[LNT] Add docker containerization files

[thopre]

Summary

LNT already strive to be easy to use both locally and in server mode.
This patch adds containerization files in a new docker/ directory (which
can later be renamed container/docker if more container gets supported).
Creating the image becomes as easy as docker-compose build and running
it is done via docker-compose up.

The service described in docker-compose.yml uses postgres but the LNT
image is controlled via DB_ variables and thus should work with any
database engine.

Note: I'm quite new to Docker so some reviews on Docker best practice
would be much welcome.

[cmatthews]

Looks good. Thanks!

[thopre]

• Quote variables
• use exec to call gunicorn to avoid spawning a new process

lnt/trunk/docker/.env

+DB_USER=lntuser
+DB_BASE=lnt

lnt/trunk/docker/Dockerfile

+FROM python:2.7-alpine
+
+RUN apk update \
+  && apk add --no-cache --virtual .build-deps git g++ postgresql-dev yaml-dev \
+  && apk add --no-cache libpq \
+  && git clone https://git.llvm.org/git/lnt /var/src/lnt \
+  && python /var/src/lnt/setup.py install --server \
+  && rm -rf /var/src \
+  && apk --purge del .build-deps \
+  && mkdir /var/log/lnt
+
+COPY docker-entrypoint.sh wait_db /usr/local/bin/
+
+VOLUME /var/log
+
+EXPOSE 8000
+
+ENV DB_ENGINE= DB_HOST= DB_USER= DB_PWD= DB_BASE=
+
+ENTRYPOINT docker-entrypoint.sh

lnt/trunk/docker/docker-compose.yml

+version: '3'
+
+services:
+  lnt:
+    build:
+      context: .
+    container_name: lnt
+    image: lnt
+    environment:
+      - DB_ENGINE=postgres
+      - DB_HOST=lnt-postgres
+      - DB_PWD
+    depends_on:
+      - db
+    deploy:
+      restart_policy:
+        condition: on-failure
+    ports:
+      - "8000:8000"
+
+  db:
+    container_name: lnt-postgres
+    image: postgres:alpine
+    environment:
+      - POSTGRES_PASSWORD=${DB_PWD}
+      - POSTGRES_USER=${DB_USER}
+      - POSTGRES_DB=${DB_BASE}

lnt/trunk/docker/docker-entrypoint.sh

+#!/bin/sh
+
+DB_PATH=${DB_ENGINE:-postgresql}://${DB_USER:-lntuser}:${DB_PWD:?}@${DB_HOST:?}
+DB_BASE=${DB_BASE:-lnt}
+
+if [ ! -r /etc/lnt.cfg ]; then
+  DB_BASE_PATH="${DB_PATH}/${DB_BASE}" wait_db
+  lnt create /var/lib/lnt \
+    --config /etc/lnt.cfg \
+    --wsgi lnt_wsgi.py \
+    --tmp-dir /tmp/lnt \
+    --db-dir "${DB_PATH}" \
+    --default-db "${DB_BASE}"
+fi
+
+cd /var/lib/lnt
+exec gunicorn lnt_wsgi:application \
+  --bind 0.0.0.0:8000 \
+  --workers 8 \
+  --timeout 300 \
+  --name lnt_server \
+  --log-file /var/log/lnt/lnt.log \
+  --access-logfile /var/log/lnt/gunicorn_access.log \
+  --max-requests 250000 "$@"

lnt/trunk/docker/wait_db

+#!/usr/bin/env python
+
+import os
+from sqlalchemy import create_engine
+
+db_base_path = os.environ['DB_BASE_PATH']
+
+engine = create_engine(db_base_path)
+started = False
+
+while not started:
+    try:
+        engine.execute("SELECT 1")
+        started = True
+    except Exception as inst:
+        pass