router: update known bucket count when rs removed

When replicaset was removed, router didn't update
router.known_bucket_count value. It is used by discovery to decide
when to turn on aggressive discovery. And by router.info() to
provide alerts, change status.

As a result, in case of replicaset removal, known_bucket_count
was left bigger than it actually is, and it could be fixed only
by restart.

Discovery could become non-agressive too early, and router.info()
could show weird alerts about bucke_count being configured
differently on storages and router. Besides, router.info().bucket
was showing not realistic numbers.

Author: Gerold103

test/router/router2.result

@@ -250,6 +250,67 @@ vshard.router.static.discovery_fiber
  | - null
  | ...
 
+--
+-- Known bucket count should be updated properly when replicaset
+-- is removed from the config.
+--
+vshard.router.info().bucket
+ | ---
+ | - unreachable: 0
+ |   available_ro: 0
+ |   unknown: 0
+ |   available_rw: 3000
+ | ...
+rs1_uuid = util.replicasets[1]
+ | ---
+ | ...
+rs1 = cfg.sharding[rs1_uuid]
+ | ---
+ | ...
+cfg.sharding[rs1_uuid] = nil
+ | ---
+ | ...
+vshard.router.cfg(cfg)
+ | ---
+ | ...
+vshard.router.info().bucket
+ | ---
+ | - unreachable: 0
+ |   available_ro: 0
+ |   unknown: 1500
+ |   available_rw: 1500
+ | ...
+cfg.sharding[rs1_uuid] = rs1
+ | ---
+ | ...
+vshard.router.cfg(cfg)
+ | ---
+ | ...
+vshard.router.discovery_set('on')
+ | ---
+ | ...
+function wait_all_rw()                                                          \
+    local total = vshard.router.bucket_count()                                  \
+    local res = vshard.router.info().bucket.available_rw == total               \
+    if not res then                                                             \
+        vshard.router.discovery_wakeup()                                        \
+    end                                                                         \
+    return res                                                                  \
+end
+ | ---
+ | ...
+test_run:wait_cond(wait_all_rw)
+ | ---
+ | - true
+ | ...
+vshard.router.info().bucket
+ | ---
+ | - unreachable: 0
+ |   available_ro: 0
+ |   unknown: 0
+ |   available_rw: 3000
+ | ...
+
 _ = test_run:switch("default")
  | ---
  | ...

test/router/router2.test.lua

@@ -95,6 +95,30 @@ vshard.router.static.discovery_fiber
 vshard.router.discovery_set('once')
 vshard.router.static.discovery_fiber
 
+--
+-- Known bucket count should be updated properly when replicaset
+-- is removed from the config.
+--
+vshard.router.info().bucket
+rs1_uuid = util.replicasets[1]
+rs1 = cfg.sharding[rs1_uuid]
+cfg.sharding[rs1_uuid] = nil
+vshard.router.cfg(cfg)
+vshard.router.info().bucket
+cfg.sharding[rs1_uuid] = rs1
+vshard.router.cfg(cfg)
+vshard.router.discovery_set('on')
+function wait_all_rw()                                                          \
+    local total = vshard.router.bucket_count()                                  \
+    local res = vshard.router.info().bucket.available_rw == total               \
+    if not res then                                                             \
+        vshard.router.discovery_wakeup()                                        \
+    end                                                                         \
+    return res                                                                  \
+end
+test_run:wait_cond(wait_all_rw)
+vshard.router.info().bucket
+
 _ = test_run:switch("default")
 _ = test_run:cmd("stop server router_1")
 _ = test_run:cmd("cleanup server router_1")

vshard/router/init.lua

@@ -908,14 +908,17 @@ local function router_cfg(router, cfg, is_reload)
     router.failover_ping_timeout = vshard_cfg.failover_ping_timeout
     router.sync_timeout = vshard_cfg.sync_timeout
     local old_route_map = router.route_map
+    local known_bucket_count = 0
     router.route_map = table_new(router.total_bucket_count, 0)
     for bucket, rs in pairs(old_route_map) do
         local new_rs = router.replicasets[rs.uuid]
         if new_rs then
             router.route_map[bucket] = new_rs
             new_rs.bucket_count = new_rs.bucket_count + 1
+            known_bucket_count = known_bucket_count + 1
         end
     end
+    router.known_bucket_count = known_bucket_count
     if router.failover_fiber == nil then
         router.failover_fiber = util.reloadable_fiber_create(
             'vshard.failover.' .. router.name, M, 'failover_f', router)