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>
48 lines
948 B
Go
48 lines
948 B
Go
package ready
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import (
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"sort"
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"strings"
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"sync"
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)
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// list is structure that holds the plugins that signals readiness for this server block.
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type list struct {
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sync.RWMutex
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rs []Readiness
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names []string
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}
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// Append adds a new readiness to l.
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func (l *list) Append(r Readiness, name string) {
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l.Lock()
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defer l.Unlock()
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l.rs = append(l.rs, r)
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l.names = append(l.names, name)
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}
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// Ready return true when all plugins ready, if the returned value is false the string
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// contains a comma separated list of plugins that are not ready.
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func (l *list) Ready() (bool, string) {
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l.RLock()
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defer l.RUnlock()
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ok := true
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s := []string{}
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for i, r := range l.rs {
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if r == nil {
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continue
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}
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if !r.Ready() {
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ok = false
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s = append(s, l.names[i])
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} else {
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// if ok, this plugin is ready and will not be queried anymore.
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l.rs[i] = nil
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}
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}
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if ok {
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return true, ""
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}
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sort.Strings(s)
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return false, strings.Join(s, ",")
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}
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