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add streaming reconnect example and fix mod
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| /* | ||
| * Flow Go SDK | ||
| * | ||
| * Copyright 2019 Dapper Labs, Inc. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
|
||
| package main | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
|
|
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| "github.com/onflow/flow-go-sdk/access/grpc" | ||
|
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| "github.com/onflow/flow-go-sdk" | ||
| "github.com/onflow/flow-go-sdk/examples" | ||
| ) | ||
|
|
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| func main() { | ||
| demo() | ||
| } | ||
|
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| // This is an example of streaming events, and handling reconnect when errors are encountered on the stream. | ||
|
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| func demo() { | ||
| ctx := context.Background() | ||
| flowClient, err := grpc.NewClient("access.testnet.nodes.onflow.org:9000") | ||
| examples.Handle(err) | ||
|
|
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| block, err := flowClient.GetLatestBlock(ctx, true) | ||
| examples.Handle(err) | ||
| fmt.Printf("Block Height: %d\n", block.Height) | ||
| fmt.Printf("Block ID: %s\n", block.ID) | ||
|
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| data, errChan, initErr := flowClient.SubscribeEvents(ctx, block.ID, 0, flow.EventFilter{}) | ||
| examples.Handle(initErr) | ||
|
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| reconnect := func(height uint64) { | ||
| fmt.Printf("Reconnecting at block %d\n", height) | ||
|
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| var err error | ||
| flowClient, err = grpc.NewClient("access.testnet.nodes.onflow.org:9000") | ||
| examples.Handle(err) | ||
|
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| data, errChan, err = flowClient.SubscribeEvents(ctx, flow.EmptyID, height, flow.EventFilter{}) | ||
| examples.Handle(err) | ||
| } | ||
|
|
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| // track the most recently seen block height. we will use this when reconnecting | ||
| lastHeight := block.Height | ||
| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| return | ||
|
|
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| case eventData, ok := <-data: | ||
| if !ok { | ||
| if ctx.Err() != nil { | ||
| return // graceful shutdown | ||
| } | ||
| // unexpected close | ||
| reconnect(lastHeight + 1) | ||
| continue | ||
| } | ||
|
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| fmt.Printf("~~~ Height: %d ~~~\n", eventData.Height) | ||
| printEvents(eventData.Events) | ||
|
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| lastHeight = eventData.Height | ||
|
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| case err, ok := <-errChan: | ||
| if !ok { | ||
| if ctx.Err() != nil { | ||
| return // graceful shutdown | ||
| } | ||
| // unexpected close | ||
| reconnect(lastHeight + 1) | ||
| continue | ||
| } | ||
|
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| fmt.Printf("~~~ ERROR: %s ~~~\n", err.Error()) | ||
| reconnect(lastHeight + 1) | ||
| continue | ||
| } | ||
| } | ||
|
|
||
| } | ||
|
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| func printEvents(events []flow.Event) { | ||
| for _, event := range events { | ||
| fmt.Printf("\nType: %s\n", event.Type) | ||
| fmt.Printf("Values: %v\n", event.Value) | ||
| fmt.Printf("Transaction ID: %s\n", event.TransactionID) | ||
| } | ||
| } |
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