Database.PostgreSQL.Replicant.Protocol

This module implements the Postgres streaming replication protocol.

See: https://www.postgresql.org/docs/9.5/protocol-replication.html

Documentation

data IdentifySystem

The information returned by the IDENTIFY_SYSTEM command establishes the stream's log start, position, and information about the database.

Constructors

IdentifySystem

Fields

• identifySystemSytemId :: ByteString
• identifySystemTimeline :: ByteString
• identifySystemLogPos :: LSN
• identifySystemDbName :: Maybe ByteString

Instances

Eq IdentifySystem

Defined in Database.PostgreSQL.Replicant.Protocol

Methods

(==) :: IdentifySystem -> IdentifySystem -> Bool

(/=) :: IdentifySystem -> IdentifySystem -> Bool

Show IdentifySystem

Defined in Database.PostgreSQL.Replicant.Protocol

Methods

showsPrec :: Int -> IdentifySystem -> ShowS

show :: IdentifySystem -> String

showList :: [IdentifySystem] -> ShowS

identifySystemCommand :: ByteString

identifySystemSync :: ReplicantConnection -> IO (Maybe IdentifySystem)

Synchronously execute the IDENTIFY SYSTEM command which returns some basic system information about the server.

startReplicationCommand :: ReplicantConnection -> ByteString -> LSN -> IO ByteString

Create a START_REPLICATION_SLOT query, escaping the slot name passed in by the user.

handleCopyOutData :: TChan PrimaryKeepAlive -> WalProgressState -> ReplicantConnection -> (Change -> IO LSN) -> IO ()

This handles the COPY OUT mode messages. PostgreSQL uses this mode to copy the data from a WAL log file to the socket in the streaming replication protocol.

handleReplicationRow :: TChan PrimaryKeepAlive -> WalProgressState -> ReplicantConnection -> ByteString -> (Change -> IO LSN) -> IO ()

handleReplicationError :: ReplicantConnection -> IO ()

Used to re-throw an exception received from the server.

handleReplicationNoop :: IO ()

startReplicationStream :: ReplicantConnection -> ByteString -> LSN -> Int -> (Change -> IO LSN) -> IO ()

Initiate the streaming replication protocol handler. This will race the keep-alive and copy data handler threads. It will catch and rethrow exceptions from either thread if any fails or returns.

keepAliveHandler :: ReplicantConnection -> TChan PrimaryKeepAlive -> WalProgressState -> IO ()

This listens on the channel for primary keep-alive messages from the server and responds to them with the update status message using the current WAL stream state. It will attempt to buffer prior update messages when the socket is blocked.

sendStatusUpdate :: ReplicantConnection -> WalProgressState -> IO ()