mesh-controller/cmd/mesh-controller/bindings.go

package main

import (
	"context"
	"fmt"

	"github.com/novox/mesh-controller/internal/catalogue"
	"github.com/novox/mesh-controller/internal/conditions"
)

// A binding to data moves only by a person (novox/hq ADR 0232, issue 273).
//
// The resolver keeps each consumer of a provision that keeps its data at the provider it was last
// sent (catalogue/bound.go) and says what it would have moved. This is where that is said: on the
// push that composed it, and by the self-check's D12 every run, as an urgent condition naming the
// consumer, both providers and the pin that confirms the move.

// The condition kinds of D12.
const (
	// kindBindingKept is a move the resolver refused: the consumer is still where its data is.
	kindBindingKept = "binding-kept"
	// kindBindingMoved is a consumer about to be sent another provider than the one on record with
	// no pin naming it — what the resolver exists to make impossible, said if it ever is not.
	kindBindingMoved = "binding-moved"
	// kindBindingMoving is a move a pin asked for, not yet sent: a person's act, said so that the
	// data is moved before the push that carries it.
	kindBindingMoving = "binding-moving"
)

// probeBindingsID is the self-check's id for this probe, and the source of what it raises.
const probeBindingsID = "D12"

// keptObservation is the urgent condition for one refused move.
func keptObservation(k catalogue.KeptBinding) conditions.Observation {
	return conditions.Observation{Scope: conditions.ScopeMachine, ID: bindingID(k.Machine, k.Consumer, k.Provision),
		Token: kindBindingKept, Kind: kindBindingKept, Machine: k.Machine, Also: otherMachines(k.Machine, k.Bound.Node, k.Would.Node),
		Severity: conditions.Urgent, Resolver: conditions.ResolverOperator,
		Summary: fmt.Sprintf("on %s, the mesh %s", k.Machine, k.String())}
}

func bindingID(machine, consumer, provision string) string {
	return machine + "." + consumer + "." + provision
}

func otherMachines(machine string, nodes ...string) []string {
	var out []string
	seen := map[string]bool{machine: true}
	for _, n := range nodes {
		if n != "" && !seen[n] {
			seen[n] = true
			out = append(out, n)
		}
	}
	return out
}

// reportKept says every move a machine's resolution refused, on the push composing it, and raises its
// condition at once where this process keeps the conditions: a push is when a person is looking.
func reportKept(ctx context.Context, plan catalogue.Resolution) {
	for _, k := range plan.Kept {
		fmt.Printf("%s: the mesh %s\n", plan.Node, k)
		if conditionsFrom != nil {
			o := keptObservation(k)
			o.Source = probeBindingsID
			if _, err := conditionsFrom.Observe(ctx, o); err != nil {
				fmt.Printf("%s: and the condition for it could not be raised: %v\n", plan.Node, err)
			}
		}
	}
}

// probeBindings is D12: every consumer of a provision that keeps its data is bound where it was last
// sent, on every machine — the resolver kept it there (said, urgent, until a person pins), or a pin
// moves it (said, so the data goes first), and never anything else.
func probeBindings(ctx context.Context, d *doctor) ([]conditions.Observation, error) {
	inv := d.open.inventory
	nodes, err := inv.Nodes(ctx)
	if err != nil {
		return nil, err
	}
	var out []conditions.Observation
	for _, n := range nodes {
		plan, _, err := planFor(ctx, d.open, n.Name)
		if err != nil {
			if unresolvable(err) {
				// D1 says it, with the binding that refused it when that is why.
				continue
			}
			return nil, fmt.Errorf("%s cannot be worked out: %w", n.Name, err)
		}
		bound, err := inv.BindingsFor(ctx, n.Name)
		if err != nil {
			return nil, err
		}
		pins, err := inv.PinsFor(ctx, n.Name)
		if err != nil {
			return nil, err
		}
		out = append(out, bindingFindings(plan, bound, pins)...)
	}
	return out, nil
}

// bindingFindings is what one machine's resolution says against its record.
func bindingFindings(plan catalogue.Resolution, bound map[string]map[string]catalogue.Chosen,
	pins map[string]catalogue.Chosen) []conditions.Observation {
	var out []conditions.Observation
	for _, k := range plan.Kept {
		out = append(out, keptObservation(k))
	}
	said := map[string]bool{}
	for _, need := range plan.Needs {
		if !need.KeepsData || need.ByRecord {
			continue
		}
		was, recorded := bound[need.For][need.Name]
		now := catalogue.Chosen{Node: need.From, Module: need.Module}
		if !recorded || was == now || (was.Module == "" && was.Node == now.Node) {
			continue
		}
		id := bindingID(plan.Node, need.For, need.Name)
		if said[id] {
			continue
		}
		said[id] = true
		o := conditions.Observation{Scope: conditions.ScopeMachine, ID: id, Machine: plan.Node,
			Also: otherMachines(plan.Node, was.Node, now.Node), Resolver: conditions.ResolverOperator}
		if pin, pinned := pins[need.Name]; pinned && pin.Node == now.Node && (pin.Module == "" || pin.Module == now.Module) {
			o.Token, o.Kind, o.Severity = kindBindingMoving, kindBindingMoving, conditions.Warning
			o.Summary = fmt.Sprintf("on %s, %s's %s moves from %s to %s at the next push, by the pin — its data "+
				"is on %s: move it first", plan.Node, need.For, need.Name, was, now, was)
		} else {
			o.Token, o.Kind, o.Severity = kindBindingMoved, kindBindingMoved, conditions.Urgent
			o.Summary = fmt.Sprintf("on %s, %s's %s would be sent %s, and it is bound to %s, where its data is, "+
				"with no pin naming %s — a move nothing asked for", plan.Node, need.For, need.Name, now, was, now)
		}
		out = append(out, o)
	}
	return out
}