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path: root/rpc/client_example_test.go
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-rw-r--r--rpc/client_example_test.go57
1 files changed, 31 insertions, 26 deletions
diff --git a/rpc/client_example_test.go b/rpc/client_example_test.go
index 84b4b67bb..3462b3685 100644
--- a/rpc/client_example_test.go
+++ b/rpc/client_example_test.go
@@ -22,6 +22,7 @@ import (
"time"
"github.com/ethereum/go-ethereum/rpc"
+ "golang.org/x/net/context"
)
// In this example, our client whishes to track the latest 'block number'
@@ -41,7 +42,16 @@ func ExampleClientSubscription() {
// Connect the client.
client, _ := rpc.Dial("ws://127.0.0.1:8485")
subch := make(chan Block)
- go subscribeBlocks(client, subch)
+
+ // Ensure that subch receives the latest block.
+ go func() {
+ for i := 0; ; i++ {
+ if i > 0 {
+ time.Sleep(2 * time.Second)
+ }
+ subscribeBlocks(client, subch)
+ }
+ }()
// Print events from the subscription as they arrive.
for block := range subch {
@@ -52,32 +62,27 @@ func ExampleClientSubscription() {
// subscribeBlocks runs in its own goroutine and maintains
// a subscription for new blocks.
func subscribeBlocks(client *rpc.Client, subch chan Block) {
- for i := 0; ; i++ {
- if i > 0 {
- time.Sleep(2 * time.Second)
- }
-
- // Subscribe to new blocks.
- sub, err := client.EthSubscribe(subch, "newBlocks")
- if err == rpc.ErrClientQuit {
- return // Stop reconnecting if the client was closed.
- } else if err != nil {
- fmt.Println("subscribe error:", err)
- continue
- }
+ ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+ defer cancel()
- // The connection is established now.
- // Update the channel with the current block.
- var lastBlock Block
- if err := client.Call(&lastBlock, "eth_getBlockByNumber", "latest"); err != nil {
- fmt.Println("can't get latest block:", err)
- continue
- }
- subch <- lastBlock
+ // Subscribe to new blocks.
+ sub, err := client.EthSubscribe(ctx, subch, "newBlocks")
+ if err != nil {
+ fmt.Println("subscribe error:", err)
+ return
+ }
- // The subscription will deliver events to the channel. Wait for the
- // subscription to end for any reason, then loop around to re-establish
- // the connection.
- fmt.Println("connection lost: ", <-sub.Err())
+ // The connection is established now.
+ // Update the channel with the current block.
+ var lastBlock Block
+ if err := client.CallContext(ctx, &lastBlock, "eth_getBlockByNumber", "latest"); err != nil {
+ fmt.Println("can't get latest block:", err)
+ return
}
+ subch <- lastBlock
+
+ // The subscription will deliver events to the channel. Wait for the
+ // subscription to end for any reason, then loop around to re-establish
+ // the connection.
+ fmt.Println("connection lost: ", <-sub.Err())
}