Qfyilyi

A few situations in my app trigger a Clean up batch to run. It will process many records. In some situations multiple of such Cleanup batches will be triggered by independent user operations.

If the batch work on the same record we sometime see locking or currupt data.

Is there any means to sequence batches of the same type (class) without complicated scheduling solutions? Maybe with the FlexQueue and its Holding state?

Typical designs for this involve a temporary object. The idea is the code that kicks off the deletion inserts some sort of temporary record, and then checks if a batch is running or queued. If so, it skips calling the batch. The batch itself checks if there's any temporary records to process in its finish method, and if so, restarts the batch with a fresh query. This is similar to the Mutex idea from Aidan, but allows potential restarts of failed records; one temporary record per record to delete. Having this second object should mostly help resolve the problem, although specific versions of this might need additional work. It's kind of hard to predict ahead of time, as it depends on the types of relationships and objects involved. For example, you might want to upsert these temporary records somehow to avoid duplicates, which would slightly increase database contention but may reduce number of batches that need to run.

If the batch querry is same, then it makes sense to abort the currently running batch and execute a new one which will also pick up records of last batch.

Also, if the batch is in Holding or Queued state that means the Start method was not called and thus when start method will be called, it will also pick up new records, meaning we dont need to run a new batch.

public static void addBatchIfNotRunning(Id apexBatchClassId){



    ApexAsyncJob asyncJobList = [Select Id From ApexAsyncJob where ApexClassId=:apexBatchClassId AND JobType='BatchApex' and Status In ('Processing','Preparing','Holding','Queued')];

    boolean isNeedToInitiateNewBatch = true;

    if(!asyncJobList.isEmpty()){

        for(ApexAsyncJob as : asyncJobList){

            if(as.Status == ''Processing' || as.Status == 'Preparing'){ //As start method of batch is running or run, it wont pick new records so abort it

                System.abortJob(as.Id);



            }else{

                //Batch is already queued or in Holding stage so it will pick up new records

                isNeedToInitiateNewBatch = false;

            }



        }

    }

    if(isNeedToInitiateNewBatch){

        //Initiate Batch

    }



}