Commit Graph

14 Commits

Author SHA1 Message Date
Felix Lange
0042f13d47 eth/downloader: separate state sync from queue (#14460)
* eth/downloader: separate state sync from queue

Scheduling of state node downloads hogged the downloader queue lock when
new requests were scheduled. This caused timeouts for other requests.
With this change, state sync is fully independent of all other downloads
and doesn't involve the queue at all.

State sync is started and checked on in processContent. This is slightly
awkward because processContent doesn't have a select loop. Instead, the
queue is closed by an auxiliary goroutine when state sync fails. We
tried several alternatives to this but settled on the current approach
because it's the least amount of change overall.

Handling of the pivot block has changed slightly: the queue previously
prevented import of pivot block receipts before the state of the pivot
block was available. In this commit, the receipt will be imported before
the state. This causes an annoyance where the pivot block is committed
as fast block head even when state downloads fail. Stay tuned for more
updates in this area ;)

* eth/downloader: remove cancelTimeout channel

* eth/downloader: retry state requests on timeout

* eth/downloader: improve comment

* eth/downloader: mark peers idle when state sync is done

* eth/downloader: move pivot block splitting to processContent

This change also ensures that pivot block receipts aren't imported
before the pivot block itself.

* eth/downloader: limit state node retries

* eth/downloader: improve state node error handling and retry check

* eth/downloader: remove maxStateNodeRetries

It fails the sync too much.

* eth/downloader: remove last use of cancelCh in statesync.go

Fixes TestDeliverHeadersHang*Fast and (hopefully)
the weird cancellation behaviour at the end of fast sync.

* eth/downloader: fix leak in runStateSync

* eth/downloader: don't run processFullSyncContent in LightSync mode

* eth/downloader: improve comments

* eth/downloader: fix vet, megacheck

* eth/downloader: remove unrequested tasks anyway

* eth/downloader, trie: various polishes around duplicate items

This commit explicitly tracks duplicate and unexpected state
delieveries done against a trie Sync structure, also adding
there to import info logs.

The commit moves the db batch used to commit trie changes one
level deeper so its flushed after every node insertion. This
is needed to avoid a lot of duplicate retrievals caused by
inconsistencies between Sync internals and database. A better
approach is to track not-yet-written states in trie.Sync and
flush on commit, but I'm focuing on correctness first now.

The commit fixes a regression around pivot block fail count.
The counter previously was reset to 1 if and only if a sync
cycle progressed (inserted at least 1 entry to the database).
The current code reset it already if a node was delivered,
which is not stong enough, because unless it ends up written
to disk, an attacker can just loop and attack ad infinitum.

The commit also fixes a regression around state deliveries
and timeouts. The old downloader tracked if a delivery is
stale (none of the deliveries were requestedt), in which
case it didn't mark the node idle and did not send further
requests, since it signals a past timeout. The current code
did mark it idle even on stale deliveries, which eventually
caused two requests to be in flight at the same time, making
the deliveries always stale and mass duplicating retrievals
between multiple peers.

* eth/downloader: fix state request leak

This commit fixes the hang seen sometimes while doing the state
sync. The cause of the hang was a rare combination of events:
request state data from peer, peer drops and reconnects almost
immediately. This caused a new download task to be assigned to
the peer, overwriting the old one still waiting for a timeout,
which in turned leaked the requests out, never to be retried.
The fix is to ensure that a task assignment moves any pending
one back into the retry queue.

The commit also fixes a regression with peer dropping due to
stalls. The current code considered a peer stalling if they
timed out delivering 1 item. However, the downloader never
requests only one, the minimum is 2 (attempt to fine tune
estimated latency/bandwidth). The fix is simply to drop if
a timeout is detected at 2 items.

Apart from the above bugfixes, the commit contains some code
polishes I made while debugging the hang.

* core, eth, trie: support batched trie sync db writes

* trie: rename SyncMemCache to syncMemBatch
2017-06-22 15:26:03 +03:00
S. Matthew English
061889d4ea rlp, trie, contracts, compression, consensus: improve comments (#14580) 2017-06-12 14:45:17 +02:00
Felix Lange
4047ccad2f trie: add start key to NodeIterator constructors
The 'step' method is split into two parts, 'peek' and 'push'. peek
returns the next state but doesn't make it current.

The end of iteration was previously tracked by setting 'trie' to nil.
End of iteration is now tracked using the 'iteratorEnd' error, which is
slightly cleaner and requires less code.
2017-04-25 02:14:31 +02:00
Felix Lange
a13e920af0 trie: clean up iterator constructors
Make it so each iterator has exactly one public constructor:

- NodeIterators can be created through a method.
- Iterators can be created through NewIterator on any NodeIterator.
2017-04-25 02:14:31 +02:00
Nick Johnson
555273495b trie: add difference iterator (#3637)
This PR implements a differenceIterator, which allows iterating over trie nodes
that exist in one trie but not in another. This is a prerequisite for most GC
strategies, in order to find obsolete nodes.
2017-02-22 23:49:34 +01:00
Felix Lange
f2da6581ba all: fix issues reported by honnef.co/go/simple/cmd/gosimple 2017-01-06 18:18:07 +01:00
Felix Lange
35a7dcb162 all: gofmt -w -s 2017-01-06 15:52:03 +01:00
Felix Lange
d3b751e4d9 trie: remove dependency on ethdb
This removes the core/types -> leveldb dependency.
2017-01-06 14:15:22 +01:00
Péter Szilágyi
90b16a3e85
core/state, eth/downloader, trie: reset fast-failure on progress 2016-10-31 14:19:14 +02:00
Felix Lange
cd791bd855 core, trie: replace state caches with trie journal 2016-09-28 11:27:28 +03:00
Péter Szilágyi
b8d59d9c98 core/state, trie: switch iterator panics to error fields 2016-02-16 12:37:00 +02:00
Péter Szilágyi
5a057a8ded core/state, trie: surface iterator entry hashes 2016-02-16 12:21:08 +02:00
Péter Szilágyi
7e29b0b5b4 core/state, trie: add node iterator, test state/trie sync consistency 2016-02-16 12:21:08 +02:00
Péter Szilágyi
ab27bee25a core, eth, trie: direct state trie synchronization 2015-10-19 10:03:09 +03:00