cortex-tenant

Prometheus remote write proxy which marks timeseries with a Cortex tenant ID based on labels.

Architecture

Overview

Cortex tenants (separate namespaces where metrics are stored to and queried from) are identified by X-Scope-OrgID HTTP header on both writes and queries.

Problem is that Prometheus can't be configured to send this header Actually in some recent version (year 2021 onwards) this functionality was added, but the tenant is the same for all jobs. This makes it impossible to use a single Prometheus (or an HA pair) to write to multiple tenants.

This software solves the problem using the following logic:

• Receive Prometheus remote write
• Search each timeseries for a specific label name and extract a tenant ID from its value. If the label wasn't found then it can fall back to a configurable default ID. If none is configured then the write request will be rejected with HTTP code 400
• Optionally removes this label from the timeseries
• Groups timeseries by tenant
• Issues a number of parallel per-tenant HTTP requests to Cortex with the relevant tenant HTTP header (X-Scope-OrgID by default)

Usage

• Get rpm or deb for amd64 from the Releases page. For building see below.

HTTP Endpoints

• GET /alive returns 200 by default and 503 if the service is shutting down (if timeout_shutdown setting is > 0)
• POST /push receives metrics from Prometheus - configure remote write to send here

Configuration

Application expects the config file at /etc/cortex-tenant.yml by default.

# Where to listen for incoming write requests from Prometheus
listen: 0.0.0.0:8080
# Profiling API, remove to disable
listen_pprof: 0.0.0.0:7008
# Where to send the modified requests (Cortex)
target: http://127.0.0.1:9091/receive
# Log level
log_level: warn
# HTTP request timeout
timeout: 10s
# Timeout to wait on shutdown to allow load balancers detect that we're going away.
# During this period after the shutdown command the /alive endpoint will reply with HTTP 503.
# Set to 0s to disable.
timeout_shutdown: 10s
# Max number of parallel incoming HTTP requests to handle
concurrency: 10
# Whether to forward metrics metadata from Prometheus to Cortex
# Since metadata requests have no timeseries in them - we cannot divide them into tenants
# So the metadata requests will be sent to the default tenant only, if one is not defined - they will be dropped
metadata: false

tenant:
  # Which label to look for the tenant information
  label: tenant
  # Whether to remove the tenant label from the request
  label_remove: true
  # To which header to add the tenant ID
  header: X-Scope-OrgID
  # Which tenant ID to use if the label is missing in any of the timeseries
  # If this is not set or empty then the write request with missing tenant label
  # will be rejected with HTTP code 400
  default: foobar
  # Enable if you want all metrics from Prometheus to be accepted with a 204 HTTP code
  # regardless of the response from Cortex. This can lose metrics if Cortex is
  # throwing rejections.
  accept_all: false

Prometheus configuration example

remote_write:
  - name: cortex_tenant
    url: http://127.0.0.1:8080/push

scrape_configs:
  - job_name: job1
    scrape_interval: 60s
    static_configs:
      - targets:
          - target1:9090
        labels:
          tenant: foobar

  - job_name: job2
    scrape_interval: 60s
    static_configs:
      - targets:
          - target2:9090
        labels:
          tenant: deadbeef

This would result in job1 metrics ending up in the foobar tenant in cortex and job2 in deadbeef.

Building

make build should create you an amd64 binary.

If you want deb or rpm packages then install FPM and then run make rpm or make deb to create the packages.

Containerization

To use the current container you need to overwrite the default configuration file, mount your configuration into to /data/cortex-tenant.yml.

You can overwrite the default config by starting the container with:

docker container run \
-v <CONFIG_LOCATION>:/data/cortex-tenant.yml \
ghcr.io/blind-oracle/cortex-tenant:1.6.1

... or build your own Docker image:

FROM ghcr.io/blind-oracle/cortex-tenant:1.6.1
ADD my-config.yml /data/cortex-tenant.yml

Deploy on Kubernetes

deploy/k8s directory contains the deployment, service and configmap manifest files for deploying this on Kubernetes. You can overwrite the default config by editing the configuration parameters in the configmap manifest.

kubectl apply -f deploy/k8s/cortex-tenant-deployment.yaml
kubectl apply -f deploy/k8s/cortex-tenant-service.yaml
kubectl apply -f deploy/k8s/config-file-configmap.yml