How to implement retry callout logic in batch class?

Question

I am trying to write a batch class which retries to do the callout 3 times if a record failed to send to a web service.

global class LeadExporterFailedRetry implements Database.Batchable<Sobject>,Database.allowscallouts{

global  String jobName;
global Boolean bAutoSchedule = false;
global Integer DEFAULT_RESTART_TIME = 1;
global Integer restartTimeInMins = DEFAULT_RESTART_TIME;
global set<Id> leadIds = new set<Id>();
global set<Id> leadInfoIds = new set<Id>();
global Map<Id,Lead> IdToLeadMap = new Map<Id,Lead>();//Map to hold the leads
global Map<Id,LeadInfo__c> IdToLeadInfoMap = new Map<Id,LeadInfo__c>();//Map to hold the leadinfos

/*
    @Param: Jobname -
    @Param: iRestartTimeInMins - time in minutes after which job should restart itself.
*/
/*
public LeadExporterFailedRetry(String theJobName, Integer iRestartTimeInMins) {

    jobName = theJobName;       
    if(iRestartTimeInMins > 0){
        restartTimeInMins = iRestartTimeInMins;
        bAutoSchedule = true;
    }
}
*/
global database.QueryLocator start(database.BatchableContext bc){

    return Database.getQueryLocator('select Contact__c,Lead__c,Lead_Exporter__c,LeadInfo__c,Response_Code__c,Result__c,Sent_Time__c,Retry_Count__c,Zip_Code__c from Lead_Export_Result__c where Result__c=\'Failed\' and Retry_Count__c !=3 and id =\'a0p4B000000MHEH\'');
}
global void execute(database.BatchableContext bc,list<Lead_Export_Result__c> scope){

   list<Lead_Export_Result__c> LEResults = scope;

    For(Lead_Export_Result__c LeTemp : scope){

        if(LeTemp.Lead__c != null)
            leadIds.add(LeTemp.Lead__c);   

        if(LeTemp.LeadInfo__c != null)
            leadInfoIds.add(LeTemp.LeadInfo__c);
    }

    list<lead> LeadList = [select id,Do_Not_export__c,email,LastName,FirstName,Primary_Phone__c from Lead where id in :leadIds];

    list<LeadInfo__c> LeadInfoList = [select id,Message__c,Lead_Address__c,Lead_City__c,Lead_State__c,Lead_Zip_Code__c from LeadInfo__c where id in :leadInfoIds];

    for(Lead leadTemp: LeadList){
        IdToLeadMap.put(leadTemp.id, leadTemp);
    }

    for(LeadInfo__c leadInfoTemp: LeadInfoList){
        IdToLeadInfoMap.put(leadInfoTemp.id, leadInfoTemp);
    }

    for(Lead_Export_Result__c LeVar: LEResults){

        Lead leadP = IdToLeadMap.get(LeVar.Lead__c);
        LeadInfo__c LeadinfoP = IdToLeadInfoMap.get(LeVar.LeadInfo__c);
        String payload = MovotoUtilities.buildExportRealTimePayload(LeVar.Lead_Exporter__c, leadP, LeadinfoP); 
        system.debug('lead id:'+leadP.id);
        while(LeVar.Result__c != 'Success' || (LeVar.Retry_Count__c != 1)){
            system.debug('inside retry');
            Lead_Export_Result__c Expores =  SendOutboundMessage.LeadExporter( LeadinfoP.Id+'',  '',  leadP.Id+'', LeVar.Lead_Exporter__c+'', false, UserInfo.getsessionId(),UserInfo.getuserId(),  payload);
            if(Expores.Result__c == 'Failed'){
                if(LeVar.Retry_Count__c == null)
                        LeVar.Retry_Count__c = 0;
                LeVar.Retry_Count__c = LeVar.Retry_Count__c + 1;
            }
            else  
                LeVar.Result__c = 'Success';             
        }
        if(LeVar.Result__c == 'Failed'){
            leadP.Do_Not_export__c = true;
            leadP.status = 'Lead Export Failure';
        }
    } 

    if(LEResults !=null && !LEResults.isEmpty()){

        update LEResults;
    }
}

 global void finish(database.BatchableContext bc){

 }
}

I am getting the error that "You have uncommitted work pending. Please commit or rollback before calling out". need a help on this

Answer 1

The message would seem to indicate that you are attempting to do DML operations before callouts. In your code I only see the one DML statement and it's at the end of the execute method. So I must conclude that one of your other methods such as MovotoUtilities.buildExportRealTimePayload or SendOutboundMessage.LeadExporter contains DML statements.

So you'll want to find a way to refactor that avoids doing any DML until all callouts are done. It could also do some DML asynchronously (i.e. via Queueable) but there's a cap on how many of those a batch can call, so you'd need to bulkify the method you're calling.