Commit graph

384 commits

Author SHA1 Message Date
Roman Khimov
0fceaf12d2 core: deal with bad transaction Inputs
They may not really have a reference. Fixes #671.
2020-02-14 09:42:10 +03:00
Roman Khimov
992ccc0b26
Merge pull request #664 from nspcc-dev/sort-validator-keys
core: sort GetValidators() result
2020-02-13 21:46:26 +03:00
Evgeniy Kulikov
8d410a6659
Add JSON tags for RPC response types
- Attribute should have 2 fields (usage, data)
- VOut should have 4 (5) fields (asset, value, address, n)
- Script should have 2 fields (invocation, verification)
2020-02-13 19:06:54 +03:00
Roman Khimov
d4cd134aef core: sort GetValidators() result
As C# node does it. Technically it's only needed for consensus and could be
implemented in the appropriate package, but for better compatibility with C#
node we're better returning it sorted right here.
2020-02-13 17:07:27 +03:00
Roman Khimov
26af9200b0 core: refactor voting processing, fix pending tx subtractions
Deduplicate code and add missing token check for subtractions that are being
done in GetValidators() for pending transactions.
2020-02-13 13:07:34 +03:00
Roman Khimov
c8a248596e core: introduce ValidatorsCount, make a proper count
We were completely lacking ValidatorsCount that is supposed to track the
number of votes with particular count of consensus nodes which in theory can
change the number of active consensus nodes (if it ever to exceed the number
of standby validators), so we were not producing the right count and based on
that not giving the right set of validators.

Fixes #512.
2020-02-13 13:07:34 +03:00
Roman Khimov
357b675090 core: don't choose duplicating standby validators
We may already have chosen some of standby validators, so don't repeat.
2020-02-13 13:07:34 +03:00
Roman Khimov
f9c6a0d77c core: make voting choose the best validators
They need to be sorted in order for voting system to work.
2020-02-13 13:07:34 +03:00
Roman Khimov
2ff7ceb8cf core: properly update validator votes for Account descriptor
ValidatorsCount is not implemented yet, but we need to update validators
properly, adding account's vote to their votes count.
2020-02-13 13:07:34 +03:00
Roman Khimov
8310b76d28 core: properly save votes when processing Account descriptor
They were ignored basically.
2020-02-13 13:07:34 +03:00
Roman Khimov
807309a0de core/state: only drop unregistered non-voted validators
Simple as that: UnregisteredAndHasNoVotes != !RegisteredAndHasVotes

Registered validators should stay in the DB, we might be in the process of
updating votes for them and that starts with subtraction.
2020-02-13 13:07:34 +03:00
Roman Khimov
38d0efc96c core: fix Registered state descriptor processing
It has simple boolean value encoded, no `strconv` needed (it actually chokes
on such input).
2020-02-12 21:27:40 +03:00
Roman Khimov
803fb39bb0 transaction: fix wrong state descriptor serdes
Wrong field order.
2020-02-12 21:23:28 +03:00
Evgenii Stratonikov
0a894db7f8 storage: add Exists flag to KeyValue in batch
Set Exists flag if an item with the specified key was already
present in storage before persisting.
2020-02-12 12:16:31 +03:00
Evgenii Stratonikov
b1d9e1132d cli: dump storage changes into JSON files 2020-02-12 12:16:31 +03:00
Evgenii Stratonikov
fb9af98179 storage: implement GetBatch() to view storage changes
GetBatch returns changes to be persisted.
2020-02-12 12:16:31 +03:00
Roman Khimov
38de2af073
Merge pull request #655 from nspcc-dev/fix-mempool-deadlock-on-reverification
core: get transactions from dao when mempool should not be used
2020-02-11 13:34:23 +03:00
Roman Khimov
292051d8df core: get transactions from dao when mempool should not be used
All of these places deal strictly with the chain and shouldn't ever be
bothered with mempool. It also fixes a deadlock on reverification of
non-standard tx:

1 @ 0x42f62f 0x43fbe9 0x43fbbf 0x43f95d 0x967059 0x966f66 0x972c7c 0x974e13 0x97a5d9 0x97bdf0 0x976147 0x966cc0 0x970f70 0x96c8cb 0x9ba858 0x45ca51
	0x43f95c	sync.runtime_SemacquireMutex+0x3c							/usr/local/go/src/runtime/sema.go:71
	0x967058	sync.(*RWMutex).RLock+0x128								/usr/local/go/src/sync/rwmutex.go:50
	0x966f65	github.com/CityOfZion/neo-go/pkg/core/mempool.(*Pool).TryGetValue+0x35			/go/src/github.com/CityOfZion/neo-go/pkg/core/mempool/mem_pool.go:229
	0x972c7b	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).GetTransaction+0x4b			/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:782
	0x974e12	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).References+0x132			/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:944
	0x97a5d8	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).GetScriptHashesForVerifying+0x58	/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:1410
	0x97bdef	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).verifyTxWitnesses+0x4f		/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:1545
	0x976146	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).isTxStillRelevant+0x216		/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:1067
	0x966cbf	github.com/CityOfZion/neo-go/pkg/core/mempool.(*Pool).RemoveStale+0xff			/go/src/github.com/CityOfZion/neo-go/pkg/core/mempool/mem_pool.go:208
	0x970f6f	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).storeBlock+0x2ecf			/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:614
	0x96c8ca	github.com/CityOfZion/neo-go/pkg/core.(*Blockchain).AddBlock+0xea			/go/src/github.com/CityOfZion/neo-go/pkg/core/blockchain.go:308
	0x9ba857	github.com/CityOfZion/neo-go/pkg/network.(*blockQueue).run+0x157			/go/src/github.com/CityOfZion/neo-go/pkg/network/blockqueue.go:48
2020-02-10 18:53:22 +03:00
Anna Shaleva
9b03f968b1 core: fixe FreeGasLimit constraint
Lack of FreeGasLimit in privnet leads to gas limit exceeding in case of transactions with small amount of GAS to be used for invoke operation (< real cost of the transaction). Solution: Fixed constraint in case when FreeGasLimit == 0. So now we are able to perform transactions in privnet with FreeGasLimit = 0 for free.
2020-02-10 18:07:19 +03:00
Roman Khimov
9b9adb28c1
Merge pull request #642 from nspcc-dev/feature/emit
vm, compiler: move Emit* functions to a separate package

Closes #449, #534.
2020-02-08 15:56:48 +03:00
Roman Khimov
7ccf7974b6 core: substitute bad notifications with error messages
Tesnet sync failed with:
Feb 07 00:04:19 nodoka neo-go[1747]: 2020-02-07T00:04:19.838+0300        WARN        blockQueue: failed adding block into the blockchain        {"error": "failed to store notifications: not supported", "blockHeight": 713984, "nextIndex": 713985}

because some (not so) smart contract emitted a notification with an
InteropItem inside.
2020-02-07 15:34:59 +03:00
Evgenii Stratonikov
8243a8b3a7 emit: use io.BinWriter instead of bytes.Buffer 2020-02-06 18:45:37 +03:00
Evgenii Stratonikov
4d8a3a359b vm: move Emit* functions to a separate package
Also strip 'Emit' prefix because 'emit' is now
in the package name.
2020-02-06 18:45:37 +03:00
Roman Khimov
ab14a4619d
Merge pull request #647 from nspcc-dev/fix-mempool-and-chain-locking
Fix mempool and chain locking

This allows us easily make 1000 Tx/s in 4-nodes privnet, fixes potential
double spends and improves mempool testing coverage.
2020-02-06 18:43:29 +03:00
Evgenii Stratonikov
9204b95d5b core: fix GAS price definitions 2020-02-06 18:19:08 +03:00
Roman Khimov
18695e660b mempool: drop RemoveOverCapacity(), handle it right in the Add()
Simplifies things a lot and removes useless code.
2020-02-06 17:50:11 +03:00
Roman Khimov
684cbf5bac mempool: make it almost 100% test-covered 2020-02-06 17:50:11 +03:00
Roman Khimov
6672f4b26f mempool: iterate over slice in GetVerifiedTransactions()
It's more efficient and keeps transactions sorted by priority.
2020-02-06 16:59:20 +03:00
Roman Khimov
e97396e56c mempool: test addition of conflicting tx to the pool 2020-02-06 15:57:20 +03:00
Roman Khimov
1133bbe584 mempool: remove unverified transactions pool
Our mempool only contains valid verified transactions all the time, it never
has any unverified ones. Unverified pool made some sense for quick unverifying
after the new block acceptance (and gradual background reverification), but
reverification needs some non-trivial locking between blockchain and mempool
and internal mempool state locking (reverifying tx and moving it between
unverified and verified pools must be atomic). But our current reverification
is fast enough (and has all the appropriate locks), so bothering with
unverified pool makes little sense.
2020-02-06 15:45:16 +03:00
Roman Khimov
b675903f52 mempool/core: redesign mempool dances on block acceptance
We not only need to remove transactions stored in the block, but also
invalidate some potential double spends caused by these transactions. Usually
new block contains a substantial number of transactions from the pool, so it's
easier to make one pass over it only keeping valid items rather than remove
them one by one and make an additional pass to recheck inputs/witnesses.
2020-02-06 15:45:16 +03:00
Roman Khimov
b567ce86ac mempool: implement insertion to sorted slice
Which is way faster than sort.Sort'ing things all the time.
2020-02-06 15:44:18 +03:00
Roman Khimov
35183b6dba mempool: reverse the order of sorted slice
Chopping off the last element of the slice if way easier than doing it with
the first one.
2020-02-06 15:44:16 +03:00
Roman Khimov
794027a90b mempool: use one slice for both priorities
It doesn't harm as we have transactions naturally ordered by fee anyway and it
makes managing them a little easier. This also makes slices store item itself
instead of pointers to it which reduces the pressure on the memory subsystem.
2020-02-06 15:43:45 +03:00
Roman Khimov
325bea3fa9 mempool: cache Feer invocation results in the item
They shouldn't depend on the chain state and for the same transaction they
should always produce the same result. Thus, it makes no sense recalculating
them over and over again.
2020-02-06 15:41:56 +03:00
Roman Khimov
e01bfeeb4d mempool: remove lock indirection from the Pool
After the f0bb886be3 with all methods of Pool
being pointer-based it makes no sense having this lock as a pointer.
2020-02-06 15:41:56 +03:00
Roman Khimov
a928ad9cfa mempool: make item an internal thing of mempool package
Nobody outside should care about these details, mempool operates on
transactions and that's it.
2020-02-06 15:41:56 +03:00
Roman Khimov
f0e3a31bc8 mempool: fix appending to sorted pools
Appending and not changing the real Items is utterly wrong.
2020-02-06 15:41:56 +03:00
Roman Khimov
f9963cca37 core: short-circuit verifyInputs when there are no inputs 2020-02-06 15:41:56 +03:00
Roman Khimov
70b3839fd0 core/mempool: fix AddBlock and tx pooling concurrency issues
Eliminate races between tx checks and adding them to the mempool, ensure the
chain doesn't change while we're working with the new tx. Ensure only one
block addition attempt could be in progress.
2020-02-06 15:41:52 +03:00
Roman Khimov
f0bb886be3 mempool: make all methods pointer methods
Makes no sense copying the Pool around.
2020-02-04 17:36:11 +03:00
Roman Khimov
388fed06e5 transaction: forbid serializing invalid transactions
Transaction that has no data is invalid and can't be serialized, so throw an
error if someone tries to.
2020-02-03 16:33:03 +03:00
Evgeniy Kulikov
eb59460032
Merge pull request #614 from nspcc-dev/configurable-mempool-size
config: add MemPoolSize configuration parameter
2020-01-23 13:25:27 +03:00
Roman Khimov
d6784e8f45 config: add MemPoolSize configuration parameter
Allow tuning/experimenting with mempool.
2020-01-23 13:10:44 +03:00
Evgenii Stratonikov
303b82cc44 core: set free GAS limit via config 2020-01-22 14:32:21 +03:00
Evgenii Stratonikov
4718375db1 rpc: return amount of consumed GAS in invoke* 2020-01-22 14:31:57 +03:00
Evgenii Stratonikov
4eae55143f core: restrict GAS available for invocation transactions
There are 10 GAS available for free plus any amount of GAS
attached to a transaction.
2020-01-22 14:31:54 +03:00
Roman Khimov
32213b1454
Merge pull request #601 from nspcc-dev/refactoring/core
core: refactor out Block, BlockBase and Header, closes #597.
2020-01-20 16:19:20 +03:00
Roman Khimov
46b82b4fb5 keys: don't return error from PrivateKey.Sign
As it can't ever happen.
2020-01-17 17:00:30 +03:00
Evgenii Stratonikov
28183b81d6 mempool: simplify names of exported types
With the move to a separate package, naming can be simplified:
MemPool -> Pool, PoolItem -> Item, PoolItems -> Items.
2020-01-16 10:16:24 +03:00
Evgenii Stratonikov
fed6fba9b6 core: refactor out MemPool 2020-01-16 10:16:24 +03:00
Evgenii Stratonikov
79bceb3e40 block: use require in tests 2020-01-16 10:16:24 +03:00
Evgenii Stratonikov
489b88afbb block: rename BlockBase to Base 2020-01-16 10:16:24 +03:00
Evgenii Stratonikov
63c56cca5c core: refactor out Block, BlockBase and Header structs
See #597.
2020-01-16 10:16:24 +03:00
Evgenii Stratonikov
9dc5571327 core,rpc: close Blockchain in tests
If blockchain is not closed, logging in defer can occur
after test has finished, which will lead to a panic with
"Log in goroutine after Test* has completed".
2020-01-10 11:47:56 +03:00
Evgenii Stratonikov
637c99eda7 core: simplify newInteropContext 2020-01-10 11:14:29 +03:00
Evgenii Stratonikov
aecdf470e7 cli,pkg: use zap.Logger 2020-01-10 11:14:27 +03:00
Evgenii Stratonikov
9c79684516 storage: panic on error in boltdb.Seek
Error in Seek means something is terribly wrong (e.g. db was not opened) and
error drop is not the right thing to do, because caller
will continue working with the wrong view.
2020-01-09 15:17:35 +03:00
Roman Khimov
c306d2f07c
Merge pull request #581 from nspcc-dev/feat/storage_find
core: implement Neo.Storage.Find interop, closes #422.
2019-12-26 15:46:46 +03:00
Evgenii Stratonikov
48cf4f4a84 core: implement Neo.Storage.Find interop 2019-12-26 15:21:41 +03:00
Roman Khimov
f8887b63ba
Merge pull request #578 from nspcc-dev/fix/sign
consensus: verify payloads correctly, closes #555.
2019-12-26 13:07:40 +03:00
Evgenii Stratonikov
714c466c2c core: add ScriptFromWitness function
Extracting verification script from witness became a common task.
This commit adds such a possibility.
2019-12-26 10:49:56 +03:00
Roman Khimov
9145855d2c
Merge pull request #579 from nspcc-dev/refactor-crypto
This moves some functionality into micro-packages, improves testing,
unexports some code and fixes bugs along the way.
2019-12-25 18:12:50 +03:00
Roman Khimov
b246653f62 address: rename functions as per #579 comments
Make them more clear to understand.
2019-12-25 17:34:18 +03:00
Roman Khimov
e685e9bf9a address: move into its own package
Doesn't really belong to the crypto.
2019-12-25 15:22:02 +03:00
Roman Khimov
ee28fb08f6 crypto: move merkle tree into the hash package
It's all about hashes, so it makes sense putting it there.
2019-12-25 11:28:59 +03:00
Vsevolod Brekelov
7f1844a39e transaction: add unmarshaling for TXType 2019-12-25 01:44:37 +03:00
Evgenii Stratonikov
5bc32b523a vm: implement Neo.Iterator.* interops 2019-12-24 10:21:47 +03:00
Evgenii Stratonikov
3ff7fd5262 vm: implement Neo.Enumerator.* interops 2019-12-24 10:21:46 +03:00
Roman Khimov
bf84e1f2fb core: cache top block
Turns out, our dApps use it a lot and we were going to the DB to get it which
is a useless waste of time. Technically we could also remove blockHeight here,
but not doing it at the moment as it's more involved.

It eliminates this time waste from the pprof graph, but doesn't change 1.4M ->
1.5M 100K mainnet block import test case in any noticeable way.
2019-12-23 19:18:12 +03:00
Roman Khimov
deb76c5199 core: add negative non-interop test for all interops
Try to feed some garbage into these functions.
2019-12-23 16:14:43 +03:00
Roman Khimov
76d69ee5ee core: restore proper interops ordering 2019-12-23 16:14:43 +03:00
Roman Khimov
c287a9e93c core: implement Neo.Witness.GetVerificationScript interop 2019-12-23 16:14:43 +03:00
Roman Khimov
9d638d0fee core: implement Neo.InvocationTransaction.GetScript 2019-12-23 16:14:43 +03:00
Roman Khimov
a7457d08a1 vm/core: add ID support for SYSCALL, redo interop registration
This solves two problems:
 * adds support for shortened SYSCALL form that uses IDs (similar to #434, but
   for NEO 2.0, supporting both forms), which is important for compatibility
   with C# node and mainnet chain that uses it from some height
 * reworks interop plugging to use callbacks rather than appending to the map,
   these map mangling functions are clearly visible in the VM profiling
   statistics and we want spawning a VM to be fast, so it makes sense
   optimizing it. This change moves most of the work to the init() phase
   making VM setup cheaper.

Caveats:
 * InteropNameToID accepts `[]byte` because that's the thing we have in
   SYSCALL processing and that's the most often usecase for it, it leads to
   some conversions in other places but that's acceptable because those are
   either tests or init()
 * three getInterop functions are: `getDefaultVMInterop`, `getSystemInterop`
   and `getNeoInterop`

Our 100K (1.4M->1.5M) block import time improves by ~4% with this change.
2019-12-19 13:35:42 +03:00
Evgenii Stratonikov
884779e501 *: goimports 2019-12-17 14:51:28 +03:00
Roman Khimov
7a5e995030 core: add MemPool Verify() test 2019-12-14 00:05:45 +03:00
Roman Khimov
5d68f88196 core: fix and speed up mempool Verify()
First of all, it was wrong, it was not checking for inputs really, it compared
tx hashes for some reason, second, when it did compare inputs it compared only
the PrevIndex part of them which is also wrong.

Also, there is absolutely no reason to go through GetVerifiedTransactions()
here, we don't need this copy of pointers and it can also be outdated by the
time we're to finish our check.

Before:
BenchmarkTXPerformanceTest-4
    5000            485506 ns/op           65886 B/op        409 allocs/op
ok      github.com/CityOfZion/neo-go/integration        3.212s

After:
enchmarkTXPerformanceTest-4
    5000            371104 ns/op           44367 B/op        408 allocs/op
ok      github.com/CityOfZion/neo-go/integration        2.712s
2019-12-13 23:23:33 +03:00
Roman Khimov
e631e75718 core: optimize GetVerifiedTransactions()
This simple change improves our BenchmarkTXPerformanceTest by 14%, just
because we don't waste time on reallocations during append().

Before:
   10000            439754 ns/op          218859 B/op        428 allocs/op
ok      github.com/CityOfZion/neo-go/integration        5.423s

After:
   10000            369833 ns/op           87209 B/op        412 allocs/op
ok      github.com/CityOfZion/neo-go/integration        4.612s
2019-12-13 19:57:17 +03:00
Roman Khimov
a9401e2ec7 core: do not write new dao elements into DB
It's useless work being done before it's actually needed. These (updated with
new values) are going to be written with some kind of Put anyway, so writing
them here is just a waste of time.
2019-12-13 19:57:17 +03:00
Roman Khimov
6896b40dee state: use open-coded array (de)serialization for accounts
We're spending a lot of time here, 100K blocks import starting at 1.4M, before
this patch:
real    4m17,748s
user    6m23,316s
sys     0m37,866s

After:
real    3m54,968s
user    5m56,547s
sys     0m39,398s

9% is quite a substantial improvement to justify this change.
2019-12-13 19:57:17 +03:00
Roman Khimov
0d0a27d271 core: add cachedDao to cache accounts and contracts
Importing 100K blocks starting at 1.4M, before this patch:
real    6m0,356s
user    8m52,293s
sys     0m47,372s

After this patch:
real    4m17,748s
user    6m23,316s
sys     0m37,866s

Almost 30% better.
2019-12-13 19:57:17 +03:00
Roman Khimov
212cf44e26 core: get data from dao in interops
It's more logically correct as Blockchain can be several transactions behind
in terms of its state.
2019-12-13 17:17:14 +03:00
Roman Khimov
0abd55c2c2 vm: add cached ScriptHash() to Context
Avoid recalculating it over and over again in interop.
2019-12-13 17:05:03 +03:00
Roman Khimov
09223236f9 core: add Persist() to dao()
Hide its internals a little, which is gonna be useful for future composition.
2019-12-12 21:17:13 +03:00
Roman Khimov
eb1749d190 core: remove persisting from GetValidators()
It's a getter function and even though it's quite fancy with its transactions
processing (for consensus operation) it shouldn't ever change the state of the
Blockchain. If we're to change anything here these changes may conflict with
the actual block processing later or may lead to broken state (if transactions
won't be approved for some reason).
2019-12-12 21:14:33 +03:00
Roman Khimov
31dbc35279 core: gofmt dao_test.go 2019-12-12 21:05:36 +03:00
Roman Khimov
c5ed3b788b core: simplify dao creation with newDao() 2019-12-12 21:04:55 +03:00
Roman Khimov
8b3080b972 io: rename Read/WriteBytes to Read/WriteB
go vet is not happy about them:
  pkg/io/binaryReader.go:92:21: method ReadByte() byte should have signature ReadByte() (byte, error)
  pkg/io/binaryWriter.go:75:21: method WriteByte(u8 byte) should have signature WriteByte(byte) error
2019-12-12 20:19:50 +03:00
Roman Khimov
54d888ba70 io: add type-specific read/write methods
This seriously improves the serialization/deserialization performance for
several reasons:
 * no time spent in `binary` reflection
 * no memory allocations being made on every read/write
 * uses fast ReadBytes everywhere it's appropriate

It also makes Fixed8 Serializable just for convenience.
2019-12-12 20:19:50 +03:00
Roman Khimov
89d7f6d26e core/tx: microoptimize block/tx hashing
Don't hash the data twice.
2019-12-12 18:01:30 +03:00
Vsevolod Brekelov
c93a8d2bc4 core: extracted same logic to separate methods 2019-12-11 13:14:45 +03:00
Vsevolod Brekelov
c1f39d5c7b internal: moved testutil method to internal package 2019-12-11 13:14:43 +03:00
Vsevolod Brekelov
2d42b14a1d core: renames entities-> state and removed State prefix 2019-12-11 13:14:18 +03:00
Vsevolod Brekelov
8809fe437d core: unit tests for dao 2019-12-11 13:13:51 +03:00
Vsevolod Brekelov
c0e59ebd4e core: unit tests for entities 2019-12-11 13:05:31 +03:00
Vsevolod Brekelov
c7ac4b6dff core: fix encoding and decoding for notification event 2019-12-11 13:05:31 +03:00
Vsevolod Brekelov
ec17654986 core: refactoring blockchain state and storage
add dao which takes care about all CRUD operations on storage
remove blockchain state since everything is stored on change
remove storage operations from structs(entities)
move structs to entities package
2019-12-11 13:05:31 +03:00
Roman Khimov
d0f9a28196 vm/core: improve block import speed with PublicKey caching
This change (closely related to the neo-project/neo#1321 proposal) speeds up
1.4M mainnet blocks import by 30%. Basically, we're eliminating key decoding
for block's multisignature that has the same keys most of the time.

Things I don't like about this patch:
 * yet another parameter for verifyHashAgainstScript()
 * vm keys are not copied in/out

But it's rather simple and solves the problem for this particular case, so I
think it's worth it.
2019-12-10 19:13:29 +03:00
Roman Khimov
f1856bfa8b core/tx: remove publickey indirection from assets and txes
It makes very little sense having pointers here, these structures MUST have
some kind of key and this key is not gonna be wandering somewhere on its
own. Fixes a part of #519.
2019-12-09 18:33:04 +03:00