What user does ISM run as?

I’m running into an issue with a new policy, one that was automatically created by Data Prepper for handling otel-v1-apm-span indices. I have several ISM policies that I created manually that are working fine, but the new policy created by Data Prepper does not work. I get the following error, among others, when it tries to run:

[2022-10-08T23:07:49,194][INFO ][o.o.s.p.PrivilegesEvaluator] [elasticsearch-phx1-0019] No index-level perm match for User [name=plugin, backend_roles=[], requestedTenant=null] Resolved [aliases=[*], allIndices=[*], types=[*], originalRequested=[*], remoteIndices=[]] [Action [indices:admin/rollover]] [RolesChecked [logstash, own_index, graylog_role, universal_graylog_role]]

The user plugin does not exist in my system, I’m not sure where that username is configured. I also don’t understand why it’s trying to associate with the list of “Roles Checked” since those roles are associated with a user that does exist, but is only used to write data into Opensearch.

I guess I could create a user called plugin and grant it permissions, but I’d like to know where that name comes from and if it’s configurable, so that I can use an existing user in my system instead.