open-consul/watch/watch.go

189 lines
4.9 KiB
Go

package watch
import (
"context"
"fmt"
"io"
"sync"
"time"
consulapi "github.com/hashicorp/consul/api"
"github.com/mitchellh/mapstructure"
)
const DefaultTimeout = 10 * time.Second
// Plan 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 Plan struct {
Datacenter string
Token string
Type string
HandlerType string
Exempt map[string]interface{}
Watcher WatcherFunc
Handler HandlerFunc
LogOutput io.Writer
address string
client *consulapi.Client
lastIndex uint64
lastResult interface{}
stop bool
stopCh chan struct{}
stopLock sync.Mutex
cancelFunc context.CancelFunc
}
type HttpHandlerConfig struct {
Path string `mapstructure:"path"`
Method string `mapstructure:"method"`
Timeout time.Duration `mapstructure:"-"`
TimeoutRaw string `mapstructure:"timeout"`
Header map[string][]string `mapstructure:"header"`
TLSSkipVerify bool `mapstructure:"tls_skip_verify"`
}
// WatcherFunc is used to watch for a diff
type WatcherFunc func(*Plan) (uint64, interface{}, error)
// HandlerFunc is used to handle new data
type HandlerFunc func(uint64, interface{})
// Parse takes a watch query and compiles it into a WatchPlan or an error
func Parse(params map[string]interface{}) (*Plan, error) {
return ParseExempt(params, nil)
}
// ParseExempt takes a watch query and compiles it into a WatchPlan or an error
// Any exempt parameters are stored in the Exempt map
func ParseExempt(params map[string]interface{}, exempt []string) (*Plan, error) {
plan := &Plan{
stopCh: make(chan struct{}),
Exempt: make(map[string]interface{}),
}
// 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
}
if err := assignValue(params, "type", &plan.Type); err != nil {
return nil, err
}
// Ensure there is a watch type
if plan.Type == "" {
return nil, fmt.Errorf("Watch type must be specified")
}
// Get the specific handler
if err := assignValue(params, "handler_type", &plan.HandlerType); err != nil {
return nil, err
}
switch plan.HandlerType {
case "http":
if _, ok := params["http_handler_config"]; !ok {
return nil, fmt.Errorf("Handler type 'http' requires 'http_handler_config' to be set")
}
config, err := parseHttpHandlerConfig(params["http_handler_config"])
if err != nil {
return nil, fmt.Errorf(fmt.Sprintf("Failed to parse 'http_handler_config': %v", err))
}
plan.Exempt["http_handler_config"] = config
delete(params, "http_handler_config")
case "script":
// Let the caller check for configuration in exempt parameters
}
// Look for a factory function
factory := watchFuncFactory[plan.Type]
if factory == nil {
return nil, fmt.Errorf("Unsupported watch type: %s", plan.Type)
}
// Get the watch func
fn, err := factory(params)
if err != nil {
return nil, err
}
plan.Watcher = fn
// Remove the exempt parameters
if len(exempt) > 0 {
for _, ex := range exempt {
val, ok := params[ex]
if ok {
plan.Exempt[ex] = val
delete(params, ex)
}
}
}
// 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)
}
return plan, nil
}
// 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 {
return fmt.Errorf("Expecting %s to be a string", name)
}
*out = val
delete(params, name)
}
return nil
}
// 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 {
return fmt.Errorf("Expecting %s to be a boolean", name)
}
*out = val
delete(params, name)
}
return nil
}
// Parse the 'http_handler_config' parameters
func parseHttpHandlerConfig(configParams interface{}) (*HttpHandlerConfig, error) {
var config HttpHandlerConfig
if err := mapstructure.Decode(configParams, &config); err != nil {
return nil, err
}
if config.Path == "" {
return nil, fmt.Errorf("Requires 'path' to be set")
}
if config.Method == "" {
config.Method = "POST"
}
if config.TimeoutRaw == "" {
config.Timeout = DefaultTimeout
} else if timeout, err := time.ParseDuration(config.TimeoutRaw); err != nil {
return nil, fmt.Errorf(fmt.Sprintf("Failed to parse timeout: %v", err))
} else {
config.Timeout = timeout
}
return &config, nil
}