db0b16b615
Add a ready plugin that allows plugin to signal when they are ready.
Once a plugin is ready it is not queried again.
This uses same mechanism as the health plugin: each plugin needs to
implement an interface.
Implement readines for the *erratic* plugin to aid in testing.
Add README.md and tests moduled after the health plugin; which will be
relegated to just providing process health. In similar vein to health
this is a process wide setting.
With this Corefile:
~~~
. {
erratic
whoami
ready
}
bla {
erratic
whoami
}
~~~
ready will lead to:
~~~ sh
% curl localhost:8181/ready
% dig @localhost -p 1053 mx example.org
% curl localhost:8181/ready
OK%
~~~
Meanwhile CoreDNS logs:
~~~
.:1053
bla.:1053
2019-02-26T20:59:07.137Z [INFO] CoreDNS-1.3.1
2019-02-26T20:59:07.137Z [INFO] linux/amd64, go1.11.4,
CoreDNS-1.3.1
linux/amd64, go1.11.4,
2019-02-26T20:59:11.415Z [INFO] plugin/ready: Still waiting on: "erratic"
2019-02-26T20:59:13.510Z [INFO] plugin/ready: Still waiting on: "erratic"
~~~
*ready* can be used in multiple server blocks and will do the right
thing; query all those plugins from all server blocks for readiness.
This does a similar thing to the prometheus plugin.
Signed-off-by: Miek Gieben <miek@miek.nl>
75 lines
1.2 KiB
Go
75 lines
1.2 KiB
Go
package ready
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import (
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"net"
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"github.com/coredns/coredns/core/dnsserver"
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"github.com/coredns/coredns/plugin"
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"github.com/mholt/caddy"
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)
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func init() {
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caddy.RegisterPlugin("ready", caddy.Plugin{
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ServerType: "dns",
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Action: setup,
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})
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}
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func setup(c *caddy.Controller) error {
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addr, err := parse(c)
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if err != nil {
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return plugin.Error("ready", err)
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}
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rd := &ready{Addr: addr}
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uniqAddr.Set(addr, rd.onStartup, rd)
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c.OncePerServerBlock(func() error {
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c.OnStartup(func() error {
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return uniqAddr.ForEach()
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})
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return nil
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})
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c.OnStartup(func() error {
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// Each plugin in this server block will (if they support it) report readiness.
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plugs := dnsserver.GetConfig(c).Handlers()
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for _, p := range plugs {
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if r, ok := p.(Readiness); ok {
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plugins.Append(r, p.Name())
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}
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}
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return nil
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})
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c.OnRestart(rd.onRestart)
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c.OnFinalShutdown(rd.onFinalShutdown)
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return nil
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}
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func parse(c *caddy.Controller) (string, error) {
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addr := ""
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i := 0
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for c.Next() {
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if i > 0 {
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return "", plugin.ErrOnce
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}
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i++
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args := c.RemainingArgs()
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switch len(args) {
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case 0:
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case 1:
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addr = args[0]
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if _, _, e := net.SplitHostPort(addr); e != nil {
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return "", e
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}
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default:
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return "", c.ArgErr()
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}
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}
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return addr, nil
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}
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