metropolis/node/core/cluster/cluster.go

// Copyright 2020 The Monogon Project Authors.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package cluster implements low-level clustering logic, especially logic
// regarding to bootstrapping, registering into and joining a cluster. Its goal
// is to provide the rest of the node code with the following:
//   - A mounted plaintext storage.
//   - Node credentials/identity.
//   - A locally running etcd server if the node is supposed to run one, and a
//     client connection to that etcd cluster if so.
//   - The state of the cluster as seen by the node, to enable code to respond to
//     node lifecycle changes.
package cluster

import (
	"context"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"sync"

	"github.com/cenkalti/backoff/v4"
	"google.golang.org/protobuf/proto"

	"source.monogon.dev/metropolis/node/core/consensus"
	"source.monogon.dev/metropolis/node/core/localstorage"
	"source.monogon.dev/metropolis/node/core/network"
	"source.monogon.dev/metropolis/node/core/roleserve"
	"source.monogon.dev/metropolis/pkg/supervisor"
	apb "source.monogon.dev/metropolis/proto/api"
	cpb "source.monogon.dev/metropolis/proto/common"
	ppb "source.monogon.dev/metropolis/proto/private"
)

type state struct {
	mu sync.RWMutex

	oneway bool

	configuration *ppb.SealedConfiguration
}

type Manager struct {
	storageRoot    *localstorage.Root
	networkService *network.Service
	roleServer     *roleserve.Service

	state

	// consensus is the spawned etcd/consensus service, if the Manager brought
	// up a Node that should run one.
	consensus *consensus.Service
}

// NewManager creates a new cluster Manager. The given localstorage Root must
// be places, but not yet started (and will be started as the Manager makes
// progress). The given network Service must already be running.
func NewManager(storageRoot *localstorage.Root, networkService *network.Service, rs *roleserve.Service) *Manager {
	return &Manager{
		storageRoot:    storageRoot,
		networkService: networkService,
		roleServer:     rs,

		state: state{},
	}
}

func (m *Manager) lock() (*state, func()) {
	m.mu.Lock()
	return &m.state, m.mu.Unlock
}

func (m *Manager) rlock() (*state, func()) {
	m.mu.RLock()
	return &m.state, m.mu.RUnlock
}

// Run is the runnable of the Manager, to be started using the Supervisor. It
// is one-shot, and should not be restarted.
func (m *Manager) Run(ctx context.Context) error {
	state, unlock := m.lock()
	if state.oneway {
		unlock()
		// TODO(q3k): restart the entire system if this happens
		return fmt.Errorf("cannot restart cluster manager")
	}
	state.oneway = true
	unlock()

	configuration, err := m.storageRoot.ESP.Metropolis.SealedConfiguration.Unseal()
	if err == nil {
		supervisor.Logger(ctx).Info("Sealed configuration present. attempting to join cluster")

		// Read Cluster Directory and unmarshal it. Since the node is already
		// registered with the cluster, the directory won't be bootstrapped from
		// Node Parameters.
		cd, err := m.storageRoot.ESP.Metropolis.ClusterDirectory.Unmarshal()
		if err != nil {
			return fmt.Errorf("while reading cluster directory: %w", err)
		}
		return m.join(ctx, configuration, cd)
	}

	if !errors.Is(err, localstorage.ErrNoSealed) {
		return fmt.Errorf("unexpected sealed config error: %w", err)
	}

	supervisor.Logger(ctx).Info("No sealed configuration, looking for node parameters")

	params, err := m.nodeParams(ctx)
	if err != nil {
		return fmt.Errorf("no parameters available: %w", err)
	}

	switch inner := params.Cluster.(type) {
	case *apb.NodeParameters_ClusterBootstrap_:
		err = m.bootstrap(ctx, inner.ClusterBootstrap)
	case *apb.NodeParameters_ClusterRegister_:
		err = m.register(ctx, inner.ClusterRegister)
	default:
		err = fmt.Errorf("node parameters misconfigured: neither cluster_bootstrap nor cluster_register set")
	}

	if err == nil {
		supervisor.Logger(ctx).Info("Cluster enrolment done.")
	}
	return err
}

func (m *Manager) nodeParamsFWCFG(ctx context.Context) (*apb.NodeParameters, error) {
	bytes, err := os.ReadFile("/sys/firmware/qemu_fw_cfg/by_name/dev.monogon.metropolis/parameters.pb/raw")
	if err != nil {
		return nil, fmt.Errorf("could not read firmware enrolment file: %w", err)
	}

	config := apb.NodeParameters{}
	err = proto.Unmarshal(bytes, &config)
	if err != nil {
		return nil, fmt.Errorf("could not unmarshal: %v", err)
	}

	return &config, nil
}

// nodeParamsGCPMetadata attempts to retrieve the node parameters from the
// GCP metadata service. Returns nil if the metadata service is available,
// but no node parameters are specified.
func (m *Manager) nodeParamsGCPMetadata(ctx context.Context) (*apb.NodeParameters, error) {
	const metadataURL = "http://169.254.169.254/computeMetadata/v1/instance/attributes/metropolis-node-params"
	req, err := http.NewRequestWithContext(ctx, "GET", metadataURL, nil)
	if err != nil {
		return nil, fmt.Errorf("could not create request: %w", err)
	}
	req.Header.Set("Metadata-Flavor", "Google")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("HTTP request failed: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		if resp.StatusCode == http.StatusNotFound {
			return nil, nil
		}
		return nil, fmt.Errorf("non-200 status code: %d", resp.StatusCode)
	}
	decoded, err := io.ReadAll(base64.NewDecoder(base64.StdEncoding, resp.Body))
	if err != nil {
		return nil, fmt.Errorf("cannot decode base64: %w", err)
	}
	config := apb.NodeParameters{}
	err = proto.Unmarshal(decoded, &config)
	if err != nil {
		return nil, fmt.Errorf("failed unmarshalling NodeParameters: %w", err)
	}
	return &config, nil
}

func (m *Manager) nodeParams(ctx context.Context) (*apb.NodeParameters, error) {
	boardName, err := getDMIBoardName()
	if err != nil {
		supervisor.Logger(ctx).Warningf("Could not get board name, cannot detect platform: %v", err)
	}
	supervisor.Logger(ctx).Infof("Board name: %q", boardName)

	// When running on GCP, attempt to retrieve the node parameters from the
	// metadata server first. Retry until we get a response, since we need to
	// wait for the network service to assign an IP address first.
	if isGCPInstance(boardName) {
		var params *apb.NodeParameters
		op := func() error {
			supervisor.Logger(ctx).Info("Running on GCP, attempting to retrieve node parameters from metadata server")
			params, err = m.nodeParamsGCPMetadata(ctx)
			return err
		}
		err := backoff.Retry(op, backoff.WithContext(backoff.NewExponentialBackOff(), ctx))
		if err != nil {
			supervisor.Logger(ctx).Errorf("Failed to retrieve node parameters: %v", err)
		}
		if params != nil {
			supervisor.Logger(ctx).Info("Retrieved parameters from GCP metadata server")
			return params, nil
		}
		supervisor.Logger(ctx).Infof("\"metropolis-node-params\" metadata not found")
	}

	// Retrieve node parameters from qemu's fwcfg interface or ESP.
	// TODO(q3k): probably abstract this away and implement per platform/build/...
	paramsFWCFG, err := m.nodeParamsFWCFG(ctx)
	if err != nil {
		supervisor.Logger(ctx).Warningf("Could not retrieve node parameters from qemu fwcfg: %v", err)
		paramsFWCFG = nil
	} else {
		supervisor.Logger(ctx).Infof("Retrieved node parameters from qemu fwcfg")
	}
	paramsESP, err := m.storageRoot.ESP.Metropolis.NodeParameters.Unmarshal()
	if err != nil {
		supervisor.Logger(ctx).Warningf("Could not retrieve node parameters from ESP: %v", err)
		paramsESP = nil
	} else {
		supervisor.Logger(ctx).Infof("Retrieved node parameters from ESP")
	}
	if paramsFWCFG == nil && paramsESP == nil {
		return nil, fmt.Errorf("could not find node parameters in ESP or qemu fwcfg")
	}
	if paramsFWCFG != nil && paramsESP != nil {
		supervisor.Logger(ctx).Warningf("Node parameters found both in both ESP and qemu fwcfg, using the latter")
		return paramsFWCFG, nil
	} else if paramsFWCFG != nil {
		return paramsFWCFG, nil
	} else {
		return paramsESP, nil
	}
}

// logClusterDirectory verbosely logs the whole Cluster Directory passed to it.
func logClusterDirectory(ctx context.Context, cd *cpb.ClusterDirectory) {
	for _, node := range cd.Nodes {
		var addresses []string
		for _, add := range node.Addresses {
			addresses = append(addresses, add.Host)
		}
		supervisor.Logger(ctx).Infof("    Addresses: %s", strings.Join(addresses, ","))
	}
}