This is a short tutorial describing how to monitor your Kubernetes cluster container logs using Loki stack. But why? Because it is easier to view, filter your logs in Grafana and to store them persistently in Loki rather than viewing them in a terminal.
Let’s get started! Assuming you already have Microk8s installed, enable the following addons:
You can enable an add-on by running microk8s enable. Ex: microk8s enable dns
addons:
enabled:
dns # CoreDNS
ha-cluster # Configure high availability on the current node
metrics-server # K8s Metrics Server for API access to service metrics
storage # Storage class; allocates storage from host directory
Note: Microk8s comes with a bundled kubectl and helm3. Just run microk8s kubectl or microk8s helm3. If you want to use your host kubectl you can configure it via: microk8s config > ~/.kube/config.
Warning: Be extra careful when running the microk8s config > ~/.kube/config command because it will overwrite the old config file.
Then proceed by installingLoki. Loki will store all the logs using object storage. This is efficient but the trade-off is that you can’t do complex aggregations and searches against your data. We are going to install Loki for exploration purposes but if you’re looking for a production ready version, check out the loki distributed helm chart.
Run the following helm commands to install Loki. You may want to install helm or use microk8s helm3 command.
You should get the following pods and services by running kubectl get pods and kubectl get services:
NAME READY STATUS RESTARTS AGE
loki-0 1/1 Running 0 9m8s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.152.183.1 <none> 443/TCP 54m
loki-headless ClusterIP None <none> 3100/TCP 9m23s
loki ClusterIP 10.152.183.187 <none> 3100/TCP 9m23s
Now, we can safely install Promtail. Promtail will import all the container logs into Loki and it should work auto-magically by auto-discovering all the pods that are running inside your cluster.
Finally, we need to visualize the logs using Grafana. Install it by running the helm command and then, edit the service to change its type from ClusterIP to NodePort.
Changing the service type to NodePort will allow you to visit Grafana in your browser without the need of adding an ingester.
❗❗To use vscode as the default editor export the following environment variable: KUBE_EDITOR=code -w
helm install grafana grafana/grafana
kubectl edit service/grafana
# Change metadata.spec.type to NodePort
# Grab the service's port using kubectl get services and look for 32204:
# grafana NodePort 10.152.183.84 <none> 80:32204/TCP 6d
Note: If you’re on Windows to access the service you will need to run kubectl cluster-info and use the IP address of the cluster. On Linux you should be able to access http://localhost:32204.
kubectl cluster-info
Kubernetes control plane is running at https://172.20.138.170:16443
To access Grafana visit: http://172.20.138.170:32204 where 32204 is the service’s NodePort.
Grab your Grafana admin password by following the instructions from the helm notes. The notes are displayed after Grafana has been installed. If you don’t have base64 on your OS check out CyberChef, it can decode base64 text.
After you’ve successfully logged in, head to Settings -> DataSources and add the Loki data source.
Head back to the Explore menu and display Loki’s logs using the Loki data source in Grafana. You can click log browser to view all available values for the app label.
Promtail should now import logs into Loki and create labels dynamically for each newly created container. If you followed along, congratulations!
In this article I will explore the topic of sharding a Mongo Database that runs on Kubernetes. Before we get started, if you want to follow along, please install the tools listed in the prerequisites section, and if you want to learn more about sharding, check out this fantastic article Sharding Pattern.
After the installation completes, save the database’s root password and replica set key. While doing this the first time I messed up and didn’t save them properly.
Run the following commands to print the password and replica set key on the command line. If you’re on Windows I have provided you with a Powershell function for base64 and if you’re on Unix don’t forget to pass –decode to base64.
kubectl get secret --namespace default my-release-mongodb-sharded -o jsonpath="{.data.mongodb-root-password}" | base64
kubectl get secret --namespace default my-release-mongodb-sharded -o jsonpath="{.data.mongodb-replica-set-key}" | base64
Sharding the Database
Verify that all your pods are running and start a shell connection to the mongos server.
To enable sharding on the database and collection, I’m going to insert some dummy data in my_data database and my_users collections. The script used to insert the data is attached at the end of this blog post.
If you’ve made it this far, congrats, you’ve enabled sharding, now let’s define some rules.
Since we’re going to use a range sharding strategy based on the key t, and I have two shards available I would like my data to be distributed in the following way:
To test the rules, use the provided python script, modify the times variable and run it with various values.
You can run db.my_users.getShardDistribution() to view the data distribution on the shards.
[direct: mongos]> db.my_users.getShardDistribution()
Shard my-mongo-mongodb-sharded-shard-0 at my-mongo-mongodb-sharded-shard-0/my-mongo-mongodb-sharded-shard0-data-0.my-mongo-mongodb-sharded-headless.default.svc.cluster.local:27017,my-mongo-mongodb-sharded-shard0-data-1.my-mongo-mongodb-sharded-headless.default.svc.cluster.local:27017
{
data: '144KiB',
docs: 1667,
chunks: 1,
'estimated data per chunk': '144KiB',
'estimated docs per chunk': 1667
}
Shard my-mongo-mongodb-sharded-shard-1 at my-mongo-mongodb-sharded-shard-1/my-mongo-mongodb-sharded-shard1-data-0.my-mongo-mongodb-sharded-headless.default.svc.cluster.local:27017,my-mongo-mongodb-sharded-shard1-data-1.my-mongo-mongodb-sharded-headless.default.svc.cluster.local:27017
{
data: '195KiB',
docs: 2336,
chunks: 3,
'estimated data per chunk': '65KiB',
'estimated docs per chunk': 778
}
Adding More Shards
To add more shards to the cluster all we need to do is run helm upgrade, if you don’t mess up the replica set key like I did it should work on the first run.
After you save the correct password and replica set key, search for the volumes that belong to the shards which have the wrong replica set key and delete them. In my case I only delete the volumes which belong to the 3rd shard that I’ve added, since counting starts from 0, I’m looking for shard2 in the name.
Shading a MongoDB can seem intimidating at first, but with some practice in advance you can do it! If sharding doesn’t work out for you, you can Convert Sharded Cluster to Replica Set, but, be prepared with some backups.
Thanks for reading 📚 and happy hacking! 🔩🔨
Base64 Powershell Function
function global:Convert-From-Base64 {
[CmdletBinding()]
[Alias('base64')]
param (
[parameter(ValueFromPipeline,Mandatory=$True,Position=0)]
[string] $EncodedText
)
process {
[System.Text.Encoding]::ASCII.GetString([System.Convert]::FromBase64String($EncodedText))
}
}
I wanted to self host my WordPress blog and for that I’ve chosen a hosting provider which I no longer recommend..
Because I’m lazy and I don’t know how to configure web servers that well I’ve used XXX’s WordPress one click install, the package installed WordPress and did the following things:
Enables the UFW firewall to allow only SSH (port 22, rate limited), HTTP (port 80), and HTTPS (port 443) access.
Sets the MySQL root password, runs mysql_secure_installation, and creates a wordpress user with the necessary permissions.
Sets up the debian-sys-maint user in MySQL so the system’s init scripts for MySQL will work without requiring the MySQL root user password.
Creates the initial WordPress configuration file to set up salt keys and allow the WordPress instance to connect to the database.
Disables XML-RPC to help prevent DDoS and other brute force attacks.
(Should you require xmlrpc, run “a2disconf block-xmlrpc” from the
terminal to disable blocking
Modifies some of PHP’s settings to increase the maximum filesize and execution time.
Configures Apache with UseCanonicalName On to mitigate CVE-2017-8295.
This is pretty convenient as you can setup a fully functional blog in less than 10 minutes, the only thing that is missing is a email configuration.
But, there’s is a problem. Apache2 is old, harder to configure, secure and maintain… I didn’t like it so I wanted to replace it with Nginx.
Initial Preparation
The first step I did was to turn off Apache2 and block the web ports via XXX’s cloud firewall. Blocking the ports is important because I don’t want to serve my initial WordPress configuration file as a txt by accident.
Now, to test that our configuration is valid we run nginx -t. You shouldn’t see any errors.
Note: You should replace the domain.tld with our own domain. I already had the Let’s Encrypt certificate on the machine, if you don’t have one then you should generate one using certbot.
Uninstalling Apache2
You should start the website and check if it’s running correctly, then you may uninstall apache2.
Nucu Labs 