core/internal/containerd/main.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 containerd

import (
	"context"
	"fmt"
	"io"
	"os"
	"os/exec"
	"time"

	"git.monogon.dev/source/nexantic.git/core/internal/localstorage"
	"git.monogon.dev/source/nexantic.git/core/pkg/logbuffer"
)

type Service struct {
	EphemeralVolume *localstorage.EphemeralContainerdDirectory

	Log      *logbuffer.LogBuffer
	RunscLog *logbuffer.LogBuffer
}

func (s *Service) Run(ctx context.Context) error {
	if s.Log == nil {
		s.Log = logbuffer.New(5000, 16384)
	}
	if s.RunscLog == nil {
		s.RunscLog = logbuffer.New(5000, 16384)
	}

	cmd := exec.CommandContext(ctx, "/containerd/bin/containerd", "--config", "/containerd/conf/config.toml")
	cmd.Stdout = s.Log
	cmd.Stderr = s.Log
	cmd.Env = []string{"PATH=/containerd/bin", "TMPDIR=" + s.EphemeralVolume.Tmp.FullPath()}

	runscFifo, err := os.OpenFile(s.EphemeralVolume.RunSCLogsFIFO.FullPath(), os.O_CREATE|os.O_RDONLY, os.ModeNamedPipe|0777)
	if err != nil {
		return err
	}
	go func() {
		for {
			n, err := io.Copy(s.RunscLog, runscFifo)
			if n == 0 && err == nil {
				// Hack because pipes/FIFOs can return zero reads when nobody is writing. To avoid busy-looping,
				// sleep a bit before retrying. This does not loose data since the FIFO internal buffer will
				// stall writes when it becomes full. 10ms maximum stall in a non-latency critical process (reading
				// debug logs) is not an issue for us.
				time.Sleep(10 * time.Millisecond)
			} else if err != nil {
				// TODO: Use supervisor.Logger() and Error() before exiting. Should never happen.
				fmt.Println(err)
				return // It's likely that this will busy-loop printing errors if it encounters one, so bail
			}
		}
	}()

	// TODO(lorenz): Healthcheck against CRI RuntimeService.Status() and SignalHealthy

	err = cmd.Run()
	fmt.Fprintf(s.Log, "containerd stopped: %v\n", err)
	return err
}