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eventmeter.go
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/
eventmeter.go
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// eventmeter - generic system to subscribe to events and record their frequency.
package eventmeter
import (
"context"
"encoding/json"
"fmt"
"sync"
"time"
metrics "github.com/rcrowley/go-metrics"
"github.com/tendermint/tendermint/libs/events"
"github.com/tendermint/tendermint/libs/log"
client "github.com/tendermint/tendermint/rpc/lib/client"
)
const (
// Get ping/pong latency and call LatencyCallbackFunc with this period.
latencyPeriod = 1 * time.Second
// Check if the WS client is connected every
connectionCheckPeriod = 100 * time.Millisecond
)
// EventMetric exposes metrics for an event.
type EventMetric struct {
ID string `json:"id"`
Started time.Time `json:"start_time"`
LastHeard time.Time `json:"last_heard"`
MinDuration int64 `json:"min_duration"`
MaxDuration int64 `json:"max_duration"`
// tracks event count and rate
meter metrics.Meter
// filled in from the Meter
Count int64 `json:"count"`
Rate1 float64 `json:"rate_1" amino:"unsafe"`
Rate5 float64 `json:"rate_5" amino:"unsafe"`
Rate15 float64 `json:"rate_15" amino:"unsafe"`
RateMean float64 `json:"rate_mean" amino:"unsafe"`
// so the event can have effects in the eventmeter's consumer. runs in a go
// routine.
callback EventCallbackFunc
}
func (metric *EventMetric) Copy() *EventMetric {
metricCopy := *metric
metricCopy.meter = metric.meter.Snapshot()
return &metricCopy
}
// called on GetMetric
func (metric *EventMetric) fillMetric() *EventMetric {
metric.Count = metric.meter.Count()
metric.Rate1 = metric.meter.Rate1()
metric.Rate5 = metric.meter.Rate5()
metric.Rate15 = metric.meter.Rate15()
metric.RateMean = metric.meter.RateMean()
return metric
}
// EventCallbackFunc is a closure to enable side effects from receiving an
// event.
type EventCallbackFunc func(em *EventMetric, data interface{})
// EventUnmarshalFunc is a closure to get the query and data out of the raw
// JSON received over the RPC WebSocket.
type EventUnmarshalFunc func(b json.RawMessage) (string, events.EventData, error)
// LatencyCallbackFunc is a closure to enable side effects from receiving a latency.
type LatencyCallbackFunc func(meanLatencyNanoSeconds float64)
// DisconnectCallbackFunc is a closure to notify a consumer that the connection
// has died.
type DisconnectCallbackFunc func()
// EventMeter tracks events, reports latency and disconnects.
type EventMeter struct {
wsc *client.WSClient
mtx sync.Mutex
queryToMetricMap map[string]*EventMetric
unmarshalEvent EventUnmarshalFunc
latencyCallback LatencyCallbackFunc
disconnectCallback DisconnectCallbackFunc
subscribed bool
quit chan struct{}
logger log.Logger
}
func NewEventMeter(addr string, unmarshalEvent EventUnmarshalFunc) *EventMeter {
return &EventMeter{
wsc: client.NewWSClient(addr, "/websocket", client.PingPeriod(1*time.Second)),
queryToMetricMap: make(map[string]*EventMetric),
unmarshalEvent: unmarshalEvent,
logger: log.NewNopLogger(),
}
}
// SetLogger lets you set your own logger.
func (em *EventMeter) SetLogger(l log.Logger) {
em.logger = l
em.wsc.SetLogger(l.With("module", "rpcclient"))
}
// String returns a string representation of event meter.
func (em *EventMeter) String() string {
return em.wsc.Address
}
// Start boots up event meter.
func (em *EventMeter) Start() error {
if err := em.wsc.Start(); err != nil {
return err
}
em.quit = make(chan struct{})
go em.receiveRoutine()
go em.disconnectRoutine()
err := em.subscribe()
if err != nil {
return err
}
em.subscribed = true
return nil
}
// Stop stops event meter.
func (em *EventMeter) Stop() {
close(em.quit)
if em.wsc.IsRunning() {
em.wsc.Stop()
}
}
// Subscribe for the given query. Callback function will be called upon
// receiving an event.
func (em *EventMeter) Subscribe(query string, cb EventCallbackFunc) error {
em.mtx.Lock()
defer em.mtx.Unlock()
if err := em.wsc.Subscribe(context.TODO(), query); err != nil {
return err
}
metric := &EventMetric{
meter: metrics.NewMeter(),
callback: cb,
}
em.queryToMetricMap[query] = metric
return nil
}
// Unsubscribe from the given query.
func (em *EventMeter) Unsubscribe(query string) error {
em.mtx.Lock()
defer em.mtx.Unlock()
return em.wsc.Unsubscribe(context.TODO(), query)
}
// GetMetric fills in the latest data for an query and return a copy.
func (em *EventMeter) GetMetric(query string) (*EventMetric, error) {
em.mtx.Lock()
defer em.mtx.Unlock()
metric, ok := em.queryToMetricMap[query]
if !ok {
return nil, fmt.Errorf("unknown query: %s", query)
}
return metric.fillMetric().Copy(), nil
}
// RegisterLatencyCallback allows you to set latency callback.
func (em *EventMeter) RegisterLatencyCallback(f LatencyCallbackFunc) {
em.mtx.Lock()
defer em.mtx.Unlock()
em.latencyCallback = f
}
// RegisterDisconnectCallback allows you to set disconnect callback.
func (em *EventMeter) RegisterDisconnectCallback(f DisconnectCallbackFunc) {
em.mtx.Lock()
defer em.mtx.Unlock()
em.disconnectCallback = f
}
///////////////////////////////////////////////////////////////////////////////
// Private
func (em *EventMeter) subscribe() error {
for query := range em.queryToMetricMap {
if err := em.wsc.Subscribe(context.TODO(), query); err != nil {
return err
}
}
return nil
}
func (em *EventMeter) receiveRoutine() {
latencyTicker := time.NewTicker(latencyPeriod)
for {
select {
case resp := <-em.wsc.ResponsesCh:
if resp.Error != nil {
em.logger.Error("expected some event, got error", "err", resp.Error.Error())
continue
}
query, data, err := em.unmarshalEvent(resp.Result)
if err != nil {
em.logger.Error("failed to unmarshal event", "err", err)
continue
}
if query != "" { // FIXME how can it be an empty string?
em.updateMetric(query, data)
}
case <-latencyTicker.C:
if em.wsc.IsActive() {
em.callLatencyCallback(em.wsc.PingPongLatencyTimer.Mean())
}
case <-em.wsc.Quit():
return
case <-em.quit:
return
}
}
}
func (em *EventMeter) disconnectRoutine() {
ticker := time.NewTicker(connectionCheckPeriod)
for {
select {
case <-ticker.C:
if em.wsc.IsReconnecting() && em.subscribed { // notify user about disconnect only once
em.callDisconnectCallback()
em.subscribed = false
} else if !em.wsc.IsReconnecting() && !em.subscribed { // resubscribe
em.subscribe()
em.subscribed = true
}
case <-em.wsc.Quit():
return
case <-em.quit:
return
}
}
}
func (em *EventMeter) updateMetric(query string, data events.EventData) {
em.mtx.Lock()
defer em.mtx.Unlock()
metric, ok := em.queryToMetricMap[query]
if !ok {
// we already unsubscribed, or got an unexpected query
return
}
last := metric.LastHeard
metric.LastHeard = time.Now()
metric.meter.Mark(1)
dur := int64(metric.LastHeard.Sub(last))
if dur < metric.MinDuration {
metric.MinDuration = dur
}
if !last.IsZero() && dur > metric.MaxDuration {
metric.MaxDuration = dur
}
if metric.callback != nil {
go metric.callback(metric.Copy(), data)
}
}
func (em *EventMeter) callDisconnectCallback() {
em.mtx.Lock()
if em.disconnectCallback != nil {
go em.disconnectCallback()
}
em.mtx.Unlock()
}
func (em *EventMeter) callLatencyCallback(meanLatencyNanoSeconds float64) {
em.mtx.Lock()
if em.latencyCallback != nil {
go em.latencyCallback(meanLatencyNanoSeconds)
}
em.mtx.Unlock()
}