It can't ever happen. We're guaranteed to have a consistent chain of headers
(we're verifying them above, if we're not verifying --- it's not our fault)
that starts at HeaderHeight that was actual when we were asking for it
previously. HeaderHeight can only move forward, so if that happened that would
be filtered out by the condition below and the first one can't happen. Though
to be absolutely sure change the second check to only pass "+1" headers (which
is what we want).
It's used in two places now:
* Blockchain.AddBlock()
This one does transaction duplication check of its own, doing it in
Verify() is just a waste of time. Merkle tree root hash value check is
still relevant though
* Block.DecodeBinary()
We're decoding blocks for the following purposes:
- on restore from dump
The block will be added to the chain via AddBlock() and that will do a
full check of it (if configured to do so)
- on retrieving the block from the DB (DAO)
We trust the DB, if it's gone wild, this check won't really help
- on receiving the block via P2P
It's gonna be put into block queue and then end up in AddBlock() which
will check it
- on receiving the block via RPC (submitblock)
It is to be passed into AddBlock()
- on receiving the block via RPC in a client
That's the only problematic case probably, but RPC client has to trust
the server and it can check for the signature if it really
cares. Or a separate in-client check might be added.
As we can see nothing really requires this verification to be done the way it
is now, AddBlock can just have a Merkle check and DecodeBinary can do fine
without it at all.
It's a no-op and there is nothing we can do about it, header contents could
only be checked against chain state, there is nothing to check for internal
consistency.
NewMerkleTree is a memory hog, we can do better than that:
BenchmarkMerkle/NewMerkleTree-8 13 88434670 ns/op 20828207 B/op 300035 allocs/op
BenchmarkMerkle/CalcMerkleRoot-8 15 69264150 ns/op 0 B/op 0 allocs/op
It's not needed, we're either creating a new one and assigning it 6 lines
above or we're changing already existing big.Int via a pointer, so no update
is needed.
There is nothing requiring us to do so. It also is bad because it allows for
new transaction to replace some already existing one with the same fee
parameters just because it has "better" hash.
But the other thing is that for transactions with equal fees it's always
better for us to append them to the end of the list, instead of inserting them
in the middle, so this change allows to reduce slice item movements and gain
some 6-7% increase for single-node TPS.
Time is not really relevant for us here and we don't use this timestamp in any
way. Yet it occupies 24 bytes and we do two clock_gettime calls to get it.
Replace it with blockStamp which is going to be used in the future for
transaction retransmissions.
It allows to improve single-node TPS by another 3%.
We're constantly checking for transactions there and most of the time this
check is not successful (meaning that the transaction in question is
new). Bloom filter easily reduces the need to search over the DB in 99% of
these cases and gives some 13% increase in single-node TPS.
Now we have VerifyTx() and PoolTx() APIs that either verify transaction in
isolation or verify it against the mempool (either the primary one or the one
given) and then add it there. There is no possibility to check against the
mempool, but not add a transaction to it, but I doubt we really need it.
It allows to remove some duplication between old PoolTx and verifyTx where
they both tried to check transaction against mempool (verifying first and then
adding it). It also saves us utility token balance check because it's done by
the mempool anyway and we no longer need to do that explicitly in verifyTx.
It makes AddBlock() and verifyBlock() transaction's checks more correct,
because previously they could miss that even though sender S has enough
balance to pay for A, B or C, he can't pay for all of them.
Caveats:
* consensus is running concurrently to other processes, so things could
change while verifyBlock() is iterating over transactions, this will be
mitigated in subsequent commits
Improves TPS value for single node by at least 11%.
Fixes#667, fixes#668.
New transactions are added to the chain with blocks. If there is no
transaction X at height N in DAO, it could only be added with block N+1, so
it has to be present there. Therefore we can replace `dao.HasTransaction()`
check with a search through in-block transactions. HasTransaction() is nasty
in that it may add useless load the DB and this code is being run with a big
Blockchain lock held, so we don't want to be delayed here at all.
Improves single-node TPS by ~2%.
The end effect is almost as if `VerifyTransactions: false` was set in the
config, but without actually compromising the guarantees provided by it.
It almost doubles performance for single-mode benchmarks and makes block
processing smoother (more smaller blocks are being produced).
According to manifest, OnPersist.ReturnType is void, so we shouldn't
return anything from it. It's not so important, as we drop this value at
the end of OnPersist invocation.
C# node is quite picky as it expects there to be exactly one value returned,
but our testchain actually adds 4 signatures for multisig cases instead of 3
which makes it technically incompatible with C# node.
We currently can't process events in codegen, so we have to provide
them via .yml config file. Do not delete the rest of the code connected
with conversion of MethodDebugInfo.Event into manifest.Event as we have
issue #1038.
As it's returned sorted now. Fixes state change mismatch for
NextValidators. It also partially reverts
2f8e7e4d33 and significantly changes the test
chain as the fees are no longer being sent to the same account.
When calling external contracts we expect exactly 1 value to be on
stack. For methods returning nothing, `Null` value is pushed, otherwise
it is an error.`
We were checking blocked accounts twice which is obviously excessive. We also
have our accounts sorted, so we can rely on that in CheckPolicy(). It also
doesn't make much sense to check MaxBlockSystemFee in Blockchain code, policy
contract can handle that.
It no longer depends on blockchain state and there can't ever be an error, in
fact we can always iterate over signers, so copying these hashes doesn't make
much sense at all as well as sorting arrays in verifyTxWitnesses (witnesses
order must match signers order).
It's not needed any more with Go 1.13 as we have wrapping/unwrapping in base
packages. All errors.Wrap calls are replaced with fmt.Errorf, some strings are
improved along the way.
In 121c9664b we should take into account isValid flag of
NativePolicy contract while retrieving MaxVerificationGas native
policy value. Otherwise we won't be able to get MaxVerificationGas
after the node was restarted, because this value is not truly
stored along with the other native policy values.
This commit fixes bug with headers verification after the node
restarting with an existing storage:
```
2020-08-03T12:52:56.158+0300 WARN failed processing headers {"error": "vm failed to execute the script with error: error encountered at instruction 0 (PUSHDATA1): gas limit is exceeded", "errorVerbose": "vm failed to execute the script with error: error encountered at instruction 0 (PUSHDATA1): gas limit is exceeded\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHashAgainstScript\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1454\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHeaderWitnesses\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1517\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).verifyHeader\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:1175\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).addHeaders\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:484\ngithub.com/nspcc-dev/neo-go/pkg/core.(*Blockchain).AddHeaders\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/core/blockchain.go:453\ngithub.com/nspcc-dev/neo-go/pkg/network.(*Server).handleHeadersCmd\n\t/home/neospcc/Documents/GitProjects/nspcc-dev/neo-go/pkg/network/server.go:454\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1373"}
```
We need to compact our in-memory MPT from time to time, otherwise it quickly
fills up all available memory. This raises two obvious quesions --- when to do
that and to what level do that.
As for 'when', I think it's quite easy to use our regular persistence interval
as an anchor (and it also frees up some memory), but we can't do that in the
persistence routine itself because of synchronization issues (adding some
synchronization primitives would add some cost that I'd also like to avoid),
so do it indirectly by comparing persisted and current height in `storeBlock`.
Choosing proper level is another problem, but if we're to roughly estimate one
full branch node to use 1K of memory (usually it's way less than that) then we
can easily store 1K of these nodes and that gives us a depth of 10 for our
trie.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
This was differing from C# notion of PrevHash. It's not a previous root, but
rather a hash of the previous serialized MPTRoot structure (that is to be
signed by CNs).
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Because trie size is rather big, it can't be stored in memory.
Thus some form of caching should also be implemented. To avoid
marshaling/unmarshaling of items which are close to root and are used
very frequenly we can save them across the persists.
This commit implements pruning items at the specified depth,
replacing them by hash nodes.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Because there is no distinct type field in JSONized nodes, distinction
is made via payload itself, thus all unmarshaling is done via
NodeObject.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
