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Deploying to Kubernetes

Kubernetes (often abbreviated as k8s) is a common orchestration platform for automating the deployment, scaling, and management of containerized applications.

Files

This directory contains example spec yaml which can get you up and running locally in minikube or the kubernetes instance offered by Docker Desktop. They can also serve as examples to be modified for deployment to a kuberentes cluster hosted remotely.

file description
k8s.00.namespace.yml creates a godbledger namespace
k8s.01.mysql.secrets.yml creates a secret resource with MYSQL credentials
k8s.02.mysql.volume.yml creates a persistent storage volume for the mysql database
k8s.03.mysql.yml spins up mysql deployment and service
k8s.04.godbledger.yml spins up a godbledger deployment (running the godbledger app on port 8080) and service
k8s.config.toml a config file with connection details to mysql and godbledger

Couple of notes on these files:

  • they are all configured with a single namespace called godbledger

  • there is nothing here which requires these resources to be in a single namespace

  • how you organize your kubernetes deployments is up to you, but notice that there is a metadata.namespace property in each of these resources which may need to updated if you make different choices.

Apply

You can run these commands from any directory; simply adjust the pathed arguments accordingly.

  1. Build the godbledger:latest container image:

    make build-docker

  2. Create a Namespace to contain the godbledger resources:

    kubectl apply -f ./k8s.00.namespace.yml

  3. Create a Secret resource to store the mysql root password and godbledger user credentials:

    kubectl apply -f ./k8s.01.mysql.secrets.yml

  4. Create a Persistent Volume and Persistent Volume Claim to store the mysql data files:

    kubectl apply -f ./k8s.02.mysql.volume.yml

    A PersistentVolume (PV) is "a storage resource provisioned by an administrator". It maps some storage location from outside the cluster to be accessable to (i.e. mountable by) workloads running inside the cluster.

    Persistent storage is important for a database server running inside kubernetes because by design, most resources in kubernetes are ephemeral and can be destroyed and recreated automatically by the orchestration layer for a variety of reasons. By storing the msyql data files outside the ephemeral container you ensure that it is more durable and will survive across mysql pod restarts.

    A PersistentVolumeClaim (PVC) is "a user's request for and claim to a Persistent Volume".

    In this case we are creating a mysql-pv-claim claim for the mysql server to own the mysql-pv-volume volume.

  5. Create the mysql server deployment:

    kubectl apply -f ./k8s.03.mysql.yml

    This creates a mysql Deployment and mysql Service resource which is listening inside the cluster on mysql:3306.

    Root password and credentials for the godbledger user are pulled dynamically from the mysql-creds secret resources configured in step 3.

    The nodePort:30036 setting binds the service to receive traffic directed to port 30036 on the host node (i.e. localhost:30036 from your host machine).

    The godbledger user credentials and This nodePort value is configured also in k8s.config.toml to allow reporter running on the host machine to connect directly to the mysql server:

    DatabaseType = "mysql"
DatabaseLocation = "godbledger:password@tcp(localhost:30036)/ledger?charset=utf8mb4,utf8"
    Host = "127.0.0.1"
RPCPort = "30080"

  6. Create the godbledger Deployment and godbledger Service:

    kubectl apply -f ./k8s.04.godbledger.yml

    This creates a godbledger deployment and service able to receive traffic internally via cluster DNS at godbledger:8080 and over the nodePort on port 30080.

    This nodePort value is configured also in k8s.config.toml to allow ledger-cli running on the host machine to connect directly to the godbledger server:

    Host = "127.0.0.1"
RPCPort = "30080"

  7. Run apps locally and connect to your kubernetes deployments:

    • build the apps from source (if you don't have them installed locally):

      make build-native

    • ledger-cli connects to the godbledger server API over gRPC:

      ledger-cli --config ./k8s.config.toml

    • reporter connects directly to the database:

      reporter --config ./k8s.config.toml