diff options
Diffstat (limited to 'vendor/github.com/coreos/go-systemd/v22/dbus/subscription.go')
-rw-r--r-- | vendor/github.com/coreos/go-systemd/v22/dbus/subscription.go | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/vendor/github.com/coreos/go-systemd/v22/dbus/subscription.go b/vendor/github.com/coreos/go-systemd/v22/dbus/subscription.go new file mode 100644 index 000000000..7e370fea2 --- /dev/null +++ b/vendor/github.com/coreos/go-systemd/v22/dbus/subscription.go @@ -0,0 +1,333 @@ +// Copyright 2015 CoreOS, Inc. +// +// 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 dbus + +import ( + "errors" + "log" + "time" + + "github.com/godbus/dbus/v5" +) + +const ( + cleanIgnoreInterval = int64(10 * time.Second) + ignoreInterval = int64(30 * time.Millisecond) +) + +// Subscribe sets up this connection to subscribe to all systemd dbus events. +// This is required before calling SubscribeUnits. When the connection closes +// systemd will automatically stop sending signals so there is no need to +// explicitly call Unsubscribe(). +func (c *Conn) Subscribe() error { + c.sigconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0, + "type='signal',interface='org.freedesktop.systemd1.Manager',member='UnitNew'") + c.sigconn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0, + "type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged'") + + return c.sigobj.Call("org.freedesktop.systemd1.Manager.Subscribe", 0).Store() +} + +// Unsubscribe this connection from systemd dbus events. +func (c *Conn) Unsubscribe() error { + return c.sigobj.Call("org.freedesktop.systemd1.Manager.Unsubscribe", 0).Store() +} + +func (c *Conn) dispatch() { + ch := make(chan *dbus.Signal, signalBuffer) + + c.sigconn.Signal(ch) + + go func() { + for { + signal, ok := <-ch + if !ok { + return + } + + if signal.Name == "org.freedesktop.systemd1.Manager.JobRemoved" { + c.jobComplete(signal) + } + + if c.subStateSubscriber.updateCh == nil && + c.propertiesSubscriber.updateCh == nil { + continue + } + + var unitPath dbus.ObjectPath + switch signal.Name { + case "org.freedesktop.systemd1.Manager.JobRemoved": + unitName := signal.Body[2].(string) + c.sysobj.Call("org.freedesktop.systemd1.Manager.GetUnit", 0, unitName).Store(&unitPath) + case "org.freedesktop.systemd1.Manager.UnitNew": + unitPath = signal.Body[1].(dbus.ObjectPath) + case "org.freedesktop.DBus.Properties.PropertiesChanged": + if signal.Body[0].(string) == "org.freedesktop.systemd1.Unit" { + unitPath = signal.Path + + if len(signal.Body) >= 2 { + if changed, ok := signal.Body[1].(map[string]dbus.Variant); ok { + c.sendPropertiesUpdate(unitPath, changed) + } + } + } + } + + if unitPath == dbus.ObjectPath("") { + continue + } + + c.sendSubStateUpdate(unitPath) + } + }() +} + +// SubscribeUnits returns two unbuffered channels which will receive all changed units every +// interval. Deleted units are sent as nil. +func (c *Conn) SubscribeUnits(interval time.Duration) (<-chan map[string]*UnitStatus, <-chan error) { + return c.SubscribeUnitsCustom(interval, 0, func(u1, u2 *UnitStatus) bool { return *u1 != *u2 }, nil) +} + +// SubscribeUnitsCustom is like SubscribeUnits but lets you specify the buffer +// size of the channels, the comparison function for detecting changes and a filter +// function for cutting down on the noise that your channel receives. +func (c *Conn) SubscribeUnitsCustom(interval time.Duration, buffer int, isChanged func(*UnitStatus, *UnitStatus) bool, filterUnit func(string) bool) (<-chan map[string]*UnitStatus, <-chan error) { + old := make(map[string]*UnitStatus) + statusChan := make(chan map[string]*UnitStatus, buffer) + errChan := make(chan error, buffer) + + go func() { + for { + timerChan := time.After(interval) + + units, err := c.ListUnits() + if err == nil { + cur := make(map[string]*UnitStatus) + for i := range units { + if filterUnit != nil && filterUnit(units[i].Name) { + continue + } + cur[units[i].Name] = &units[i] + } + + // add all new or changed units + changed := make(map[string]*UnitStatus) + for n, u := range cur { + if oldU, ok := old[n]; !ok || isChanged(oldU, u) { + changed[n] = u + } + delete(old, n) + } + + // add all deleted units + for oldN := range old { + changed[oldN] = nil + } + + old = cur + + if len(changed) != 0 { + statusChan <- changed + } + } else { + errChan <- err + } + + <-timerChan + } + }() + + return statusChan, errChan +} + +type SubStateUpdate struct { + UnitName string + SubState string +} + +// SetSubStateSubscriber writes to updateCh when any unit's substate changes. +// Although this writes to updateCh on every state change, the reported state +// may be more recent than the change that generated it (due to an unavoidable +// race in the systemd dbus interface). That is, this method provides a good +// way to keep a current view of all units' states, but is not guaranteed to +// show every state transition they go through. Furthermore, state changes +// will only be written to the channel with non-blocking writes. If updateCh +// is full, it attempts to write an error to errCh; if errCh is full, the error +// passes silently. +func (c *Conn) SetSubStateSubscriber(updateCh chan<- *SubStateUpdate, errCh chan<- error) { + if c == nil { + msg := "nil receiver" + select { + case errCh <- errors.New(msg): + default: + log.Printf("full error channel while reporting: %s\n", msg) + } + return + } + + c.subStateSubscriber.Lock() + defer c.subStateSubscriber.Unlock() + c.subStateSubscriber.updateCh = updateCh + c.subStateSubscriber.errCh = errCh +} + +func (c *Conn) sendSubStateUpdate(unitPath dbus.ObjectPath) { + c.subStateSubscriber.Lock() + defer c.subStateSubscriber.Unlock() + + if c.subStateSubscriber.updateCh == nil { + return + } + + isIgnored := c.shouldIgnore(unitPath) + defer c.cleanIgnore() + if isIgnored { + return + } + + info, err := c.GetUnitPathProperties(unitPath) + if err != nil { + select { + case c.subStateSubscriber.errCh <- err: + default: + log.Printf("full error channel while reporting: %s\n", err) + } + return + } + defer c.updateIgnore(unitPath, info) + + name, ok := info["Id"].(string) + if !ok { + msg := "failed to cast info.Id" + select { + case c.subStateSubscriber.errCh <- errors.New(msg): + default: + log.Printf("full error channel while reporting: %s\n", err) + } + return + } + substate, ok := info["SubState"].(string) + if !ok { + msg := "failed to cast info.SubState" + select { + case c.subStateSubscriber.errCh <- errors.New(msg): + default: + log.Printf("full error channel while reporting: %s\n", msg) + } + return + } + + update := &SubStateUpdate{name, substate} + select { + case c.subStateSubscriber.updateCh <- update: + default: + msg := "update channel is full" + select { + case c.subStateSubscriber.errCh <- errors.New(msg): + default: + log.Printf("full error channel while reporting: %s\n", msg) + } + return + } +} + +// The ignore functions work around a wart in the systemd dbus interface. +// Requesting the properties of an unloaded unit will cause systemd to send a +// pair of UnitNew/UnitRemoved signals. Because we need to get a unit's +// properties on UnitNew (as that's the only indication of a new unit coming up +// for the first time), we would enter an infinite loop if we did not attempt +// to detect and ignore these spurious signals. The signal themselves are +// indistinguishable from relevant ones, so we (somewhat hackishly) ignore an +// unloaded unit's signals for a short time after requesting its properties. +// This means that we will miss e.g. a transient unit being restarted +// *immediately* upon failure and also a transient unit being started +// immediately after requesting its status (with systemctl status, for example, +// because this causes a UnitNew signal to be sent which then causes us to fetch +// the properties). + +func (c *Conn) shouldIgnore(path dbus.ObjectPath) bool { + t, ok := c.subStateSubscriber.ignore[path] + return ok && t >= time.Now().UnixNano() +} + +func (c *Conn) updateIgnore(path dbus.ObjectPath, info map[string]interface{}) { + loadState, ok := info["LoadState"].(string) + if !ok { + return + } + + // unit is unloaded - it will trigger bad systemd dbus behavior + if loadState == "not-found" { + c.subStateSubscriber.ignore[path] = time.Now().UnixNano() + ignoreInterval + } +} + +// without this, ignore would grow unboundedly over time +func (c *Conn) cleanIgnore() { + now := time.Now().UnixNano() + if c.subStateSubscriber.cleanIgnore < now { + c.subStateSubscriber.cleanIgnore = now + cleanIgnoreInterval + + for p, t := range c.subStateSubscriber.ignore { + if t < now { + delete(c.subStateSubscriber.ignore, p) + } + } + } +} + +// PropertiesUpdate holds a map of a unit's changed properties +type PropertiesUpdate struct { + UnitName string + Changed map[string]dbus.Variant +} + +// SetPropertiesSubscriber writes to updateCh when any unit's properties +// change. Every property change reported by systemd will be sent; that is, no +// transitions will be "missed" (as they might be with SetSubStateSubscriber). +// However, state changes will only be written to the channel with non-blocking +// writes. If updateCh is full, it attempts to write an error to errCh; if +// errCh is full, the error passes silently. +func (c *Conn) SetPropertiesSubscriber(updateCh chan<- *PropertiesUpdate, errCh chan<- error) { + c.propertiesSubscriber.Lock() + defer c.propertiesSubscriber.Unlock() + c.propertiesSubscriber.updateCh = updateCh + c.propertiesSubscriber.errCh = errCh +} + +// we don't need to worry about shouldIgnore() here because +// sendPropertiesUpdate doesn't call GetProperties() +func (c *Conn) sendPropertiesUpdate(unitPath dbus.ObjectPath, changedProps map[string]dbus.Variant) { + c.propertiesSubscriber.Lock() + defer c.propertiesSubscriber.Unlock() + + if c.propertiesSubscriber.updateCh == nil { + return + } + + update := &PropertiesUpdate{unitName(unitPath), changedProps} + + select { + case c.propertiesSubscriber.updateCh <- update: + default: + msg := "update channel is full" + select { + case c.propertiesSubscriber.errCh <- errors.New(msg): + default: + log.Printf("full error channel while reporting: %s\n", msg) + } + return + } +} |