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Herald

Herald means a messanger.
It is a simple app to test pub/sub of backing emqx MQTT broker.
Herald is written with elio library.

herald.concept




Prerequisites

⚙️ Setting Go on WSL

Covers Go settings on WSL.


⚙️ Setting up elio

Before start, set up elio project.

git clone https://github.com/cppis/elio && cd elio
go mod vendor
export ELIO_ROOT=$(pwd)

Now, $ELIO_ROOT is the project root path.


⚙️ Setting Docker on WSL

Covers Docker settings on WSL.


⚙️ Setting Kubernetes on WSL

Covers Kind+Skaffold settings on WSL for continuous developing a Kubernetes-native app.


⚙️ Setting Service Ports

Covers the port settings for the Kubernetes Service.




Running app on Host

You can easily run a Herald container on the host (without MQTT Broker):

herald.container


🚀 Using go run

To run Herald service, run the following command:

HERALD_IN_URL="0.0.0.0:7003" go run ./app/herald

You can change the listening url of service Herald by changing
environment variable HERALD_IN_URL.


🚀 Using Docker

To run Herald container, run the following command:

docker run -d -e HERALD_IN_URL="0.0.0.0:7003" -p 7003:7003 --name herald cppis/herald:latest

To kill Herald container, run the following command:

docker rm -f herald




Running app on Kubernetes

You can easily run a Herald + emqx(MQTT Broker) chart on the kubernetes cluster.

herald.chart


If the kubernetes cluster does not exist, Follow the next step Create a Kind cluster.
If you have, Follow the next step 'Using Helm' or 'Using Skaffold'.


🚀 Create a Kind cluster

To create a kind, run the following command:

kind create cluster --config app/assets.k8s/kind.cluster.yaml --name elio

To check if the kind cluster is up and running, run the following command:

kubectl config current-context
  kind-elio

🚀 Using Helm

To deploy using helm, run the following command:

helm upgrade --install herald app/herald/assets.k8s/helm

helm uninstall herald


🚀 Using Skaffold

To run herald using Skaffold,
run the following command in the Project root directory:

skaffold -f app/herald/assets.k8s/skaffold.yaml dev

To debugging Skaffold, use option -vdebug.

To change detection triggered to manual mode, use option --trigger=manual.

Or, to run Herald in debugging mode using Skaffold, run the following command:

skaffold -f app/herald/assets.k8s/skaffold.yaml debug




Testing app

You can test echo easily by using telnet.

app protocol is custom t2p like http.
procotol header is separated by newline(\n or \r\n).
And packet delimiter is double newline(\n\n or \r\n\r\n).


🚀 connect

connect to echo using telnet

telnet localhost 7003

🚀 echo

echo message

echo<newline>
{message}<newline><newline>

🚀 sub

subcribe to topic

sub<newline>
{topic}<newline><newline>

🚀 unsub

unsubcribe from topic

unsub<newline>
{topic}<newline><newline>

🚀 pub

publish message to topic

pub<newline>
{topic}<newline>
{message}<newline><newline>




Ending app

🏁 Kubernetes resource cleanup

After running skaffold run or skaffold deploy and deploying your app to a cluster, running skaffold delete will remove all the resources you deployed. Cleanup is enabled by default, it can be turned off by --cleanup=false


🏁 Ctrl + C

When running skaffold dev or skaffold debug, pressing Ctrl+C (SIGINT signal) will kick off the cleanup process which will mimic the behavior of skaffold delete. If for some reason the Skaffold process was unable to catch the SIGINT signal, skaffold delete can always be run later to clean up the deployed Kubernetes resources.

To enable image pruning, you can run Skaffold with both --no-prune=false and --cache-artifacts=false:

skaffold dev --no-prune=false --cache-artifacts=false

🏁 Delete a Kind cluster

To delete a Kind cluster, run the following command:

kind delete cluster --name elio




Troubleshooting

Shows some tips to solve the problem.