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Kafka FetchSnapshot Response Wire Format v0 — Binary Protocol Layout

What is FetchSnapshot?

KRaft follower controllers or newly joining brokers download a point-in-time metadata snapshot when they've fallen too far behind to catch up via the log. After a long outage or when joining a mature cluster, a broker fetches the snapshot first, then applies incremental log entries.

Related Errors

POSITION_OUT_OF_RANGE · SNAPSHOT_NOT_FOUND

Wire Diagram

Response Header · flexible
message_size int32 · 4B
correlation_id int32 · 4B
tagged var
FetchSnapshotResponse v0
ThrottleTimeMs int32 · 4B
ErrorCode int16 · 2B
Topics array
tagged var
Name string (compact)
Partitions array
tagged var
Index int32 · 4B
ErrorCode int16 · 2B
SnapshotId struct
CurrentLeader struct
Size int64 · 8B
Position int64 · 8B
UnalignedRecords records (compact)
tagged var
EndOffset int64 · 8B
Epoch int32 · 4B
tagged var
LeaderId int32 · 4B
LeaderEpoch int32 · 4B
tagged var

Schema & Example

Schema
{
  "ThrottleTimeMs": int32,
  "ErrorCode": int16,
  "Topics": [{
      "Name": string,
      "Partitions": [{
          "Index": int32,
          "ErrorCode": int16,
          "SnapshotId": {
            "EndOffset": int64,
            "Epoch": int32
          },
          "CurrentLeader": {
            "LeaderId": int32,
            "LeaderEpoch": int32
          },
          "Size": int64,
          "Position": int64,
          "UnalignedRecords": records
      }]
  }]
}
Example
{
  "ThrottleTimeMs": 0,
  "ErrorCode": 0,
  "Topics": [{
      "Name": "orders",
      "Partitions": [{
          "Index": 3,
          "ErrorCode": 0,
          "SnapshotId": {
            "EndOffset": 150382,
            "Epoch": 17
          },
          "CurrentLeader": {
            "LeaderId": 1,
            "LeaderEpoch": 17
          },
          "Size": 1048576,
          "Position": 0,
          "UnalignedRecords": "<binary>"
      }]
  }]
}