Why is my rule that reacts on event "After updating an existing user account" firing twice?

Question

I have a rule that e-mails me if a user updates a value of a field on their profile (this value is the name that is displayed for that user on the site; I e-mail changes to the names to make sure no one changes their name to something insulting, etc.)

However, the rule fires twice for a reason I don't understand.

The rule has a condition compare data value in which it checks to see if the account-unchanged and account variables have different values for the same field. When I look at the rules debug log, I see that during Reacting on event 'After updating an existing user account', there is a second Reacting on event 'After updating an existing user account' within the first, and so the rule gets triggered twice. How can I prevent this from happening?

If it helps, here is the rule:

{ "rules_notify_if_user_changes_name" : {
    "LABEL" : "Notify if user changes name",
    "PLUGIN" : "reaction rule",
    "REQUIRES" : [ "rules" ],
    "ON" : [ "user_update" ],
    "IF" : [
      { "NOT data_is" : {
          "data" : [ "account-unchanged:field-acc-displayname" ],
          "value" : [ "account:field-acc-displayname" ]
        }
      }
    ],
    "DO" : [
      { "mail" : {
          "to" : "myemail@myemail.com",
          "subject" : "[account-unchanged:field-acc-displayname] changed name to [account:field-acc-displayname] (UID: [account:uid])",
          "message" : "[account-unchanged:field-acc-displayname] changed name to [account:field-acc-displayname] (UID: [account:uid])",
          "language" : [ "" ]
        }
      }
    ]
  }
}

Answer 1

It sounds like some other module code is calling a user_save on hook_user_update triggering the rules event a second time.

Answer 2

It is a not ideal solution (meaning performance, rule still run twice) but IT WORKS!! I saw on drupal.org a patch for node module in core and did not like it. This solution need no code or patches. Only once my data is saved, I have a lot of modules enabled, so is very difficult to know which one is causing rules trigger twice. I added a hidden "Boolean Trick field" on my contentype (should work also on user bundle) and set it default value to true, you need conditional rules module to do it, and I did the following in rules, simple but effective:

Answer 3

If you're able to execute PHP in your rules you can do this as a condition:

//lets see when we last changed this user $vnam = $account->uuid.":last_saved"; $retVal = TRUE; $t_changed = variable_get($vnam,0); $now = time(); variable_set($vnam,$now); //within 10 seconds, no second trigger if (($now - $t_changed) <= 10){ $retVal = FALSE; } return $retVal; // done saving changed timestamp