AccountAfterUpdate.trigger

// AccountAfterUpdate.trigger
trigger AccountAfterUpdate on Account (after update) {
    if (!Territory2Controller.inFutureContext) {
        List<Id> accountIds = new List<Id>();
        for (Account acc : Trigger.new) {
            accountIds.add(acc.Id);
        }
        Territory2Controller.runTerritoryRules(accountIds, UserInfo.getSessionId());
    }
}



// Territory2Controller.cls

public with sharing class Territory2Controller {

    public static boolean inFutureContext = false;

    @Future(Callout=true)
    public static void runTerritoryRules(List<Id> accountIds, String sessionId) {
        Territory2Controller.inFutureContext = true;
        List<String> accountTags = new List<String>();
        String accountTag = '';

        String requestTemplate = '';
        ...
        ...
        ...
        HttpRequest request = new HttpRequest();
        String urlString = System.Url.getSalesforceBaseUrl().toExternalForm()
                + '/services/Soap/u/43.0/' + UserInfo.getOrganizationId();
        request.setEndpoint(urlString);
        request.setMethod('POST');
        request.setHeader('Content-Type', 'text/xml');
        request.setBody(requestTemplate);
        String s = String.valueOf(new Http().send(request).getBody());
    }
}