K8s FDW for Postgres

Ever wanted to fetch information about a Kubernetes cluster directly from Postgres? Now you can!

Let me play with it!

master is pushed to Docker Hub by Travis. You can run it with:

docker run -v <path-to-kubeconfig>:/kubeconfig --rm --name=k8s_fdw liztio/k8s_fdw:latest

Then you can get a Postgres shell with:

docker exec -ti k8s_fdw /bin/sh -c 'psql --user postgres'

Examples

Execute following SQL statements to load an extension:

CREATE EXTENSION IF NOT EXISTS k8s_fdw;

CREATE SERVER IF NOT EXISTS kind
  FOREIGN DATA WRAPPER k8s_fdw
  OPTIONS (kubeconfig '/kubeconfig');

CREATE FOREIGN TABLE IF NOT EXISTS pods (
  name      text OPTIONS (alias 'metadata.name')
, namespace text OPTIONS (alias 'metadata.namespace')
, container text OPTIONS (alias '{.spec.containers[0].image}')
, labels   jsonb OPTIONS (alias 'metadata.labels')
)
  SERVER kind
  OPTIONS (
    namespace 'kube-system'
  , apiVersion 'v1'
  , kind 'Pod'
  );

And finally, run the query:

SELECT * FROM pods;

Build

This project uses [bazel][https://bazel.build] as a build system. To just build the SO file:

bazel build //src:libgo_fdw.so

Install

To install an extension just copy it to your Postgres installation. At the end of the build process you'll see following lines:

/usr/bin/install -c -m 755 ./bazel-bin/src/libgo_fdw.so  '/usr/lib/postgresql/10/lib/go_fdw.so'
/usr/bin/install -c -m 644 .//k8s_fdw.control '/usr/share/postgresql/10/extension/'
/usr/bin/install -c -m 644 .//k8s_fdw--0.1.sql  '/usr/share/postgresql/10/extension/'

Docker

You can execute the same commands to install an extension locally.

Testing

Hacking

An official documentation for FDW callbacks can be found here. And the documentation for Postgres sources is here.

Docker Images

Bazel can create and install docker images for you.

bazel run //:k8s_fdw_image

Will create an image named bazel:k8s_fdw_image. You can then run it with:

docker run -v /tmp/config:/kubeconfig --rm --name=k8s_fdw bazel:k8s_fdw_image

nealf/k8s-fdw