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Sample log search alert queries that include ADX and ARG

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A log search alert rule monitors a resource by using a Log Analytics query to evaluate logs at a set frequency. You can include data from Azure Data Explorer and Azure Resource Graph in your log search alert rule queries.

This article provides examples of log search alert rule queries that use Azure Data Explorer and Azure Resource Graph. For more information about creating a log search alert rule, see Create a log search alert rule.

Queries that check virtual machine health

This query finds virtual machines marked as critical that haven't had a heartbeat in the last 2 minutes.

    arg("").Resources
    | where type == "microsoft.compute/virtualmachines"
    | summarize LastCall = max(case(isnull(TimeGenerated), make_datetime(1970, 1, 1), TimeGenerated)) by name, id
    | extend SystemDown = case(LastCall < ago(2m), 1, 0)
    | where SystemDown == 1

This query finds virtual machines marked as critical that had a heartbeat more than 24 hours ago, but that haven't had a heartbeat in the last 2 minutes.

{
    arg("").Resources
    | where type == "microsoft.compute/virtualmachines"
    | where tags.BusinessCriticality =~ 'critical' and subscriptionId == '123-456-123-456'
    | join kind=leftouter (
    Heartbeat
    | where TimeGenerated > ago(24h)
    )
    on $left.name == $right.Resource
    | summarize LastCall = max(case(isnull(TimeGenerated), make_datetime(1970, 1, 1), TimeGenerated)) by name, id
    | extend SystemDown = case(LastCall < ago(2m), 1, 0)
    | where SystemDown == 1
}

Query that filters virtual machines that need to be monitored

   {
    let RuleGroupTags = dynamic(['Linux']);
    Perf | where ObjectName == 'Processor' and CounterName == '% Idle Time' and (InstanceName in ('_Total,'total'))
    | extend CpuUtilisation = (100 - CounterValue)   
    | join kind=inner hint.remote=left (arg("").Resources
        | where type =~ 'Microsoft.Compute/virtualMachines'
    | project _ResourceId=tolower(id), tags) on _ResourceId
    | project-away _ResourceId1
    | where  (tostring(tags.monitorRuleGroup) in (RuleGroupTags)) 
}

Query that finds resources with certificates that are going to expire within 30 days

{
    arg("").Resources
    | where type == "microsoft.web/certificates"
    | extend ExpirationDate = todatetime(properties.expirationDate)
    | project ExpirationDate, name, resourceGroup, properties.expirationDate
    | where ExpirationDate < now() + 30d
    | order by ExpirationDate asc
}

Query that alerts when a new resource is created in the subscription

{
    arg("").resourcechanges
    | extend changeTime = todatetime(properties.changeAttributes.timestamp), 
    changeType = tostring(properties.changeType),targetResourceType = tostring(properties.targetResourceType),
    changedBy = tostring(properties.changeAttributes.changedBy),
    createdResource = tostring(properties.targetResourceId)
    | where changeType == "Create" and changeTime <ago(1h)
    | project changeTime,createdResource,changedBy

}

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