Server Client

The server client uses direct Hedera operator credentials to create checkpoint topics and publish checkpoint commitments.

Create a ClientDirect link to Create a Client

TypeScript
Go
Python

// HCS-27 TypeScript support is not yet available.
// Coming soon to @hashgraphonline/standards-sdk.

import "github.com/hashgraph-online/standards-sdk-go/pkg/hcs27"

client, err := hcs27.NewClient(hcs27.ClientConfig{
	OperatorAccountID:  os.Getenv("HEDERA_ACCOUNT_ID"),
	OperatorPrivateKey: os.Getenv("HEDERA_PRIVATE_KEY"),
	Network:            "testnet",
})
if err != nil {
	log.Fatal(err)
}

import os
from standards_sdk_py.hcs27 import Hcs27Client


client = Hcs27Client(
    operator_id=os.environ["HEDERA_ACCOUNT_ID"],
    operator_private_key=os.environ["HEDERA_PRIVATE_KEY"],
    network="testnet",
)

Create a Checkpoint TopicDirect link to Create a Checkpoint Topic

TypeScript
Go
Python

// Not yet available.

topicID, txID, err := client.CreateCheckpointTopic(ctx, hcs27.CreateTopicOptions{
	TTLSeconds:          86400,
	UseOperatorAsAdmin:  true,
	UseOperatorAsSubmit: true,
})
if err != nil {
	log.Fatal(err)
}
fmt.Printf("Created checkpoint topic: %s (tx: %s)\n", topicID, txID)

txID = client.create_checkpoint_topic(ttl_seconds=86400, use_operator_as_admin=True, use_operator_as_submit=True)
fmt.printf("Created checkpoint topic: %s (tx: %s)\n", topicID, txID)

Publish a CheckpointDirect link to Publish a Checkpoint

TypeScript
Go
Python

// Not yet available.

metadata := hcs27.CheckpointMetadata{
	Type:   "ans-checkpoint-v1",
	Stream: hcs27.StreamID{Registry: "my-app", LogID: "events"},
	Log: &hcs27.LogProfile{
		Algorithm: "sha-256",
		Leaf:      "rfc6962-leaf",
		Merkle:    "rfc6962-node",
	},
	Root: hcs27.RootCommitment{
		TreeSize:    150,
		RootHashB64: "8zVIY3QJBOdTYR8dnLOzedEfym4Jl7f1xy8pciLEMew",
	},
	Previous: &hcs27.PreviousCommitment{
		TreeSize:    100,
		RootHashB64: "kZ4L2bPe1sX...",
	},
	BatchRange: hcs27.BatchRange{Start: 101, End: 150},
}

result, err := client.PublishCheckpoint(ctx, topicID, metadata, "batch 101-150", "")
if err != nil {
	log.Fatal(err)
}
fmt.Printf("Published checkpoint (seq: %d, tx: %s)\n", result.SequenceNumber, result.TransactionID)

metadata = hcs27.CheckpointMetadata{
# Type:   "ans-checkpoint-v1",
# Stream: {"registry": "my-app", "log_id": "events"},
# Log: &hcs27.LogProfile{
# Algorithm: "sha-256",
# Leaf:      "rfc6962-leaf",
# Merkle:    "rfc6962-node",
# Root: hcs27.RootCommitment{
# TreeSize:    150,
# RootHashB64: "8zVIY3QJBOdTYR8dnLOzedEfym4Jl7f1xy8pciLEMew",
# Previous: &hcs27.PreviousCommitment{
# TreeSize:    100,
# RootHashB64: "kZ4L2bPe1sX...",
# BatchRange: {"start": 101, "end": 150},

result = client.publish_checkpoint(topicID, metadata, "batch 101-150")
fmt.printf("Published checkpoint (seq: %d, tx: %s)\n", result.SEQUENCE_NUMBER, result.TRANSACTION_I_D)

Notes

If the serialized checkpoint exceeds 1024 bytes, the SDK automatically publishes the metadata via HCS-1 and replaces the inline payload with an hcs://1/<topicId> reference plus a metadata_digest for integrity verification.
The message memo field must be under 300 characters.

Retrieve CheckpointsDirect link to Retrieve Checkpoints

TypeScript
Go
Python

// Not yet available.

records, err := client.GetCheckpoints(ctx, topicID, nil)
if err != nil {
	log.Fatal(err)
}

for _, record := range records {
	fmt.Printf("Seq %d: root=%s treeSize=%d\n",
		record.Sequence,
		record.EffectiveMetadata.Root.RootHashB64,
		record.EffectiveMetadata.Root.TreeSize,
	)
}

records = client.get_checkpoints(topicID, None)

for record in records :
fmt.printf("Seq %d: root=%s treeSize=%d\n", record.SEQUENCE, record.EffectiveMetadata.Root.RootHashB64, record.EffectiveMetadata.Root.TreeSize)

Validate a Checkpoint ChainDirect link to Validate a Checkpoint Chain

TypeScript
Go
Python

// Not yet available.

if err := hcs27.ValidateCheckpointChain(records); err != nil {
	log.Fatalf("Chain validation failed: %v", err)
}
fmt.Println("Checkpoint chain is valid")

err = hcs27.validate_checkpoint_chain(records); err != nil {)
log.fatalf("Chain validation failed: %v", err)
fmt.println("Checkpoint chain is valid")

Resolve HCS-1 ReferencesDirect link to Resolve HCS-1 References

When checkpoint metadata overflows, the SDK stores it via HCS-1. You can resolve references manually:

TypeScript
Go
Python

// Not yet available.

payload, err := client.ResolveHCS1Reference(ctx, "hcs://1/0.0.789012")
if err != nil {
	log.Fatal(err)
}
fmt.Printf("Resolved %d bytes of metadata\n", len(payload))

payload = client.resolve_h_c_s1_reference("hcs://1/0.0.789012")
fmt.printf("Resolved %d bytes of metadata\n", len(payload))

Create a ClientDirect link to Create a Client​

Create a Checkpoint TopicDirect link to Create a Checkpoint Topic​

Publish a CheckpointDirect link to Publish a Checkpoint​

Retrieve CheckpointsDirect link to Retrieve Checkpoints​

Validate a Checkpoint ChainDirect link to Validate a Checkpoint Chain​

Resolve HCS-1 ReferencesDirect link to Resolve HCS-1 References​