Manifest Manager Logic

Source code reference location

The newManager function calls the run method - passing in the manager struct that includes the leasech channel - which invokes a perpetual for loop to await events on various channels.

The manifest manager instance is returned to the handleLease method in service.go.

func newManager(h *service, daddr dtypes.DeploymentID) *manager {
    session := h.session.ForModule("manifest-manager")

    ...

    go m.lc.WatchChannel(h.lc.ShuttingDown())
    go m.run(h.managerch)

    return m
}

The handleLease method in service.go continues and calls another handleLease method in manager.go passing in lease events received on the bus.

func (s *service) handleLease(ev event.LeaseWon, isNew bool) {
    ....

    manager := s.ensureManager(ev.LeaseID.DeploymentID())

    manager.handleLease(ev)
}

The handleLease method in manager.go puts the event onto the leasech channel.

func (m *manager) handleLease(ev event.LeaseWon) {
    select {
    case m.leasech <- ev:
    case <-m.lc.ShuttingDown():
        m.log.Error("not running: handle manifest", "lease", ev.LeaseID)
    }
}

When the manifest manager run method receives an event on the leasech channel the maybeFetchData method is called and results is placed onto the runch channel.

func (m *manager) run(donech chan<- *manager) {
    ..

loop:
    for {
        ....
        select {
        ....
        case ev := <-m.leasech:
            m.log.Info("new lease", "lease", ev.LeaseID)
            m.clearFetched()
            m.maybeScheduleStop()
            runch = m.maybeFetchData(ctx, runch)

The maybeFetchData method attempts to fetch deployment and lease data with associated downstream logic.

func (m *manager) maybeFetchData(ctx context.Context, runch <-chan runner.Result) <-chan runner.Result {
    if runch != nil {
        return runch
    }

    if !m.fetched || time.Since(m.fetchedAt) > m.config.CachedResultMaxAge {
        m.clearFetched()
        return m.fetchData(ctx)
    }
    return runch
}