*** a/src/backend/replication/README
--- b/src/backend/replication/README
***************
*** 4,14 **** Walreceiver - libpqwalreceiver API
  ----------------------------------
  
  The transport-specific part of walreceiver, responsible for connecting to
! the primary server and receiving WAL files, is loaded dynamically to avoid
! having to link the main server binary with libpq. The dynamically loaded
! module is in libpqwalreceiver subdirectory.
  
! The dynamically loaded module implements three functions:
  
  
  bool walrcv_connect(char *conninfo, XLogRecPtr startpoint)
--- 4,14 ----
  ----------------------------------
  
  The transport-specific part of walreceiver, responsible for connecting to
! the primary server, receiving WAL files and sending messages, is loaded
! dynamically to avoid having to link the main server binary with libpq.
! The dynamically loaded module is in libpqwalreceiver subdirectory.
  
! The dynamically loaded module implements four functions:
  
  
  bool walrcv_connect(char *conninfo, XLogRecPtr startpoint)
***************
*** 16,22 **** bool walrcv_connect(char *conninfo, XLogRecPtr startpoint)
  Establish connection to the primary, and starts streaming from 'startpoint'.
  Returns true on success.
  
- 
  bool walrcv_receive(int timeout, unsigned char *type, char **buffer, int *len)
  
  Retrieve any message available through the connection, blocking for
--- 16,21 ----
***************
*** 26,31 **** otherwise false. On success, a pointer to the message payload is stored in
--- 25,34 ----
  returned buffer is valid until the next call to walrcv_* functions, the
  caller should not attempt freeing it.
  
+ void walrcv_send(const char *buffer, int nbytes)
+ 
+ Send a message to XLOG stream.
+ 
  void walrcv_disconnect(void);
  
  Disconnect.
***************
*** 45,55 **** to fetch more WAL (if streaming replication is configured).
  Walreceiver is a postmaster subprocess, so the startup process can't fork it
  directly. Instead, it sends a signal to postmaster, asking postmaster to launch
  it. Before that, however, startup process fills in WalRcvData->conninfo,
! and initializes the starting point in WalRcvData->receivedUpto.
  
  As walreceiver receives WAL from the master server, and writes and flushes
! it to disk (in pg_xlog), it updates WalRcvData->receivedUpto. Startup process
! polls that to know how far it can proceed with WAL replay.
  
  Walsender IPC
  -------------
--- 48,62 ----
  Walreceiver is a postmaster subprocess, so the startup process can't fork it
  directly. Instead, it sends a signal to postmaster, asking postmaster to launch
  it. Before that, however, startup process fills in WalRcvData->conninfo,
! and initializes the starting point in WalRcvData->receiveStart.
  
  As walreceiver receives WAL from the master server, and writes and flushes
! it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
! the startup process to know how far WAL replay can advance.
! 
! Walreceiver sends information about replication progress to the master server
! whenever either it writes or flushes new WAL, or the specified interval elapses.
! This is used for reporting purpose.
  
  Walsender IPC
  -------------
***************
*** 80,90 **** phase. A walsenders will look like a regular backends until it's done with the
  initialization and has marked itself in PMSignal array, and at process
  termination, after unmarking the PMSignal slot.
  
! Each walsender allocates an entry from the WalSndCtl array, and advertises
! there how far it has streamed WAL already. This is used at checkpoints, to
! avoid recycling WAL that hasn't been streamed to a slave yet. However,
! that doesn't stop such WAL from being recycled when the connection is not
! established.
  
  
  Walsender - walreceiver protocol
--- 87,95 ----
  initialization and has marked itself in PMSignal array, and at process
  termination, after unmarking the PMSignal slot.
  
! Each walsender allocates an entry from the WalSndCtl array, and tracks
! information about replication progress. User can monitor them via
! statistics views.
  
  
  Walsender - walreceiver protocol