[oracle] adding integration

[truthbk]

What's this PR do?

Adds the Oracle integration.

Originally written by @handigarde (DataDog/dd-agent#2460).

[truthbk]

Adding a note for steps needed to allow access to cx_Oracle (will also be including in oracle.yaml.example).

To install cx_Oracle the following steps are needed:

# Download Oracle Instant Client (example dir: ~/oracle)
mkdir -p /opt/oracle/ && cd /opt/oracle/
unzip ~/oracle/instantclient-basic-linux.x64-12.1.0.2.0.zip
unzip ~/oracle/instantclient-sdk-linux.x64-12.1.0.2.0.zip

export LD_RUN_PATH=/opt/oracle/instantclient_12_1
export ORACLE_HOME=/opt/oracle/instantclient_12_1

/opt/datadog-agent/embedded/bin/pip install cx_Oracle

From this point the LD_LIBRARY_PATH on the host will need to point to /opt/oracle/instantclient_12_1 when starting/restarting the agent

[truthbk]

If you run into issues on this step: /opt/datadog-agent/embedded/bin/pip install cx_Oracle try the following:

ln -sf /opt/oracle/instantclient_12_1/libclntsh.so.12.1 /opt/oracle/instantclient_12_1/libclntsh.so
ln -sf /opt/oracle/instantclient_12_1/libclntshcore.so.12.1 /opt/oracle/instantclient_12_1/libclntshcore.so

after creating these symlinks please try again.

[handigarde]

One more update to the tablespace metrics. Switching away from DBA_TABLESPACE_USAGE_METRICS which is known to have a few bugs. Now using sys.dba_data_files for tablespace usage

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 60 days. It will be closed if no further activity occurs in the next two weeks. Thank you for participating in the Datadog open source community. If you need more time, or have any questions, let us know.

[jeremy-lq]

@handigarde

If you're still interested in having this merged and are willing to become the maintainer, please let us know. I'm happy to explain the process a bit more if you have questions. Also note we have Office Hours today if you'd like to chat about this real-time. Thank you for the contribution.

[jeremy-lq]

Closing, as an Oracle integration is being added to integrations-core here: DataDog/integrations-core#680