open-consul/watch/watch.go

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package watch
import (
"fmt"
"io"
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"sync"
consulapi "github.com/hashicorp/consul/api"
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)
// WatchPlan is the parsed version of a watch specification. A watch provides
// the details of a query, which generates a view into the Consul data store.
// This view is watched for changes and a handler is invoked to take any
// appropriate actions.
type WatchPlan struct {
Datacenter string
Token string
Type string
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Exempt map[string]interface{}
Func WatchFunc
Handler HandlerFunc
LogOutput io.Writer
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address string
client *consulapi.Client
lastIndex uint64
lastResult interface{}
stop bool
stopCh chan struct{}
stopLock sync.Mutex
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}
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// WatchFunc is used to watch for a diff
type WatchFunc func(*WatchPlan) (uint64, interface{}, error)
// HandlerFunc is used to handle new data
type HandlerFunc func(uint64, interface{})
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// Parse takes a watch query and compiles it into a WatchPlan or an error
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func Parse(params map[string]interface{}) (*WatchPlan, error) {
return ParseExempt(params, nil)
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}
// ParseExempt takes a watch query and compiles it into a WatchPlan or an error
// Any exempt parameters are stored in the Exempt map
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func ParseExempt(params map[string]interface{}, exempt []string) (*WatchPlan, error) {
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plan := &WatchPlan{
stopCh: make(chan struct{}),
}
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// Parse the generic parameters
if err := assignValue(params, "datacenter", &plan.Datacenter); err != nil {
return nil, err
}
if err := assignValue(params, "token", &plan.Token); err != nil {
return nil, err
}
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if err := assignValue(params, "type", &plan.Type); err != nil {
return nil, err
}
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// Ensure there is a watch type
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if plan.Type == "" {
return nil, fmt.Errorf("Watch type must be specified")
}
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// Look for a factory function
factory := watchFuncFactory[plan.Type]
if factory == nil {
return nil, fmt.Errorf("Unsupported watch type: %s", plan.Type)
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}
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// Get the watch func
fn, err := factory(params)
if err != nil {
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return nil, err
}
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plan.Func = fn
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// Remove the exempt parameters
if len(exempt) > 0 {
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plan.Exempt = make(map[string]interface{})
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for _, ex := range exempt {
val, ok := params[ex]
if ok {
plan.Exempt[ex] = val
delete(params, ex)
}
}
}
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// Ensure all parameters are consumed
if len(params) != 0 {
var bad []string
for key := range params {
bad = append(bad, key)
}
return nil, fmt.Errorf("Invalid parameters: %v", bad)
}
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return plan, nil
}
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// assignValue is used to extract a value ensuring it is a string
func assignValue(params map[string]interface{}, name string, out *string) error {
if raw, ok := params[name]; ok {
val, ok := raw.(string)
if !ok {
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return fmt.Errorf("Expecting %s to be a string", name)
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}
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*out = val
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delete(params, name)
}
return nil
}
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// assignValueBool is used to extract a value ensuring it is a bool
func assignValueBool(params map[string]interface{}, name string, out *bool) error {
if raw, ok := params[name]; ok {
val, ok := raw.(bool)
if !ok {
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return fmt.Errorf("Expecting %s to be a boolean", name)
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}
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*out = val
delete(params, name)
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}
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return nil
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}