Add the monitoring goroutine to the controller.

Periodically checks the state of each Varnish instance, and updates
their configurations (for example if they don't have an up-to-date
Ingress configuration).

cmd/varnish/monitor.go

+/*
+ * Copyright (c) 2018 UPLEX Nils Goroll Systemoptimierung
+ * All rights reserved
+ *
+ * Author: Geoffrey Simmons <geoffrey.simmons@uplex.de>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+* VCL housekeeping
+  * either discard the previously active VCL immediately on new vcl.use
+  * or periodically clean up
+
+* monitoring
+  * periodically call ping, status, panic.show when otherwise idle
+*/
+
+package varnish
+
+import (
+	"time"
+
+	"code.uplex.de/uplex-varnish/varnishapi/pkg/admin"
+)
+
+const monitorIntvl = time.Second * 30
+
+func (vc *VarnishController) checkInst(inst *varnishSvc) {
+	inst.admMtx.Lock()
+	defer inst.admMtx.Unlock()
+
+	adm, err := admin.Dial(inst.addr, vc.admSecret, admTimeout)
+	if err != nil {
+		vc.log.Errorf("Error connecting to %s: %v", inst.addr, err)
+		return
+	}
+	defer adm.Close()
+	inst.Banner = adm.Banner
+	vc.log.Infof("Connected to Varnish instance %s", inst.addr)
+
+	pong, err := adm.Ping()
+	if err != nil {
+		vc.log.Error("Error pinging at %s: %v", inst.addr, err)
+		return
+	}
+	vc.log.Infof("Succesfully pinged instance %s: %+v", inst.addr, pong)
+
+	state, err := adm.Status()
+	if err != nil {
+		vc.log.Error("Error getting status at %s: %v", inst.addr, err)
+		return
+	}
+	vc.log.Infof("Status at %s: %s", inst.addr, state)
+
+	// XXX panic.show
+	// XXX discard cold & unlabelled ingress configs
+}
+
+func (vc *VarnishController) monitor() {
+	vc.log.Info("Varnish monitor starting")
+
+	for {
+		time.Sleep(monitorIntvl)
+
+		for svc, insts := range vc.varnishSvcs {
+			vc.log.Infof("Monitoring Varnish instances in %s", svc)
+
+			for _, inst := range insts {
+				vc.checkInst(inst)
+			}
+
+			vc.updateVarnishInstances(insts)
+		}
+	}
+}