETHEUS_RW2_COMPLIANCE_CONFIG_FILE` environment variable.
+
+## Running Tests
+
+```bash
+# Run all compliance tests
+go test -v
+
+# Run tests for a specific area
+go test -v -run TestHistograms
+go test -v -run TestMetrics
+
+# Run tests with detailed output
+go test -v -count=1
+```
+
+## HTML visualisation
+
+This repository contains a `index.html` that enables viewing the results of the compliance tests.
+
+It loads a `results.json` that can be generated with:
+
+```bash
+go test -json | tee results.json
+```
+
+## Protocol Compliance Levels
+
+Tests are marked with compliance levels:
+- **MUST**: Required by specification
+- **SHOULD**: Recommended by specification
+
+Use `t.Attr("rfcLevel", "MUST")` or `t.Attr("rfcLevel", "SHOULD")` to identify compliance levels.
+
+## Response Validation
+
+The test suite validates:
+- HTTP status codes (2xx for success, 4xx for client errors, 5xx for server errors)
+- Required response headers (`X-Prometheus-Remote-Write-*-Written`)
+
+## License
+
+Licensed under the Apache License, Version 2.0. See LICENSE file for details.
+
+## Contributing
+
+This is part of the Prometheus project. Please follow the standard Prometheus contribution guidelines.

remotewrite/receiver/go.mod

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+module github.com/prometheus/complicance/remotewrite2
+
+go 1.25.0
+
+require (
+	github.com/golang/snappy v1.0.0
+	github.com/prometheus/common v0.65.0
+	github.com/prometheus/prometheus v0.305.0
+	github.com/stretchr/testify v1.10.0
+)
+
+require (
+	cloud.google.com/go/auth v0.16.2 // indirect
+	cloud.google.com/go/auth/oauth2adapt v0.2.8 // indirect
+	cloud.google.com/go/compute/metadata v0.7.0 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/azcore v1.18.0 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.10.1 // indirect
+	github.com/Azure/azure-sdk-for-go/sdk/internal v1.11.1 // indirect
+	github.com/AzureAD/microsoft-authentication-library-for-go v1.4.2 // indirect
+	github.com/alecthomas/units v0.0.0-20240927000941-0f3dac36c52b // indirect
+	github.com/aws/aws-sdk-go-v2 v1.36.3 // indirect
+	github.com/aws/aws-sdk-go-v2/config v1.29.14 // indirect
+	github.com/aws/aws-sdk-go-v2/credentials v1.17.67 // indirect
+	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.16.30 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/configsources v1.3.34 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.6.34 // 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 v1.12.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.12.15 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sso v1.25.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/ssooidc v1.30.1 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sts v1.33.19 // indirect
+	github.com/aws/smithy-go v1.22.2 // indirect
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // 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 v1.4.2 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/go-viper/mapstructure/v2 v2.2.1 // indirect
+	github.com/gobwas/glob v0.2.3 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang-jwt/jwt/v5 v5.2.2 // 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 v2.14.2 // indirect
+	github.com/grafana/regexp v0.0.0-20240518133315-a468a5bfb3bc // 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/knadh/koanf/maps v0.1.2 // indirect
+	github.com/knadh/koanf/providers/confmap v1.0.0 // indirect
+	github.com/knadh/koanf/v2 v2.2.0 // indirect
+	github.com/kylelemons/godebug v1.1.0 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/internal/exp/metrics v0.128.0 // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.128.0 // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/processor/deltatocumulativeprocessor v0.128.0 // 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 v1.22.0 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/otlptranslator v0.0.0-20250527173959-2573485683d5 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	github.com/prometheus/sigv4 v0.2.0 // indirect
+	github.com/puzpuzpuz/xsync/v3 v3.5.1 // indirect
+	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
+	go.opentelemetry.io/collector/component v1.34.0 // indirect
+	go.opentelemetry.io/collector/confmap v1.34.0 // indirect
+	go.opentelemetry.io/collector/confmap/xconfmap v0.128.0 // indirect
+	go.opentelemetry.io/collector/consumer v1.34.0 // indirect
+	go.opentelemetry.io/collector/featuregate v1.34.0 // indirect
+	go.opentelemetry.io/collector/internal/telemetry v0.128.0 // indirect
+	go.opentelemetry.io/collector/pdata v1.34.0 // indirect
+	go.opentelemetry.io/collector/pipeline v0.128.0 // indirect
+	go.opentelemetry.io/collector/processor v1.34.0 // indirect
+	go.opentelemetry.io/collector/semconv v0.128.0 // indirect
+	go.opentelemetry.io/contrib/bridges/otelzap v0.11.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace v0.61.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.61.0 // indirect
+	go.opentelemetry.io/otel v1.36.0 // indirect
+	go.opentelemetry.io/otel/log v0.12.2 // indirect
+	go.opentelemetry.io/otel/metric v1.36.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.36.0 // indirect
+	go.opentelemetry.io/otel/trace v1.36.0 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.27.0 // indirect
+	golang.org/x/crypto v0.39.0 // indirect
+	golang.org/x/net v0.41.0 // indirect
+	golang.org/x/oauth2 v0.30.0 // indirect
+	golang.org/x/sys v0.33.0 // indirect
+	golang.org/x/text v0.26.0 // indirect
+	golang.org/x/time v0.12.0 // indirect
+	google.golang.org/api v0.238.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250603155806-513f23925822 // indirect
+	google.golang.org/grpc v1.73.0 // indirect
+	google.golang.org/protobuf v1.36.6 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	k8s.io/apimachinery v0.32.3 // indirect
+	k8s.io/client-go v0.32.3 // indirect
+	k8s.io/klog/v2 v2.130.1 // indirect
+	k8s.io/utils v0.0.0-20241104100929-3ea5e8cea738 // indirect
+	sigs.k8s.io/yaml v1.4.0 // indirect
+)