I am getting DML Limit exception in Flow without using any DML statements

Question

I have a flow that generates an encrypted token for new Campaign Member records. This works perfectly fine for creating one record at a time. When I try to create 188 campaign members I get error An Apex error occurred: System.LimitException: ued:Too many DML statements: 151. I'm not using any DML statements (to my knowledge: update, insert, create, upsert, delete) in the apex class so I'm not sure why I'm getting this limit exception. I'm putting the records in a collection variable in the flow so if the DML error were to occur it should occur in the update part of the flow, not in the apex class.

Any help is greatly appreciated. I'm currently working to put this into a trigger as I don't think this is possible with flow, although it should be.

Apex Class

//called from Flow
public class encrypt 
{
    @InvocableMethod
    public static List<List<CampaignMember>> CmId(List<CampaignMember> ListCampaignMembers)
    {
        //String encryptedToken2 = ued.UserCryptoHelper.doEncryptWithUrlEncoding(encryptedToken, 'UTF');
        for(CampaignMember cm : ListCampaignMembers)
        {
            Guest_User_Encryption__c gue = [select Site_Name__c, Guest_User_ID__c from Guest_User_Encryption__c where Site_Name__c =: cm.Site_Name__c];
            String encryptedToken = System.EncodingUtil.urlEncode(ued.UserCryptoHelper.doEncrypt(cm.id, gue.Guest_User_ID__c),'UTF-8');
            cm.Encrypted_Record_Id__c = encryptedToken;
        }
        List<List<CampaignMember>> returnList = new List<List<CampaignMember>>();
        returnlist.add(listCampaignMembers);
        return returnList;
    }
}

Answer 1

First, your code isn't properly bulkified. Even if you didn't get a DML error where you did, you should still hit the SOQL limit for having a query inside a loop.

Second, keep in mind that flows are bulkified automatically. You must not return all the campaign members from the input into an element of the output. This is injecting parallel records into the wrong flows (namely, the first one). I'm surprised you didn't get a different runtime error, since the input list of 188 members was being mapped to an output of just 1.

Your bulkified, correctly mapped output should look like:

public class encrypt {
    @InvocableMethod public static List<CampaignMember> cmId(List<CampaignMember> campaignMembersIn) {
        Map<String, Guest_User_Encryption__c> encryptions = new Map<String, Guest_User_Encryption__c>();
        for(CampaignMember campaignMember: campaignMembersIn) {
            encryptions.put(campaignMember.Site_Name__c, null);
        }
        for(Guest_User_Encryption__c guestUserEncryption: [SELECT Site_Name__c, Guest_User_ID__c FROM Guest_User_Encryption__c WHERE Site_Name__c = :encryptions.keySet()]) {
            encryptions.put(guestUserEncryption.Site_Name__c, guestUserEncryption);
        }
        for(CampaignMember campaignMember: campaignMembersIn) {
            Guest_User_Encryption__c gue = guestUserEncryption.get(campaignMember.Site_Name__c);
            campaignMember.Encrypted_Record_Id__c = EncodingUtil.urlEncode(ued.UserCryptoHelper.doEncrypt(campaignMember.Id, gue.Guest_User_ID__c),'UTF-8');
        }
        return campaignMembersIn;
    }
}

Third, I installed this package, which I presume you're using, and tested the following code:

for(Integer i = 0; i < 200; i++) {
    ued.UserCryptoHelper.doEncrypt('hello world');
}

To which I get:

FATAL_ERROR|System.LimitException: ued:Too many DML statements: 151

Checking the logs, I see it's writing to some custom setting data:

DML_BEGIN|[106]|Op:Update|Type:ued__User_Encryption_Settings__c|Rows:1
DML_END|[106]

This occurs for every single call, ultimately causing the DML exception you see.

This library is not suitable for your intended purpose. You'll need to find a library that supports bulk encryption, does not write to the database, or roll your own encryption.