Kubectl – View Pods Per Node in Kubernetes

You can use this command to view how many pods are on each node in Kubernetes using just kubect.

kubectl get pods -A -o=custom-columns=NODE:.spec.nodeName | sort | uniq -c | sort -n

In our case, we have a limit of 25 pods per node, so we have daemon sets fail to roll out if nodes already have 25 pods. So, this is helpful.

It can also be helpful when decoming nodes as you track the removal of pods from them.

Querying LDAP From Python the Easy Way

Historically, using LDAP in python could be fairly painful because you had to install python-ldap, which could be hard depending on your environment. E.g. getting that installed in a Jupyter notebook where I work proved impossible without changing the underlying docker image for the notebook.

Most search results will still lead you to python-dap, but now you can and should use python-ldap3 instead. This library is pure-python and does not have any awkward OS dependencies. So, it “just works” and is much lighter.

Here is an example of how to login with a service account and query a user via email.

import ldap3

# Put in params up top.

search_base = 'DC=foo,DC=bar'
search_filter = '(&(mail=john.doe@somecompany.com))'
attrs = ["*"]

server = ldap3.Server(LDAP_URI)
with ldap3.Connection(server, auto_bind=True, user=SERVICE_ACCOUNT, password=SERVICE_ACCOUNT_PASSWORD) as conn:
    conn.search(search_base, search_filter, attributes=attrs)

To run this, you just have to do a quick pip install as shown below. I recommend you use the latest version; but I locked it here just to remind you that locking a version is smart in most python projects. Version drift causes many production issues.

pip install ldap3==2.9.1

Using Presto/Trino CLI w/ TLS & Passwords Enabled

Not much of a post here, just recording a good way to automatically run queries in the presto cli.

./presto-cli-350-executable.jar \
      --server https://your.cluster.dns:443 \
      --catalog hive \
      --schema default \
      --client-request-timeout "10s" \
      --user "john.humphreys" \
      --password \
      --execute "select * from some_db.some_table limit 10"

If you need the password as well, you can pipe it into the command with the yes command in Linux. I also suspect there is an environment variable you can pre-set for that, but I didn’t dig in to double check.

Python – Find IPs for DNS Name

We were recently trying to find all the IPs we needed to open in a firewall from an Apache proxy. So, we had to resolve a huge number of DNS records to IPs (and relevant ports) programmatically.

I found this very elegant way of getting all the IPs for a DNS name, I hope you find it useful!

import socket
net_info = socket.getaddrinfo("stackoverflow.com", None)
ip_list = set([x[0] for x in [x[4] for x in net_info]])


{'', '', '', ''}

Using Athena From DBeaver with your IAM Role / Profile

I just spent about 30 minutes working out how to connect to DBeaver using my normal AWS credentials file / default credentials.

Thankfully I stumbled across this GitHub and it worked like a charm: https://github.com/dbeaver/dbeaver/issues/3918#issuecomment-511484596.

Here are the relevant notes (slightly modified for easier understanding):

  1. Do your normal AWS login process to refresh your credentials (in our case, we use okta + gimme_aws_creds for this).
  2. Go to driver properties on your DBeaver Athena connection and set:
    • AwsCredentialsProviderClass to com.simba.athena.amazonaws.auth.profile.ProfileCredentialsProvider
    • AwsCredentialsProviderArguments equal to the name of the profile you want to use (see ~/.aws/config to see which profiles you have) – we use “default”.
  3. Test Connection and it should work.