From b2dec60e05d38630d567900ef668aadf66ddfc33 Mon Sep 17 00:00:00 2001
From: root <root@vps-18a7a2b7.vps.ovh.ca>
Date: Tue, 13 Feb 2024 16:10:38 -0500
Subject: refactor like a mastor

---
 src/mariadb-push-replica.sh | 161 +++++++++++++++++++++++++++++++-------------
 1 file changed, 114 insertions(+), 47 deletions(-)

diff --git a/src/mariadb-push-replica.sh b/src/mariadb-push-replica.sh
index 7134864..e133fad 100755
--- a/src/mariadb-push-replica.sh
+++ b/src/mariadb-push-replica.sh
@@ -124,18 +124,18 @@ stop_mariadb_server_and_remove_database_files()
 {
 	livedb=/var/lib/mysql
 	set -e
-	if [ -e "$livedb" ]
+	set -o pipefail
+	[ -e "$livedb" ] || return 0
+
+	if [ "$(systemctl is-active mariadb)" = active ]
 	then
-		if [ "$(systemctl is-active mariadb)" = active ]
-		then
-			systemctl stop mariadb
-		fi
-		livedb_backup=$livedb~$(date -Ins)
-		mv -v -T -- "$livedb" "$livedb_backup"
-		mkdir "$livedb"
-		chown --reference="$livedb_backup" "$livedb"
-		chmod --reference="$livedb_backup" "$livedb"
+		systemctl stop mariadb
 	fi
+	livedb_backup=$livedb~$(date -Ins)
+	mv -v -T -- "$livedb" "$livedb_backup"
+	mkdir "$livedb"
+	chown --reference="$livedb_backup" "$livedb"
+	chmod --reference="$livedb_backup" "$livedb"
 }
 
 restore_from_backup()
@@ -321,56 +321,117 @@ printarray()
 
 # Call run_replica from here to avoid
 # piping the database back to caller
-# unnecessarily
+# unnecessarily.  Better would be
+# a direct connect from mariadb client
+# to remote mariadb server; but that
+# requires transmitting credentials.
+# Credential-transporter.  Transporter-transporter.
+# Well, a transporter protein is more like a provenance tag,
+# and the transporter code is the receptor to the transporter
+# which is the provenance checker.  But anyway we have that
+# with ssh, except we don't: we are assuming the primary
+# has the ssh root of the replica!  Insanity!  Now this only works
+# because the code runs on the primary; unless we forward the
+# ssh auth with the ssh agent; but that only makes the security
+# flaw temporary not solved; in fact, the replica should receive
+# the transmission on some limited authorization channel; which
+# _could_ be ssh; in fact, the dump could transparently be either
+# live or else cached on the server side; it could be the
+# rsync.net backup even; but ... it needs to include
+# the btrfs snap similarly ... .
 send_mariadb_dump()
 {
-	(set -x
-	mariadb-dump "${@:2}") |
-	replica_host="$1" run_replica pipe_into_mariadb
+	(
+		set -x
+		mariadb-dump "${@:2}"
+	) |
+	replica_host="$1" run_replica receive_mariadb_dump
 }
 
-pipe_into_mariadb()
+receive_mariadb_dump()
 {
-	pv -f | mariadb
+	pv -f | mariadb --skip-reconnect
 }
 
-mariadbdump_transfer_missing_databases()
+save_array()
 {
-	declare -a primary_dbs
-	mapfile -t primary_dbs < \
-		<(</dev/null run_primary \
-			mariadb_list_databases | sort -u)
-
-	declare -a replica_dbs
-	mapfile -t replica_dbs < \
-		<(</dev/null run_replica \
-			mariadb_list_databases | sort -u)
+	declare -n _to_save="$1"
+	case "$2 $3" in
+		'from zfile' )
+			mapfile -d '' -t _to_save < "$4"
+			;;
+		'from lines' )
+			mapfile -t _to_save < "$4"
+			;;
+		* )
+			false
+			;;
+	esac
+}
 
-	declare -a dbs_missing_from_replica
-	mapfile -t dbs_missing_from_replica < \
-		<(comm -23 -- \
-			<(printarray primary_dbs) \
-			<(printarray replica_dbs))
+mariadb_scan_databases()
+{
+	declare -g -a primary_dbs
+	save_array primary_dbs from lines <(
+		run_primary mariadb_list_databases </dev/null |
+		sort -u
+	)
+
+	declare -g -a replica_dbs
+	save_array replica_dbs from lines <(
+		run_replica mariadb_list_databases </dev/null |
+		sort -u
+	)
+
+	declare -g -a primary_dbs_not_on_replica
+	save_array primary_dbs_not_on_replica from zfile <(
+		subtract_arrays primary_dbs replica_dbs
+	)
+}
 
+mariadbdump_transfer_missing_databases()
+{
+	mariadb_scan_databases
 	declare -a to_replicate
 	if [ $# = 0 ]
 	then
-		to_replicate=("${dbs_missing_from_replica[@]}")
+		to_replicate=("${primary_dbs_not_on_replica[@]}")
+		printf "Missing on ${replica_host}: %s\n" \
+			"${to_replicate[@]}"
+		exit
 	else
-		mapfile -t to_replicate < \
-			<(comm -12 -- \
-				<(printarray dbs_missing_from_replica) \
-				<(printlines "$@"))
-	fi
-	if [ ${#to_replicate[@]} -gt 0 ]
-	then
-		run_primary \
-			send_mariadb_dump "$replica_host" \
-			--master-data \
-			--gtid \
-			--single-transaction \
-			--databases "${to_replicate[@]}"
+		save_array to_replicate from lines \
+			<(intersection_lines \
+				<(printarray primary_dbs_not_on_replica) \
+				<(printlines "$@" | sort -u))
 	fi
+	mariadbdump_transfer_databases \
+		"$replica_host" \
+		"${to_replicate[@]}"
+}
+
+mariadbdump_transfer_databases()
+{
+	[ $# -ge 2 ] || return
+	run_primary \
+		send_mariadb_dump "$1" \
+		--master-data \
+		--gtid \
+		--single-transaction \
+		--databases "${@:2}"
+}
+
+intersection_lines()
+{
+	comm -12 -- "$1" "$2"
+}
+
+subtract_arrays()
+{
+	declare -n _a="$1" _b="$2"
+	comm -z -23 -- \
+		<(printf '%s\0' "${_a[@]}") \
+		<(printf '%s\0' "${_b[@]}")
 }
 
 main()
@@ -398,8 +459,14 @@ list_databases()
 {
 mariadb -t "$@" <<.
 select
-	@@hostname,
-	@@server_id,
+	@@hostname
+,	@@server_id
+,	count(schema_name) as 'databases'
+,	@@gtid_slave_pos
+from
+	information_schema.schemata
+;
+select
 	schema_name as 'database'
 from
 	information_schema.schemata
-- 
cgit v1.2.3