private void storeReindexing(ApplicationId applicationId) {
        if ( ! applicationRepository.configserverConfig().hostedVespa()) return;

        List<Reindexing> entries = session.getActivationTriggers().reindexings();
        if (entries.isEmpty()) return;

        applicationRepository.modifyReindexing(applicationId, reindexing -> {
            for (Reindexing entry : entries)
                reindexing = reindexing.withPending(entry.clusterId(), entry.documentType(), session.getSessionId());

            return reindexing;
        });
        deployLogger.log(Level.INFO, String.format("Scheduled reindexing of %d document types across %d clusters: %s",
                                                   entries.size(),
                                                   entries.stream().map(Reindexing::clusterId).distinct().count(),
                                                   entries.stream().collect(groupingBy(Reindexing::clusterId)).entrySet().stream()
                                                          .map(typesInCluster -> typesInCluster.getKey() + ": " +
                                                                                 typesInCluster.getValue().stream()
                                                                                               .map(Reindexing::documentType).collect(joining(", ")))
                                                          .collect(joining("; "))));
    }
Activates this. If it is not already prepared, this will call prepare first.
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/Deployment.java