[PATCH guest-common 04/19] vzdump: add options for parallel guest backups and overlapping jobs

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

A node only ever runs one backup job, and that job backs up its guests
one after the other. How long a job takes thus depends on how its
guests happen to be spread over the nodes, and a short job has to wait
until a long one finished, failing once the lock wait time is
exceeded.

The new 'concurrency' option allows backing up several guests of a job
at the same time, up to the backup concurrency of the node. The
bandwidth limit then applies to each of them, as its description now
says. The 'overlap' option lets a job run alongside other jobs that
allow it as well. It is off by default, as existing hook scripts may
rely on job phases never overlapping.

With overlapping jobs the same guest can be part of two running
backups, and with cluster-wide limits a guest backup can wait for a
slot, so the lock wait now also bounds these waits.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 src/PVE/VZDump/Common.pm | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/PVE/VZDump/Common.pm b/src/PVE/VZDump/Common.pm
index 67a4cf4..f98c9ae 100644
--- a/src/PVE/VZDump/Common.pm
+++ b/src/PVE/VZDump/Common.pm
@@ -297,7 +297,7 @@ my $confdesc = {
     },
     bwlimit => {
         type => 'integer',
-        description => "Limit I/O bandwidth (in KiB/s).",
+        description => "Limit I/O bandwidth of each guest backup (in KiB/s).",
         optional => 1,
         minimum => 0,
         default => 0,
@@ -327,11 +327,27 @@ my $confdesc = {
     },
     lockwait => {
         type => 'integer',
-        description => "Maximal time to wait for the global lock (minutes).",
+        description =>
+            "Maximal time to wait for the global lock, for guests that another backup"
+            . " is currently processing, and for cluster-wide backup slots (minutes).",
         optional => 1,
         minimum => 0,
         default => 3 * 60, # 3 hours
     },
+    concurrency => {
+        type => 'integer',
+        description => "Maximal number of guests to back up at the same time on each node."
+            . " Defaults to, and is limited by, the backup concurrency configured for the node.",
+        optional => 1,
+        minimum => 1,
+    },
+    overlap => {
+        type => 'boolean',
+        description => "Allow running at the same time as other backups on the same node that"
+            . " also allow it. The job phases of their hook scripts can then overlap.",
+        optional => 1,
+        default => 0,
+    },
     stopwait => {
         type => 'integer',
         description => "Maximal time to wait until a guest system is stopped (minutes).",
-- 
2.47.3