Invoke-ClientContextWithRetry.ps1 - Executes a client context query, with logic to handle service throttling and other transient errors.

Invoke-ClientContextWithRetry.ps1

function Invoke-ClientContextWithRetry
{
    [cmdletbinding()]
    param
    (
        [parameter(Mandatory=$true)][Microsoft.SharePoint.Client.ClientContext]$ClientContext,
        [parameter(Mandatory=$false)][int]$Delay = 10,
        [parameter(Mandatory=$false)][int]$RetryAttempts = 5
    )

    begin
    {
        $executions = 1 
    }
    process
    {
        do
        {
            try
            {
                $ClientContext.ExecuteQuery()
                return
            }
            catch [System.Net.WebException]
            {
                $response = $_.Exception.Response -as [System.Net.HttpWebResponse]
                $statusCode = [int]$response.StatusCode

                Write-Verbose "Full Exception Details: $($_.Exception)"
                Write-Verbose "Status Code: $statusCode"

                # 429 and 503 are throttling exceptions
                if( $response -and ($statusCode -eq 429 -or $statusCode -eq 503) )
                {
                    Write-Warning -Message "Execution attempt $executions was throttled, trying again in $Delay seconds."

                    $executions++
                    Start-Sleep -Seconds $Delay
                }
                # seeing erroneous 403 exceptions that require a retry
                elseif( $response -and $statusCode -eq 403 )                
                {
                    Write-Warning -Message "Execution attempt $executions was forbidden, trying again in $Delay seconds."

                    $executions++
                    Start-Sleep -Seconds $Delay
                }
                elseif( $response -and $statusCode -eq 404 )                
                {
                    Write-Warning -Message "A site with the URL $($ClientContext.Url) was not found in the tenant."
                    return
                }
                else                
                {
                    Write-Error -Message "An error occurred connecting to $($ClientContext.Url). Exception: $($_.Exception.Message)"
                    return
                }
            }
            catch
            {
                Write-Verbose "Full Exception Details: $($_.Exception)"

                if( $_.Exception.Message -match "Access to this Web site has been blocked")
                {
                    Write-Warning -Message "Cannot contact site at the specified URL $ContextUrl. Access to this Web site has been blocked." 
                    return
                }

                Write-Error -Message "Unexpected execution exception: $($_.Exception.Message)" 
            }
        }
        while( $executions -le $RetryAttempts )


        Write-Error -Message "$($MyInvocation.MyCommand.Name) - Exceeded retry threshold for context URL: $($ClientContext.Url)"
    }
    end
    {
    } 
}