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Cauldron_of_Penguins's avatar
Cauldron_of_Penguins
Copper Contributor
Sep 05, 2019

Handling CSOM 429 Errors from PowerShell Scripts

I have a PowerShell script which processes a large number of lists, it *will* get 429 errors. I could put a sleep in there, but how long? Too long will make an already long-running script unnecessar...
powershell
sharepoint
Kevin_Morgan's avatar
Kevin_Morgan
Iron Contributor
Sep 05, 2019

Cauldron_of_Penguins 

 

Hope you have to get Retry-After field from catched error object.

try
{
   .......................
}
catch
{   
    Write-Host "Retry-After:" $_.Exception.Response.Headers["Retry-After"] 
}

 

Cauldron_of_Penguins's avatar
Cauldron_of_Penguins
Copper Contributor
Sep 05, 2019

Kevin_Morgan 

Hey Kevin, I put a breakpoint in my catch block. 

$_ looks good (it's the correct exception), but $_.Response is null.

 

 

Hit Line breakpoint on 'C:\Users\..\Desktop\Testing\LVT Test.ps1:44'
07:35:59 .\Desktop > $_.Exception.Response.Headers["Retry-After"]
Cannot index into a null array.
At line:1 char:1
+ $_.Exception.Response.Headers["Retry-After"]
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : NullArray
 

07:36:05 .\Desktop > $_
Exception calling "ExecuteQuery" with "0" argument(s): "The remote server returned an 
error: (429)."
At C:\Users\..\Desktop\Testing\LVT 
Test.ps1:39 char:9
+         $ctx.ExecuteQuery()
+         ~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : WebException
 

07:36:13 .\Desktop > $_.ResPonse

07:36:22 .\Desktop > $_.ResPonse -eq $null
True

07:36:44 .\Desktop >

 

 

 

I tried to get the Response details with: 

 

$streamReader = [System.IO.StreamReader]::new($_.Exception.Response.GetResponseStream())
$ErrResp = $streamReader.ReadToEnd()
$streamReader.Close()
Write-Verbose $ErrResp

 

This get me the string '429 TOO MANY REQUESTS' which might be workable to identify it as a 429 (I wonder if it will always be in English..?). I don't see the response Retry-After.

 

    • Cauldron_of_Penguins's avatar
      Cauldron_of_Penguins
      Copper Contributor
      Sep 06, 2019

      Hey Kevin_Morgan 

       

      I had seen that. I have not decorated my requests in my test script, primarily because I am trying to cause 429's there! 

      I have also not decorated the real script. I should, and will, but this only reduces the probability of receiving a 429. The process for this script (necessarily) enumerates all the libraries in the tenant and updates them. This tenant is huuuuge. 

      So I feel that, even with a well decorated script, I will still get 429s and need to handle them. 

       

      I'm looking at two options:

      1) sleep in a suitable location. How long? If I sleep too frequently and too long, the script will run much longer than necessary; If I don't sleep frequently or long enough then I don't solve the problem. MS returns the header for a good reason.

      2) Switch to REST. I believe REST will give me the headers, though my quick testing seems to be giving me 406's instead of 429's.

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