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plugin/health: add OnRestartFailed (#2812)

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Add OnReStartFailed which makes the health plugin stay up if the
Corefile is corrupt and we revert to the previous version.

Also needs a fix for the channel handling

See #2659

Testing it will log the following when restarting with a corrupted
Corefile

~~~
2019-05-04T18:01:59.431Z [INFO] linux/amd64, go1.12.4,
CoreDNS-1.5.0
linux/amd64, go1.12.4,
[INFO] SIGUSR1: Reloading
[INFO] Reloading
[ERROR] Restart failed: Corefile:5 - Error during parsing: Unknown directive 'bdhfhdhj'
[ERROR] SIGUSR1: starting with listener file descriptors: Corefile:5 - Error during parsing: Unknown directive 'bdhfhdhj'
~~~

After which the curl still works.

This also needed a change to reset the channel used for the metrics
go-routine which gets closed on shutdown, otherwise you'll see:

~~~
^C[INFO] SIGINT: Shutting down
panic: close of closed channel

goroutine 90 [running]:
github.com/coredns/coredns/plugin/health.(*health).OnFinalShutdown(0xc000089bc0, 0xc000063d88, 0x4afe6d)
~~~

Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2019-05-04 21:06:25 +01:00
committed by Yong Tang
parent 890cdb5cab
commit 076b8d4fba
3 changed files with 3 additions and 10 deletions
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7
plugin/health/README.md
View File

@@ -76,10 +76,3 @@ Set a lameduck duration of 1 second:
}
}
~~~
## Bugs
When reloading, the health handler is stopped before the new server instance is started. If that
new server fails to start, then the initial server instance is still available and DNS queries still
served, but health handler stays down. Health will not reply HTTP request until a successful reload
or a complete restart of CoreDNS.

3
plugin/health/health.go
View File

@@ -28,6 +28,7 @@ func (h *health) OnStartup() error {
if h.Addr == "" {
h.Addr = ":8080"
}
h.stop = make(chan bool)
ln, err := net.Listen("tcp", h.Addr)
if err != nil {
@@ -51,8 +52,6 @@ func (h *health) OnStartup() error {
return nil
}
func (h *health) OnRestart() error { return h.OnFinalShutdown() }
func (h *health) OnFinalShutdown() error {
if !h.nlSetup {
return nil

3
plugin/health/setup.go
View File

@@ -32,8 +32,9 @@ func setup(c *caddy.Controller) error {
})
c.OnStartup(h.OnStartup)
c.OnRestart(h.OnRestart)
c.OnRestart(h.OnFinalShutdown)
c.OnFinalShutdown(h.OnFinalShutdown)
c.OnRestartFailed(h.OnStartup)
// Don't do AddPlugin, as health is not *really* a plugin just a separate webserver running.
return nil