X-Git-Url: https://ruderich.org/simon/gitweb/?a=blobdiff_plain;f=frontend%2Floop.go;fp=frontend%2Floop.go;h=5e232a3aaad6165d4d7305fb1b116056abca5ef9;hb=c899e17495d4eb932e0b4f428ec91882d845f1bc;hp=0000000000000000000000000000000000000000;hpb=9269fa3c94e700afc0be823f58ea473a2db8f3dc;p=safcm%2Fsafcm.git

diff --git a/frontend/loop.go b/frontend/loop.go
new file mode 100644
index 0000000..5e232a3
--- /dev/null
+++ b/frontend/loop.go
@@ -0,0 +1,172 @@
+// Frontend: Host synchronization and logging event loop for programs using
+// the safcm library
+
+// Copyright (C) 2021  Simon Ruderich
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package frontend
+
+import (
+	"log"
+	"os"
+	"os/signal"
+	"sort"
+	"strings"
+	"sync"
+
+	"ruderich.org/simon/safcm"
+	"ruderich.org/simon/safcm/rpc"
+)
+
+type Host interface {
+	Name() string
+	Dial(*rpc.Conn) error
+}
+
+type Loop struct {
+	DebugConn bool
+
+	LogEventFunc func(e Event, failed *bool)
+	SyncHostFunc func(*rpc.Conn, Host) error
+
+	events chan Event
+}
+
+func (l *Loop) Run(hosts []Host) bool {
+	done := make(chan bool)
+	// Collect events from all hosts and print them
+	events := make(chan Event)
+	go func() {
+		var failed bool
+		for {
+			x := <-events
+			if x.Host == nil {
+				break
+			}
+			l.LogEventFunc(x, &failed)
+		}
+		done <- failed
+	}()
+
+	hostsLeft := make(map[string]bool)
+	for _, x := range hosts {
+		hostsLeft[x.Name()] = true
+	}
+	var hostsLeftMutex sync.Mutex // protects hostsLeft
+
+	// Show unfinished hosts on Ctrl-C
+	sigint := make(chan os.Signal, 1)   // buffered for Notify()
+	signal.Notify(sigint, os.Interrupt) // = SIGINT = Ctrl-C
+	go func() {
+		// Running `ssh` processes get killed by SIGINT which is sent
+		// to all processes
+
+		<-sigint
+		log.Print("Received SIGINT, aborting ...")
+
+		// Print all queued events
+		events <- Event{} // poison pill
+		<-done
+		// "races" with <-done in the main function and will hang here
+		// if the other is faster. This is fine because then all hosts
+		// were synced successfully.
+
+		hostsLeftMutex.Lock()
+		var hosts []string
+		for x := range hostsLeft {
+			hosts = append(hosts, x)
+		}
+		sort.Strings(hosts)
+		log.Fatalf("Failed to sync %s", strings.Join(hosts, ", "))
+	}()
+
+	l.events = events // used by l.syncHost() and l.Log()
+
+	// Sync all hosts concurrently
+	var wg sync.WaitGroup
+	for _, x := range hosts {
+		x := x
+
+		// Once in sync.Host() and once in the go func below
+		wg.Add(2)
+
+		go func() {
+			err := l.syncHost(&wg, x)
+			if err != nil {
+				events <- Event{
+					Host:  x,
+					Error: err,
+				}
+			}
+			wg.Done()
+
+			hostsLeftMutex.Lock()
+			defer hostsLeftMutex.Unlock()
+			delete(hostsLeft, x.Name())
+		}()
+	}
+
+	wg.Wait()
+	events <- Event{} // poison pill
+	failed := <-done
+
+	return !failed
+}
+
+func (l *Loop) syncHost(wg *sync.WaitGroup, host Host) error {
+	conn := rpc.NewConn(l.DebugConn)
+	// Pass all connection events to main loop
+	go func() {
+		for {
+			x, ok := <-conn.Events
+			if !ok {
+				break
+			}
+			l.events <- Event{
+				Host:      host,
+				ConnEvent: x,
+			}
+		}
+		wg.Done()
+	}()
+
+	err := host.Dial(conn)
+	if err != nil {
+		conn.Kill()
+		return err
+	}
+	defer conn.Kill()
+
+	err = l.SyncHostFunc(conn, host)
+	if err != nil {
+		return err
+	}
+
+	// Terminate connection to remote host
+	err = conn.Send(safcm.MsgQuitReq{})
+	if err != nil {
+		return err
+	}
+	_, err = conn.Recv()
+	if err != nil {
+		return err
+	}
+	err = conn.Wait()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}