emissary/internal/agent/controller/gateway/controller.go

package gateway

import (
	"context"

	"forge.cadoles.com/Cadoles/emissary/internal/agent"
	"forge.cadoles.com/Cadoles/emissary/internal/spec/gateway"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type Controller struct {
	proxies             map[gateway.ID]*ReverseProxy
	currentSpecRevision int
}

// Name implements node.Controller.
func (c *Controller) Name() string {
	return "gateway-controller"
}

// Reconcile implements node.Controller.
func (c *Controller) Reconcile(ctx context.Context, state *agent.State) error {
	gatewaySpec := gateway.NewSpec()

	if err := state.GetSpec(gateway.NameGateway, gatewaySpec); err != nil {
		if errors.Is(err, agent.ErrSpecNotFound) {
			logger.Info(ctx, "could not find gateway spec, stopping all remaining proxies")

			c.stopAllProxies(ctx)

			return nil
		}

		return errors.WithStack(err)
	}

	logger.Info(ctx, "retrieved spec", logger.F("spec", gatewaySpec.SpecName()), logger.F("revision", gatewaySpec.SpecRevision()))

	if c.currentSpecRevision == gatewaySpec.SpecRevision() {
		logger.Info(ctx, "spec revision did not change, doing nothing")

		return nil
	}

	c.updateProxies(ctx, gatewaySpec)

	c.currentSpecRevision = gatewaySpec.SpecRevision()
	logger.Info(ctx, "updating current spec revision", logger.F("revision", c.currentSpecRevision))

	return nil
}

func (c *Controller) stopAllProxies(ctx context.Context) {
	for gatewayID, proxy := range c.proxies {
		logger.Info(ctx, "stopping proxy", logger.F("gatewayID", gatewayID))

		if err := proxy.Stop(); err != nil {
			logger.Error(
				ctx, "error while stopping proxy",
				logger.F("gatewayID", gatewayID),
				logger.E(errors.WithStack(err)),
			)

			delete(c.proxies, gatewayID)
		}
	}
}

func (c *Controller) updateProxies(ctx context.Context, spec *gateway.Spec) {
	// Stop and remove obsolete gateways
	for gatewayID, proxy := range c.proxies {
		if _, exists := spec.Gateways[gatewayID]; exists {
			continue
		}

		logger.Info(ctx, "stopping proxy", logger.F("gatewayID", gatewayID))

		if err := proxy.Stop(); err != nil {
			logger.Error(
				ctx, "error while stopping proxy",
				logger.F("gatewayID", gatewayID),
				logger.E(errors.WithStack(err)),
			)

			delete(c.proxies, gatewayID)
		}
	}

	// (Re)start gateways
	for gatewayID, gatewaySpec := range spec.Gateways {
		proxy, exists := c.proxies[gatewayID]
		if !exists {
			proxy = NewReverseProxy()
			c.proxies[gatewayID] = proxy
		}

		logger.Info(
			ctx, "starting proxy",
			logger.F("gatewayID", gatewayID),
			logger.F("addr", gatewaySpec.Address),
			logger.F("target", gatewaySpec.Target),
		)

		if err := proxy.Start(ctx, gatewaySpec.Address, gatewaySpec.Target); err != nil {
			logger.Error(
				ctx, "error while starting proxy",
				logger.F("gatewayID", gatewayID),
				logger.E(errors.WithStack(err)),
			)

			delete(c.proxies, gatewayID)
		}
	}
}

func NewController() *Controller {
	return &Controller{
		proxies:             make(map[gateway.ID]*ReverseProxy),
		currentSpecRevision: -1,
	}
}

var _ agent.Controller = &Controller{}