mesh-controller/cmd/mesh-controller/stores.go

package main

import (
	"context"
	"fmt"
	"time"

	"github.com/novox/mesh-controller/internal/identity"
	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/licences"
	"github.com/novox/mesh-controller/internal/store"
)

// reaching each context's store, which no other context may touch.
//
// Split out of main.go, which had reached 2,769 lines because appending was always the
// cheapest next step. That is how novox/hq ADR 0001 records `hal/sdk` reaching 34,636:
// nothing in it was wrong, and no one edit was the one that should have been a new file.

// migrate brings every held context's schema up to date.
//
// Reported per context and per migration, because this runs during a bootstrap on a machine with
// nothing else on it — the output is the only account of what happened, and "migrated" is not one.
func migrate(ctx context.Context) error {
	for _, c := range held {
		migrations, err := c.migrations()
		if err != nil {
			return err
		}

		s, err := store.Open(ctx, c.name)
		if err != nil {
			return err
		}
		defer s.Close()

		// The bootstrap raises PostgreSQL moments before this runs, and a container that is
		// running is not a database that will answer — a distinction this project has already
		// paid for once, when a crash-looping database reported itself as up between restarts.
		if err := s.Ready(ctx, 60*time.Second); err != nil {
			return err
		}

		done, err := s.Migrate(ctx, migrations)
		for _, m := range done {
			fmt.Printf("%s: applied %04d-%s\n", c.name, m.Number, m.Name)
		}
		if err != nil {
			return err
		}
		if len(done) == 0 {
			applied, err := s.AppliedMigrations(ctx)
			if err != nil {
				return err
			}
			fmt.Printf("%s: already up to date — %d migration(s)\n", c.name, len(applied))
		}
	}

	// The modules the control plane ships with itself. Recorded here rather than by hand, because
	// a mesh whose own private network is missing from the catalogue would have nothing to assign
	// and no way to say why.
	open, err := openStores(ctx)
	if err != nil {
		return err
	}
	defer open.Close()
	inv := open.inventory
	for _, m := range provided {
		if err := inv.Provide(ctx, m); err != nil {
			return err
		}
		fmt.Printf("provided %s\n", m.Module)
	}
	return nil
}

// openInventory connects and waits, the way every command that touches it needs to.
func openInventory(ctx context.Context) (*inventory.Inventory, error) {
	inv, err := inventory.Open(ctx)
	if err != nil {
		return nil, err
	}
	if err := inv.Ready(ctx, 30*time.Second); err != nil {
		inv.Close()
		return nil, err
	}
	return inv, nil
}

func openIdentity(ctx context.Context) (*identity.Identity, error) {
	ident, err := identity.Open(ctx)
	if err != nil {
		return nil, err
	}
	if err := ident.Ready(ctx, 30*time.Second); err != nil {
		ident.Close()
		return nil, err
	}
	return ident, nil
}

// openLicences connects to the context that holds which model access exists and who may use it.
func openLicences(ctx context.Context) (*licences.Licences, error) {
	held, err := licences.Open(ctx)
	if err != nil {
		return nil, err
	}
	if err := held.Ready(ctx, 30*time.Second); err != nil {
		held.Close()
		return nil, err
	}
	return held, nil
}

// stores is what one command has open.
//
// **Opened once, not once per machine.** Working out what a machine should be reaches the identity
// context for its certificate and the licence context for its model access, and both were opened —
// and waited on — inside functions called for every node in a push. Two machines hid it; fifty
// would be fifty connect-and-wait cycles for data that does not change while the push runs.
//
// Each is opened on first use rather than up front, because most commands need one context and
// paying to reach three would be the same waste from the other side.
type stores struct {
	inventory *inventory.Inventory
	identity  *identity.Identity
	licences  *licences.Licences
}

// open connects to the inventory, which every command that touches the mesh needs.
func openStores(ctx context.Context) (*stores, error) {
	inv, err := openInventory(ctx)
	if err != nil {
		return nil, err
	}
	return &stores{inventory: inv}, nil
}

// Identity is this control plane's own identity context, opened if it has not been.
func (h *stores) Identity(ctx context.Context) (*identity.Identity, error) {
	if h.identity != nil {
		return h.identity, nil
	}
	opened, err := openIdentity(ctx)
	if err != nil {
		return nil, err
	}
	h.identity = opened
	return opened, nil
}

// Licences is the context holding model access, opened if it has not been.
func (h *stores) Licences(ctx context.Context) (*licences.Licences, error) {
	if h.licences != nil {
		return h.licences, nil
	}
	opened, err := openLicences(ctx)
	if err != nil {
		return nil, err
	}
	h.licences = opened
	return opened, nil
}

// Close lets go of everything that was opened, in any order: they are separate connections to
// separate databases and none of them knows about the others.
func (h *stores) Close() {
	if h.licences != nil {
		h.licences.Close()
	}
	if h.identity != nil {
		h.identity.Close()
	}
	if h.inventory != nil {
		h.inventory.Close()
	}
}