functions/Test-DbaNetworkLatency.ps1

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Function Test-DbaNetworkLatency {
<#
 .SYNOPSIS
 Tests how long a query takes to return from SQL Server
 
 .DESCRIPTION
 This function is intended to help measure SQL Server network latency by establishing a connection and making a simple query. This is a better alternative
 than ping because it actually creates the connection to the SQL Server, and times not ony the entire routine, but also how long the actual queries take vs
 how long it takes to get the results.
 
 By default, this command will execute "SELECT TOP 100 * FROM INFORMATION_SCHEMA.TABLES" three times.
  
 It will then output how long the entire connnection and command took, as well as how long *only* the execution of the command took.
  
 This allows you to see if the issue is with the connection or the SQL Server itself.
 
 .PARAMETER SqlInstance
 The target SQL Server instance.
 
 .PARAMETER SqlCredential
 Optional alternative Windows or SQL Login
  
 .PARAMETER Query
 Specifies the query to be executed. By default, "SELECT TOP 100 * FROM INFORMATION_SCHEMA.TABLES" will be executed on master. To execute in other databases, use fully qualified table names.
 
 .PARAMETER Count
 Specifies how many times the query should be executed. By default, the query is executed three times.
 
 .PARAMETER WhatIf
 Shows what would happen if the command were to run. No actions are actually performed.
 
 .PARAMETER Confirm
 Prompts you for confirmation before executing any changing operations within the command.
 
 .PARAMETER Silent
 Use this switch to disable any kind of verbose messages
 
 .NOTES
 Tags: Performance, Network
 Website: https://dbatools.io
 Copyright: (C) Chrissy LeMaire, clemaire@gmail.com
 License: GNU GPL v3 https://opensource.org/licenses/GPL-3.0
 
 .LINK
 https://dbatools.io/Test-DbaNetworkLatency
 
 .EXAMPLE
 Test-DbaNetworkLatency -SqlInstance sqlserver2014a, sqlcluster
 
 Times the roundtrip return of "SELECT TOP 100 * FROM INFORMATION_SCHEMA.TABLES" on sqlserver2014a and sqlcluster using Windows credentials.
 
 .EXAMPLE
 Test-DbaNetworkLatency -SqlInstance sqlserver2014a -SqlCredential $cred
 
 Times the execution results return of "SELECT TOP 100 * FROM INFORMATION_SCHEMA.TABLES" on sqlserver2014a using SQL credentials.
 
 .EXAMPLE
 Test-DbaNetworkLatency -SqlInstance sqlserver2014a, sqlcluster, sqlserver -Query "select top 10 * from otherdb.dbo.table" -Count 10
 
 Times the execution results return of "select top 10 * from otherdb.dbo.table" 10 times on sqlserver2014a, sqlcluster, and sqlserver using Windows credentials.
 
#>

    [CmdletBinding()]
    [OutputType([System.Object[]])]
    param (
        [parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [Alias("ServerInstance", "SqlServer")]
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]$SqlCredential,
        [string]$Query = "select top 100 * from INFORMATION_SCHEMA.TABLES",
        [int]$Count = 3,
        [switch]$Silent
    )
    process {
        foreach ($instance in $SqlInstance) {
            try {
                $start = [System.Diagnostics.Stopwatch]::StartNew()
                $currentcount = 0
                try {
                    Write-Message -Level Verbose -Message "Connecting to $instance"
                    $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $sqlcredential
                }
                catch {
                    Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue
                }
                
                do {
                    
                    if (++$currentcount -eq 1) {
                        $first = [System.Diagnostics.Stopwatch]::StartNew()
                    }
                    
                    $null = $server.Query($query)
                    if ($currentcount -eq $count) {
                        $last = $first.elapsed
                    }
                }
                while ($currentcount -lt $count)
                
                $end = $start.elapsed
                
                $totaltime = $end.TotalMilliseconds
                $average = $totaltime / $count
                
                $totalwarm = $last.TotalMilliseconds
                if ($Count -eq 1) {
                    $averagewarm = $totalwarm
                }
                else {
                    $averagewarm = $totalwarm / ($count - 1)
                }
                
                
                [PSCustomObject]@{
                    ComputerName = $server.NetName
                    InstanceName = $server.ServiceName
                    SqlInstance = $server.DomainInstanceName
                    Count = $count
                    Total = [prettytimespan]::FromMilliseconds($totaltime)
                    Avg = [prettytimespan]::FromMilliseconds($average)
                    ExecuteOnlyTotal = [prettytimespan]::FromMilliseconds($totalwarm)
                    ExecuteOnlyAvg = [prettytimespan]::FromMilliseconds($averagewarm)
                } | Select-DefaultView -Property ComputerName, InstanceName, SqlInstance, 'Count as ExecutionCount', Total, 'Avg as Average', ExecuteOnlyTotal, 'ExecuteOnlyAvg as ExecuteOnlyAverage' #backwards compat
            }
            catch {
                Stop-Function -Message "Error occurred: $_" -InnerErrorRecord $_ -Continue
            }
        }
    }
    end {
        Test-DbaDeprecation -DeprecatedOn "1.0.0" -Silent:$false -Alias Test-SqlNetworkLatency
    }
}