Summary
I downloaded the geth source, modified the source code to specify the fast sync pivot block, compiled the code, removed the old chaindata and started the fast syncing. Once this is complete, I'll be back to running the regular geth binaries.
UPDATE This experiment failed. There were a few different errors with my hack that prevented the blockchain to fast sync to the specified block and then normal sync after the specified block. Back to full archive node sync.
Anyone has any suggestions?
Details
I downloaded the source code for geth and modified the source code for section that calculates the fast sync pivot point eth/downloader/downloader.go, lines 419-441:
case FastSync:
// Calculate the new fast/slow sync pivot point
if d.fsPivotLock == nil {
pivotOffset, err := rand.Int(rand.Reader, big.NewInt(int64(fsPivotInterval)))
if err != nil {
panic(fmt.Sprintf("Failed to access crypto random source: %v", err))
}
if height > uint64(fsMinFullBlocks)+pivotOffset.Uint64() {
pivot = height - uint64(fsMinFullBlocks) - pivotOffset.Uint64()
}
} else {
// Pivot point locked in, use this and do not pick a new one!
pivot = d.fsPivotLock.Number.Uint64()
}
// If the point is below the origin, move origin back to ensure state download
if pivot < origin {
if pivot > 0 {
origin = pivot - 1
} else {
origin = 0
}
}
glog.V(logger.Debug).Infof("Fast syncing until pivot block #%d", pivot)
I modified the last line above to change the Debug into Info and added the following two lines below the code above:
glog.V(logger.Info).Infof("Fast syncing until pivot block #%d", pivot)
if (pivot >= 2394190) {
pivot = 2394190;
}
glog.V(logger.Info).Infof("Fast syncing until modified pivot block #%d", pivot)
I recompiled and started off the fast sync process using the modified binaries:
Iota:go-ethereum user$ make geth
...
Done building.
Run "build/bin/geth" to launch geth.
I checked the version of the modified geth:
Iota:go-ethereum user$ build/bin/geth version
Geth
Version: 1.5.3-unstable
I removed the old damaged chaindata:
Iota:go-ethereum user$ build/bin/geth removedb
/Users/bok/Library/Ethereum/chaindata
Remove this database? [y/N] y
Removing...
Removed in 35.242291ms
I started the fast sync:
Iota:go-ethereum user$ build/bin/geth --fast --cache=1024 console
I1120 23:44:44.870142 ethdb/database.go:83] Allotted 1024MB cache and 1024 file handles to /Users/user/Library/Ethereum/geth/chaindata
I1120 23:44:44.878926 ethdb/database.go:176] closed db:/Users/user/Library/Ethereum/geth/chaindata
...
I1121 08:33:51.340811 eth/downloader/downloader.go:441] Fast syncing until pivot block #2664150
I1121 08:33:51.340847 eth/downloader/downloader.go:445] Fast syncing until modified pivot block #2394190
After the fast syncing is complete, I'll go back to using the regular geth binaries.
Best Answer
This is a community wiki, with the hope that it can be updated by the community as developments take place.
Here's latest from Ethereum Core developer Péter:
You should be able to update to this when the next release, Geth 1.4.6 is available imminently according to Péter. (Geth 1.5 will be released later.)
--cache=1024should usually be specified in addition to--fast, otherwise the default uses a much smaller cache (--cache=16). A 50% speed increase is possible just by increasing the cache.If you stop
geth --fast, you can rungeth --cache=1024without needing to delete anything.The flags
--jitvmand--jitcachemay also give a speed increase.