github.com/vipernet-xyz/tm@v0.34.24/spec/p2p/messages/state-sync.md (about) 1 --- 2 order: 5 3 --- 4 5 # State Sync 6 7 ## Channels 8 9 State sync has four distinct channels. The channel identifiers are listed below. 10 11 | Name | Number | 12 |-------------------|--------| 13 | SnapshotChannel | 96 | 14 | ChunkChannel | 97 | 15 | LightBlockChannel | 98 | 16 | ParamsChannel | 99 | 17 18 ## Message Types 19 20 ### SnapshotRequest 21 22 When a new node begin state syncing, it will ask all peers it encounters if it has any 23 available snapshots: 24 25 | Name | Type | Description | Field Number | 26 |----------|--------|-------------|--------------| 27 28 ### SnapShotResponse 29 30 The receiver will query the local ABCI application via `ListSnapshots`, and send a message 31 containing snapshot metadata (limited to 4 MB) for each of the 10 most recent snapshots: and stored at the application layer. When a peer is starting it will request snapshots. 32 33 | Name | Type | Description | Field Number | 34 |----------|--------|-----------------------------------------------------------|--------------| 35 | height | uint64 | Height at which the snapshot was taken | 1 | 36 | format | uint32 | Format of the snapshot. | 2 | 37 | chunks | uint32 | How many chunks make up the snapshot | 3 | 38 | hash | bytes | Arbitrary snapshot hash | 4 | 39 | metadata | bytes | Arbitrary application data. **May be non-deterministic.** | 5 | 40 41 ### ChunkRequest 42 43 The node running state sync will offer these snapshots to the local ABCI application via 44 `OfferSnapshot` ABCI calls, and keep track of which peers contain which snapshots. Once a snapshot 45 is accepted, the state syncer will request snapshot chunks from appropriate peers: 46 47 | Name | Type | Description | Field Number | 48 |--------|--------|-------------------------------------------------------------|--------------| 49 | height | uint64 | Height at which the chunk was created | 1 | 50 | format | uint32 | Format chosen for the chunk. **May be non-deterministic.** | 2 | 51 | index | uint32 | Index of the chunk within the snapshot. | 3 | 52 53 ### ChunkResponse 54 55 The receiver will load the requested chunk from its local application via `LoadSnapshotChunk`, 56 and respond with it (limited to 16 MB): 57 58 | Name | Type | Description | Field Number | 59 |---------|--------|-------------------------------------------------------------|--------------| 60 | height | uint64 | Height at which the chunk was created | 1 | 61 | format | uint32 | Format chosen for the chunk. **May be non-deterministic.** | 2 | 62 | index | uint32 | Index of the chunk within the snapshot. | 3 | 63 | hash | bytes | Arbitrary snapshot hash | 4 | 64 | missing | bool | Arbitrary application data. **May be non-deterministic.** | 5 | 65 66 Here, `Missing` is used to signify that the chunk was not found on the peer, since an empty 67 chunk is a valid (although unlikely) response. 68 69 The returned chunk is given to the ABCI application via `ApplySnapshotChunk` until the snapshot 70 is restored. If a chunk response is not returned within some time, it will be re-requested, 71 possibly from a different peer. 72 73 The ABCI application is able to request peer bans and chunk refetching as part of the ABCI protocol. 74 75 ### LightBlockRequest 76 77 To verify state and to provide state relevant information for consensus, the node will ask peers for 78 light blocks at specified heights. 79 80 | Name | Type | Description | Field Number | 81 |----------|--------|----------------------------|--------------| 82 | height | uint64 | Height of the light block | 1 | 83 84 ### LightBlockResponse 85 86 The receiver will retrieve and construct the light block from both the block and state stores. The 87 receiver will verify the data by comparing the hashes and store the header, commit and validator set 88 if necessary. The light block at the height of the snapshot will be used to verify the `AppHash`. 89 90 | Name | Type | Description | Field Number | 91 |---------------|---------------------------------------------------------|--------------------------------------|--------------| 92 | light_block | [LightBlock](../../core/data_structures.md#lightblock) | Light block at the height requested | 1 | 93 94 State sync will use [light client verification](../../light-client/verification.README.md) to verify 95 the light blocks. 96 97 98 If no state sync is in progress (i.e. during normal operation), any unsolicited response messages 99 are discarded. 100 101 ### ParamsRequest 102 103 In order to build tendermint state, the state provider will request the params at the height of the snapshot and use the header to verify it. 104 105 | Name | Type | Description | Field Number | 106 |----------|--------|----------------------------|--------------| 107 | height | uint64 | Height of the consensus params | 1 | 108 109 110 ### ParamsResponse 111 112 A reciever to the request will use the state store to fetch the consensus params at that height and return it to the sender. 113 114 | Name | Type | Description | Field Number | 115 |----------|--------|---------------------------------|--------------| 116 | height | uint64 | Height of the consensus params | 1 | 117 | consensus_params | [ConsensusParams](../../core/data_structures.md#ConsensusParams) | Consensus params at the height requested | 2 | 118 119 120 ### Message 121 122 Message is a [`oneof` protobuf type](https://developers.google.com/protocol-buffers/docs/proto#oneof). The `oneof` consists of eight messages. 123 124 | Name | Type | Description | Field Number | 125 |----------------------|--------------------------------------------|----------------------------------------------|--------------| 126 | snapshots_request | [SnapshotRequest](#snapshotrequest) | Request a recent snapshot from a peer | 1 | 127 | snapshots_response | [SnapshotResponse](#snapshotresponse) | Respond with the most recent snapshot stored | 2 | 128 | chunk_request | [ChunkRequest](#chunkrequest) | Request chunks of the snapshot. | 3 | 129 | chunk_response | [ChunkRequest](#chunkresponse) | Response of chunks used to recreate state. | 4 | 130 | light_block_request | [LightBlockRequest](#lightblockrequest) | Request a light block. | 5 | 131 | light_block_response | [LightBlockResponse](#lightblockresponse) | Respond with a light block | 6 | 132 | params_request | [ParamsRequest](#paramsrequest) | Request the consensus params at a height. | 7 | 133 | params_response | [ParamsResponse](#paramsresponse) | Respond with the consensus params | 8 |