Commit Graph

58 Commits

Author SHA1 Message Date
tersec c31fbc3977
remove most std/options imports (#4778) 2023-03-31 20:46:47 +00:00
Etan Kissling 969c6f73ae
misc local `EIP4844` > `Deneb` bumps (#4717)
* misc local `EIP4844` > `Deneb` bumps

* fix
2023-03-11 00:28:19 +00:00
henridf 90640cce05
Update sync to use post-decoupling RPC (#4701)
* Update sync to use post-decoupling RPCs

blob_sidecars_by_range returns a flat list of sidecars, which must
then be grouped per-slot.

* Add test for groupBlobs

* createBlobs: convert proc to func
2023-03-07 20:19:17 +00:00
zah 067ba13c52
Capella metadata for Sepolia (#4615)
Other changes:

Renamed the `EIP_4844_FORK_*` config constants to `DENEB_FORK_*` as
this matches the latest spec and it's already used in the official
Sepolia config.
2023-02-15 14:44:09 +00:00
henridf 59e41dc65d
EIP4844 sync (#4581)
* EIP4844 Sync

* Pass eip4844 fork epoch rather than cfg to syncmanager

* Fix sync

* Update test

* map->mapIt
2023-02-11 20:48:35 +00:00
Jacek Sieka f3ddea6c86
Skip execution payload verification for finalized blocks (#4591)
While syncing the finalized portion of the chain, the execution client
cannot efficiently sync and most of the time returns `SYNCING` - in this
PR, we use CL-verified optmistic sync as long as the block is claimed to
be finalized, only occasionally updating the EL with progress.

Although a peer might lie about what is finalized and what isn't,
eventually we'll call the execution client - thus, all a dishonest
client can do is delay execution verification slightly. Gossip blocks in
particular are never assumed to be finalized.
2023-02-06 08:22:08 +01:00
tersec aacc8d702d
remove Nim 1.2-compatible `push raise`s and update copyright notice years (#4528) 2023-01-20 14:14:37 +00:00
Jacek Sieka 75c7195bfd
Backfill only up to MIN_EPOCHS_FOR_BLOCK_REQUESTS blocks (#4421)
When backfilling, we only need to download blocks that are newer than
MIN_EPOCHS_FOR_BLOCK_REQUESTS - the rest cannot reliably be fetched from
the network and does not have to be provided to others.

This change affects only trusted-node-synced clients - genesis sync
continues to work as before (because it needs to construct a state by
building it from genesis).

Those wishing to complete a backfill should do so with era files
instead.
2022-12-23 08:42:55 +01:00
Etan Kissling 2eb56f6e1b
rename `PeerScoreXyzBlocks` -> `PeerScoreXyzValues` (#4318)
The various `PeerScore` constants are used for both beacon blocks and
LC objects, and will likely also find use for EIP4844 blob sidecars.
Renaming them to use more generically applicable names not referring
to blocks explicitly aymore.
2022-11-11 11:34:28 +00:00
Etan Kissling 94b3df25f8
remove unused `sync_queue` types (#4316)
`SyncManagerError` and `sync_queue.BeaconBlocksRes` are unused and can
be removed for cleanup (verified with `{.deprecated.}`).
2022-11-11 10:41:30 +00:00
Jacek Sieka 63a3f2b1ad
Tighten chunk decoding limits (#4264)
* cap maximum number of chunks to download from peer (fixes #1620)
* drop support for requesting blocks via v1 / phase0 protocol
* tighten bounds checking of fixed-size messages
2022-10-27 18:51:43 +02:00
Etan Kissling 8936212f93
descore on empty response for range w known block (#4050)
The sync protocol does not distinguish between:
- All requested slots are empty
- Peer does not have data available about requested range

Therefore, we treat EOF for `beacon_blocks_by_range` and for
`beacon_blocks_by_range` as valid responses, as if the entire epoch
really contained no single block for any slot. Once a followup response
provides new blocks, we detect that some blocks were missing and rewind.

During backfill, we also request the known-to-exist `backfill.slot`,
so we can actually detect whether an epoch really does not have blocks
or whether a response is incomplete (`PeerScoreNoBlocks`).
2022-09-03 23:12:58 +02:00
Miran dfd4afc9f2
compatibility with Nim 1.4+ (#3888) 2022-07-29 10:53:42 +00:00
Eugene Kabanov 1b6651dfc3
Fix /eth/v1/node/syncing (#3720)
* Fix REST `/eth/v1/node/syncing` call to return values even if SyncManager is not running.

* Use syncManager.inProgress as is_syncing indicator.
2022-06-14 22:26:23 +02:00
Etan Kissling 7b04a94d43
fix #3674 (Sync progress >100% on checkpoint sync) (#3736)
Corrects an off-by-1 in the reported sync percentage computation.
New logic is based on `SyncQueue.total` and `SyncQueue.progress`
with `pivot` instead of `sq.startSlot`.
2022-06-13 20:00:36 +03:00
Etan Kissling 15967c4076
keep track of latest blocks for optimistic sync (#3715)
When launched with `--light-client-enable` the latest blocks are fetched
and optimistic candidate blocks are passed to a callback (log for now).
This helps accelerate syncing in the future (optimistic sync).
2022-06-10 14:16:37 +00:00
Jacek Sieka 7ec1521c52
use unsigned literals (#3717)
in the hopes of avoiding potential for conversion bugs on i386
2022-06-08 11:09:33 +00:00
Jacek Sieka b35584632b
sync: remove `step` from sync client implementation (#3678)
* sync: remove `step` from sync client implementation

Deprecated in the spec:
https://github.com/ethereum/consensus-specs/pull/2856 - future PR:s will
deprecate server support as well.
2022-06-06 16:56:59 +03:00
Eugene Kabanov 50f9596108
Eliminate rpc_types.nim usage. (#3692) 2022-06-02 09:39:08 +00:00
Etan Kissling 01efa93cf6
add light client (standalone) (#3653)
Introduces a new library for syncing using libp2p based light client
sync protocol, and adds a new `nimbus_light_client` executable that uses
this library for syncing. The new executable emits log messages when
new beacon block headers are received, and is integrated into testing.
2022-05-31 12:45:37 +02:00
Eugene Kabanov 5592c7c674
NoMonitor and removed clock check for SyncManager. (#3420)
* Add `NoMonitor` flag to stop SyncManager from monitoring sync situation.

* Remove `toleranceValue` and `PeerScoreHeadTooNew`.

Co-authored-by: Etan Kissling <etan@status.im>
2022-04-14 15:17:44 +02:00
Jacek Sieka f70ff38b53
enable `styleCheck:usages` (#3573)
Some upstream repos still need fixes, but this gets us close enough that
style hints can be enabled by default.

In general, "canonical" spellings are preferred even if they violate
nep-1 - this applies in particular to spec-related stuff like
`genesis_validators_root` which appears throughout the codebase.
2022-04-08 16:22:49 +00:00
Jacek Sieka 4207b127f9
era: load blocks and states (#3394)
* era: load blocks and states

Era files contain finalized history and can be thought of as an
alternative source for block and state data that allows clients to avoid
syncing this information from the P2P network - the P2P network is then
used to "top up" the client with the most recent data. They can be
freely shared in the community via whatever means (http, torrent, etc)
and serve as a permanent cold store of consensus data (and, after the
merge, execution data) for history buffs and bean counters alike.

This PR gently introduces support for loading blocks and states in two
cases: block requests from rest/p2p and frontfilling when doing
checkpoint sync.

The era files are used as a secondary source if the information is not
found in the database - compared to the database, there are a few key
differences:

* the database stores the block indexed by block root while the era file
indexes by slot - the former is used only in rest, while the latter is
used both by p2p and rest.
* when loading blocks from era files, the root is no longer trivially
available - if it is needed, it must either be computed (slow) or cached
(messy) - the good news is that for p2p requests, it is not needed
* in era files, "framed" snappy encoding is used while in the database
we store unframed snappy - for p2p2 requests, the latter requires
recompression while the former could avoid it
* front-filling is the process of using era files to replace backfilling
- in theory this front-filling could happen from any block and
front-fills with gaps could also be entertained, but our backfilling
algorithm cannot take advantage of this because there's no (simple) way
to tell it to "skip" a range.
* front-filling, as implemented, is a bit slow (10s to load mainnet): we
load the full BeaconState for every era to grab the roots of the blocks
- it would be better to partially load the state - as such, it would
also be good to be able to partially decompress snappy blobs
* lookups from REST via root are served by first looking up a block
summary in the database, then using the slot to load the block data from
the era file - however, there needs to be an option to create the
summary table from era files to fully support historical queries

To test this, `ncli_db` has an era file exporter: the files it creates
should be placed in an `era` folder next to `db` in the data directory.
What's interesting in particular about this setup is that `db` remains
as the source of truth for security purposes - it stores the latest
synced head root which in turn determines where a node "starts" its
consensus participation - the era directory however can be freely shared
between nodes / people without any (significant) security implications,
assuming the era files are consistent / not broken.

There's lots of future improvements to be had:

* we can drop the in-memory `BlockRef` index almost entirely - at this
point, resident memory usage of Nimbus should drop to a cool 500-600 mb
* we could serve era files via REST trivially: this would drop backfill
times to whatever time it takes to download the files - unlike the
current implementation that downloads block by block, downloading an era
at a time almost entirely cuts out request overhead
* we can "reasonably" recreate detailed state history from almost any
point in time, turning an O(slot) process into O(1) effectively - we'll
still need caches and indices to do this with sufficient efficiency for
the rest api, but at least it cuts the whole process down to minutes
instead of hours, for arbitrary points in time

* CI: ignore failures with Nim-1.6 (temporary)

* test fixes

Co-authored-by: Ștefan Talpalaru <stefantalpalaru@yahoo.com>
2022-03-23 09:58:17 +01:00
Etan Kissling 3ffab01b07
Refactor and optimize sync logs. (#3451)
* Refactor and optimize logs.

* Introduce shortLog(SyncRequest).

* Address review comment.

* make sync queue logs more consistent

Adds a few minor logging improvements:
- Fixes a typo (`was happened` -> `has happened`)
- Avoids passing `reset_slot` argument to log statement multiple times
- Uses same `rewind_to_slot` label when logging in both sync directions
- Consistent rewind point logging

Co-authored-by: cheatfate <eugene.kabanov@status.im>
2022-03-03 09:05:33 +01:00
Etan Kissling 6849536742 fix `firstSlot` computation for backfill sync
When initializing backfill sync, the implementation intends to start at
the first unknown slot (`1` before tail). However, an incorrect variable
is passed, and backfill sync actually starts at the tail slot instead.
This patch corrects this by passing the intended variable. The problem
was introduced with the original backfill implementation at #3263.
2022-02-14 18:53:38 +02:00
Etan Kissling d1f97e209a
remove unused `sleepTime` from `SyncManager` (#3384)
The `SyncManager` has a leftover optional `sleepTime` parameter in
its constructor that used to configure the sync loop polling rate.
This parameter was replaced with a constant in #1602 and is no longer
functional. This patch removes the `sleepTime` leftovers.
2022-02-14 12:05:01 +01:00
Etan Kissling a28900c348
fix slot number display during sync (#3383)
#3304 introduced a regression to the sync status string displayed in the
status bar; during the main forward sync, the current slot is no longer
reported and always displays as `0`. This patch corrects the computation
to accurately report the current slot once more.
2022-02-14 12:04:04 +01:00
Etan Kissling 15fc7534cf
remove unused `maxStatusAge` from `SyncManager` (#3382)
The `SyncManager` has a leftover optional `maxStatusAge` parameter in
its constructor that used to configure the libp2p `Status` polling rate.
This parameter was replaced with a constant in #1827 and is no longer
functional. This patch removes the `maxStatusAge` leftovers.
2022-02-13 16:17:13 +01:00
Jacek Sieka 1760f4d7a7
move wallet/deposit commands to separate files (#3372)
These commands have little to do with the "normal" beacon node operation
- ergo, they deserve to live in their own module.

* clean up imports/exports
2022-02-11 21:40:49 +01:00
Jacek Sieka c7abc97545
harden and speed up block sync (#3358)
* harden and speed up block sync

The `GetBlockBy*` server implementation currently reads SSZ bytes from
database, deserializes them into a Nim object then serializes them right
back to SSZ - here, we eliminate the deser/ser steps and send the bytes
straight to the network. Unfortunately, the snappy recoding must still
be done because of differences in framing.

Also, the quota system makes one giant request for quota right before
sending all blocks - this means that a 1024 block request will be
"paused" for a long time, then all blocks will be sent at once causing a
spike in database reads which potentially will see the reading client
time out before any block is sent.

Finally, on the reading side we make several copies of blocks as they
travel through various queues - this was not noticeable before but
becomes a problem in two cases: bellatrix blocks are up to 10mb (instead
of .. 30-40kb) and when backfilling, we process a lot more of them a lot
faster.

* fix status comparisons for nodes syncing from genesis (#3327 was a bit
too hard)
* don't hit database at all for post-altair slots in GetBlock v1
requests
2022-02-07 19:20:10 +02:00
Jacek Sieka f70aceef37
Harden handling of unviable forks (#3312)
* Harden handling of unviable forks

In our current handling of unviable forks, we allow peers to send us
blocks that come from a different fork - this is not necessarily an
error as it can happen naturally, but it does open up the client to a
case where the same unviable fork keeps getting requested - rather than
allowing this to happen, we'll now give these peers a small negative
score - if it keeps happening, we'll disconnect them.

* keep track of unviable forks in quarantine, to avoid filling it with
known junk
* collect peer scores in single module
* descore peers when they send unviable blocks during sync
* don't give score for duplicate blocks
* increase quarantine size to a level that allows finality to happen
under optimal conditions - this helps avoid downloading the same blocks
over and over in case of an unviable fork
* increase initial score for new peers to make room for one more failure
before disconnection
* log and score invalid/unviable blocks in requestmanager too
* avoid ChainDAG dependency in quarantine
* reject gossip blocks with unviable parent
* continue processing unviable sync blocks in order to build unviable
dag

* docs

* Update beacon_chain/consensus_object_pools/block_pools_types.nim

* add unviable queue test
2022-01-26 13:20:08 +01:00
Eugene Kabanov 0ea6dfa517
Fix current slot value and finishing progress for backfilling. (#3304) 2022-01-21 10:35:54 +01:00
Jacek Sieka 570379d3d9
Backfiller (#3263)
Backfilling is the process of downloading historical blocks via P2P that
are required to fulfill `GetBlocksByRange` duties - this happens during
both trusted node and finalized checkpoint syncs.

In particular, backfilling happens after syncing to head, such that
attestation work can start as soon as possible.

* Fix SyncQueue initialization procedure.
Remove usage of `awaitne`.
Add cancellation support.
Remove unneeded `sleepAsync()` if peer's head is older than needed.
Add `direction` field to all logs.
Fix syncmanager wedge issue.
Add proper resource cleaning procedure on backward sync finish.

Co-authored-by: cheatfate <eugene.kabanov@status.im>
2022-01-20 08:25:45 +01:00
tersec 9c0c9c98ce
complete switch to beacon_chain/specs/datatypes/bellatrix (#3295) 2022-01-18 13:36:52 +00:00
Jacek Sieka 68247f81b3
Trusted node sync (#3209)
* Trusted node sync

Trusted node sync, aka checkpoint sync, allows syncing tyhe chain from a
trusted node instead of relying on a full sync from genesis.

Features include:

* sync from any slot, including the latest finalized slot
* backfill blocks either from the REST api (default) or p2p (#3263)

Future improvements:

* top up blocks between head in database and some other node - this
makes for an efficient backup tool
* recreate historical state to enable historical queries

* fixes

* load genesis from network metadata
* check checkpoint block root against state
* fix invalid block root in rest json decoding
* odds and ends

* retry looking for epoch-boundary checkpoint blocks
2022-01-17 10:27:08 +01:00
Jacek Sieka d57c2dc4e5
use tail block as sync pivot (#3276)
When syncing, we show how much of the sync has completed - with
checkpoint sync, the syncing does not always go from slot 0 to head, but
rather can start in the middle.

To show a consistent `%` between restarts, we introduce the concept of a
pivot point, such that if I sync 10% of the chain, then restart the
client, it picks up at 10% (instead of counting from 0).

What it looks like:
```
INF ... sync="01d12h41m (15.96%) 13.5158slots/s (QDDQDDQQDP:339018)" ...
```
2022-01-13 10:37:53 +01:00
tersec 6ef3834f4a
fix type-conversions-to-self, unexport from nimbus_beacon_node, and rm unused vars/procs (#3211) 2021-12-20 12:21:17 +01:00
Jacek Sieka 118840d241
SyncManager cleanups for backfill support (#3189)
* SyncManager cleanups for backfill support

Cleanups, fixes and simplifications, in anticipation of backfill support
for the `SyncManager`:

* reformat sync progress indicator to show time left and % done more
prominently:
  * old: `sync="sPssPsssss:2:2.4229:00h57m (2706898)"`
  * new: `sync="14d12h31m (0.52%) 1.1378slots/s (wQQQQQDDQQ:1287520)"`
* reset average speed when going out of sync
* pass all block errors to sync manager, including duplicate/unviable
* penalize peers for reporting a head block that is outside of our
expected wall clock time (they're likely on a different network or
trying to disrupt sync)
* remove `SyncFailureKind` (unused)
* remove `inRange` (unused)
* add `Q` for sync queue requests that are in the `SyncQueue` but not
yet in the `BlockProcessor` queue
* update last slot in `SyncQueue` after getting peer status
* fix race condition between `wakeupWaiters` and `resetWait`, where
workers would not be correctly reset if block verification returned a
completed future without event loop
* log syncmanager direction

* Fix ordering issue.
Some of the requests size of which are not equal to `chunkSize` could be processed in wrong order which could lead to sync process freezes.

Co-authored-by: cheatfate <eugene.kabanov@status.im>
2021-12-16 15:57:16 +01:00
Eugene Kabanov b05734f610
Backward sync support for SyncManager. (#3131)
* Unbundle SyncQueue from sync_manager.nim.
Unbundle Peer scores constants to peer_scores.nim.
Add Forward/Backward enum.

* Further improvements and tests.

* Adopt getRewindPoint() and fix MissingParent handler.

* Remove unused procedures.
Refactor `result` usage.
Fix resetWait().

* Add all the tests and fix the issue with rewind point.

* Fix get() issue.

* Fix flaky tests.

* test fixes

Co-authored-by: Jacek Sieka <jacek@status.im>
2021-12-08 22:15:29 +01:00
Jacek Sieka 233d756518
Logging and startup improvements (#3038)
* Logging and startup improvements

Color support for released binaries!

* startup scripts no longer log to file by default - this only affects
source builds - released binaries don't support file logging
* add --log-stdout option to control logging to stdout (colors, json)
* detect tty:s vs redirected logs and log accordingly
* add option to disable log colors at runtime
* simplify several "common" logs, showing the most important information
earlier and more clearly
* remove line numbers / file information / tid - these take up space and
are of little use to end users
  * still enabled in debug builds and tools
* remove `testnet_servers_image` compile-time option
* server images, released binaries and compile-from-source now offer
the same behaviour and features
* fixes https://github.com/status-im/nimbus-eth2/issues/2326
* fixes https://github.com/status-im/nimbus-eth2/issues/1794
* remove instanteneous block speed from sync message, keeping only
average

before:

```
INF 2021-10-28 16:45:59.000+02:00 Slot start                                 topics="beacnde" tid=386429 file=nimbus_beacon_node.nim:884 lastSlot=2384027 wallSlot=2384028 delay=461us84ns peers=0 head=75a10ee5:3348 headEpoch=104 finalized=cd6804ba:3264 finalizedEpoch=102 sync="wwwwwwwwww:0:0.0000:0.0000:00h00m (3348)"
INF 2021-10-28 16:45:59.046+02:00 Slot end                                   topics="beacnde" tid=386429 file=nimbus_beacon_node.nim:821 slot=2384028 nextSlot=2384029 head=75a10ee5:3348 headEpoch=104 finalizedHead=cd6804ba:3264 finalizedEpoch=102 nextAttestationSlot=-1 nextProposalSlot=-1 nextActionWait=n/a
```

after:

```
INF 2021-10-28 22:43:23.033+02:00 Slot start                                 topics="beacnde" slot=2385815 epoch=74556 sync="DDPDDPUDDD:10:5.2258:01h19m (2361088)" peers=37 head=eacd2dae:2361096 finalized=73782:a4751487 delay=33ms687us715ns
INF 2021-10-28 22:43:23.291+02:00 Slot end                                   topics="beacnde" slot=2385815 nextActionWait=n/a nextAttestationSlot=-1 nextProposalSlot=-1 head=eacd2dae:2361096
```

* fix comment

* documentation updates

* mention `--log-file` may be deprecated in the future
* update various docs
2021-11-02 18:06:36 +01:00
Jacek Sieka 4f7a8cf79d
register vc duties with subnet tracker (#2949)
* 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
2021-10-18 11:11:44 +02:00
tersec 9c0d9b546a
successfull -> successful (#2842) 2021-09-01 18:08:24 +02:00
Jacek Sieka 01596c45dd
cleanups and fixes (#2827)
* import cleanup
* fix json-rpc exception handlers
* avoid unnecessary presto client import
* introduce ForkedBeaconBlock, some altair logging
* url fixes
2021-08-27 11:00:06 +02:00
tersec 6e46445da2
switch result = foo to expression return; unexport rest of logtrace symbols (#2788) 2021-08-17 09:51:39 +00:00
Jacek Sieka 7a622e8505
rework spec imports (#2779)
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
2021-08-12 13:08:20 +00:00
Jacek Sieka 9697b73e71
forkedbeaconstate_helpers -> forks (#2772)
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
2021-08-10 22:46:35 +02:00
Jacek Sieka 3d7bee8502
REST API client, JSON-RPC cleanups (#2756)
This refactoring puts the JSON-RPC and REST APIs on more equal footing
by renaming and moving things around, creating a separation between
client and server, and documenting what they are - the aim is to have a
simple-to-use base to start from when developing API clients, as well as
make it easier to navigate the code when looking for the legacy JSON-RPC
interface vs the new REST API.

* move REST client, serialization and supporting types to spec/eth2_apis
* REST stuff now starts with `rest_`, JSON-RPC stuff starts with `rpc_`,
more or less
* simplify imports such that there's a simple module to import for both
server and client
* map REST type and proc names to yaml spec more closely - in
particular, reuse operation and type names in `rest_types` to make
comparisons against spec more easy
* cleaner separation between client and server modules - modules common
between server and client such as `rest_types` and serialization move to
the spec folder - this allows the client to be built with less knowledge
about server internals
2021-08-03 17:17:11 +02:00
Jacek Sieka 2d6a661ac6
Syncv2 (#2723)
* 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>
2021-07-15 21:01:07 +02:00
Jacek Sieka 7f52ffb8d9
clean up block processing (#2610)
* gossip_to_consensus -> block_processor (it's processing only blocks,
but not only from gossip)
* measure queue and validation time for blocks
* measure assignment and state loading times for updateStateData
* avoid some unnecessary block copies in block sync
* warn that database is corrupt if we hit tail without a state
2021-05-28 19:34:00 +03:00
Eugene Kabanov 5b5ea2e813
Fix integer overflow issue in sync_manager. (#2564)
* Make Refactor rewind point assignment more concrete.

* Fix overflow issue in getRewindPoint().
Add tests.
2021-05-18 12:25:14 +02:00