gRCP Health Check with Powershell

Question

Hello.
I am checking periodically gRPC health of several microservices, every two seconds, it is working since I got the response they are serving, the output is { "status": "SERVING" }

 while ($true) {grpcurl -d '{ \"service1\": \"name1\" }' -H "authorization: key key"  host1:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service2\": \"name2\" }' -H "authorization: key key"  host2:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service3\": \"name3\" }' -H "authorization: key key"  host3:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service4\": \"name4\" }' -H "authorization: key key"  host4:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service5\": \"name5\" }' -H "authorization: key key"  host5:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service6\": \"name6\" }' -H "authorization: key key" host6:port grpc.health.v1.Health/Check>> grpcurl -d '{ \"service7\": \"name7\" }' -H "authorization: key key" host7:port grpc.health.v1.Health/Check;start-sleep 2}

Now I need a notification if the output is not "SERVING" while the code keeps running in a loop, how can I achieve this?

Please note, one or more service can fail but other can be ok so notification should only about the ones are not answering "SERVING", thanks,

Answer 1

There are ways to make this more efficient, and to also handle those times when grpcurl doesn't return anything in STDOUT (e.g. the host cannot be contacted, authentication fails, etc.) but writes an error message to STDERR, but I'll leave that part up to you,

Give this one a try:

function Serving{
    param(
        $val
    )
    if ($val -isnot [array]){
        return $false
    }
    if ($val.count -ne 3){
        return $false
    }
    Try{
        $p = $val -join "" | ConvertFrom-Json -ErrorAction STOP
        if ($p.status -eq 'serving'){
            $true
        }
        else{
            $false
        }
    }
    Catch{
        Write-Host "'$p' is not JSON"
        $false
    }
}
while ($true) {
    $beep = $false
    [array]$response = grpcurl -d '{ \"service1\": \"name1\" }' -H "authorization: key key"  host1:port grpc.health.v1.Health/Check
    if (-Not (Serving $response)){
        Write-Host "Service1 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service2\": \"name2\" }' -H "authorization: key key"  host2:port grpc.health.v1.Health/Check
    if (-Not (Serving $response)){
        Write-Host "Service2 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service3\": \"name3\" }' -H "authorization: key key"  host3:port grpc.health.v1.Health/Check
    if (-Not (Serving $response)){
        Write-Host "Service3 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service4\": \"name4\" }' -H "authorization: key key"  host4:port grpc.health.v1.Health/Check 
    if (-Not (Serving $response)){
        Write-Host "Service4 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service5\": \"name5\" }' -H "authorization: key key"  host5:port grpc.health.v1.Health/Check
    if (-Not (Serving $response)){
        Write-Host "Service5 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service6\": \"name6\" }' -H "authorization: key key"  host6:port grpc.health.v1.Health/Check
    if (-Not (Serving $response)){
        Write-Host "Service6 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    [array]$response = grpcurl -d '{ \"service7\": \"name7\" }' -H "authorization: key key"  host7:port grpc.health.v1.Health/Check 
    if (-Not (Serving $response)){
        Write-Host "Service7 isn't serving" -ForegroundColor Yellow
        $beep = $true
    }
    if ($beep){
        [console]::beep(500, 300)
    }
    Start-Sleep 2 
}

Answer 2

If the response from grpcurl is JSON, then this should get you the correct output:

while ($true) {
    $responses = @()
    $responses += grpcurl -d '{ \"service1\": \"name1\" }' -H "authorization: key key"  host1:port grpc.health.v1.Health/Check
    $responses += grpcurl -d '{ \"service2\": \"name2\" }' -H "authorization: key key"  host2:port grpc.health.v1.Health/Check
    $responses += grpcurl -d '{ \"service3\": \"name3\" }' -H "authorization: key key"  host3:port grpc.health.v1.Health/Check 
    $responses += grpcurl -d '{ \"service4\": \"name4\" }' -H "authorization: key key"  host4:port grpc.health.v1.Health/Check 
    $responses += grpcurl -d '{ \"service5\": \"name5\" }' -H "authorization: key key"  host5:port grpc.health.v1.Health/Check 
    $responses += grpcurl -d '{ \"service6\": \"name6\" }' -H "authorization: key key"  host6:port grpc.health.v1.Health/Check 
    $responses += grpcurl -d '{ \"service7\": \"name7\" }' -H "authorization: key key"  host7:port grpc.health.v1.Health/Check 
    $ctr = 0
    [array]$bad = @()
    ForEach ($response in $responses) {
        $ctr++
        $pp = $response | ConvertFrom-Json
        if ($pp.status -ne 'SERVING') {
            $bad += $ctr
        }      
    }
    if ($bad.count -gt 0) {
        [console]::beep(500, 300)
        $bad |
            ForEach-Object {
                Write-Host "host$($_): $($responses[$_ - 1])" -ForegroundColor Yellow
            }

    }
    Start-Sleep 2 
}

Answer 3

I am getting an error, I guess is due to expects a string and the output is

host1: {
host2: "status": "SERVING"
host3: }

• $pp = $response | ConvertFrom-Json
• ~~~~~~~~~~~~~~~~
• CategoryInfo : NotSpecified: (:) [ConvertFrom-Json], ArgumentException
• FullyQualifiedErrorId : System.ArgumentException,Microsoft.PowerShell.Commands.ConvertFromJsonCommand

Answer 4

I am sure, the output is always one of these four (and expect to do and action when is not "SERVING"):

host: {
host: "status": "SERVING"
host: }

host: {
host: "status": "NOT_SERVING"
host: }

host: {
host: "status": "UNKNOWN"
host: }

host: {
host: "status": "SERVICE UNKNOWN "
host: }

Answer 5

wondering why ConvertFrom-Json fails it this ouput are in JSON format, is due to there are 3 lines of each output answer? and does not match the pattern?