Change session transfer duration unit (#5338)

* Change session transfer duration unit

* Update buckets

* Change metric name to start clean

Author: aerosol

lib/plausible/session/transfer.ex

@@ -18,7 +18,7 @@ defmodule Plausible.Session.Transfer do
   @cmd_dump_cache :get
   @cmd_takeover_done :done
 
-  def telemetry_event, do: [:plausible, :sessions, :transfer]
+  def telemetry_event, do: [:plausible, :sessions, :takeover]
 
   @doc """
   Starts the `:sessions` transfer supervisor.

lib/plausible/telemetry/plausible_metrics.ex

@@ -83,9 +83,19 @@ defmodule Plausible.PromEx.Plugins.PlausibleMetrics do
           metric_prefix ++ [:sessions, :transfer, :duration],
           event_name: Plausible.Session.Transfer.telemetry_event(),
           reporter_options: [
-            buckets: [100, 250, 500, 750, 1000, 2500, 5000, 7500, 10_000]
+            buckets: [
+              100_000,
+              250_000,
+              500_000,
+              750_000,
+              1_000_000,
+              2_500_000,
+              5_000_000,
+              7_500_000,
+              10_000_000
+            ]
           ],
-          unit: {:native, :millisecond},
+          unit: {:native, :microsecond},
           measurement: :duration
         )
       ]