zkevm

zkEVM DataStreamer

Go implementation of a generic fast data streamer library.

Use case for the zkEVM Node: Sequencer data stream service to stream L2 blocks and L2 txs.

GENERAL DIAGRAM

Description of the diagram elements:

• Sequencer: uses the data streamer library through the API to send L2 blocks and L2 transactions to the stream. It's an use case of the datastreamer component.

• Data Streamer: creates the stream server, it manages the stream file and allows stream clients to connect using a TCP socket. For such stream clients, it offers a series of commands via the TCP port.

• Stream File: stores all the streaming data. It is a custom binary file organized into data pages with a preceding header page.

• Bookmarks DB: stores an index for the bookmarks that are available in the streaming file. It uses a LevelDB using the library goleveldb.

• Streamer Client: creates a stream client, it manages the data streamer connection and allows to execute the TCP commands available in the server.

STREAM FILE

The binary file format is described below.

Header page

• The first page is the header.
• Header page size = 4096 bytes

Magic numbers

At the beginning of the file there are the following magic bytes (file signature): polygonDATSTREAM

HEADER ENTRY format (HeaderEntry)

u8 packetType = 1 // 1:Header
u32 headerLength = 38 // Total length of header entry
u8 Version // Stream file version (starting from 1)
u64 SystemID // E.g.: ChainID
u64 streamType // 1:Sequencer
u64 TotalLength // Total bytes used in the file
u64 TotalEntries // Total number of data entries

Data page

• From the second page starts the data pages.
• Page size = 1 MB

DATA ENTRY format (FileEntry)

u8 packetType // 2:Data entry, 0:Padding
u32 Length // Total length of data entry (17 bytes + length(data))
u32 Type // 0xb0:Bookmark, 1:Event1, 2:Event2,...
u64 Number // Entry number (sequential starting with 0)
u8[] data

NOTE: If an entry does not fit in the remaining page space, the entry will be stored in the next page.

File diagram

STREAM TCP COMMANDS

• All the commands available for the stream clients return first a response, a Result entry defined in a later section.
• Some commands like Start or Header may return more data.

Below is the detail of the available commands:

Start

Syncs from the entry number (fromEntryNumber) and starts receiving data streaming from that entry.

Command format sent by the client:

u64 command = 1
u64 streamType // e.g. 1:Sequencer
u64 fromEntryNumber

If already started terminates the connection.

StartBookmark

Syncs from the bookmark (fromBookmark) and starts receiving data streaming from the entry pointed by that bookmark.

Command format sent by the client:

u64 command = 4
u64 streamType // e.g. 1:Sequencer
u32 bookmarkLength // Length of fromBookmark (Max bookmark length value is 16)
u8[] fromBookmark

If already started or bookmarkLength exceeds the maximum length, terminates the connection.

Stop

Stops the reception of the streaming transmission.

Command format sent by the client:

u64 command = 2
u64 streamType // e.g. 1:Sequencer

If not started terminates the connection.

GetHeader

Gets the current stream file header (HeaderEntry format defined in the STREAM FILE section), so stream clients can know the total number of entries and the size of the stream file.

Command format sent by the client:

u64 command = 3
u64 streamType // e.g. 1:Sequencer

If streaming already started terminates the connection.

GetEntry

Gets the data from the entry (entryNumber) in the format FileEntry defined in the STREAM FILE section).

Command format sent by the client:

u64 command = 4
u64 streamType // e.g. 1:Sequencer
u64 entryNumber

If streaming already started terminates the connection.

GetBookmark

Gets the data from the entry pointed by the bookmark (bookmark) in the format FileEntry defined in the STREAM FILE section).

Command format sent by the client:

u64 command = 5
u64 streamType // e.g. 1:Sequencer
u32 bookmarkLength // Length of bookmark (Max bookmark length value is 16)
u8[] bookmark

If streaming already started or bookmarkLength exceeds the maximum length, terminates the connection.

RESULT FORMAT (ResultEntry)

Remember that all these TCP commands firstly return a response in the following detailed format:

u8 packetType // 0xff:Result
u32 length // Total length of the entry
u32 errorNum // Error code (0:OK)
u8[] errorStr

BOOKMARKS

Bookmarks make possible to the clients to sync the streaming from a business logic point.

• No need to store the latest stream entry number received.
• Using the API, bookmarks to business logic data are added in the send data to stream implementation.
• e.g. zkEVM Sequencer streaming: each L2 block number has its own bookmark. Clients can request to start the stream from a L2 block number.

STREAM RELAY

Stream relay server included in the datastream library allows scaling the number of stream connected clients.

• Data Streamer Relay acts as a stream client towards the main data stream server, and also acts as a stream server towards the stream clients connected to it.

DATA STREAMER INTERFACE (API)

SERVER API

• Create and start a datastream server (StreamServer) using the NewServer function followed by the Start function.
• Send data to stream by starting an atomic operation through StartAtomicOp, adding entry events (AddStreamEntry) and bookmarks (AddStreamBookmark), and commit the operation CommitAtomicOp.

Send data API

• StartAtomicOp()
• AddStreamBookmark(u8[] bookmark) -> returns u64 entryNumber
• AddStreamEntry(u32 entryType, u8[] data) -> returns u64 entryNumber
• CommitAtomicOp()
• RollbackAtomicOp()

Query data API

• GetHeader() -> returns struct HeaderEntry
• GetEntry(u64 entryNumber) -> returns struct FileEntry
• GetBookmark(u8[] bookmark) -> returns u64 entryNumber
• GetFirstEventAfterBookmark(u8[] bookmark) -> returns struct FileEntry
• GetDataBetweenBookmarks(bookmarkFrom []byte, bookmarkTo []byte) ([]byte, error) -> returns the array of data, ignoring bookmarks, between the given ones

Update data API

• UpdateEntryData(u64 entryNumber, u32 entryType, u8[] newData)

CLIENT API

• Create and start a datastream client (StreamClient) using the NewClient function followed by the Start function.
• Executes server commands by calling ExecCommandStart, ExecCommandStartBookmark, ExecCommandGetHeader, ExecCommandGetEntry, ExecCommandGetBookmark, or ExecCommandStop.

Streaming API

• ExecCommandStart(fromEntry): Initiates the stream starting from the entry number specified in the parameter.
• ExecCommandStartBookmark(fromBookmark): Initiates the stream starting from the entry pointed by the bookmark specified in the parameter.
• ExecCommandStop(): Stops receiving stream.
• SetProcessEntryFunc(f ProcessEntryFunc): Sets the callback function for each entry received. Overrides default function that just prints the entry fields.

Query data API

• ExecCommandGetHeader() -> returns struct HeaderEntry: Fetches stream file header info and returns it.
• ExecCommandGetEntry(fromEntry) -> returns struct FileEntry: Fetches entry data from the specified entry number and returns it.
• ExecCommandGetBookmark(fromBookmark) -> returns struct FileEntry: Fetches entry data pointed by the specified bookmark and returns it.

DATASTREAM CLI DEMO APP

Build the binary datastream demo app (dsapp):

make build-dsapp

Run the app without parameters to see the available commands:

./dsapp

NAME:
   dsapp - Run a datastream server/client/relay demo cli app

USAGE:
   dsapp [global options] command [command options] [arguments...]

COMMANDS:
   server   Run datastream server
   client   Run datastream client
   relay    Run datastream relay
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --help, -h  show help

SERVER

Use the help option to check available parameters for the server command:

./dsapp help server

NAME:
   dsapp server - Run datastream server

USAGE:
   dsapp server [command options] [arguments...]

OPTIONS:
   --port value   exposed port for clients to connect (default: 6900)
   --file value   datastream data file name (*.bin) (default: datastream.bin)
   --log value    log level (debug|info|warn|error) (default: info)
   --sleep value  initial sleep and sleep between atomic operations in ms (default: 0)
   --opers value  number of atomic operations (server will terminate after them) (default: 1000000)
   --help, -h     show help

Run a datastream server with default parameters (port: 6900, file: datastream.bin, log: info):

./dsapp server

Or run a datastream server with custom parameters:

./dsapp server --port 6969 --file seqstream.bin --log warn

CLIENT

Use the help option to check available parameters for the client command:

./dsapp help client

NAME:
   dsapp client - Run datastream client

USAGE:
   dsapp client [command options] [arguments...]

OPTIONS:
   --server value        datastream server address to connect (IP:port) (default: 127.0.0.1:6900)
   --from value          entry number to start the sync/streaming from (latest|0..N) (default: latest)
   --frombookmark value  bookmark to start the sync/streaming from (0..N) (has preference over --from parameter)
   --header              query file header information (default: false)
   --entry value         entry number to query data (0..N)
   --bookmark value      entry bookmark to query entry data pointed by it (0..N)
   --log value           log level (debug|info|warn|error) (default: info)
   --help, -h            show help

Run a datastream client with default parameters (server: 127.0.0.1:6900, from: latest, log: info)

./dsapp client

Or run a datastream client with custom parameters:

./dsapp client --server 127.0.0.1:6969 --from 0 --log debug

Or just get the current stream header file information:

./dsapp client --server 127.0.0.1:6969 --header

RELAY

Use the help option to check available parameters for the relay command:

./dsapp help relay

NAME:
   dsapp relay - Run datastream relay

USAGE:
   dsapp relay [command options] [arguments...]

OPTIONS:
   --server value  datastream server address to connect (IP:port) (default: 127.0.0.1:6900)
   --port value    exposed port for clients to connect (default: 7900)
   --file value    relay data file name (*.bin) (default: datarelay.bin)
   --log value     log level (debug|info|warn|error) (default: info)
   --help, -h      show help

Run a datastream relay with default parameters (server: 127.0.0.1:6900, port: 7900, file: datarelay.bin, log: info)

./dsapp relay

USE CASE: zkEVM SEQUENCER ENTRIES

Sequencer data stream service to stream L2 blocks and L2 txs

List of events (entry types):

Start L2 Block

• Entry type = 1
• Entry data:

u64 batchNum
u64 blockL2Num
u64 timestamp
u32 deltaTimestamp
u32 L1InfoTreeIndex
u8[32] l1BlockHash
u8[32] globalExitRoot
u8[20] coinbase
u16 forkID
u32 chainID

L2 TX

• Entry type = 2
• Entry data:

u8 gasPricePercentage
u8 isValid // Intrinsic
u8[32] stateRoot
u32 encodedTXLength
u8[] encodedTX

End L2 Block

• Entry type = 3
• Entry data:

u64 blockL2Num
u8[32] l2BlockHash
u8[32] stateRoot

Update GER

• Entry type = 4
• Entry data:

u64 batchNum
u64 timestamp
u8[32] globalExitRoot
u8[20] coinbase
u16 forkID
u32 chainID
u8[32] stateRoot