[Mellanox] Fix inconsistence in the shared headroom pool initialization

cfgmgr/buffer_pool_mellanox.lua

@@ -133,7 +133,7 @@ local function iterate_profile_list(all_items)
     return 0
 end
 
-local function fetch_buffer_pool_size_from_appldb()
+local function fetch_buffer_pool_size_from_appldb(shp_enabled)
     local buffer_pools = {}
     redis.call('SELECT', config_db)
     local buffer_pool_keys = redis.call('KEYS', 'BUFFER_POOL|*')
@@ -158,7 +158,18 @@ local function fetch_buffer_pool_size_from_appldb()
         end
         xoff = redis.call('HGET', 'BUFFER_POOL_TABLE:' .. buffer_pools[i], 'xoff')
         if not xoff then
-            table.insert(result, buffer_pools[i] .. ':' .. size)
+            if shp_enabled and size == "0" and buffer_pools[i] == "ingress_lossless_pool" then
+                -- During initialization, if SHP is enabled
+                --   1. the buffer pool sizes, xoff have initialized to 0, which means the shared headroom pool is disabled
+                --   2. but the buffer profiles already indicate the shared headroom pool is enabled
+                --   3. later on the buffer pool sizes are updated with xoff being non-zero
+                -- In case the orchagent starts handling buffer configuration between 2 and 3,
+                -- It is inconsistent between buffer pools and profiles, which fails Mellanox SAI sanity check
+                -- To avoid it, it indicates the shared headroom pool is enabled by setting a very small buffer pool and shared headroom pool sizes
+                table.insert(result, buffer_pools[i] .. ':2048:1024')
+            else
+                table.insert(result, buffer_pools[i] .. ':' .. size)
+            end
         else
             table.insert(result, buffer_pools[i] .. ':' .. size .. ':' .. xoff)
         end
@@ -295,7 +306,7 @@ local fail_count = 0
 fail_count = fail_count + iterate_all_items(all_pgs, true)
 fail_count = fail_count + iterate_all_items(all_tcs, false)
 if fail_count > 0 then
-    fetch_buffer_pool_size_from_appldb()
+    fetch_buffer_pool_size_from_appldb(shp_enabled)
     return result
 end
 
@@ -305,7 +316,7 @@ local all_egress_profile_lists = redis.call('KEYS', 'BUFFER_PORT_EGRESS_PROFILE_
 fail_count = fail_count + iterate_profile_list(all_ingress_profile_lists)
 fail_count = fail_count + iterate_profile_list(all_egress_profile_lists)
 if fail_count > 0 then
-    fetch_buffer_pool_size_from_appldb()
+    fetch_buffer_pool_size_from_appldb(shp_enabled)
     return result
 end
 

tests/test_buffer_dynamic.py

@@ -865,3 +865,41 @@ def test_bufferPortMaxParameter(self, dvs, testlog):
             dvs.port_admin_set('Ethernet0', 'down')
 
         self.cleanup_db(dvs)
+
+
+    def test_bufferPoolInitWithSHP(self, dvs, testlog):
+        self.setup_db(dvs)
+
+        try:
+            # 1. Enable the shared headroom pool
+            default_lossless_buffer_parameter = self.config_db.get_entry('DEFAULT_LOSSLESS_BUFFER_PARAMETER', 'AZURE')
+            default_lossless_buffer_parameter['over_subscribe_ratio'] = '2'
+            self.config_db.update_entry('DEFAULT_LOSSLESS_BUFFER_PARAMETER', 'AZURE', default_lossless_buffer_parameter)
+
+            # 2. Stop the orchagent
+            _, oa_pid = dvs.runcmd("pgrep orchagent")
+            dvs.runcmd("kill -s SIGSTOP {}".format(oa_pid))
+
+            # 3. Remove the size from CONFIG_DB|BUFFER_POOL.ingress_lossless_pool
+            original_ingress_lossless_pool = self.config_db.get_entry('BUFFER_POOL', 'ingress_lossless_pool')
+            try:
+                self.config_db.delete_field('BUFFER_POOL', 'ingress_lossless_pool', 'size')
+                self.config_db.delete_field('BUFFER_POOL', 'ingress_lossless_pool', 'xoff')
+            except Exception as e:
+                pass
+
+            # 4. Remove the ingress_lossless_pool from the APPL_DB
+            self.app_db.delete_entry('BUFFER_POOL_TABLE', 'ingress_lossless_pool')
+
+            # 5. Mock it by adding a "TABLE_SET" entry to trigger the fallback logic
+            self.app_db.update_entry("BUFFER_PG_TABLE_SET", "", {"NULL": "NULL"})
+
+            # 6. Invoke the lua plugin
+            _, output = dvs.runcmd("redis-cli --eval /usr/share/swss/buffer_pool_vs.lua")
+            assert "ingress_lossless_pool:2048:1024" in output
+
+        finally:
+            self.config_db.update_entry('BUFFER_POOL', 'ingress_lossless_pool', original_ingress_lossless_pool)
+            self.config_db.delete_entry('DEFAULT_LOSSLESS_BUFFER_PARAMETER', 'AZURE')
+            self.app_db.delete_entry("BUFFER_PG_TABLE_SET", "")
+            dvs.runcmd("kill -s SIGCONT {}".format(oa_pid))