* batch-verify sync messages for a small perf boost
Generally reuses the same structure as attestation and aggregate
verification
* normalize `signatures` and `signature_batch` to use the same pattern
of verification
* normalize parameter names, order etc for signature stuff in general
* avoid calling `blsSign` directly - instead, go through `signatures`
consistently
This PR fixes two issues with block publishing:
* Gossip-valid blocks are published before integrating them into the
chain, giving broadcasting a head start, both for rest block and
* Outright invalid blocks from the API that could lead to the descoring
of the node are no longer broadcast
Bonus:
* remove undocumented and duplicated `post_v1_validator_block` JSON-RPC
call
Validator clients such as Vouch can be configured to work with multiple
beacon nodes simultaneously. In this configuration, the validator client
will try to broadcast the gossip messages through each of the connected
beacon nodes which may lead to a situation where some of the nodes see a
message arriving from the network before it arrives through the REST API.
This should not be considered an error and the beacon node should still
broadcast the message as the intented purpose of the Vouch strategy is
to ensure that the message will reach as many peers as possible.
Renames and cleanups split out from the validator monitoring branch, so
as to reduce conflict area vs other PR:s
* add constants for expected message timing
* name validators after the messages they validate, mostly, to make
grepping easier
* unify field naming of EpochInfo across forks to make cross-fork code
easier
Currently, we don't have a good answer to the question "are we synced
yet" - the sync manager syncs based on the peers it's connected to, but
just because some peer looks like it should be synced from doesn't mean
we're out of sync.
Instead, we use a very silly time-based heuristic - the problem with
that is that the network can go into a rut where nobody produces blocks
- better heuristics would be needed here, but in the meantime, a command
line option can get us out of a tight spot - this PR places such an
option in the client, in the unlikely event it should be needed (most
likely in a testnet).
* ncli_db: add putState, putBlock
These tools allow modifying an existing nimbus database for the purpose
of recovery or reorg, moving the head, tail and genesis to arbitrary
points.
* remove potentially expensive `putState` in `BeaconStateDB`
* introduce `latest_block_root` which computes the root of the latest
applied block from the `latest_block_header` field (instead of passing
it in separately)
* avoid some unnecessary BeaconState copies during init
* discover https://github.com/nim-lang/Nim/issues/19094
* prefer `HashedBeaconState` in a few places to avoid recomputing state
root
* fetch latest block root from state when creating blocks
* harden `get_beacon_proposer_index` against invalid slots and document
* move random spec function tests to `test_spec.nim`
* avoid unnecessary state root computation before block proposal
* `SyncCommitteeIndex` -> `SyncSubcommitteeIndex`
* `syncCommitteePeriod` -> `sync_committee_period` (spec spelling)
* tighten period comparisons
* fix assert when validating committee message with non-altair state in
REST api
* register vc duties with subnet tracker
* fix activation logging during startup
* cache slot signature to avoid duplicate signature work
* schedule aggregation duties one slot at a time to avoid CPU spike at
each epoch
* lower aggregation subnet pre-subscription time to 4 slots (lowers
bandwidth and CPU usage)
* update stability subnets in ENR on startup
* log gossip state
* perform gossip subscriptions just before the next slot starts
* document stuff
* add random include
* don't overwrite subscription state when not subscribed
* log target gossip state
* updating gossip status once is enough
* add test
* remove syncQueueLen - this one is not updated at the end of the sync
and may cause gossip to disconnect itself completely - use a simple head
distance instead
* fix gossip disconnection - if in hysteresis, node.gossipState will be
set to disabled even though we don't disable topic subscriptions
* fix extra duty registration call
So far, `withState` and `withBlck` templates could only be used to have
convenience access to fork-agnostic BeaconState and BeaconBlock fields.
This patch:
- injects an additional `stateFork` constant that allows to use
`when` expressions to also access Altair and Merge-specific fields.
- introduces a `withStateAndBlck` template to support operating on both
a `BeaconState` and `BeaconBlock` at a time.
- makes sync committee related functions Merge aware.
- changes a couple if-else trees for forks into case statements so that
forgotten future forks are promoted to compile-time errors.
There are a number of locations in the code that get attestations on a
forked beacon state. For attestation pools test, a convenience wrapper
was available to reduce clutter. This patch integrates that wrapper into
the core component so that it can also take advantage of the wrapper.
The initialization of a `SyncAggregate` to its default value is not very
intuitive. There is an `init` function in `sync_committee_msg_pool` that
provides a convenience wrapper. This patch exports that initializer so
that the rest of the code base can also take advantage of it.
The phase0 and altair overloads of `makeBeaconBlock` slightly differ in
their signatures which makes using them unnecessarily verbose.
- A placeholder `sync_aggregate` argument similar to `executionPayload`
is added to the phase0 overload to match the altair signature.
- A wrapper operating on `ForkedHashedBeaconState` is introduced.
* Placing callbacks into strategic places.
* Initial events call implementation.
* Post rebase fixes.
* Change addSyncContribution() implementation.
* Add `attestation-sent` event.
Remove gcsafe, raises from callbacks implementations.
Move `attestation-received` fire at the end of attestation processing.
* Address review comments.
Other changes:
* Add server getBlockV2(), and produceBlockV2().
* Add getBlockV2() to REST test suite.
* Add client getBlockV2(), and produceBlockV2().
* Fix URLs in comments.
* Add some primitives and fix some issues in forks.nim.
* Switch `validator_client` to V2 calls usage.
* Bump `chronos` with imports fixes.
* Bump `nim-json-serialization` for `requireAllFields`.
* cleanups
* use ForkedTrustedSignedBeaconBlock.ionit where appropriate
* move `is_aggregator` to `spec/`
* use `errReject` in a few more places
* update enr fork id when time is auspicious
* use network broadcast functions
* Return Ignore for aggregate signature validation timeouts
...consistently between aggregates and attestations.
* clean up some more reject/ignore rules
* shorten texts a bit
* errReject->checkedReject, use err helpers throughout
* get rid of quarantine in exitpool as well
* Fix getForkSchedule call.
Create cache of all configuration endpoints at node startup.
Add prepareJsonResponse() call to create cached responses.
Mark all procedures with `raises`.
* Add getForkSchedule to VC.
Fix getForkSchedule return type for API.
More `raises` annotations.
Fix VC fork_service.nim.
* Use `push raises` instead of inline `raises`.
* Improvements for REST API aggregated attestations and attestations processing.
* Rename eth2_network.sendXXX procedures to eth2_network.broadcastXXX.
Add broadcastBeaconBlock() and broadcastAggregateAndProof().
Fix links to specification in REST API declarations.
Add implementation for v2 getStateV2().
Add validator_duties.sendXXX procedures which not only broadcast data, but also validate it.
Fix JSON-RPC/REST to use new validator_duties.sendXXX procedures instead of own implementations.
* Fix validator_client online nodes count incorrect value.
Fix aggregate and proof attestation could be sent too late.
* Adding timeout for block wait in attestations processing.
Fix compilation errors.
* Attempt to debug aggregate and proofs.
* Fix Beacon AIP to use `sendAttestation`.
Add link comment to produceBlockV2.
* Add debug logs before publish operation for blocks, attestations and aggregated attestations.
Fix attestations publishing issue.
* logging fixes
`indexInCommnittee` already logged in attestation
Co-authored-by: Jacek Sieka <jacek@status.im>
* send attestations and exit messages on fork-appropriate topic
* document why use wall clock over attestation slot
* centralize some fork-topic-picking-logic in eth2_network
* pick up new test in summary
* allow specified GetTimeFn for testing purposes
* add GenesisTime and use it in eth2_network
* replace GetTimeFn and GenesisTime with GetBeaconTimeFn
* reorganize ssz dependencies
This PR continues the work in
https://github.com/status-im/nimbus-eth2/pull/2646,
https://github.com/status-im/nimbus-eth2/pull/2779 as well as past
issues with serialization and type, to disentangle SSZ from eth2 and at
the same time simplify imports and exports with a structured approach.
The principal idea here is that when a library wants to introduce SSZ
support, they do so via 3 files:
* `ssz_codecs` which imports and reexports `codecs` - this covers the
basic byte conversions and ensures no overloads get lost
* `xxx_merkleization` imports and exports `merkleization` to specialize
and get access to `hash_tree_root` and friends
* `xxx_ssz_serialization` imports and exports `ssz_serialization` to
specialize ssz for a specific library
Those that need to interact with SSZ always import the `xxx_` versions
of the modules and never `ssz` itself so as to keep imports simple and
safe.
This is similar to how the REST / JSON-RPC serializers are structured in
that someone wanting to serialize spec types to REST-JSON will import
`eth2_rest_serialization` and nothing else.
* split up ssz into a core library that is independendent of eth2 types
* rename `bytes_reader` to `codec` to highlight that it contains coding
and decoding of bytes and native ssz types
* remove tricky List init overload that causes compile issues
* get rid of top-level ssz import
* reenable merkleization tests
* move some "standard" json serializers to spec
* remove `ValidatorIndex` serialization for now
* remove test_ssz_merkleization
* add tests for over/underlong byte sequences
* fix broken seq[byte] test - seq[byte] is not an SSZ type
There are a few things this PR doesn't solve:
* like #2646 this PR is weak on how to handle root and other
dontSerialize fields that "sometimes" should be computed - the same
problem appears in REST / JSON-RPC etc
* Fix a build problem on macOS
* Another way to fix the macOS builds
Co-authored-by: Zahary Karadjov <zahary@gmail.com>
The spec imports are a mess to work with, so this branch cleans them up
a bit to ensure that we avoid generic sandwitches and that importing
stuff generally becomes easier.
* reexport crypto/digest/presets because these are part of the public
symbol set of the rest of the spec types
* don't export `merge` types from `base` - this causes circular deps
* fix circular deps in `ssz/spec_types` - this is the first step in
disentangling ssz from spec
* be explicit about phase0 vs altair - longer term, `altair` will become
the "natural" type set, then merge and so on, so no point in giving
`phase0` special preferential treatment
Simpler module name for stuff that covers forks
* check that runtime config matches database state
* also include some assorted altair cleanups
* use "standard" genesis fork in local testnet to work around missing
runtime config support
* bump libp2p
* altair sync v2
Use V2 sync requests after the altair fork has happened, according to
the wall clock
* Fix the behavior of the v1 req/resp calls after Altair
Co-authored-by: Zahary Karadjov <zahary@gmail.com>
* Initial commit.
* Exporting getConfig().
* Add beacon node checking procedures.
* Post rebase fixes.
* Use runSlotLoop() from nimbus_beacon_node.
Fallback implementation.
Fixes for ETH2 REST serialization.
* Add beacon_clock.durationToNextSlot().
Move type declarations from beacon_rest_api to json_rest_serialization.
Fix seq[ValidatorIndex] serialization.
Refactor ValidatorPool and add some utility procedures.
Create separate version of validator_client.
* Post-rebase fixes.
Remove CookedPubKey from validator_pool.nim.
* Now we should be able to produce attestations and aggregate and proofs.
But its not working yet.
* Debugging attestation sending.
* Add durationToNextAttestation.
Optimize some debug logs.
Fix aggregation_bits encoding.
Bump chronos/presto.
* Its alive.
* Fixes for launch_local_testnet script.
Bump chronos.
* Switch client API to not use `/api` prefix.
* Post-rebase adjustments.
* Fix endpoint for publishBlock().
* Add CONFIG_NAME.
Add more checks to ensure that beacon_node is compatible.
* Add beacon committee subscription support to validator_client.
* Fix stacktrace should be an array of strings.
Fix committee subscriptions should not be `data` keyed.
* Log duration to next block proposal.
* Fix beacon_node_status import.
* Use jsonMsgResponse() instead of jsonError().
* Fix graffityBytes usage.
Remove unnecessary `await`.
Adjust creation of SignedBlock instance.
Remove legacy files.
* Rework durationToNextSlot() and durationToNextEpoch() to use `fromNow`.
* Fix race condition for block proposal and attestations for same slot.
Fix local_testnet script to properly kill tasks on Windows.
Bump chronos and nim-http-tools, to allow connections to infura.io (basic auth).
* Catch services errors.
Improve performance of local_testnet.sh script on Windows.
Fix race condition when attestation producing.
* Post-rebase fixes.
* Bump chronos and presto.
* Calculate block publishing delay.
Fix pkill in one more place.
* Add error handling and timeouts to firstSuccess() template.
Add onceToAll() template.
Add checkNodes() procedure.
Refactor firstSuccess() template.
Add error checking to api.nim calls.
* Deprecated usage onceToAll() for better stability.
Address comment and send attestations asap.
* Avoid unnecessary loop when calculating minimal duration.
* Implement split preset/config support
This is the initial bulk refactor to introduce runtime config values in
a number of places, somewhat replacing the existing mechanism of loading
network metadata.
It still needs more work, this is the initial refactor that introduces
runtime configuration in some of the places that need it.
The PR changes the way presets and constants work, to match the spec. In
particular, a "preset" now refers to the compile-time configuration
while a "cfg" or "RuntimeConfig" is the dynamic part.
A single binary can support either mainnet or minimal, but not both.
Support for other presets has been removed completely (can be readded,
in case there's need).
There's a number of outstanding tasks:
* `SECONDS_PER_SLOT` still needs fixing
* loading custom runtime configs needs redoing
* checking constants against YAML file
* yeerongpilly support
`build/nimbus_beacon_node --network=yeerongpilly --discv5:no --log-level=DEBUG`
* load fork epoch from config
* fix fork digest sent in status
* nicer error string for request failures
* fix tools
* one more
* fixup
* fixup
* fixup
* use "standard" network definition folder in local testnet
Files are loaded from their standard locations, including genesis etc,
to conform to the format used in the `eth2-networks` repo.
* fix launch scripts, allow unknown config values
* fix base config of rest test
* cleanups
* bundle mainnet config using common loader
* fix spec links and names
* only include supported preset in binary
* drop yeerongpilly, add altair-devnet-0, support boot_enr.yaml
* Implement the new Altair req/resp protocols
Also fixes the altair message-id computation by providing the correct
forkdigest prefix in `isAltairTopic`.
Co-authored-by: Tanguy Cizain <tanguycizain@gmail.com>
We generally send out attestations 250 ms after the block arrives.
Recent efficiency improvements have led to a slightly increased
incidence of "slot 0" issues where attestations are dropped by other
nodes because they have not yet had time to process the block due to
epoch processing taking time.
This PR mitigates the problem by increasing the window between receiving
the block and sending out attestations.
* add blockchain_dag altair database reading; add rollback tests; fix some unnecessary type conversions
* remove debugging scaffolding
* proposeSignedBlock() will need to be async for merge; introduce altair types to VC
* add Altair support to the block quarantine
* switch some spec/datatypes imports to spec/datatypes/base
* add Altair support to block_clearance
* allow runtime configuration of Altair transition slot
* enable Altair in block_sim, including in CI
* remove false OnBlockAdded dependency on phase.HashedBeaconState
* introduce altair data types into block_clearance; update some alpha.6 spec refs to alpha.7; add get_active_validator_indices_len ForkedHashedBeaconState wrapper
* switch many modules from using datatypes (with phase0 states/blocks) to datatypes/base (fork-independent); update spec refs from alpha.6 to alpha.7 and remove rm'd G2_POINT_AT_INFINITY
* switch more modules from using datatypes (with phase0 states/blocks) to datatypes/base (fork-independent); update spec refs from alpha.6 to alpha.7
* remove unnecessary phase0-only wrapper of get_attesting_indices(); allow signatures_batch to process either fork; remove O(n^2) nested loop in process_inactivity_updates(); add altair support to getAttestationsforTestBlock()
* add Altair versions of asSigVerified(), asTrusted(), and makeBeaconBlock()
* fix spec URL to be Altair for Altair makeBeaconBlock()
* use ForkedHashedBeaconState in StateData
* fix FAR_FUTURE_EPOCH -> slot overflow; almost always use assign()
* avoid stack allocation in maybeUpgradeStateToAltair()
* create and use dispatch functions for check_attester_slashing(), check_proposer_slashing(), and check_voluntary_exit()
* use getStateRoot() instead of various state.data.hbsPhase0.root
* remove withStateVars.hashedState(), which doesn't work as a design anymore
* introduce spec/datatypes/altair into beacon_chain_db
* fix inefficient codegen for getStateField(largeStateField)
* state_transition_slots() doesn't either need/use blocks or runtime presets
* combine process_slots(HBS)/state_transition_slots(HBS) which differ only in last-slot htr optimization
* getStateField(StateData, ...) was replaced by getStateField(ForkedHashedBeaconState, ...)
* fix rollback
* switch some state_transition(), process_slots, makeTestBlocks(), etc to use ForkedHashedBeaconState
* remove state_transition(phase0.HashedBeaconState)
* remove process_slots(phase0.HashedBeaconState)
* remove state_transition_block(phase0.HashedBeaconState)
* remove unused callWithBS(); separate case expression from if statement
* switch back from nested-ref-object construction to (ref Foo)(Bar())
* write uncompressed validator keys to database
Loading 150k+ validator keys on startup in compressed format takes a lot
of time - better store them in uncompressed format which makes behaviour
just after startup faster / more predictable.
* refactor cached validator key access
* fix isomorphic cast to work with non-var instances
* remove cooked pubkey cache - directly use database cache in chaindag
as well (one less cache to keep in sync)
* bump blscurve, introduce loadValid for known-to-be-valid keys
Instead of keeping a validator key list per EpochRef, this PR introduces
a single shared validator key list in ChainDAG, and cleans up some other
ChainDAG and key-related issues.
The PR does not introduce the validator key list in the state transition
- this is because we batch-check all signatures before entering the spec
code, thus the spec code never hits the cache.
A future refactor should _probably_ remove the threadvar altogether.
There's a few other small fixes in here that make the flow easier to
read:
* fix `var ChainDAGRef` -> `ChainDAGRef`
* fix `var QuarantineRef` -> `QuarantineRef`
* consistent `dag` variable name
* avoid using threadvar pubkey cache in most cases
* better error messages in batch signature checking
* use StateData in place of BeaconState outside state transition code
* propagate more StateData usage
* remove withStateVars().state
* wrap get_beacon_committee(BeaconState, ...) as gbc(StateData, ...)
* switch makeAttestation() to use StateData
* use StateData wrapper/dispatcher for get_committee_count_per_slot()
* convert AttestationCache.init(), weak subjectivity functions, and updateValidatorMetrics()
* add get_shuffled_active_validator_indices(StateData) and get_block_root_at_slot(StateData)
* switch makeAttestationData() to StateData
* sync AllTests-mainnet.md after rebase
* Error when specifying an invalid --data-dir (or --validator-dir)
* Error when entering an invalid validator public key (e.g. invalid hex value)
* Warning when attempting to export a validator not present in the local database
Some unnecessary remains of the v1 mode has been removed as well
* Revert "Revert "Upgrade database schema" (#2570)"
This reverts commit 6057c2ffb4.
* ssz: fix loading empty lists into existing instances
Not a problem earlier because we didn't reuse instances
* bump nim-eth
* bump nim-web3
The `kvstore` design we're using now turns out to not be the best way to
use `sqlite` - in particular, there are some significant benefits to
using rowid in certain situations and to keep data in separate tables.
With this branch, there are massive improvements in startup time
(seconds instead of minutes) and state/block storage and pruning times
(milliseconds instead of seconds) - these improvements can in particular
be seen on slow drives and translate directly into better attestation
performance.
* update kvstore to new keyspace design
* remove `DirStoreRef` and the hidden `--state-db-kind` option - this
was an experiment to store large blobs in files, but with the new
kvstore, there's no compelling reason to do so
* remove `DbMap` - unused and would need updating for new keyspace
design
* introduce separate tables for each data type (blocks, states etc)
* remove "WITHOUT ROWID" pessimization for tables with large blobs
* close DbSeq statements explicitly (and earlier)
* store beacon block summaries in separate table, without SSZ
compression and load them all with single query on startup
* stop storing backwards compat full states
* mark genesis beacon block as trusted
* avoid faststreams when loading SSZ data
* remove `DisagreementBehavior` (unused)
Currently, we have a bit of a convoluted flow where when sending
attestations, we start broadcasting them over gossip then pass them to
the attestation validation to include them in the local attestation pool
- it should be the other way around: we should be checking attestations
_before_ gossipping them - this serves as an additional safety net to
ensure that we don't publish junk - this becomes more important when
publishing attestations from the API.
Also, the REST API was performing its own validation meaning
attestations coming from REST would be validated twice - finally, the
JSON RPC wasn't pre-validating and would happily broadcast invalid
attestations.
* Unified attestation production pipeline with the same flow for gossip,
locally and API-produced attestations: all are now validated and entered
into the pool, then broadcast/republished
* Refactor subnet handling with specific SubnetId alias, streamlining
where subnets are computed, avoiding the need to pass around the number
of active validators
* Move some of the subnet handling code to eth2_network
* Use BitArray throughout for subnet handling
This PR reduces the number of database queries for slashing protection
from 5 reads and 1 write to 2 reads and 1 write in the optimistic case.
In the process, it removes user-level support for writing the database
in the version 1 format in order to simplify the code flow, and prevent
code rot. In particular, the v1 format was not covered by any unit tests
and has no advantages over v2. The concrete code to read and write it
remains for now, in particular to support upgrades from v1 to v2.
The branch also removes the use of concepts which doesn't work with
checked exceptions - in particular, this highlights code that both
raises exceptions and returns error codes, which could be cleaned up in
the future.
* Cache internal validator ID
* Rely on unique index to check for trivial duplicate votes
* Combine two surround vote queries into one
* Combine API for checking and registering slashing into single function
The slashing DB is normally not a bottleneck, but may become one with
high attached validator counts.
With the introduction of batching and lazy attestation aggregation, it
no longer makes sense to enqueue attestations between the signature
check and adding them to the attestation pool - this only takes up
valuable CPU without any real benefit.
* add successfully validated attestations to attestion pool directly
* avoid copying participant list around for single-vote attestations,
pass single validator index instead
* release decompressed gossip memory earlier, specially during async
message validation
* use cooked signatures in a few more places to avoid reloads and errors
* remove some Defect-raising versions of signature-loading
* release decompressed data memory before validating message
* avoid creating indexed attestation just to check signatures - above
all, don't create it when not checking signatures ;)
* avoid pointer op when adding attestation to pool
* better iterator for yielding attestations
* add metric / log for attestation packing time
This is a revamp of the attestation pool that cleans up several aspects
of attestation processing as the network grows larger and block space
becomes more precious.
The aim is to better exploit the divide between attestation subnets and
aggregations by keeping the two kinds separate until it's time to either
produce a block or aggregate. This means we're no longer eagerly
combining single-vote attestations, but rather wait until the last
moment, and then try to add singles to all aggregates, including those
coming from the network.
Importantly, the branch improves on poor aggregate quality and poor
attestation packing in cases where block space is running out.
A basic greed scoring mechanism is used to select attestations for
blocks - attestations are added based on how much many new votes they
bring to the table.
* Collect single-vote attestations separately and store these until it's
time to make aggregates
* Create aggregates based on single-vote attestations
* Select _best_ aggregate rather than _first_ aggregate when on
aggregation duty
* Top up all aggregates with singles when it's time make the attestation
cut, thus improving the chances of grabbing the best aggregates out
there
* Improve aggregation test coverage
* Improve bitseq operations
* Simplify aggregate signature creation
* Make attestation cache temporary instead of storing it in attestation
pool - most of the time, blocks are not being produced, no need to keep
the data around
* Remove redundant aggregate storage that was used only for RPC
* Use tables to avoid some linear seeks when looking up attestation data
* Fix long cleanup on large slot jumps
* Avoid some pointers
* Speed up iterating all attestations for a slot (fixes#2490)
* batch attestations
* Fixes (but now need to investigate the chronos 0 .. 4095 crash similar to https://github.com/status-im/nimbus-eth2/issues/1518
* Try to remove the processing loop to no avail :/
* batch aggregates
* use resultsBuffer size for triggering deadline schedule
* pass attestation pool tests
* Introduce async gossip validators. May fix the 4096 bug (reentrancy issue?) (similar to sync unknown blocks #1518)
* Put logging at debug level, add speed info
* remove unnecessary batch info when it is known to be one
* downgrade some logs to trace level
* better comments [skip ci]
* Address most review comments
* only use ref for async proc
* fix exceptions in eth2_network
* update async exceptions in gossip_validation
* eth2_network 2nd pass
* change to sleepAsync
* Update beacon_chain/gossip_processing/batch_validation.nim
Co-authored-by: Jacek Sieka <jacek@status.im>
Co-authored-by: Jacek Sieka <jacek@status.im>
Since quite a lot of additional procs were now compiled as generics, this lead to compiler bugs that had
to be worked-around:
* The `Domain` type was renamed to `Eth2Domain` to avoid compilation errors
due to conflicts with `nativesockets.Domain`.
Similarly, `eth2_network.KeyPair` was renamed to `NetKeyPair`.
* A new more robust version of `hexToByteArray` was added to stew
* set upper bound on EpochRef cache
* max 32 EpochRef instances
* less memory waste in BlockRef by removing EpochRef seq that is mostly
unused (~20mb)
* less memory waste in dag block lookup by not keeping an extra copy of
digest (~70mb)
* fix `==` and `$` for Eth2Digest
* remove `ChainDAG.tmpState` (~50mb?)
all in all, this branch cuts mainnet memory usage by ~160-180mb and puts
limits on EpochRef cache usage - where normally it hovered around 950mb
before, it's now sitting at 600-700mb on my machine.
* docs
Jacek Sieka
tersec
zah
Eugene Kabanov
Etan Kissling
Ștefan Talpalaru
Mamy André-Ratsimbazafy