Certain way to check if a participant is published using SMPClientReadOnly?

[RohiNof]

Hi,

With the new Peppol Lookup website in place (https://lookup.peppol.org), I want to make sure we are using a certain programmatic way to verify if a participant is published before sending messages.

Currently, our code looks like this:

fun isParticipantPublished(participantID: IParticipantIdentifier): Boolean {
    val sml = ESML.PEPPOL_PRODUCTION  // prod env

    val client = SMPClientReadOnly(
        PeppolNaptrURLProvider.INSTANCE,
        participantID,
        sml
    )

    return client.getServiceGroup(participantID) != null
}

My questions are:

1. Is using SMPClientReadOnly with PeppolNaptrURLProvider.INSTANCE and ESML.PEPPOL_PRODUCTION the authoritative and certain way to check if a participant is published?
2. How does this compare to looking up a participant on https://lookup.peppol.org/? Can that website result ever differ from the SMPClient lookup?
3. Any recommendations for ensuring certainty in checks before sending messages via AS4?

Thanks for your guidance!

[phax]

Hi @RohiNof,
ad 1. Yes your check even goes one step further. Only val client = SMPClientReadOnly(...) already performs the underlying DNS lookup and in the end determines the existence. The return client.getServiceGroup(participantID) != null additionally performs an HTTP query at the SMP and therefore creates load. Effectively some PeppolNaptrURLProvider.INSTANCE.getSMPURIOfParticipant(pid,ESML.PEPPOL_PRODUCTION.getDNSZone() that is not throwing an exception does the trick.

ad 2. Yes it can differ if the DNS queries are performed on different DNS servers. But these differences are usually only temporarily

ad 3. Well, when sending via phase4/phoss-ap these checks are performed out of the box and part of the sending report as well. But in the end you always have the theoretical gap between 2 identical queries that something can happen. So I am no big fan of querying twice...

[RohiNof]

Thanks for the clear explanation, really helpful!