isle/go/cmd/entrypoint/daemon_util.go

package main

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"isle/daemon"
	"isle/toolkit"
	"net"
	"net/http"
	"os"

	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
)

const (
	daemonHTTPSocketDefaultPath = "/tmp/isle-daemon.sock"
	daemonHTTPSocketPathEnvVar  = "ISLE_DAEMON_HTTP_SOCKET_PATH"
	daemonHTTPRPCPath           = "/rpc/v0.json"
)

func httpSocketPath() string {
	return toolkit.EnvOr(
		daemonHTTPSocketPathEnvVar,
		func() string { return daemonHTTPSocketDefaultPath },
	)
}

func newHTTPServer(
	ctx context.Context, logger *mlog.Logger, daemonInst *daemon.Daemon,
) (
	*http.Server, error,
) {
	socketPath := httpSocketPath()
	ctx = mctx.Annotate(ctx, "socketPath", socketPath)

	if err := os.Remove(socketPath); errors.Is(err, fs.ErrNotExist) {
		// No problem
	} else if err != nil {
		return nil, fmt.Errorf(
			"removing %q prior to listening: %w", socketPath, err,
		)
	} else {
		logger.WarnString(
			ctx, "Deleted existing socket file prior to listening, it's possible a previous daemon failed to shutdown gracefully",
		)
	}

	l, err := net.Listen("unix", socketPath)
	if err != nil {
		return nil, fmt.Errorf(
			"listening on socket %q: %w", socketPath, err,
		)
	}

	if err := os.Chmod(socketPath, 0660); err != nil {
		return nil, fmt.Errorf(
			"setting permissions of %q to 0660: %w", socketPath, err,
		)
	}

	logger.Info(ctx, "HTTP server socket created")
	httpMux := http.NewServeMux()
	httpMux.Handle(daemonHTTPRPCPath, daemonInst.HTTPRPCHandler())

	srv := &http.Server{Handler: httpMux}

	go func() {
		if err := srv.Serve(l); !errors.Is(err, http.ErrServerClosed) {
			logger.Fatal(ctx, "HTTP server unexpectedly shut down", err)
		}
	}()

	return srv, nil
}