docker-postgis/README.md

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# docker-postgis

A simple docker container that runs PostGIS

Visit our page on the docker hub at: https://hub.docker.com/r/kartoza/postgis/

There are a number of other docker postgis containers out there. This one
differentiates itself by:

* provides ssl support out of the box
* connections are restricted to the docker subnet
* a default database 'gis' is created for you so you can use this container 'out of the
  box' when it runs with e.g. QGIS
* replication support included
* Ability to create multiple database when you spin the database.
* Enable multiple extensions in the database when setting it up
* Gdal drivers automatically registered for pg raster
* Support for out-of-db rasters

We will work to add more security features to this container in the future with
the aim of making a PostGIS image that is ready to be used in a production
environment (though probably not for heavy load databases).

There is a nice 'from scratch' tutorial on using this docker image on Alex Urquhart's
blog [here](https://alexurquhart.com/post/set-up-postgis-with-docker/) - if you are
just getting started with docker, PostGIS and QGIS, we really recommend that you use it.

## Tagged versions

The following convention is used for tagging the images we build:

kartoza/postgis:[postgres_major_version]-[postgis-point-releases]

So for example:

``kartoza/postgis:13.0`` Provides PostgreSQL 13.0, PostGIS 3.0

**Note:** We highly recommend that you use tagged versions because
successive minor versions of PostgreSQL write their database clusters
into different database directories - which will cause your database
to appear to be empty if you are using persistent volumes for your
database storage.

## Getting the image

There are various ways to get the image onto your system:


The preferred way (but using most bandwidth for the initial image) is to
get our docker trusted build like this:

```
docker pull kartoza/postgis:image_version
```



## Building the image

To build the image yourself do:

```
docker build -t kartoza/postgis git://github.com/kartoza/docker-postgis
```

Alternatively clone the repository and build against any preferred branch

```
git clone git://github.com/kartoza/docker-postgis
git checkout branch_name
```

Then do:

```
docker build -t kartoza/postgis .
```

Or build against a specific PostgreSQL version

```
docker build --build-arg POSTGRES_MAJOR_VERSION=13 --build-arg POSTGIS_MAJOR=3 -t kartoza/postgis:POSTGRES_MAJOR_VERSION .
```
#### Alternative base distributions builds

There are build args for `DISTRO` (=debian), `IMAGE_VERSION` (=buster)
and `IMAGE_VARIANT` (=slim) which can be used to control the base image used
(but it still needs to be Debian based and have PostgreSQL official apt repo).

For example making Ubuntu 20.04 based build (for better arm64 support)
First build the base image using instructions in the folder `base_build`  using the
build script from [Kartoza base image builds](https://github.com/kartoza/docker-postgis/blob/develop/base_build/build.sh)

Then build the `PostGIS Image` to match the base build

```
docker build --build-arg DISTRO=ubuntu --build-arg IMAGE_VERSION=focal --build-arg IMAGE_VARIANT="" -t kartoza/postgis .
```

#### Locales

By default, the image build will include **all** `locales` to cover any value for `locale` settings such as `DEFAULT_COLLATION`, `DEFAULT_CTYPE` or `DEFAULT_ENCODING`.

You can safely delete all `locales` except for the ones you need in `scripts/locale.gen`. This will speed up the build considerably.

### Environment variables

#### Cluster Initializations

With a minimum setup, our image will use an initial cluster located in the
`DATADIR` environment variable. If you want to use persistence, mount these
locations into your volume/host. By default, `DATADIR` will point to `/var/lib/postgresql/{major-version}`.
You can instead mount the parent location like this:

* `-v data-volume:/var/lib/postgresql`

This default cluster will be initialized with default locale settings `C.UTF-8`.
If, for instance, you want to create a new cluster with your own settings (not using the default cluster).
You need to specify different empty directory, like this

```shell script
-v data-volume:/opt/postgres/data \
-e DATADIR:/opt/postgres/data \
-e DEFAULT_ENCODING="UTF8" \
-e DEFAULT_COLLATION="id_ID.utf8" \
-e DEFAULT_CTYPE="id_ID.utf8" \
-e --auth="md5" \
-e INITDB_EXTRA_ARGS="<some more initdb command args>"
```

The containers will use above parameters to initialize a new db cluster in the
specified directory. If the directory is not empty, then initialization parameter will be ignored.

These are some initialization parameters that will only get used to initialize a new cluster.
If the container uses an existing cluster, it is ignored (for example, when the container restarts).

* `DEFAULT_ENCODING`: cluster encoding
* `DEFAULT_COLLATION`: cluster collation
* `DEFAULT_CTYPE`: cluster ctype
* `WAL_SEGSIZE`: WAL segsize option
* `--auth` : PASSWORD AUTHENTICATION
* `INITDB_EXTRA_ARGS`: extra parameter that will be passed down to `initdb` command

In addition to that, we have another parameter: `RECREATE_DATADIR` that can be used to force database reinitializations.
If this parameter is specified as `TRUE` it will act as explicit consent to delete `DATADIR` and create
new db cluster.

* `RECREATE_DATADIR`: Force database reinitialization in the location `DATADIR`

If you used `RECREATE_DATADIR` and successfully created a new cluster. Remember
that you should remove this parameter afterwards. Because, if it was not omitted,
it will always recreate new db cluster after every container restarts.

#### Postgres Encoding

The database cluster is initialised with the following encoding settings

`
-E "UTF8" --lc-collate="en_US.UTF-8" --lc-ctype="en_US.UTF-8"
`

or

`
-E "UTF8" --lc-collate="C.UTF-8" --lc-ctype="C.UTF-8"
`

If you use default `DATADIR` location.

If you need to set up a database cluster with other encoding parameters you need
to pass the environment variables when you initialize the cluster.

* -e DEFAULT_ENCODING="UTF8"
* -e DEFAULT_COLLATION="en_US.UTF-8"
* -e DEFAULT_CTYPE="en_US.UTF-8"

Initializing a new cluster can be done by using different `DATADIR` location and
mounting an empty volume. Or use parameter `RECREATE_DATADIR` to forcefully
delete the current cluster and create a new one. Make sure to remove parameter
`RECREATE_DATADIR` after creating the cluster.


#### Basic configuration

You can use the following environment variables to pass a
username, password and/or default database name(or multiple databases comma separated).

* `-e POSTGRES_USER=<PGUSER>`
* `-e POSTGRES_PASS=<PGPASSWORD>`
**NB** You should use a strong passwords. If you are using docker-compose make sure
docker can interpolate the password. Example using a password with a `$` you will
need to escape it ie `$$`
* `-e POSTGRES_DBNAME=<PGDBNAME>`
* `-e POSTGRES_MULTIPLE_EXTENSIONS=postgis,hstore,postgis_topology,postgis_raster,pgrouting`

You can pass as many extensions as you need.
* `-e SHARED_PRELOAD_LIBRARIES='pg_cron'`
Some extensions need to be registered in the postgresql.conf
as shared_preload_libraries. pg_cron should always be added because
the extension is installed with the image.
* `-e SSL_CERT_FILE=/your/own/ssl_cert_file.pem`
* `-e SSL_KEY_FILE=/your/own/ssl_key_file.key`
* `-e SSL_CA_FILE=/your/own/ssl_ca_file.pem`
* `-e DEFAULT_ENCODING="UTF8"`
* `-e DEFAULT_COLLATION="en_US.UTF-8"`
* `-e DEFAULT_CTYPE="en_US.UTF-8"`

* `-e POSTGRES_TEMPLATE_EXTENSIONS=true`

 ` Specifies whether extensions will also be installed in template1 database.`

### Schema Initialisation
* `-e SCHEMA_NAME=<PGSCHEMA>`
You can pass a comma separated value of schema names which will be created when the
  database initialises. The default behaviour is to create the schema in the first
  database specified in the environment variable `POSTGRES_DBNAME`. If you need to
  create matching schemas in all the databases that will be created you use
  the environment variable `ALL_DATABASES=TRUE`

#### Configures archive mode

This image uses the initial PostgreSQL values which disables the archiving option by default.
When `ARCHIVE_MODE` is changed to `on`, the archiving command will copy WAL files to `/opt/archivedir`

[More info: 19.5. Write Ahead Log](https://www.postgresql.org/docs/12/runtime-config-wal.html)

* `-e ARCHIVE_MODE=off`
* `-e ARCHIVE_COMMAND="test ! -f /opt/archivedir/%f && cp %p /opt/archivedir/%f"`
[More info](https://www.postgresql.org/docs/12/continuous-archiving.html#BACKUP-ARCHIVING-WAL)
* `-e ARCHIVE_CLEANUP_COMMAND="pg_archivecleanup /opt/archivedir %r"`
* `-e RESTORE_COMMAND='cp /opt/archivedir/%f "%p"'`

#### Configure WAL level
* `-e WAL_LEVEL=replica`
[More info](https://www.postgresql.org/docs/12/runtime-config-wal.html)

Maximum size to let the WAL grow to between automatic WAL checkpoints.
* `-e WAL_SIZE=4GB`
* `-e MIN_WAL_SIZE=2048MB`
* `-e WAL_SEGSIZE=1024`
* `-e MAINTAINANCE_WORK_MEM=128MB`

#### Configure networking
You can open up the PG port by using the following environment variable. By default,
the container will allow connections only from the docker private subnet.

* `-e ALLOW_IP_RANGE=<0.0.0.0/0> By default`

Postgres conf is set up to listen to all connections and if a user needs to restrict which IP address
PostgreSQL listens to you can define it with the following environment variable. The default is set to listen to
all connections.
* `-e IP_LIST=<*>`

#### Additional configuration

You can also define any other configuration to add to `extra.conf`, separated by '\n' e.g.:

* `-e EXTRA_CONF="log_destination = 'stderr'\nlogging_collector = on"`

You can alternatively mount an extra  config file into the setting's folder i.e

```
docker run --name "postgis" -v /data/extra.conf:/settings/extra.conf -p 25432:5432 -d -t kartoza/postgis
```

If you want to reinitialize the data directory from scratch, you need to do:

1. Do backup, move data, etc. Any preparations before deleting your data directory.
2. Set environment variables `RECREATE_DATADIR=TRUE`. Restart the service
3. The service will delete your `DATADIR` directory and start reinitializing your data directory from scratch.

## Docker secrets

To avoid passing sensitive information in environment variables, `_FILE` can be appended to
some of the variables to read from files present in the container. This is particularly useful
in conjunction with Docker secrets, as passwords can be loaded from `/run/secrets/<secret_name>` e.g.:

* -e POSTGRES_PASS_FILE=/run/secrets/<pg_pass_secret>

For more information see [https://docs.docker.com/engine/swarm/secrets/](https://docs.docker.com/engine/swarm/secrets/).

Currently, `POSTGRES_PASS`, `POSTGRES_USER` and `POSTGRES_DB` are supported.


## Running the container

### Using the terminal

To create a running container do:

```
docker run --name "postgis" -p 25432:5432 -d -t kartoza/postgis
```

## Convenience docker-compose.yml

For convenience we have provided a ``docker-compose.yml`` that will run a
copy of the database image and also our related database backup image (see
[https://github.com/kartoza/docker-pg-backup](https://github.com/kartoza/docker-pg-backup)).

The docker compose recipe will expose PostgreSQL on port 25432 (to prevent
potential conflicts with any local database instance you may have).

Example usage:

```
docker-compose up -d
```

**Note:** The docker-compose recipe above will not persist your data on your local
disk, only in a docker volume.

## Connect via psql

Connect with psql (make sure you first install postgresql client tools on your
host / client):


```
psql -h localhost -U docker -p 25432 -l
```

**Note:** Default postgresql user is 'docker' with password 'docker'.

You can then go on to use any normal postgresql commands against the container.

Under ubuntu 16.04 the postgresql client can be installed like this:

```
sudo apt-get install postgresql-client-12
```

## Running SQL scripts on container startup.


In some instances users want to run some SQL scripts to populate the
database. Since the environment variable POSTGRES_DB allows
us to specify multiple database that can be created on startup.
When running scripts they will only be executed against the
first database ie POSTGRES_DB=gis,data,sample
The SQL script will be executed against the gis database. Additionally, a lock file is generated in `/docker-entrypoint-initdb.d`, which will prevent the scripts from getting executed after the first container startup. Provide `IGNORE_INIT_HOOK_LOCKFILE=true` to execute the scripts on _every_ container start.

Currently you can pass `.sql` , `.sql.gz` and `.sh` files as mounted volumes.

```

docker run -d -v ./setup-db.sql:/docker-entrypoint-initdb.d/setup-db.sql kartoza/postgis`
```


## Storing data on the host rather than the container.


Docker volumes can be used to persist your data.

```
mkdir -p ~/postgres_data
docker run -d -v $HOME/postgres_data:/var/lib/postgresql kartoza/postgis`
```

You need to ensure the ``postgres_data`` directory has sufficient permissions
for the docker process to read / write it.

## Postgres SSL setup

By default the image is delivered with an unsigned SSL certificate. This helps to have an
encrypted connection to clients and avoid eavesdropping but does not help to mitigate
man in the middle (MITM) attacks.

You need to provide your own, signed private key to avoid this kind of attacks (and make
sure clients connect with verify-ca or verify-full sslmode).

The following is an example Dockerfile that sets up a container with custom ssl private key and certificate:

```
FROM kartoza/postgis:11.0-2.5

ADD ssl_cert.pem /etc/ssl/certs/ssl_cert.pem
ADD localhost_ssl_key.pem /etc/ssl/private/ssl_key.pem

RUN chmod 400 /etc/ssl/private/ssl_key.pem
```

And a docker-compose.yml to initialize with this configuration:

```
services:
  postgres:
    build:
      dockerfile: Dockerfile
      context: ssl_secured_docker
    environment:
      - SSL_CERT_FILE=/etc/ssl/certs/ssl_cert.pem
      - SSL_KEY_FILE=/etc/ssl/private/ssl_key.pem
```

See [the postgres documentation about SSL](https://www.postgresql.org/docs/11/libpq-ssl.html#LIBQ-SSL-CERTIFICATES) for more information.

See [the postgres documentation about encoding](https://www.postgresql.org/docs/11/multibyte.html) for more information.


## Postgres Replication Setup

The image supports replication out of the box. By default replication is turned off.
The two mains replication methods allowed are
* Streaming replication
* Logical replication

### Streaming replication

Replication allows you to maintain two or more synchronised copies of a database, with a
single **master** copy and one or more **replicant** copies. The animation below illustrates
this - the layer with the red boundary is accessed from the master database and the layer
with the green fill is accessed from the replicant database. When edits to the master
layer are saved, they are automatically propagated to the replicant. Note also that the
replicant is read-only.

```
docker run --name "streaming-replication" -e REPLICATION=true -e WAL_LEVEL='replica' -d -p 25432:5432  kartoza/postgis:13.0
```


![qgis](https://user-images.githubusercontent.com/178003/37755610-dd3b774a-2dae-11e8-9fa1-4877e2034675.gif)

This image is provided with replication abilities. We can
categorize an instance of the container as `master` or `replicant`. A `master`
instance means that a particular container has a role as a single point of
database write. A `replicant` instance means that a particular container will
mirror database content from a designated master. This replication scheme allows
us to sync databases. However a `replicant` is only for read-only transaction, thus
we can't write new data to it. The whole database cluster will be replicated.

#### Database permissions
Since we are using a role ${REPLICATION_USER}, we need to ensure that it has access to all
the tables in a particular schema. So if a user adds another schema called `data`
to the database `gis` he also has to update the permission for the user
with the following SQL assuming the ${REPLICATION_USER} is called replicator

     ALTER DEFAULT PRIVILEGES IN SCHEMA data GRANT SELECT ON TABLES TO replicator;


**NB** You need to setup a strong password for replication otherwise the
default password for ${REPLICATION_USER} will default to `replicator`

To experiment with the replication abilities, you can see a [docker-compose.yml](sample/replication/docker-compose.yml)
sample. There are several environment variables that you can set, such as:

Master settings:
- **ALLOW_IP_RANGE**: A pg_hba.conf domain format which will allow specified host(s)
  to connect into the container. This is needed to allow the `slave` to connect
  into `master`, so specifically this settings should allow `slave` address. It is also needed to allow clients on other hosts to connect to either the slave or the master.
- **REPLICATION_USER** User to initiate streaming replication
- **REPLICATION_PASS** Password for a user with streaming replication role

Slave settings:
- **REPLICATE_FROM**: This should be the domain name or IP address of the `master`
  instance. It can be anything from the docker resolved name like that written in the sample,
  or the IP address of the actual machine where you expose `master`. This is
  useful to create cross machine replication, or cross stack/server.
- **REPLICATE_PORT**: This should be the port number of `master` postgres instance.
  Will default to 5432 (default postgres port), if not specified.
- **DESTROY_DATABASE_ON_RESTART**: Default is `True`. Set to 'False' to prevent
  this behaviour. A replicant will always destroy its current database on
  restart, because it will try to sync again from `master` and avoid inconsistencies.
- **PROMOTE_MASTER**: Default none. If set to any value then the current replicant
  will be promoted to master.
  In some cases when the `master` container has failed, we might want to use our `replicant`
  as `master` for a while. However, the promoted replicant will break consistencies and
  is not able to revert to replicant anymore, unless it is destroyed and resynced
  with the new master.
- **REPLICATION_USER** User to initiate streaming replication
- **REPLICATION_PASS** Password for a user with streaming replication role

To run the sample replication, follow these instructions:

Do a manual image build by executing the `build.sh` script

```
./build.sh
```

Go into the `sample/replication` directory and experiment with the following Make
command to run both master and slave services.

```
make up
```

To shutdown services, execute:

```
make down
```

To view logs for master and slave respectively, use the following command:

```
make master-log
make slave-log
```

You can try experiment with several scenarios to see how replication works

#### Sync changes from master to replicant

You can use any postgres database tools to create new tables in master, by
connecting using POSTGRES_USER and POSTGRES_PASS credentials using exposed port.
In the sample, the master database was exposed on port 7777.
Or you can do it via command line, by entering the shell:

```
make master-shell
```

Then made any database changes using psql.

After that, you can see that the replicant follows the changes by inspecting the
slave database. You can, again, use database management tools using connection
credentials, hostname, and ports for replicant. Or you can do it via command line,
by entering the shell:

```
make slave-shell
```

Then view your changes using psql.

#### Promoting replicant to master

You will notice that you cannot make changes in replicant, because it is read-only.
If somehow you want to promote it to master, you can specify `PROMOTE_MASTER: 'True'`
into slave environment and set `DESTROY_DATABASE_ON_RESTART: 'False'`.

After this, you can make changes to your replicant, but master and replicant will not
be in sync anymore. This is useful if the replicant needs to take over a failover master.
However it is recommended to take additional action, such as creating a backup from the
slave so a dedicated master can be created again.

#### Preventing replicant database destroy on restart

You can optionally set `DESTROY_DATABASE_ON_RESTART: 'False'` after successful sync
to prevent the database from being destroyed on restart. With this setting you can
shut down your replicant and restart it later and it will continue to sync using the existing
database (as long as there are no consistencies conflicts).

However, you should note that this option doesn't mean anything if you didn't
persist your database volume. Because if it is not persisted, then it will be lost
on restart because docker will recreate the container.

### Logical  replication
To activate the following you need to use the environment variable

`WAL_LEVEL=logical` to get a running instance like

```
docker run --name "logical-replication" -e WAL_LEVEL=logical -d  kartoza/postgis:13.0
```
For a detailed example see the docker-compose in the folder `sample/logical_replication`.


### Support

If you require more substantial assistance from [kartoza](https://kartoza.com)  (because our work and interaction on docker-postgis is pro bono),
please consider taking out a [Support Level Agreeement](https://kartoza.com/en/shop/product/support)

## Credits

Tim Sutton (tim@kartoza.com)
Gavin Fleming (gavin@kartoza.com)
Rizky Maulana (rizky@kartoza.com)
Admire Nyakudya (admire@kartoza.com)
March 2021