[Tarantool-patches] [PATCH vshard 08/11] storage: introduce bucket_are_all_rw()

[Vladislav Shpilevoy]

In the future map-reduce code it will be needed to be able to
check if all buckets on the storage are in writable state. If they
are - any request can do anything with all the data on the
storage.

Such 'all writable' state will be pinned by a new module
'storage_ref' so as map-reduce requests could execute without
being afraid of the rebalancer.

The patch adds a function bucket_are_all_rw() which is registered
in registry.storage.

The function is not trivial because tries to cache the returned
value. It makes a lot of sense, because the value changes super
rare and the calculation costs a lot (4 lookups in an index by a
string key via FFI + each lookup returns a tuple which is +1 Lua
GC object).

The function is going to be used almost on each map-reduce
request, so it must be fast.

Part of #147
---
 test/storage/storage.result   | 37 +++++++++++++++++++++++++++++++++++
 test/storage/storage.test.lua | 14 +++++++++++++
 vshard/storage/init.lua       | 37 +++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)

diff --git a/test/storage/storage.result b/test/storage/storage.result
index 4730e20..2c9784a 100644
--- a/test/storage/storage.result
+++ b/test/storage/storage.result
@@ -808,6 +808,43 @@ assert(not ok and err.message)
 ---
 - fiber is cancelled
 ...
+--
+-- Bucket_are_all_rw() registry function.
+--
+assert(lstorage.bucket_are_all_rw())
+---
+- true
+...
+vshard.storage.internal.errinj.ERRINJ_NO_RECOVERY = true
+---
+...
+-- Let it stuck in the errinj.
+vshard.storage.recovery_wakeup()
+---
+...
+vshard.storage.bucket_force_create(10)
+---
+- true
+...
+box.space._bucket:update(10, {{'=', 2, vshard.consts.BUCKET.SENDING}})
+---
+- [10, 'sending']
+...
+assert(not lstorage.bucket_are_all_rw())
+---
+- true
+...
+box.space._bucket:update(10, {{'=', 2, vshard.consts.BUCKET.ACTIVE}})
+---
+- [10, 'active']
+...
+assert(lstorage.bucket_are_all_rw())
+---
+- true
+...
+vshard.storage.internal.errinj.ERRINJ_NO_RECOVERY = false
+---
+...
 _ = test_run:switch("default")
 ---
 ...
diff --git a/test/storage/storage.test.lua b/test/storage/storage.test.lua
index 86c5e33..33f0498 100644
--- a/test/storage/storage.test.lua
+++ b/test/storage/storage.test.lua
@@ -241,6 +241,20 @@ f:cancel()
 _ = test_run:wait_cond(function() return ok or err end)
 assert(not ok and err.message)
 
+--
+-- Bucket_are_all_rw() registry function.
+--
+assert(lstorage.bucket_are_all_rw())
+vshard.storage.internal.errinj.ERRINJ_NO_RECOVERY = true
+-- Let it stuck in the errinj.
+vshard.storage.recovery_wakeup()
+vshard.storage.bucket_force_create(10)
+box.space._bucket:update(10, {{'=', 2, vshard.consts.BUCKET.SENDING}})
+assert(not lstorage.bucket_are_all_rw())
+box.space._bucket:update(10, {{'=', 2, vshard.consts.BUCKET.ACTIVE}})
+assert(lstorage.bucket_are_all_rw())
+vshard.storage.internal.errinj.ERRINJ_NO_RECOVERY = false
+
 _ = test_run:switch("default")
 test_run:drop_cluster(REPLICASET_2)
 test_run:drop_cluster(REPLICASET_1)
diff --git a/vshard/storage/init.lua b/vshard/storage/init.lua
index ffa48b6..c3ed236 100644
--- a/vshard/storage/init.lua
+++ b/vshard/storage/init.lua
@@ -115,6 +115,10 @@ if not M then
         -- Fast alternative to box.space._bucket:count(). But may be nil. Reset
         -- on each generation change.
         bucket_count_cache = nil,
+        -- Fast alternative to checking multiple keys presence in
+        -- box.space._bucket status index. But may be nil. Reset on each
+        -- generation change.
+        bucket_are_all_rw_cache = nil,
         -- Redirects for recently sent buckets. They are kept for a while to
         -- help routers to find a new location for sent and deleted buckets
         -- without whole cluster scan.
@@ -220,12 +224,44 @@ local function bucket_count_public()
     return bucket_count()
 end
 
+--
+-- Check if all buckets on the storage are writable. The idea is the same as
+-- with bucket count - the value changes very rare, and is cached most of the
+-- time. Only that its non-cached calculation is more expensive than with count.
+--
+local bucket_are_all_rw
+
+local function bucket_are_all_rw_cache()
+    return M.bucket_are_all_rw_cache
+end
+
+local function bucket_are_all_rw_not_cache()
+    local status_index = box.space._bucket.index.status
+    local status = consts.BUCKET
+    local res = not status_index:min(status.SENDING) and
+       not status_index:min(status.SENT) and
+       not status_index:min(status.RECEIVING) and
+       not status_index:min(status.GARBAGE)
+
+    M.bucket_are_all_rw_cache = res
+    bucket_are_all_rw = bucket_are_all_rw_cache
+    return res
+end
+
+bucket_are_all_rw = bucket_are_all_rw_not_cache
+
+local function bucket_are_all_rw_public()
+    return bucket_are_all_rw()
+end
+
 --
 -- Trigger for on replace into _bucket to update its generation.
 --
 local function bucket_generation_increment()
     bucket_count = bucket_count_not_cache
+    bucket_are_all_rw = bucket_are_all_rw_not_cache
     M.bucket_count_cache = nil
+    M.bucket_are_all_rw_cache = nil
     M.bucket_generation = M.bucket_generation + 1
     M.bucket_generation_cond:broadcast()
 end
@@ -2788,6 +2824,7 @@ M.schema_upgrade_handlers = schema_upgrade_handlers
 M.schema_version_make = schema_version_make
 M.schema_bootstrap = schema_init_0_1_15_0
 
+M.bucket_are_all_rw = bucket_are_all_rw_public
 M.bucket_generation_wait = bucket_generation_wait
 lregistry.storage = M
 
-- 
2.24.3 (Apple Git-128)