Purge Old Azure Log Analytics Ingested Data

This article is based on Microsoft document:

Assuming you have a Log Analytics workspace in a resource group, you can call the API url:

POST https://management.azure.com/subscriptions/your-subsc-ription-id/resourceGroups/yor-resource-group-rg/providers/Microsoft.OperationalInsights/workspaces/your-log-analytics-name/purge?api-version=2020-08-01

You need to pass Authorization as Bearer token in the header.

The body of the POST request will contain a filter and a table like this:

  "table": "Heartbeat",
  "filters": [
      "column": "TimeGenerated",
      "operator": "<",
      "value": "2021-10-09T00:00:00"

The response will have a header like

x-ms-status-location: https://management.azure.com/subscriptions/{subscriptioId}/resourceGroups/{resourceGroupName}/providers/microsoft.operationalinsights/workspaces/{workspaceName}/operations/purge-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx?api-version=2017-01-01-preview

This is a GET url to send and see the status of the operation. This Url is also given as the body of the first POST request.

The status will be something like:

    "status": "pending"

Tip: You can find the records to delete using a simple query like this:

| where TimeGenerated > ago(32d)
| summarize count() by bin(TimeGenerated, 1d)

| where TimeGenerated > ago(32d)
| summarize count() by bin(TimeGenerated, 1d)

Tip To Log

We often like to know what happens in a procedure and also we like to figure out if we see something in the log, where in the code it happened. Therefore it is handy to start and end each procedure with log. To do this we can put a small generic code like this

Trace.WriteLine("Beginning with " + System.Reflection.MethodInfo.GetCurrentMethod().Name);

it will work just fine

JavaScript Debug Log

Date: Monday, 18 Dec 2006 14:08
By Bret Taylor, December 3, 2006

Even with the most advanced debugging tools, every program requires a little “printf debugging”: run your program, print out state as it executes, and visually verify that everything is working properly. Unfortunately, there is no built in console to print debug messages to in JavaScript, forcing many JavaScript programmers to revert to calling alert() in their code. alert is completely infeasible for a function that gets called a lot, as it halts execution until you click an OK button. This recipe creates a simple debug log window that does not halt execution:

function log(message) {
if (!log.window_ log.window_.closed) {
var win = window.open("", null, "width=400,height=200," +
"scrollbars=yes,resizable=yes,status=no," +
if (!win) return;
var doc = win.document;
doc.write("<html><head><title>Debug Log</title></head>" +
log.window_ = win;
var logLine = log.window_.document.createElement("div");

To print log messages, you just call log() within your code:

for (var i = 0; i < 10; i++) {
log("This is log message #" + i);

When you push your code to production, you can just replace the definition of log with an empty function so your users will not see your debug messages.

See the example