Augustine on the relationship between scripture and science

From The Literal Meaning of Genesis by Augustine, translated by John Hammond Taylor.

Book One, Chapter 18

In matters that are obscure and far beyond our vision, even in such as we may find treaded in Holy Scripture, different interpretations are sometimes possible without prejudice to the faith we have received. In such a case, we should not rush in headlong and so firmly take our stand on one side that, if further progress in the search of truth justly undermines this position, we too fall with it. That would be to battle not for the teaching of Holy Scripture but for our own, wishing its teaching to conform to ours, whereas we ought to wish ours to conform to that of Sacred Scripture.

Book One, Chapter 19

Usually, even a non-Christian knows something about the earth, the heavens, and the other elements of this world, about the motion and orbit of the starts and even their size and relative positions, about the predictable eclipses of the sun and moon, the cycles of the years and the seasons, about the kinds of animals, shrubs, stones, and so forth, and this knowledge he holds to as being certain from reason and experience. Now, it is a disgraceful and dangerous thing for an infidel to hear a Christian, presumably giving the meaning of Holy Scripture, talking nonsense on these topics; and we should take all means to prevent such an embarrassing situation, in which people show up vast ignorance in a Christian and laugh it to scorn. The shame is not so much than an ignorant individual is derided, but that people outside the household of faith think our sacred writers held such opinions, and, to the great loss of those for whose salvation we toil, the writers of our Scripture are criticized and rejected as unlearned men. If they find a Christian mistaken in a field which they themselves know well and hear him maintaining his foolish opinions about our books, how are they going to believe those books in matters concerning the resurrection of the dead, the hope of eternal life, and the kingdom of heaven, when they think their pages are full of falsehoods on facts which they themselves have learnt from experience and the light of reason?

nginx as HTTPS proxy for Elasticsearch

Let’s say you have your local dev environment configured to use SSL. Your dev site is accessible at https://mysite.dev/. Wonderful! Now you need to add Elasticsearch to your project. Let’s add it to docker-compose.yml, something like:

version: "2"
services:
  elasticsearch:
    image: docker.elastic.co/elasticsearch/elasticsearch:5.2.2
    environment:
      - xpack.security.enabled=false
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    ulimits:
      memlock:
        soft: -1
        hard: -1
      nofile:
        soft: 65536
        hard: 65536
      mem_limit: 1g
    volumes:
      - elasticsearchindex:/usr/share/elasticsearch/data
    ports:
      - "9200"
    network_mode: "bridge"
  # and some other services like PHP, nginx, memcached, mysql
volumes:
  elasticsearchindex:

How do you make requests to Elasticsearch from the browser?

Option 1: Set up a proxy in your app. This probably resembles what you’ll ultimately get in production. You don’t really need any security on Elasticsearch for local dev, but in production it will need some sort of access control so users can’t send arbitrary requests to the server. If you’re not using a third-party service that already handles this for you, this is where you’ll filter out invalid or dangerous requests. I prefer to let more experienced hands manage server security for me, though, and this is a lot of overhead just to set up a local dev server.

Option 2: Expose Elasticsearch directly. Since I don’t need security locally, I could just open up port 9200 on my container and make requests directly to it from the browser at http://localhost:9200/. Notice the protocol there, though. If my local site is at https://mysite.dev/, then the browser will block insecure requests to Elasticsearch.

Option 3: Use nginx as a proxy. I’m already using a reverse proxy in front of my project containers. It terminates the SSL connections and then passes through unencrypted requests to each project’s nginx server. The project’s nginx container doesn’t need to deal with SSL. It listens on port 80 and passes requests to PHP with fastcgi.

server {
	listen 80 default_server;
	server_name mysite.dev;
	# ... more server boilerplate
}

Since Elasticsearch is exposed via an HTTP API, we can create another server block to proxy Elasticsearch requests. First, make sure the nginx container can talk to the Elasticsearch container. In docker-compose.yml:

  nginx:
    image: nginx:stable-alpine
    environment:
      - VIRTUAL_HOST=mysite.dev,*.mysite.dev
    volumes:
      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
      - ./nginx/elasticsearch-proxy.conf:/etc/nginx/conf.d/elasticsearch-proxy.conf:ro
      - ./nginx/php.conf:/etc/nginx/php.conf:ro
    links:
      - php
      - elasticsearch
    ports:
      - "80"
    network_mode: "bridge"

And then create elasticsearch-proxy.conf to handle the requests:

upstream es {
	server elasticsearch:9200;
	keepalive 15;
}

server {
	listen 80;
	server_name search.mysite.dev;

	location / {
		proxy_pass http://es;
		proxy_http_version 1.1;
		proxy_set_header Connection "Keep-Alive";
		proxy_set_header Proxy-Connection "Keep-Alive";
	}
}

Now we can make requests to Elasticsearch from the browser at https://search.mysite.dev/. The nginx proxy will handle the SSL termination, and communicate with Elasticsearch using its standard HTTP API.

Create and Trust Local SSL Certificate

I use Jason Wilder’s nginx reverse proxy container as the gateway to my various Docker dev environments. Among it’s other services, it provides SSL termination, so I don’t need to worry about configuring SSL in every container I run.

The set up is pretty simple. Make a directory of certificates and mount it into the container at /etc/nginx/certs. In docker-compose.yml, it would look something like:

version: "2"
services:
  proxy:
    image: jwilder/nginx-proxy
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx/certs:/etc/nginx/certs
      - /var/run/docker.sock:/tmp/docker.sock

You’ll need to create a new certificate for each domain you want to serve. Add them to the certs dir, and the proxy will find them and serve those domains with SSL.

I’ve created a script that will create the certificate and, on OS X at least, add it to your login keychain as a trusted certificate so you can avoid SSL warnings from your browser. Create the file create-cert.sh in your certs directory and run it from there. E.g., certs/create-cert.sh mysite.dev.

#!/bin/bash
 
 
CERTDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
DOMAIN=$1
 
if [ $# -lt 1 ]; then
  echo 1>&2 "Usage: $0 domain.name"
  exit 2
fi
 
cd ${CERTDIR}
 
cat > ${DOMAIN}.cnf < <-EOF
  [req]
  distinguished_name = req_distinguished_name
  x509_extensions = v3_req
  prompt = no
  [req_distinguished_name]
  CN = *.${DOMAIN}
  [v3_req]
  keyUsage = keyEncipherment, dataEncipherment
  extendedKeyUsage = serverAuth
  subjectAltName = @alt_names
  [alt_names]
  DNS.1 = *.${DOMAIN}
  DNS.2 = ${DOMAIN}
EOF
 
openssl req \
  -new \
  -newkey rsa:2048 \
  -sha1 \
  -days 3650 \
  -nodes \
  -x509 \
  -keyout ${DOMAIN}.key \
  -out ${DOMAIN}.crt \
  -config ${DOMAIN}.cnf
 
rm ${DOMAIN}.cnf
 
if [[ $OSTYPE == darwin* ]]; then
  sudo security add-trusted-cert -d -r trustRoot -k $HOME/Library/Keychains/login.keychain ${DOMAIN}.crt
fi

Reload your proxy, and you can now visit https://mysite.dev/.

Install Language Packs with WP-CLI

I recently had the need to install all of the WordPress core language packs for a multisite network, where I didn’t know which languages would be needed on each site. Installing language packs through the WordPress admin is slow and tedious (as is anything with a GUI).

So I turned to WP-CLI. It allows you to install language packs, but still only one at a time. With a bit of shell magic, though, you can have it loop through all the available languages and install them for you:

wp core language list | grep uninstalled  | awk '{print $1}' | xargs -i wp core language install {}

Reaching localhost from a Docker container

Docker Engine has some built-in networking features to allow containers to communicate with each other and with the outside world. For example you can link two containers together to allow them to talk to each other, either via the docker run command or in your docker-compose.yml.

version: "2"
services:
  memcached:
    image: memcached:1.4-alpine
  php:
    image: php:5.6-fpm
    links:
      - memcached
  nginx:
    image: nginx:stable-alpine
    links:
      - php
    ports:
      - "80"

In our example, the php container can communicate with the memcached container, the nginx container can communicate with the php container, and the nginx container exposes its port 80 to receive connections from, for example, your web browser.

In some cases, though, your container needs to be able to reach back out to your host system. The specific use case I have is debugging with Xdebug. Using Docker for Mac, there’s not a reliable address you can use to make that connection. A container that tries to connect to localhost or 127.0.0.1 will be talking to itself, not to your host machine.

To work around this, I set up an additional IP address for my host OS’s loopback interface. I use 10.254.254.254, but you may find it conflicts with other applications you have running, so any other local address will be effective.

The command to set up this address is:

sudo ifconfig lo0 alias 10.254.254.254

Running this will allow any container you have running to connect back to your host OS using the address 10.254.254.254. You can, for example, set this in your php.ini as the remote host address for Xdebug (I prefer to set it in a reverse proxy configuration, but that’s a topic for a later post).

xdebug.remote_host=10.254.254.254

Verify that it worked with:

ifconfig lo0

Your new address should appear there along with a few other defaults.

You’ll have to run the command after every boot, unless you set a launchd script to do it for you. There are a few versions of the launchd plist file floating around, or you can make your own from one of them. Copy it into /Library/LaunchDaemons/ and your new loopback address will be set for you on every boot.