ORA-12545 When running Oracle inside Docker

When trying to make an http request from my Oracle database running inside a Docker container, I received the following error:

SQL> select utl_http.request('http://api.open-notify.org/iss-now.json') from dual;

Error starting at line : 1 in command -
select utl_http.request('http://api.open-notify.org/iss-now.json') from dual
Error report -
ORA-29273: HTTP request failed
ORA-06512: at "SYS.UTL_HTTP", line 1722
ORA-12545: Connect failed because target host or object does not exist
ORA-06512: at line 1

This puzzled me quite a bit. The error pretty much says that it cannot resolve the hostname api.open-notify.org. When I run a simple curl command from my host, I get the expected result.

$ curl http://api.open-notify.org/iss-now.json
{"message": "success", "iss_position": {"longitude": "-144.6590", "latitude": "-36.9405"}, "timestamp": 1531175688}[oracle@jcat-server sh]

Then it dawned on me to try the curl command from within the container:

docker exec -it 76f4 curl http://api.open-notify.org/iss-now.json
curl: (6) Could not resolve host: api.open-notify.org

So it was the container that could not resolve the domain name.

After some research, I found that I need to run the docker image with the –dns parameter, which tells the container where to do DNS lookups. You can add multiple –dns parameters to your run command. I used it with Google’s DNS server and the one specified in my /etc/resolv.conf file. So the run command looks something like this:

docker run -d \
  -p 1521:1521 \
  -v /u01/oradata/xe:/u01/app/oracle \
  --dns "some.ip.address.169" \
  --dns "8.8.8.8" \
  --name oracle_xe \
sath89/oracle-xe-11g

When I now try the curl command to test, I get the correct response:

$ docker exec -it 1234 curl http://api.open-notify.org/iss-now.json
{"message": "success", "iss_position": {"longitude": "-73.8368", "latitude": "-49.7166"}, "timestamp": 1531176511}

Now trying it from inside the database, works, too:

SQL> select utl_http.request('http://api.open-notify.org/iss-now.json') from dual;
UTL_HTTP.REQUEST('HTTP://API.OPEN-NOTIFY.ORG/ISS-NOW.JSON')
{"message": "success", "iss_position": {"longitude": "-67.2304", "latitude": "-48.1655"}, "timestamp": 1531176585}

BTW: Don’t forget to set your ACL!