PG-1857 Do not start basebackup w/o WAL keys

src/backend/access/transam/xlog.c

@@ -8967,6 +8967,12 @@ do_pg_backup_start(const char *backupidstr, bool fast, List **tablespaces,
 			WALInsertLockRelease();
 		} while (!gotUniqueStartpoint);
 
+		/* TODO: we should rather check if the last WAL key is encrypted */
+		if (access("pg_tde/wal_keys", F_OK) == 0)
+		{
+			state->tde_have_wal_keys = true;
+		}
+
 		/*
 		 * Construct tablespace_map file.
 		 */

src/backend/backup/basebackup.c

@@ -269,6 +269,7 @@ perform_base_backup(basebackup_options *opt, bbsink *sink,
 
 	state.startptr = backup_state->startpoint;
 	state.starttli = backup_state->starttli;
+	state.tde_have_wal_keys = backup_state->tde_have_wal_keys;
 
 	/*
 	 * Once do_pg_backup_start has been called, ensure that any failure causes

src/backend/backup/basebackup_copy.c

@@ -86,7 +86,7 @@ static void bbsink_copystream_cleanup(bbsink *sink);
 
 static void SendCopyOutResponse(void);
 static void SendCopyDone(void);
-static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli);
+static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli, bool wal_keys);
 static void SendTablespaceList(List *tablespaces);
 
 static const bbsink_ops bbsink_copystream_ops = {
@@ -146,7 +146,7 @@ bbsink_copystream_begin_backup(bbsink *sink)
 	mysink->msgbuffer[0] = 'd'; /* archive or manifest data */
 
 	/* Tell client the backup start location. */
-	SendXlogRecPtrResult(state->startptr, state->starttli);
+	SendXlogRecPtrResult(state->startptr, state->starttli, state->tde_have_wal_keys);
 
 	/* Send client a list of tablespaces. */
 	SendTablespaceList(state->tablespaces);
@@ -298,7 +298,7 @@ bbsink_copystream_end_backup(bbsink *sink, XLogRecPtr endptr,
 							 TimeLineID endtli)
 {
 	SendCopyDone();
-	SendXlogRecPtrResult(endptr, endtli);
+	SendXlogRecPtrResult(endptr, endtli, false);
 }
 
 /*
@@ -338,17 +338,17 @@ SendCopyDone(void)
  * XLogRecPtr record (in text format)
  */
 static void
-SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli)
+SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli, bool wal_keys)
 {
 	DestReceiver *dest;
 	TupOutputState *tstate;
 	TupleDesc	tupdesc;
-	Datum		values[2];
-	bool		nulls[2] = {0};
+	Datum		values[3];
+	bool		nulls[3] = {0};
 
 	dest = CreateDestReceiver(DestRemoteSimple);
 
-	tupdesc = CreateTemplateTupleDesc(2);
+	tupdesc = CreateTemplateTupleDesc(3);
 	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "recptr", TEXTOID, -1, 0);
 
 	/*
@@ -357,12 +357,16 @@ SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli)
 	 */
 	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "tli", INT8OID, -1, 0);
 
+
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "walkeys", INT4OID, -1, 0);
+
 	/* send RowDescription */
 	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
 
 	/* Data row */
 	values[0] = CStringGetTextDatum(psprintf("%X/%X", LSN_FORMAT_ARGS(ptr)));
 	values[1] = Int64GetDatum(tli);
+	values[2] = BoolGetDatum(wal_keys);
 	do_tup_output(tstate, values, nulls);
 
 	end_tup_output(tstate);

src/bin/pg_basebackup/pg_basebackup.c

@@ -1794,6 +1794,7 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 				serverMajor;
 	int			writing_to_stdout;
 	bool		use_new_option_syntax = false;
+	bool		tde_src_wal_keys = false;
 	PQExpBufferData buf;
 
 	Assert(conn != NULL);
@@ -2058,6 +2059,10 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 		starttli = atoi(PQgetvalue(res, 0, 1));
 	else
 		starttli = latesttli;
+
+	if (PQnfields(res) >= 3)
+		tde_src_wal_keys = atoi(PQgetvalue(res, 0, 2));
+
 	PQclear(res);
 
 	if (verbose && includewal != NO_WAL)
@@ -2130,6 +2135,16 @@ BaseBackup(char *compression_algorithm, char *compression_detail,
 		if (verbose)
 			pg_log_info("starting background WAL receiver");
 
+#ifdef PERCONA_EXT
+		{
+			char tde_wal_keys_file[MAXPGPATH];
+
+			snprintf(tde_wal_keys_file, sizeof(tde_wal_keys_file), "%s/%s/%s", basedir, PG_TDE_DATA_DIR, "wal_keys");
+
+			if (tde_src_wal_keys && access(tde_wal_keys_file, F_OK) != 0)
+				pg_fatal("could not start WAL receiver, copy pg_tde from the source to the destination dir");
+		}
+#endif
 		if (client_compress->algorithm == PG_COMPRESSION_GZIP)
 		{
 			wal_compress_algorithm = PG_COMPRESSION_GZIP;

src/include/access/xlogbackup.h

@@ -30,6 +30,7 @@ typedef struct BackupState
 	bool		started_in_recovery;	/* backup started in recovery? */
 	XLogRecPtr	istartpoint;	/* incremental based on backup at this LSN */
 	TimeLineID	istarttli;		/* incremental based on backup on this TLI */
+	bool		tde_have_wal_keys;
 
 	/* Fields saved at the end of backup */
 	XLogRecPtr	stoppoint;		/* backup stop WAL location */

src/include/backup/basebackup_sink.h

@@ -72,6 +72,7 @@ typedef struct bbsink_state
 	bool		bytes_total_is_valid;
 	XLogRecPtr	startptr;
 	TimeLineID	starttli;
+	bool		tde_have_wal_keys;
 } bbsink_state;
 
 /*