martin/README.md

# Martin

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Martin is a [PostGIS](https://github.com/postgis/postgis) [vector tiles](https://github.com/mapbox/vector-tile-spec) server suitable for large databases. Martin is written in [Rust](https://github.com/rust-lang/rust) using [Actix](https://github.com/actix/actix-web) web framework.

![Martin](https://raw.githubusercontent.com/urbica/martin/master/logo.png)

- [Requirements](#requirements)
- [Installation](#installation)
- [Usage](#usage)
- [API](#api)
- [Using with Mapbox GL JS](#using-with-mapbox-gl-js)
- [Using with Leaflet](#using-with-leaflet)
- [Using with deck.gl](#using-with-deckgl)
- [Table Sources](#table-sources)
  - [Table Sources List](#table-sources-list)
  - [Table Source TileJSON](#table-source-tilejson)
  - [Table Source Tiles](#table-source-tiles)
- [Composite Sources](#composite-sources)
  - [Composite Source TileJSON](#composite-source-tilejson)
  - [Composite Source Tiles](#composite-source-tiles)
- [Function Sources](#function-sources)
  - [Function Sources List](#function-sources-list)
  - [Function Source TileJSON](#function-source-tilejson)
  - [Function Source Tiles](#function-source-tiles)
- [Command-line Interface](#command-line-interface)
- [Environment Variables](#environment-variables)
- [Configuration File](#configuration-file)
- [Using with Docker](#using-with-docker)
- [Using with Docker Compose](#using-with-docker-compose)
- [Using with Nginx](#using-with-nginx)
  - [Rewriting URLs](#rewriting-urls)
  - [Caching tiles](#caching-tiles)
- [Building from Source](#building-from-source)
- [Debugging](#debugging)
- [Development](#development)
- [Recipes](#recipes)
  - [Using with DigitalOcean PostgreSQL](#using-with-digitalocean-postgresql)
  - [Using with Heroku PostgreSQL](#using-with-heroku-postgresql)

## Requirements

Martin requires PostGIS >= 2.4.0.

## Installation

You can download martin from [Github releases page](https://github.com/urbica/martin/releases).

| Platform | Downloads (latest)      |
| -------- | ----------------------- |
| Linux    | [64-bit][rl-linux-tar]  |
| macOS    | [64-bit][rl-macos-tar]  |
| Windows  | [64-bit][rl-winx64-zip] |

[rl-linux-tar]: https://github.com/urbica/martin/releases/latest/download/martin-Linux-x86_64.tar.gz
[rl-macos-tar]: https://github.com/urbica/martin/releases/latest/download/martin-Darwin-x86_64.tar.gz
[rl-winx64-zip]: https://github.com/urbica/martin/releases/latest/download/martin-Windows-x86_64.zip

If you are using macOS and [Homebrew](https://brew.sh/) you can install martin using Homebrew tap.

```shell
brew tap urbica/tap
brew install martin
```

You can also use [official Docker image](https://hub.docker.com/r/urbica/martin)

```shell
docker run -p 3000:3000 -e DATABASE_URL=postgres://postgres@localhost/db urbica/martin
```

## Usage

Martin requires a database connection string. It can be passed as a command-line argument or as a `DATABASE_URL` environment variable.

```shell
martin postgres://postgres@localhost/db
```

Martin provides [TileJSON](https://github.com/mapbox/tilejson-spec) endpoint for each [geospatial-enabled](https://postgis.net/docs/postgis_usage.html#geometry_columns) table in your database.

## API

| Method | URL                                                                              | Description                                             |
| ------ | -------------------------------------------------------------------------------- | ------------------------------------------------------- |
| `GET`  | `/index.json`                                                                    | [Table Sources List](#table-sources-list)               |
| `GET`  | `/{schema_name}.{table_name}.json`                                               | [Table Source TileJSON](#table-source-tilejson)         |
| `GET`  | `/{schema_name}.{table_name}/{z}/{x}/{y}.pbf`                                    | [Table Source Tiles](#table-source-tiles)               |
| `GET`  | `/{schema_name1}.{table_name1},...,{schema_nameN}.{table_nameN}.json`            | [Composite Source TileJSON](#composite-source-tilejson) |
| `GET`  | `/{schema_name1}.{table_name1},...,{schema_nameN}.{table_nameN}/{z}/{x}/{y}.pbf` | [Composite Source Tiles](#composite-source-tiles)       |
| `GET`  | `/rpc/index.json`                                                                | [Function Sources List](#function-sources-list)         |
| `GET`  | `/rpc/{schema_name}.{function_name}.json`                                        | [Function Source TileJSON](#function-source-tilejson)   |
| `GET`  | `/rpc/{schema_name}.{function_name}/{z}/{x}/{y}.pbf`                             | [Function Source Tiles](#function-source-tiles)         |
| `GET`  | `/healthz`                                                                       | Martin server health check: returns `200 OK`            |

## Using with Mapbox GL JS

[Mapbox GL JS](https://github.com/mapbox/mapbox-gl-js) is a JavaScript library for interactive, customizable vector maps on the web. It takes map styles that conform to the
[Mapbox Style Specification](https://www.mapbox.com/mapbox-gl-js/style-spec), applies them to vector tiles that
conform to the [Mapbox Vector Tile Specification](https://github.com/mapbox/vector-tile-spec), and renders them using
WebGL.

You can add a layer to the map and specify martin TileJSON endpoint as a vector source URL. You should also specify a `source-layer` property. For [Table Sources](#table-sources) it is `{schema_name}.{table_name}` by default.

```js
map.addLayer({
  id: 'public.points',
  type: 'circle',
  source: {
    type: 'vector',
    url: 'http://localhost:3000/public.points.json'
  },
  'source-layer': 'public.points',
  paint: {
    'circle-color': 'red'
  }
});
```

You can also combine multiple tables into one source with [Composite Sources](#composite-sources). Each [Table Source](#table-sources) in Composite Source can be accessed with its `{schema_name}.{table_name}` as a `source-layer` property.

```js
map.addSource('points', {
  type: 'vector',
  url: `http://0.0.0.0:3000/public.points1,public.points2.json`
});

map.addLayer({
  id: 'red_points',
  type: 'circle',
  source: 'points',
  'source-layer': 'public.points1',
  paint: {
    'circle-color': 'red'
  }
});

map.addLayer({
  id: 'blue_points',
  type: 'circle',
  source: 'points',
  'source-layer': 'public.points2',
  paint: {
    'circle-color': 'blue'
  }
});
```

## Using with Leaflet

[Leaflet](https://github.com/Leaflet/Leaflet) is the leading open-source JavaScript library for mobile-friendly interactive maps.

You can add vector tiles using [Leaflet.VectorGrid](https://github.com/Leaflet/Leaflet.VectorGrid) plugin. You must initialize a [VectorGrid.Protobuf](https://leaflet.github.io/Leaflet.VectorGrid/vectorgrid-api-docs.html#vectorgrid-protobuf) with a URL template, just like in L.TileLayers. The difference is that you should define the styling for all the features.

```js
L.vectorGrid
  .protobuf('http://localhost:3000/public.points/{z}/{x}/{y}.pbf', {
    vectorTileLayerStyles: {
      'public.points': {
        color: 'red',
        fill: true
      }
    }
  })
  .addTo(map);
```

## Using with deck.gl

[deck.gl](https://deck.gl/) is a WebGL-powered framework for visual exploratory data analysis of large datasets.

You can add vector tiles using [MVTLayer](https://deck.gl/docs/api-reference/geo-layers/mvt-layer). MVTLayer `data` property defines the remote data for the MVT layer. It can be

- `String`: Either a URL template or a [TileJSON](https://github.com/mapbox/tilejson-spec) URL.
- `Array`: an array of URL templates. It allows to balance the requests across different tile endpoints. For example, if you define an array with 4 urls and 16 tiles need to be loaded, each endpoint is responsible to server 16/4 tiles.
- `JSON`: A valid [TileJSON object](https://github.com/mapbox/tilejson-spec/tree/master/2.2.0).

```js
const pointsLayer = new MVTLayer({
  data: 'http://localhost:3000/public.points.json', // 'http://localhost:3000/public.table_source/{z}/{x}/{y}.pbf'
  pointRadiusUnits: 'pixels',
  getRadius: 5,
  getFillColor: [230, 0, 0]
});

const deckgl = new DeckGL({
  container: 'map',
  mapStyle: 'https://basemaps.cartocdn.com/gl/dark-matter-gl-style/style.json',
  initialViewState: {
    latitude: 0,
    longitude: 0,
    zoom: 1
  },
  layers: [pointsLayer]
});
```

## Table Sources

Table Source is a database table which can be used to query [vector tiles](https://github.com/mapbox/vector-tile-spec). When started, martin will go through all spatial tables in the database and build a list of table sources. A table should have at least one geometry column with non-zero SRID. All other table columns will be represented as properties of a vector tile feature.

### Table Sources List

Table Sources list endpoint is available at `/index.json`

```shell
curl localhost:3000/index.json
```

**Note**: if in `watch` mode, this will rescan database for table sources.

### Table Source TileJSON

Table Source [TileJSON](https://github.com/mapbox/tilejson-spec) endpoint is available at `/{schema_name}.{table_name}.json`.

For example, `points` table in `public` schema will be available at `/public.points.json`

```shell
curl localhost:3000/public.points.json
```

### Table Source Tiles

Table Source tiles endpoint is available at `/{schema_name}.{table_name}/{z}/{x}/{y}.pbf`

For example, `points` table in `public` schema will be available at `/public.points/{z}/{x}/{y}.pbf`

```shell
curl localhost:3000/public.points/0/0/0.pbf
```

## Composite Sources

Composite Sources allows combining multiple Table Sources into one. Composite Source consists of multiple Table Sources separated by comma `{schema_name1}.{table_name1},...,{schema_nameN}.{table_nameN}`

Each [Table Source](#table-sources) in Composite Source can be accessed with its `{schema_name}.{table_name}` as a `source-layer` property.

### Composite Source TileJSON

Composite Source [TileJSON](https://github.com/mapbox/tilejson-spec) endpoint is available at `/{schema_name1}.{table_name1},...,{schema_nameN}.{table_nameN}.json`.

For example, composite source for `points` and `lines` tables in `public` schema will be available at `/public.points,public.lines.json`

```shell
curl localhost:3000/public.points,public.lines.json
```

### Composite Source Tiles

Composite Source tiles endpoint is available at `/{schema_name1}.{table_name1},...,{schema_nameN}.{table_nameN}/{z}/{x}/{y}.pbf`

For example, composite source for `points` and `lines` tables in `public` schema will be available at `/public.points,public.lines/{z}/{x}/{y}.pbf`

```shell
curl localhost:3000/public.points,public.lines/0/0/0.pbf
```

## Function Sources

Function Source is a database function which can be used to query [vector tiles](https://github.com/mapbox/vector-tile-spec). When started, martin will look for the functions with a suitable signature. A function that takes `z integer`, `x integer`, `y integer`, and `query_params json` and returns `bytea`, can be used as a Function Source.

| Argument     | Type    | Description             |
| ------------ | ------- | ----------------------- |
| z            | integer | Tile zoom parameter     |
| x            | integer | Tile x parameter        |
| y            | integer | Tile y parameter        |
| query_params | json    | Query string parameters |

**Hint**: You may want to use [TileBBox](https://github.com/mapbox/postgis-vt-util#tilebbox) function to generate bounding-box geometry of the area covered by a tile.

For example, if you have a table `public.table_source` in WGS84 (`4326` SRID), then you can use this function as a Function Source:

```sql
CREATE OR REPLACE FUNCTION public.function_source(z integer, x integer, y integer, query_params json) RETURNS bytea AS $$
DECLARE
  mvt bytea;
BEGIN
  SELECT INTO mvt ST_AsMVT(tile, 'public.function_source', 4096, 'geom') FROM (
    SELECT
      ST_AsMVTGeom(ST_Transform(ST_CurveToLine(geom), 3857), TileBBox(z, x, y, 3857), 4096, 64, true) AS geom
    FROM public.table_source
    WHERE geom && TileBBox(z, x, y, 4326)
  ) as tile WHERE geom IS NOT NULL;

  RETURN mvt;
END
$$ LANGUAGE plpgsql IMMUTABLE STRICT PARALLEL SAFE;
```

The `query_params` argument is a JSON representation of the tile request query params. For example, if user requested a tile with [urlencoded](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent) params:

```shell
curl \
  --data-urlencode 'arrayParam=[1, 2, 3]' \
  --data-urlencode 'numberParam=42' \
  --data-urlencode 'stringParam=value' \
  --data-urlencode 'booleanParam=true' \
  --data-urlencode 'objectParam={"answer" : 42}' \
  --get localhost:3000/rpc/public.function_source/0/0/0.pbf
```

then `query_params` will be parsed as:

```json
{
  "arrayParam": [1, 2, 3],
  "numberParam": 42,
  "stringParam": "value",
  "booleanParam": true,
  "objectParam": { "answer": 42 }
}
```

You can access this params using [json operators](https://www.postgresql.org/docs/current/functions-json.html):

```sql
...WHERE answer = (query_params->'objectParam'->>'answer')::int;
```

### Function Sources List

Function Sources list endpoint is available at `/rpc/index.json`

```shell
curl localhost:3000/rpc/index.json
```

**Note**: if in `watch` mode, this will rescan database for function sources.

### Function Source TileJSON

Function Source [TileJSON](https://github.com/mapbox/tilejson-spec) endpoint is available at `/rpc/{schema_name}.{function_name}.json`

For example, `points` function in `public` schema will be available at `/rpc/public.points.json`

```shell
curl localhost:3000/rpc/public.points.json
```

### Function Source Tiles

Function Source tiles endpoint is available at `/rpc/{schema_name}.{function_name}/{z}/{x}/{y}.pbf`

For example, `points` function in `public` schema will be available at `/rpc/public.points/{z}/{x}/{y}.pbf`

```shell
curl localhost:3000/rpc/public.points/0/0/0.pbf
```

## Command-line Interface

You can configure martin using command-line interface

```shell
Usage:
  martin [options] [<connection>]
  martin -h | --help
  martin -v | --version

Options:
  -h --help                         Show this screen.
  -v --version                      Show version.
  --config=<path>                   Path to config file.
  --keep-alive=<n>                  Connection keep alive timeout [default: 75].
  --listen-addresses=<n>            The socket address to bind [default: 0.0.0.0:3000].
  --pool-size=<n>                   Maximum connections pool size [default: 20].
  --watch                           Scan for new sources on sources list requests.
  --workers=<n>                     Number of web server workers.
  --ca-root-file=<path>             Loads trusted root certificates from a file. The file should contain a sequence of PEM-formatted CA certificates.
  --danger-accept-invalid-certs     Trust invalid certificates. This introduces significant vulnerabilities, and should only be used as a last resort.
```

## Environment Variables

You can also configure martin using environment variables

| Environment variable          | Example                            | Description                                   |
| ----------------------------- | ---------------------------------- | --------------------------------------------- |
| `DATABASE_URL`                | `postgres://postgres@localhost/db` | Postgres database connection                  |
| `WATCH_MODE`                  | `true`                             | Scan for new sources on sources list requests |
| `CA_ROOT_FILE`                | `./ca-certificate.crt`             | Loads trusted root certificates from a file   |
| `DANGER_ACCEPT_INVALID_CERTS` | `false`                            | Trust invalid certificates                    |

## Configuration File

If you don't want to expose all of your tables and functions, you can list your sources in a configuration file. To start martin with a configuration file you need to pass a path to a file with a `--config` argument.

```shell
martin --config config.yaml
```

You can find an example of a configuration file [here](https://github.com/urbica/martin/blob/master/tests/config.yaml).

```yaml
# The socket address to bind [default: 0.0.0.0:3000]
listen_addresses: '0.0.0.0:3000'

# Database connection string
connection_string: 'postgres://postgres@localhost:5432/db'

# Maximum connections pool size [default: 20]
pool_size: 20

# Connection keep alive timeout [default: 75]
keep_alive: 75

# Number of web server workers
worker_processes: 8

# Enable watch mode
watch: false

# Trust invalid certificates. This introduces significant vulnerabilities, and should only be used as a last resort.
danger_accept_invalid_certs: false

# Associative arrays of table sources
table_sources:
  public.table_source:
    # Table source id (required)
    id: public.table_source

    # Table schema (required)
    schema: public

    # Table name (required)
    table: table_source

    # Geometry SRID (required)
    srid: 4326

    # Geometry column name (required)
    geometry_column: geom

    # Feature id column name
    id_column: ~

    # An integer specifying the minimum zoom level
    minzoom: 0

    # An integer specifying the maximum zoom level. MUST be >= minzoom
    maxzoom: 30

    # The maximum extent of available map tiles. Bounds MUST define an area
    # covered by all zoom levels. The bounds are represented in WGS:84
    # latitude and longitude values, in the order left, bottom, right, top.
    # Values may be integers or floating point numbers.
    bounds: [-180.0, -90.0, 180.0, 90.0]

    # Tile extent in tile coordinate space
    extent: 4096

    # Buffer distance in tile coordinate space to optionally clip geometries
    buffer: 64

    # Boolean to control if geometries should be clipped or encoded as is
    clip_geom: true

    # Geometry type
    geometry_type: GEOMETRY

    # List of columns, that should be encoded as tile properties (required)
    properties:
      gid: int4

# Associative arrays of function sources
function_sources:
  public.function_source:
    # Function source id (required)
    id: public.function_source

    # Schema name (required)
    schema: public

    # Function name (required)
    function: function_source

    # An integer specifying the minimum zoom level
    minzoom: 0

    # An integer specifying the maximum zoom level. MUST be >= minzoom
    maxzoom: 30

    # The maximum extent of available map tiles. Bounds MUST define an area
    # covered by all zoom levels. The bounds are represented in WGS:84
    # latitude and longitude values, in the order left, bottom, right, top.
    # Values may be integers or floating point numbers.
    bounds: [-180.0, -90.0, 180.0, 90.0]
```

## Using with Docker

You can use official Docker image [`urbica/martin`](https://hub.docker.com/r/urbica/martin)

```shell
docker run \
  -p 3000:3000 \
  -e DATABASE_URL=postgres://postgres@localhost/db \
  urbica/martin
```

If you are running PostgreSQL instance on `localhost`, you have to change network settings to allow the Docker container to access the `localhost` network.

For Linux, add the `--net=host` flag to access the `localhost` PostgreSQL service.

```shell
docker run \
  --net=host \
  -p 3000:3000 \
  -e DATABASE_URL=postgres://postgres@localhost/db \
  urbica/martin
```

For macOS, use `host.docker.internal` as hostname to access the `localhost` PostgreSQL service.

```shell
docker run \
  -p 3000:3000 \
  -e DATABASE_URL=postgres://postgres@host.docker.internal/db \
  urbica/martin
```

For Windows, use `docker.for.win.localhost` as hostname to access the `localhost` PostgreSQL service.

```shell
docker run \
  -p 3000:3000 \
  -e DATABASE_URL=postgres://postgres@docker.for.win.localhost/db \
  urbica/martin
```

## Using with Docker Compose

You can use example [`docker-compose.yml`](https://raw.githubusercontent.com/urbica/martin/master/docker-compose.yml) file as a reference

```yml
version: '3'

services:
  martin:
    image: urbica/martin
    restart: unless-stopped
    ports:
      - 3000:3000
    environment:
      - DATABASE_URL=postgres://postgres:password@db/db
    depends_on:
      - db

  db:
    image: postgis/postgis:14-3.1-alpine
    restart: unless-stopped
    environment:
      - POSTGRES_DB=db
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    volumes:
      - ./pg_data:/var/lib/postgresql/data
```

First, you need to start `db` service

```shell
docker-compose up -d db
```

Then, after `db` service is ready to accept connections, you can start `martin`

```shell
docker-compose up -d martin
```

By default, martin will be available at [localhost:3000](http://localhost:3000/index.json)

## Using with Nginx

You can run martin behind Nginx proxy, so you can cache frequently accessed tiles and reduce unnecessary pressure on the database.

```yml
version: '3'

services:
  nginx:
    image: nginx:alpine
    restart: unless-stopped
    ports:
      - 80:80
    volumes:
      - ./cache:/var/cache/nginx
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    depends_on:
      - martin

  martin:
    image: urbica/martin
    restart: unless-stopped
    environment:
      - DATABASE_URL=postgres://postgres:password@db/db
    depends_on:
      - db

  db:
    image: postgis/postgis:14-3.1-alpine
    restart: unless-stopped
    environment:
      - POSTGRES_DB=db
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    volumes:
      - ./pg_data:/var/lib/postgresql/data
```

You can find an example Nginx configuration file [here](https://github.com/urbica/martin/blob/master/nginx.conf).

### Rewriting URLs

If you are running martin behind Nginx proxy, you may want to rewrite the request URL to properly handle tile URLs in [TileJSON](#table-source-tilejson) [endpoints](#function-source-tilejson).

```nginx
location ~ /tiles/(?<fwd_path>.*) {
    proxy_set_header  X-Rewrite-URL $uri;
    proxy_set_header  X-Forwarded-Host $host:$server_port;
    proxy_set_header  X-Forwarded-Proto $scheme;
    proxy_redirect    off;

    proxy_pass        http://martin:3000/$fwd_path$is_args$args;
}
```

### Caching tiles

You can also use Nginx to cache tiles. In the example, the maximum cache size is set to 10GB, and caching time is set to 1 hour for responses with codes 200, 204, and 302 and 1 minute for responses with code 404.

```nginx
http {
  ...
  proxy_cache_path  /var/cache/nginx/
                    levels=1:2
                    max_size=10g
                    use_temp_path=off
                    keys_zone=tiles_cache:10m;

  server {
    ...
    location ~ /tiles/(?<fwd_path>.*) {
        proxy_set_header        X-Rewrite-URL $uri;
        proxy_set_header        X-Forwarded-Host $host:$server_port;
        proxy_set_header        X-Forwarded-Proto $scheme;
        proxy_redirect          off;

        proxy_cache             tiles_cache;
        proxy_cache_lock        on;
        proxy_cache_revalidate  on;

        # Set caching time for responses
        proxy_cache_valid       200 204 302 1h;
        proxy_cache_valid       404 1m;

        proxy_cache_use_stale   error timeout http_500 http_502 http_503 http_504;
        add_header              X-Cache-Status $upstream_cache_status;

        proxy_pass              http://martin:3000/$fwd_path$is_args$args;
    }
  }
}
```

You can find an example Nginx configuration file [here](https://github.com/urbica/martin/blob/master/nginx.conf).

## Building from Source

You can clone the repository and build martin using [cargo](https://doc.rust-lang.org/cargo) package manager.

```shell
git clone git@github.com:urbica/martin.git
cd martin
cargo build --release
```

The binary will be available at `./target/release/martin`.

```shell
cd ./target/release/
./martin postgres://postgres@localhost/db
```

## Debugging

Log levels are controlled on a per-module basis, and by default all logging is disabled except for errors. Logging is controlled via the `RUST_LOG` environment variable. The value of this environment variable is a comma-separated list of logging directives.

This will enable debug logging for all modules:

```shell
export RUST_LOG=debug
martin postgres://postgres@localhost/db
```

While this will only enable verbose logging for the `actix_web` module and enable debug logging for the `martin` and `tokio_postgres` modules:

```shell
export RUST_LOG=actix_web=info,martin=debug,tokio_postgres=debug
martin postgres://postgres@localhost/db
```

## Development

Clone project

```shell
git clone git@github.com:urbica/martin.git
cd martin
```

Start `db` service using [docker-compose](https://docs.docker.com/compose/)

```shell
docker-compose up -d db
```

Then, after `db` service is ready to accept connections, you can start `martin` with

```shell
DATABASE_URL=postgres://postgres@localhost/db cargo run
```

Open `tests/debug.html` for debugging. By default, martin will be available at [localhost:3000](http://localhost:3000/index.json)

Make your changes, and check if all the tests are running

```shell
DATABASE_URL=postgres://postgres@localhost/db cargo test
```

You can also run benchmarks with

```shell
DATABASE_URL=postgres://postgres@localhost/db cargo bench
```

An HTML report displaying the results of the benchmark will be generated under `target/criterion/report/index.html`

## Recipes


### Using with DigitalOcean PostgreSQL

You can use Martin with [Managed PostgreSQL from DigitalOcean](https://www.digitalocean.com/products/managed-databases-postgresql/) with PostGIS extension

First, you need to download the CA certificate and get your cluster connection string from the [dashboard](https://cloud.digitalocean.com/databases). After that, you can use the connection string and the CA certificate to connect to the database

```
martin --ca-root-file ./ca-certificate.crt postgres://user:password@host:port/db?sslmode=require
```

### Using with Heroku PostgreSQL

You can use Martin with [Managed PostgreSQL from Heroku](https://www.heroku.com/postgres) with PostGIS extension

```
heroku pg:psql -a APP_NAME -c 'create extension postgis'
```

In order to trust the Heroku certificate, you can disable certificate validation with either `DANGER_ACCEPT_INVALID_CERTS` environment variable

```
DATABASE_URL=$(heroku config:get DATABASE_URL -a APP_NAME) DANGER_ACCEPT_INVALID_CERTS=true martin
```

or `--danger-accept-invalid-certs` command-line argument

```
martin --danger-accept-invalid-certs $(heroku config:get DATABASE_URL -a APP_NAME)
```