Driver/Erlang: Add dedicated page

Author: amotl

docs/connect/erlang.md

@@ -0,0 +1,124 @@
+(connect-erlang)=
+
+# Erlang
+
+:::{div} sd-text-muted
+Connect to CrateDB from Erlang applications.
+:::
+
+## ODBC
+
+:::{rubric} About
+:::
+
+Erlang includes an [ODBC application] out of the box that provides an
+interface to communicate with relational SQL-databases, see also
+[Erlang ODBC examples].
+
+:::{rubric} Prerequisites
+:::
+
+Install ODBC driver.
+
+`odbcinst.ini`
+```ini
+[PostgreSQL]
+Description     = PostgreSQL ODBC driver
+Driver          = /usr/local/lib/psqlodbcw.so
+```
+```shell
+odbcinst -i -d -f odbcinst.ini
+```
+
+:::{rubric} Synopsis
+:::
+
+`odbc_example.erl`
+```erlang
+-module(odbc_example).
+
+main(_) ->
+    odbc:start(),
+    {ok, Ref} = odbc:connect("Driver={PostgreSQL};Servername=localhost;Portnumber=5432;Uid=crate;Pwd=crate", []),
+    io:fwrite("~p~n", [odbc:sql_query(Ref, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3")]),
+    init:stop().
+```
+
+Start CrateDB using Docker or Podman, then compile and invoke example program.
+```shell
+docker run --rm --publish=5432:5432 crate -Cdiscovery.type=single-node
+```
+```shell
+escript odbc_example.erl
+```
+
+
+## epgsql
+
+[epgsql] is the designated Erlang PostgreSQL client library. 
+
+`rebar.config`
+```erlang
+{deps,
+ [
+  {epgsql, ".*", {git, "https://github.com/epgsql/epgsql.git", {tag, "4.8.0"}}}
+ ]}.
+```
+`epgsql_example.erl`
+```erlang
+-module(epgsql_example).
+-export([start/0]).
+
+start() ->
+    {ok, C} = epgsql:connect(#{
+        host => "localhost",
+        username => "crate",
+        password => "crate",
+        database => "doc",
+        port => 5432,
+        timeout => 4000
+    }),
+    {ok, _, Result} = epgsql:squery(C, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3"),
+    io:fwrite("~p~n", [Result]),
+    ok = epgsql:close(C),
+    init:stop().
+```
+
+Start CrateDB using Docker or Podman, then compile and invoke example program.
+```shell
+docker run --rm --publish=5432:5432 crate -Cdiscovery.type=single-node
+```
+```shell
+rebar3 compile
+erlc epgsql_example.erl
+erl -pa ebin ./_build/default/lib/epgsql/ebin ./_build/default/lib/epgsql/include -noshell -run epgsql_example
+```
+Stop the REPL using `CTRL+G`, `q`, `ENTER`.
+
+:::{rubric} CrateDB Cloud
+:::
+
+For connecting to CrateDB Cloud, start the Erlang [SSL application] first,
+use the `ssl` and `ssl_opts` arguments on `epgsql:connect`, and
+replace username, password, and hostname with values matching
+your environment.
+```erlang
+start() ->
+    ssl:start(),
+    {ok, C} = epgsql:connect(#{
+        host => "testcluster.cratedb.net",
+        username => "admin",
+        password => "password",
+        database => "doc",
+        port => 5432,
+        ssl => true,
+        ssl_opts => [{verify, verify_none}],
+        timeout => 4000
+    }),
+```
+
+
+[epgsql]: https://github.com/epgsql/epgsql
+[Erlang ODBC examples]: https://www.erlang.org/doc/apps/odbc/getting_started.html
+[ODBC application]: https://www.erlang.org/docs/28/apps/odbc/odbc.html
+[SSL application]: https://www.erlang.org/docs/28/apps/ssl/ssl_app.html

docs/connect/index.md

@@ -49,6 +49,18 @@ CrateDB drivers and adapters for supported programming languages, frameworks, an
 :margin: 4 4 0 0
 :padding: 0
 
+::::{grid-item-card} Erlang
+:link: connect-erlang
+:link-type: ref
+:link-alt: Connect to CrateDB using Erlang
+:padding: 3
+:text-align: center
+:class-card: sd-pt-3
+:class-body: sd-fs-1
+:class-title: sd-fs-6
+{fab}`erlang`
+::::
+
 ::::{grid-item-card} Java
 :link: connect-java
 :link-type: ref
@@ -182,6 +194,7 @@ application
 :maxdepth: 1
 :hidden:
 
+erlang
 java
 javascript
 php