# HealthCheck
[](https://hex.pm/packages/health_check)
A very simple library used for check Elixir service if stable.
## Motivation
In our production environment, there are several Elixir services need to check their if health:
- http server
- grpc server
- pure elixir node
and used in several scenes (most of them are service discovery):
- consul/etcd/self-define
- envoy
- rolling upgrade service
For http server, we can check the port which service listen if return 200 for specific path, and this could match all scenes. But for grpc server, it is not easy match "rolling upgrade service" scene, and it's more difficult for "pure elixir node".
So, I decide to make a library.
## Interface
- enable_maint
Set current node maint status
- disable_maint
Cancel maint status for current node
- stable?
Check current if health
## Usage
### grpc/http server
For grpc and http server, the usage is very simple. Under specific path:
`/api/health`
can return different response depend on if current node stable:
```elixir
get "/health" do
conn
|> put_status(return_status(HealthCheck.stable?()))
|> json("")
end
defp return_status(true), do: :ok
defp return_status(_), do: :service_unavailable
```
And for grpc server, could do like this:
```elixir
def check(params, _stream) do
if HealthCheck.stable?() do
if params.service == "just like you want" do
Grpc.Health.V1.HealthCheckResponse.new(%{status: :SERVING})
else
raise GRPC.RPCError, status: :not_found
end
else
Grpc.Health.V1.HealthCheckResponse.new(%{status: :NOT_SERVING})
end
end
```
### command line
For command line, before use `health_check` I have to assume you use release tool (just like: [distillery](https://github.com/bitwalker/distillery)) for you Elixir service.
Just because it is very simple if use release tool to call Elixir node internal functions from command line.
you can use:
```
$ ./bin/your_elixir_node_name rpc Elixir.HealthCheck enable_maint
```
to set the current node maint status.
similarly, you can use:
```
$ ./bin/your_elixir_node_name rpc Elixir.HealthCheck disable_maint
```
to cancel maint status for the current node.
and, you can use:
```
$ ./bin/your_elixir_node_name rpc Elixir.HealthCheck stable?
```
check the current node if stable.
### distributed node
In distributed environment, some Elixir node need to check the remote node if stable.
you can use:
```elixir
true == :rpc.call(remote_node, HealthCheck, :stable?, [], 1_000)
```
to check the remote node if stable.
Based on this, it's very simple to check the service if stable for different scenes.
## License
