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package core
import (
"context"
"errors"
"fmt"
"time"
tmpubsub "github.com/tendermint/tendermint/libs/pubsub"
tmquery "github.com/tendermint/tendermint/libs/pubsub/query"
"github.com/tendermint/tendermint/rpc/coretypes"
rpctypes "github.com/tendermint/tendermint/rpc/jsonrpc/types"
)
const (
// Buffer on the Tendermint (server) side to allow some slowness in clients.
subBufferSize = 100
// maxQueryLength is the maximum length of a query string that will be
// accepted. This is just a safety check to avoid outlandish queries.
maxQueryLength = 512
)
// Subscribe for events via WebSocket.
// More: https://docs.tendermint.com/master/rpc/#/Websocket/subscribe
func (env *Environment) Subscribe(ctx *rpctypes.Context, query string) (*coretypes.ResultSubscribe, error) {
addr := ctx.RemoteAddr()
if env.EventBus.NumClients() >= env.Config.MaxSubscriptionClients {
return nil, fmt.Errorf("max_subscription_clients %d reached", env.Config.MaxSubscriptionClients)
} else if env.EventBus.NumClientSubscriptions(addr) >= env.Config.MaxSubscriptionsPerClient {
return nil, fmt.Errorf("max_subscriptions_per_client %d reached", env.Config.MaxSubscriptionsPerClient)
} else if len(query) > maxQueryLength {
return nil, errors.New("maximum query length exceeded")
}
env.Logger.Info("Subscribe to query", "remote", addr, "query", query)
q, err := tmquery.New(query)
if err != nil {
return nil, fmt.Errorf("failed to parse query: %w", err)
}
subCtx, cancel := context.WithTimeout(ctx.Context(), SubscribeTimeout)
defer cancel()
sub, err := env.EventBus.SubscribeWithArgs(subCtx, tmpubsub.SubscribeArgs{
ClientID: addr,
Query: q,
Limit: subBufferSize,
})
if err != nil {
return nil, err
}
// Capture the current ID, since it can change in the future.
subscriptionID := ctx.JSONReq.ID
go func() {
opctx, opcancel := context.WithCancel(context.Background())
defer opcancel()
for {
msg, err := sub.Next(opctx)
if errors.Is(err, tmpubsub.ErrUnsubscribed) {
// The subscription was removed by the client.
return
} else if errors.Is(err, tmpubsub.ErrTerminated) {
// The subscription was terminated by the publisher.
resp := rpctypes.RPCServerError(subscriptionID, err)
ok := ctx.WSConn.TryWriteRPCResponse(opctx, resp)
if !ok {
env.Logger.Info("Unable to write response (slow client)",
"to", addr, "subscriptionID", subscriptionID, "err", err)
}
return
}
// We have a message to deliver to the client.
resp := rpctypes.NewRPCSuccessResponse(subscriptionID, &coretypes.ResultEvent{
Query: query,
Data: msg.Data(),
Events: msg.Events(),
})
wctx, cancel := context.WithTimeout(opctx, 10*time.Second)
err = ctx.WSConn.WriteRPCResponse(wctx, resp)
cancel()
if err != nil {
env.Logger.Info("Unable to write response (slow client)",
"to", addr, "subscriptionID", subscriptionID, "err", err)
}
}
}()
return &coretypes.ResultSubscribe{}, nil
}
// Unsubscribe from events via WebSocket.
// More: https://docs.tendermint.com/master/rpc/#/Websocket/unsubscribe
func (env *Environment) Unsubscribe(ctx *rpctypes.Context, query string) (*coretypes.ResultUnsubscribe, error) {
args := tmpubsub.UnsubscribeArgs{Subscriber: ctx.RemoteAddr()}
env.Logger.Info("Unsubscribe from query", "remote", args.Subscriber, "subscription", query)
var err error
args.Query, err = tmquery.New(query)
if err != nil {
args.ID = query
}
err = env.EventBus.Unsubscribe(ctx.Context(), args)
if err != nil {
return nil, err
}
return &coretypes.ResultUnsubscribe{}, nil
}
// UnsubscribeAll from all events via WebSocket.
// More: https://docs.tendermint.com/master/rpc/#/Websocket/unsubscribe_all
func (env *Environment) UnsubscribeAll(ctx *rpctypes.Context) (*coretypes.ResultUnsubscribe, error) {
addr := ctx.RemoteAddr()
env.Logger.Info("Unsubscribe from all", "remote", addr)
err := env.EventBus.UnsubscribeAll(ctx.Context(), addr)
if err != nil {
return nil, err
}
return &coretypes.ResultUnsubscribe{}, nil
}