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 is kept for backward compatibility but only supports watches based // on index param. To support hash based watches, set HybridHandler instead. Handler HandlerFunc HybridHandler HybridHandlerFunc LogOutput io.Writer address string client *consulapi.Client lastParamVal BlockingParamVal 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"` } // BlockingParamVal is an interface representing the common operations needed for // different styles of blocking. It's used to abstract the core watch plan from // whether we are performing index-based or hash-based blocking. type BlockingParamVal interface { // Equal returns whether the other param value should be considered equal // (i.e. representing no change in the watched resource). Equal must not panic // if other is nil. Equal(other BlockingParamVal) bool // Next is called when deciding which value to use on the next blocking call. // It assumes the BlockingParamVal value it is called on is the most recent one // returned and passes the previous one which may be nil as context. This // allows types to customize logic around ordering without assuming there is // an order. For example WaitIndexVal can check that the index didn't go // backwards and if it did then reset to 0. Most other cases should just // return themselves (the most recent value) to be used in the next request. Next(previous BlockingParamVal) BlockingParamVal } // WaitIndexVal is a type representing a Consul index that implements // BlockingParamVal. type WaitIndexVal uint64 // Equal implements BlockingParamVal func (idx WaitIndexVal) Equal(other BlockingParamVal) bool { if otherIdx, ok := other.(WaitIndexVal); ok { return idx == otherIdx } return false } // Next implements BlockingParamVal func (idx WaitIndexVal) Next(previous BlockingParamVal) BlockingParamVal { if previous == nil { return idx } prevIdx, ok := previous.(WaitIndexVal) if ok && prevIdx > idx { // This value is smaller than the previous index, reset. return WaitIndexVal(0) } return idx } // WaitHashVal is a type representing a Consul content hash that implements // BlockingParamVal. type WaitHashVal string // Equal implements BlockingParamVal func (h WaitHashVal) Equal(other BlockingParamVal) bool { if otherHash, ok := other.(WaitHashVal); ok { return h == otherHash } return false } // Next implements BlockingParamVal func (h WaitHashVal) Next(previous BlockingParamVal) BlockingParamVal { return h } // WatcherFunc is used to watch for a diff. type WatcherFunc func(*Plan) (BlockingParamVal, interface{}, error) // HandlerFunc is used to handle new data. It only works for index-based watches // (which is almost all end points currently) and is kept for backwards // compatibility until more places can make use of hash-based watches too. type HandlerFunc func(uint64, interface{}) // HybridHandlerFunc is used to handle new data. It can support either // index-based or hash-based watches via the BlockingParamVal. type HybridHandlerFunc func(BlockingParamVal, 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 }