Add the example stack payloads

The files copied to /srv/stacks/<stack>/ verbatim: compose files, vhosts,
Prometheus configuration, the webapp image source. Payloads are data, never
templated and never linted as Ansible content.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
This commit is contained in:
Lucas Winther
2026-09-16 03:58:01 +02:00
co-authored by Claude Opus 5
parent 7b52e9af9e
commit b76c76e3b0
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# server/ — the payloads
Everything under this directory is **data**. These files are copied to the hosts
verbatim: no templating, no variable substitution by Ansible, no generation.
```
server/<host>/<stack>/ a stack that runs on exactly one host
server/shared/<stack>/ a payload used by more than one host or instance
server/shared/components/ single files that belong to another stack's directory
```
The directory names under `server/` must match the inventory host names, because
the role resolves a payload as `server/{{ inventory_hostname }}/{{ stack_name }}`
unless a playbook overrides `stack_src`.
`server/` is excluded from `ansible-lint` and `yamllint`. A compose file is not
Ansible content, and most of these come from upstream projects that format them
their own way — linting them produces noise and pressure to reformat files you
want to be able to diff against upstream.
## The examples
All six are fictional. `example.com` is reserved by RFC 2606 and can never
resolve to a real service. Replace them with your own; the framework around them
is the reusable part.
| Payload | Used by | Notes |
| --- | --- | --- |
| `edge/reverse-proxy/` | `reverse-proxy.yml` | nginx-proxy + acme-companion. Owns `proxy-net`. Its `proxy-data/` subdirectories are bind mounts holding plain config files. |
| `app/static-site/` | `static-site.yml` | One container, one network, no state. The simplest thing that works. |
| `app/webapp/` | `webapp.yml`, `webapp-staging.yml` | Postgres plus an app built from `app/Dockerfile`. A second compose file holds maintenance-only services. Every credential comes from `.env`. |
| `shared/metrics/` | `metrics.yml` | Prometheus and Grafana, identical on both hosts, so it lives here rather than being duplicated per host. |
| `shared/components/banner.html` | `banner.yml` | A single file that belongs to the reverse proxy's directory on every host. |
## Conventions worth copying
**Take secrets from `.env`, and require them.** Every credential in these
payloads is written as `${VAR:?message}`. Compose then refuses to start and names
the missing variable, instead of expanding it to an empty string and starting the
service with no password. Ship a `.env.example` listing the names with no values;
the role never syncs `.env` itself.
**Pin image tags.** `nginx:1.27-alpine`, not `nginx:latest`. A `latest` tag means
a plain deploy will not pick up a new build (Compose keeps the image it has) and
an update run picks up whatever was published this morning. Both are surprises.
**Declare shared networks external.** A network two stacks need is created by the
playbook through `stack_networks`, not by whichever compose file happened to run
first. That is what lets every playbook stand on its own.
**Do not put host paths in the compose file.** Use `${PWD}` if a sibling
container needs one — the role exports it as the stack's directory on the host,
which is the only value that is correct from inside a deploy.
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# The smallest stack there is: one container, one network, no state.
#
# Deployed by ansible/playbooks/static-site.yml, which is four lines of variables
# and the stack this repository points you at when you add your first service.
services:
static-site:
container_name: static-site
image: nginx:1.27-alpine
restart: unless-stopped
networks:
- proxy-net
environment:
# Read by the reverse proxy's docker-gen companion, which writes the vhost
# and requests the certificate. Nothing here talks to the proxy directly.
VIRTUAL_HOST: www.example.com
VIRTUAL_PORT: "80"
LETSENCRYPT_HOST: www.example.com
volumes:
- ./html:/usr/share/nginx/html:ro
networks:
proxy-net:
external: true
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<!doctype html>
<meta charset="utf-8">
<title>static-site</title>
<h1>static-site</h1>
<p>
Served from <code>server/app/static-site/html/</code> in the configuration
repository, synced to <code>/srv/stacks/static-site/html</code> on the
<code>app</code> host.
</p>
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# Copy to .env ON THE HOST, not here. The compose_stack role excludes .env from
# every sync (stack_exclude), so a .env committed to this repository would be
# ignored, and a host's .env is never overwritten by a deploy.
#
# ssh [email protected]
# cd /srv/stacks/webapp && cp .env.example .env && $EDITOR .env
#
# webapp.yml refuses to deploy if .env is absent on the host, because every
# variable below is required with no default.
POSTGRES_PASSWORD=
SECRET_KEY=
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# Stands in for a real application image. The point of building from the payload
# rather than pulling is that stack_build then controls when a rebuild happens —
# see "Deploy versus update" in the README.
FROM python:3.12-slim
WORKDIR /app
COPY serve.py migrate.sh ./
RUN chmod +x migrate.sh
EXPOSE 8080
CMD ["python", "serve.py"]
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#!/usr/bin/env sh
#
# Stands in for a real migration runner. The property that matters is the one
# asserted here: running it twice must be a no-op the second time, because an
# update run can be repeated and the playbook does not remember whether the last
# one finished.
set -eu
echo "migrate: applying any pending migrations against ${DATABASE_URL%%:*}..."
echo "migrate: already up to date"
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"""Minimal stand-in for an application server."""
import http.server
import os
PORT = int(os.environ.get("PORT", "8080"))
class Handler(http.server.BaseHTTPRequestHandler):
def do_GET(self): # noqa: N802 - name fixed by the stdlib
self.send_response(200)
self.send_header("Content-Type", "text/plain; charset=utf-8")
self.end_headers()
self.wfile.write(b"webapp is running\n")
def log_message(self, fmt, *args):
print(fmt % args, flush=True)
if __name__ == "__main__":
http.server.HTTPServer(("", PORT), Handler).serve_forever()
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# Maintenance services, layered on top of docker-compose.yml with a second -f.
#
# These are one-shot `run --rm` targets, never part of the running stack, which
# is why docker-compose.yml alone is what the playbook passes to `up` via
# stack_files. Bringing the stack up with both files would start them as
# long-running services.
services:
backup:
image: postgres:17-alpine
profiles: ["maintenance"]
depends_on:
db:
condition: service_healthy
environment:
PGPASSWORD: ${POSTGRES_PASSWORD:?set it in .env on the host}
volumes:
- ./backups:/backups
entrypoint:
- sh
- -c
- 'pg_dump -h db -U webapp webapp > /backups/webapp-$(date +%Y%m%dT%H%M%S).sql'
networks:
- backend
migrate:
build:
context: ./app
image: example/webapp:local
profiles: ["maintenance"]
depends_on:
db:
condition: service_healthy
environment:
DATABASE_URL: postgres://webapp:${POSTGRES_PASSWORD:?set it in .env on the host}@db:5432/webapp
# Migrations must be safe to run twice: an update run can be repeated, and
# the playbook does not track whether the last one finished.
command: ["/app/migrate.sh"]
networks:
- backend
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# A database-backed application: the stack that needs more than "sync and up".
#
# Every credential comes from .env, with no defaults. `${VAR:?message}` makes
# Compose refuse to start and say which variable is missing, which is strictly
# better than booting with an empty password. .env lives on the host and is never
# synced from this repository, so ansible/playbooks/webapp.yml asserts it is
# there before doing anything.
services:
db:
container_name: webapp-db
image: postgres:17-alpine
restart: unless-stopped
# ./pgdata is deliberately NOT pre-created by the playbook: Postgres refuses
# to start unless its data directory is 0700 or 0750, and the image gets that
# right on first start. See "Common mistakes" in skills/adding-a-stack.
volumes:
- ./pgdata:/var/lib/postgresql/data
environment:
POSTGRES_DB: webapp
POSTGRES_USER: webapp
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:?set it in .env on the host}
healthcheck:
test: ["CMD-SHELL", "pg_isready -U webapp"]
interval: 10s
timeout: 5s
retries: 5
networks:
- backend
web:
container_name: webapp
# Built from the payload rather than pulled. stack_build in the playbook
# decides when a rebuild happens: on an update run, not on every deploy.
build:
context: ./app
image: example/webapp:local
restart: unless-stopped
depends_on:
db:
condition: service_healthy
environment:
DATABASE_URL: postgres://webapp:${POSTGRES_PASSWORD:?set it in .env on the host}@db:5432/webapp
SECRET_KEY: ${SECRET_KEY:?set it in .env on the host}
# Set by the role to stack_dest, so a path handed to a sibling container is
# the path on the host and not wherever the SSH session happened to land.
UPLOAD_HOST_DIR: ${PWD}/uploads
VIRTUAL_HOST: app.example.com
VIRTUAL_PORT: "8080"
LETSENCRYPT_HOST: app.example.com
volumes:
- ./uploads:/var/lib/webapp/uploads
networks:
- backend
- proxy-net
networks:
backend:
proxy-net:
external: true
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# The public entry point. nginx-proxy watches the Docker socket and writes a
# vhost for every container that sets VIRTUAL_HOST; acme-companion requests and
# renews the certificate for every LETSENCRYPT_HOST.
#
# Two things about this stack drive decisions elsewhere in the repository:
#
# - proxy-net is external. Every stack that wants to be reachable joins it, so
# something has to create it before any of them start. That is stack_networks
# in the role, and it is why site.yml deploys this stack first.
# - conf/, vhost/ and html/ are bind mounts holding plain files. Editing one
# changes nothing until nginx reloads, because Compose sees an unchanged
# compose file and does not recreate the container. That is what
# compose_stack_synced and the post_tasks reload are for.
services:
reverse-proxy:
container_name: reverse-proxy
image: nginxproxy/nginx-proxy:1.6
restart: unless-stopped
ports:
- "80:80"
- "443:443"
volumes:
- ./proxy-data/conf:/etc/nginx/conf.d
- ./proxy-data/vhost:/etc/nginx/vhost.d
- ./proxy-data/html:/usr/share/nginx/html
- ./proxy-data/dhparam:/etc/nginx/dhparam
- ./proxy-data/certs:/etc/nginx/certs:ro
- /var/run/docker.sock:/tmp/docker.sock:ro
networks:
- proxy-net
acme-companion:
container_name: reverse-proxy-acme
image: nginxproxy/acme-companion:2.4
restart: unless-stopped
volumes_from:
- reverse-proxy
volumes:
- ./proxy-data/certs:/etc/nginx/certs
- ./proxy-data/acme:/etc/acme.sh
- /var/run/docker.sock:/var/run/docker.sock:ro
environment:
# Let's Encrypt sends expiry warnings here.
DEFAULT_EMAIL: [email protected]
networks:
- proxy-net
networks:
proxy-net:
external: true
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# Applies to every vhost. nginx defaults to 1M, which silently truncates ordinary
# file uploads.
client_max_body_size 100M;
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# Per-vhost nginx configuration for app.example.com, included by nginx-proxy.
#
# A container that sets VIRTUAL_HOST gets its vhost generated automatically and
# needs nothing here. This file is for the cases generation cannot express:
# routes to a service that is not the vhost's main container, and access rules.
# Anything not otherwise routed goes to the public site.
location = / {
return 301 https://app.example.com/tools/;
}
# Internal-only: the metrics stack, reachable from the private network and
# nowhere else. Keep the deny rule directly beneath the allow rule — nginx takes
# the first match, so an allow added below a `deny all` does nothing.
location ^~ /internal/metrics/ {
allow 10.0.0.0/8;
deny all;
proxy_pass http://prometheus:9090/internal/metrics/;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
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<!-- Served at / by the reverse proxy on every host, as a placeholder for
requests that match no vhost. Deployed by ansible/playbooks/banner.yml,
which drops this one file into the reverse-proxy stack's html directory on
every host rather than owning a stack of its own. -->
<!doctype html>
<meta charset="utf-8">
<title>example.com</title>
<h1>Nothing is served at this address.</h1>
<p>If you expected a service here, check the vhost configuration.</p>
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# Copy to .env ON THE HOST, not here. The compose_stack role excludes .env from
# every sync (stack_exclude), so a .env committed to this repository would be
# ignored, and a host's .env is never overwritten by a deploy.
#
# ssh [email protected]
# cd /srv/stacks/metrics && cp .env.example .env && $EDITOR .env
GF_SECURITY_ADMIN_PASSWORD=
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# Prometheus and Grafana, deployed to every host from this one payload.
#
# It lives under server/shared/ rather than server/<host>/ because both hosts run
# exactly the same thing; ansible/playbooks/metrics.yml points stack_src here.
# Per-host differences (which networks exist, which extra directories to create)
# belong in the playbook, not in duplicated copies of this file.
#
# Both bind mounts below need a directory that exists with the right ownership
# before the container starts, and neither image will fix it for you:
#
# grafana-data the image runs as uid 472 and writes a SQLite database here
# prometheus-data the image runs as nobody (65534)
#
# The playbook pre-creates both. See "stack_dirs" in AGENTS.md for why that is
# the role's job and not a chown in pre_tasks.
services:
prometheus:
container_name: prometheus
image: prom/prometheus:v3.1.0
restart: unless-stopped
command:
- --config.file=/etc/prometheus/prometheus.yml
- --storage.tsdb.path=/prometheus
# Served under a sub-path by the reverse proxy, so it has to generate
# absolute URLs that include it.
- --web.external-url=https://app.example.com/internal/metrics/
- --web.route-prefix=/
volumes:
- ./prometheus.yml:/etc/prometheus/prometheus.yml:ro
- ./prometheus-data:/prometheus
networks:
- default
- proxy-net
grafana:
container_name: grafana
image: grafana/grafana-oss:11.5.1
restart: unless-stopped
networks:
- default
- proxy-net
environment:
VIRTUAL_HOST: dashboards.example.com
VIRTUAL_PORT: "3000"
LETSENCRYPT_HOST: dashboards.example.com
GF_SERVER_ROOT_URL: https://dashboards.example.com
# Compose fails the run if this is not set, rather than starting Grafana
# with a blank admin password. The value comes from the host's .env, which
# is never synced from this repository — see docs/secrets.md.
GF_SECURITY_ADMIN_PASSWORD: ${GF_SECURITY_ADMIN_PASSWORD:?set it in .env on the host}
volumes:
- ./grafana-data:/var/lib/grafana
networks:
proxy-net:
external: true
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# Bind-mounted read-only into the prometheus container. Prometheus re-reads it on
# SIGHUP, so metrics.yml reloads the container when this file changes rather than
# recreating it.
global:
scrape_interval: 30s
evaluation_interval: 30s
scrape_configs:
- job_name: prometheus
static_configs:
- targets: ["localhost:9090"]
- job_name: node
static_configs:
- targets: ["node-exporter:9100"]