[Tarantool-patches] [PATCH 3/4] memtx: use reserved slab for truncation

[Ilya Kosarev <i.kosarev@tarantool.org>]

Trying to perform space:truncate() while reaching memtx_memory limit we
could experience slab allocator failure. This behavior seems to be
quite surprising for users. Now we are using specifically preallocated
on arena slab for truncation tuples in case we are running out of
limit.
---
 src/box/box.cc                       |  27 ++++++-
 src/box/tuple.c                      |   4 ++
 src/lib/core/memory.c                |   1 +
 test/engine/engine.cfg               |   3 +
 test/engine/low_memory.lua           |   8 +++
 test/engine/stress_truncate.result   | 103 +++++++++++++++++++++++++++
 test/engine/stress_truncate.test.lua |  52 ++++++++++++++
 7 files changed, 197 insertions(+), 1 deletion(-)
 create mode 100644 test/engine/low_memory.lua
 create mode 100644 test/engine/stress_truncate.result
 create mode 100644 test/engine/stress_truncate.test.lua

diff --git a/src/box/box.cc b/src/box/box.cc
index 1b2b27d61..eea4269e7 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -1321,9 +1321,34 @@ space_truncate(struct space *space)
 	ops_buf_end = mp_encode_uint(ops_buf_end, 1);
 	assert(ops_buf_end < buf + buf_size);
 
+	struct txn *txn = NULL;
+	struct txn_savepoint *txn_svp = NULL;
+	if (!box_txn()) {
+		txn = txn_begin();
+		if (txn == NULL)
+			diag_raise();
+	} else {
+		txn_svp = box_txn_savepoint();
+		if (txn_svp == NULL)
+			diag_raise();
+	}
+	struct space *truncate_space = space_cache_find_xc(BOX_TRUNCATE_ID);
+	((struct memtx_engine *)truncate_space->engine)->arena.truncating = true;
 	if (box_upsert(BOX_TRUNCATE_ID, 0, tuple_buf, tuple_buf_end,
-		       ops_buf, ops_buf_end, 0, NULL) != 0)
+		       ops_buf, ops_buf_end, 0, NULL) != 0) {
+		((struct memtx_engine *)truncate_space->engine)->arena.truncating = false;
+		if (txn != NULL)
+			txn_rollback(txn);
+		else
+			box_txn_rollback_to_savepoint(txn_svp);
+		fiber_gc();
 		diag_raise();
+	}
+	((struct memtx_engine *)truncate_space->engine)->arena.truncating = false;
+	if (txn != NULL && txn_commit(txn) != 0) {
+		fiber_gc();
+		diag_raise();
+	}
 }
 
 int
diff --git a/src/box/tuple.c b/src/box/tuple.c
index 4d676b090..0e8aeb92e 100644
--- a/src/box/tuple.c
+++ b/src/box/tuple.c
@@ -342,6 +342,10 @@ tuple_arena_create(struct slab_arena *arena, struct quota *quota,
 	say_info("mapping %zu bytes for %s tuple arena...", prealloc,
 		 arena_name);
 
+	if (!strncmp(arena_name, "memtx", 5))
+		arena->trunc_alloc = slab_size;
+	else
+		arena->trunc_alloc = 0;
 	if (slab_arena_create(arena, quota, prealloc, slab_size, flags) != 0) {
 		if (errno == ENOMEM) {
 			panic("failed to preallocate %zu bytes: Cannot "\
diff --git a/src/lib/core/memory.c b/src/lib/core/memory.c
index f236c1887..0ce977d38 100644
--- a/src/lib/core/memory.c
+++ b/src/lib/core/memory.c
@@ -42,6 +42,7 @@ memory_init()
 	quota_init(&runtime_quota, QUOTA_MAX);
 
 	/* No limit on the runtime memory. */
+	runtime.trunc_alloc = 0;
 	slab_arena_create(&runtime, &runtime_quota, 0,
 			  SLAB_SIZE, SLAB_ARENA_PRIVATE);
 }
diff --git a/test/engine/engine.cfg b/test/engine/engine.cfg
index f1e7de274..4b9eeb5f5 100644
--- a/test/engine/engine.cfg
+++ b/test/engine/engine.cfg
@@ -5,6 +5,9 @@
     },
     "func_index.test.lua": {
         "memtx": {"engine": "memtx"}
+     },
+    "stress_truncate.test.lua": {
+        "memtx": {"engine": "memtx"}
      }
 }
 
diff --git a/test/engine/low_memory.lua b/test/engine/low_memory.lua
new file mode 100644
index 000000000..46fd26d1b
--- /dev/null
+++ b/test/engine/low_memory.lua
@@ -0,0 +1,8 @@
+#!/usr/bin/env tarantool
+os = require('os')
+box.cfg({
+    listen              = os.getenv("LISTEN"),
+    memtx_memory        = 32 * 1024 * 1024,
+})
+
+require('console').listen(os.getenv('ADMIN'))
diff --git a/test/engine/stress_truncate.result b/test/engine/stress_truncate.result
new file mode 100644
index 000000000..c5308a0ac
--- /dev/null
+++ b/test/engine/stress_truncate.result
@@ -0,0 +1,103 @@
+-- test-run result file version 2
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+
+test_run:cmd("create server master with script='engine/low_memory.lua'")
+ | ---
+ | - true
+ | ...
+test_run:cmd('start server master')
+ | ---
+ | - true
+ | ...
+test_run:cmd("switch master")
+ | ---
+ | - true
+ | ...
+
+
+test_run:cmd("setopt delimiter ';'")
+ | ---
+ | - true
+ | ...
+function create_space(name)
+    local space = box.schema.create_space(name)
+    space:format({
+        { name = "id",  type = "unsigned" },
+        { name = "val", type = "str" }
+    })
+    space:create_index('primary', { parts = { 'id' } })
+    return space
+end;
+ | ---
+ | ...
+
+function insert(space, i)
+    space:insert({ i, string.rep(string.char(32 + math.random(127-32)), math.random(1024)) })
+end;
+ | ---
+ | ...
+
+function fill_space(space, start)
+    local _, err = nil
+    local i = start
+    while err == nil do _, err = pcall(insert, space, i) i = i + 1 end
+end;
+ | ---
+ | ...
+
+function stress_truncation(i, spaces)
+    local res, space = pcall(create_space, 'test' .. tostring(i))
+    if res then spaces[i] = space return end
+    fill_space(box.space.test, box.space.test:len())
+    for _, s in pairs(spaces) do s:truncate() end
+end;
+ | ---
+ | ...
+test_run:cmd("setopt delimiter ''");
+ | ---
+ | - true
+ | ...
+
+
+_ = create_space('test')
+ | ---
+ | ...
+for i = 0, 27000 do insert(box.space.test, i) end
+ | ---
+ | ...
+
+spaces = {}
+ | ---
+ | ...
+counter = 0
+ | ---
+ | ...
+status = true
+ | ---
+ | ...
+res = nil
+ | ---
+ | ...
+while counter < 80000 do status, res = pcall(stress_truncation, counter, spaces) counter = counter + 1 end
+ | ---
+ | ...
+status
+ | ---
+ | - true
+ | ...
+res
+ | ---
+ | - null
+ | ...
+
+-- Cleanup.
+test_run:cmd('switch default')
+ | ---
+ | - true
+ | ...
+test_run:drop_cluster({'master'})
+ | ---
+ | ...
diff --git a/test/engine/stress_truncate.test.lua b/test/engine/stress_truncate.test.lua
new file mode 100644
index 000000000..761b2a9c2
--- /dev/null
+++ b/test/engine/stress_truncate.test.lua
@@ -0,0 +1,52 @@
+test_run = require('test_run').new()
+
+
+test_run:cmd("create server master with script='engine/low_memory.lua'")
+test_run:cmd('start server master')
+test_run:cmd("switch master")
+
+
+test_run:cmd("setopt delimiter ';'")
+function create_space(name)
+    local space = box.schema.create_space(name)
+    space:format({
+        { name = "id",  type = "unsigned" },
+        { name = "val", type = "str" }
+    })
+    space:create_index('primary', { parts = { 'id' } })
+    return space
+end;
+
+function insert(space, i)
+    space:insert({ i, string.rep(string.char(32 + math.random(127-32)), math.random(1024)) })
+end;
+
+function fill_space(space, start)
+    local _, err = nil
+    local i = start
+    while err == nil do _, err = pcall(insert, space, i) i = i + 1 end
+end;
+
+function stress_truncation(i, spaces)
+    local res, space = pcall(create_space, 'test' .. tostring(i))
+    if res then spaces[i] = space return end
+    fill_space(box.space.test, box.space.test:len())
+    for _, s in pairs(spaces) do s:truncate() end
+end;
+test_run:cmd("setopt delimiter ''");
+
+
+_ = create_space('test')
+for i = 0, 27000 do insert(box.space.test, i) end
+
+spaces = {}
+counter = 0
+status = true
+res = nil
+while counter < 80000 do status, res = pcall(stress_truncation, counter, spaces) counter = counter + 1 end
+status
+res
+
+-- Cleanup.
+test_run:cmd('switch default')
+test_run:drop_cluster({'master'})
-- 
2.17.1