From 431f780347f3bda4b101f13e361558b15a4c785d Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Thu, 22 Dec 2022 01:47:52 +0300
Subject: [PATCH] Implement a PG generator for hierarchical failure domains

---
 mon/lp-optimizer.js | 101 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/mon/lp-optimizer.js b/mon/lp-optimizer.js
index 8505c252..780b4c8d 100644
--- a/mon/lp-optimizer.js
+++ b/mon/lp-optimizer.js
@@ -539,6 +539,106 @@ function extract_osds(osd_tree, levels, osd_level, osds = {})
     return osds;
 }
 
+// generate random PGs with hierarchical failure domains, i.e. for example 3 DC each with 2 HOSTS
+// osd_tree = { level3_id: { level2_id: { level1_id: scalar_value } }, ... }
+//   osd_tree may contain arbitrary number of levels, but level count must be the same across the whole tree
+// size_per_level = number of items to select on each level, for example [3, 2, 1].
+//   must have the same number of items as the osd_tree level count.
+// count = PG count to generate
+// ordered = don't treat (x,y) and (y,x) as equal
+// seq_layout = true for the [DC1,DC1,DC2,DC2,DC3,DC3] layout, false for [DC1,DC2,DC3,DC1,DC2,DC3] layout
+function random_hier_combinations(osd_tree, size_per_level, count, ordered, seq_layout)
+{
+    let seed = 0x5f020e43;
+    const rng = () =>
+    {
+        seed ^= seed << 13;
+        seed ^= seed >> 17;
+        seed ^= seed << 5;
+        return seed + 2147483648;
+    };
+    const get_max_level = (o) =>
+    {
+        let lvl = 0;
+        while (o instanceof Object)
+        {
+            for (const k in o)
+            {
+                lvl++;
+                o = o[k];
+                break;
+            }
+        }
+        return lvl;
+    };
+    const max_level = get_max_level(osd_tree);
+    const gen_pg = (select) =>
+    {
+        let pg = [ osd_tree ];
+        for (let level = 0; level < max_level; level++)
+        {
+            let npg = [];
+            for (let i = 0; i < pg.length; i++)
+            {
+                const keys = pg[i] instanceof Object ? Object.keys(pg[i]) : [];
+                const max_keys = keys.length < size_per_level[level] ? keys.length : size_per_level[level];
+                for (let j = 0; j < max_keys; j++)
+                {
+                    const r = select(level, i, j, (ordered ? keys.length : (keys.length - (max_keys - j - 1))));
+                    const el = pg[i][keys[r]] instanceof Object ? pg[i][keys[r]] : keys[r];
+                    npg[seq_layout ? i*size_per_level[level]+j : j*pg.length+i] = el;
+                    keys.splice(ordered ? r : 0, ordered ? 1 : (r+1));
+                }
+                for (let j = max_keys; j < size_per_level[level]; j++)
+                    npg[seq_layout ? i*size_per_level[level]+j : j*pg.length+i] = NO_OSD;
+            }
+            pg = npg;
+        }
+        return pg;
+    };
+    const r = {};
+    // Generate random combinations including each OSD at least once
+    let has_next = true;
+    let ctr = [];
+    while (has_next)
+    {
+        let pg = gen_pg((level, i, j, n) =>
+        {
+            if (i == 0 && j == 0)
+            {
+                // Select a pre-determined OSD in the first position on each level
+                const r = ctr[level] == null || ctr[level][1] != n ? 0 : ctr[level][0];
+                ctr[level] = [ r, n ];
+                return r;
+            }
+            return rng() % n;
+        });
+        for (let i = ctr.length-1; i >= 0; i--)
+        {
+            ctr[i][0]++;
+            if (ctr[i][0] < ctr[i][1])
+                break;
+            else
+                ctr[i] = null;
+        }
+        has_next = ctr[0] != null;
+        const cyclic_pgs = [ pg ];
+        if (ordered)
+            for (let i = 1; i < pg.size; i++)
+                cyclic_pgs.push([ ...pg.slice(i), ...pg.slice(0, i) ]);
+        for (const pg of cyclic_pgs)
+            r['pg_'+pg.join('_')] = pg;
+    }
+    // Generate purely random combinations
+    while (count > 0)
+    {
+        let pg = gen_pg((l, i, j, n) => rng() % n);
+        r['pg_'+pg.join('_')] = pg;
+        count--;
+    }
+    return r;
+}
+
 // ordered = don't treat (x,y) and (y,x) as equal
 function random_combinations(osd_tree, pg_size, count, ordered)
 {
@@ -758,5 +858,6 @@ module.exports = {
     make_int_pgs,
     align_pgs,
     random_combinations,
+    random_hier_combinations,
     all_combinations,
 };