access log exporter

Receive logs from nginx

Configure nginx to forward access logs to the exporter via syslog. Add the following to your nginx server block, replacing <exporter-host> with the hostname or IP of the exporter container:

access_log syslog:server=<exporter-host>:9514,facility=local0,tag=access.log,severity=info combined;

Then start nginx alongside the exporter:

# Start the exporter
docker run -d \
  --name access-log-exporter \
  -p 9090:9090 \
  -p 9514:9514/udp \
  registry.ghost-prod.alphabravo.io/ghost-base/access-log-exporter:<tag> \
  --web.listen-address=:9090 \
  --syslog.listen-address=udp://0.0.0.0:9514

# Confirm metrics appear after nginx begins serving traffic
curl http://localhost:9090/metrics | grep nginx

Custom metrics and web listen address

The --web.listen-address flag controls which address and port the HTTP metrics server binds to. This is useful when port 9090 conflicts with another service (for example, Prometheus itself):

docker run -d \
  --name access-log-exporter \
  -p 9519:9519 \
  -p 9514:9514/udp \
  registry.ghost-prod.alphabravo.io/ghost-base/access-log-exporter:<tag> \
  --web.listen-address=:9519 \
  --syslog.listen-address=udp://0.0.0.0:9514

curl http://localhost:9519/metrics
docker rm -f access-log-exporter

Docker Compose deployment

A minimal Compose file that wires nginx and the exporter together:

services:
  nginx:
    image: registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro

  access-log-exporter:
    image: registry.ghost-prod.alphabravo.io/ghost-base/access-log-exporter:<tag>
    command:
      - --web.listen-address=:9090
      - --syslog.listen-address=udp://0.0.0.0:9514
    ports:
      - "9090:9090"
      - "9514:9514/udp"

In nginx.conf, direct the access log at the exporter service by name:

access_log syslog:server=access-log-exporter:9514,facility=local0,tag=access.log,severity=info combined;

Prometheus scrape configuration

Add the following job to your prometheus.yml to scrape the exporter:

scrape_configs:
  - job_name: access-log-exporter
    static_configs:
      - targets: ["access-log-exporter:9090"]

Image variants

Ghost hardened images come in different variants depending on their intended use.

Available image tags for access-log-exporter:

Tag selection guidance:

• Use registry.ghost-prod.alphabravo.io/ghost-base/access-log-exporter:<version> for standard production deployments
• Use major version tags (like :<major>) for automatic minor updates (not recommended for production)

Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

• Run as the nonroot user
• Do not include a shell or a package manager
• Contain only the minimal set of libraries needed to run the app

Build-time variants typically include dev in the variant name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

• Run as the root user
• Include a shell and package manager
• Are used to build or compile applications

FIPS variants include fips in the variant name and tag. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations.

Runtime requirements specific to FIPS:

Migrate to a Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes:

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. Inspect the image variants to identify which packages are already installed.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Ghost hardened images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

Ghost hardened images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Ghost hardened images and update your Dockerfile if necessary.