Topic: Electrum server on Windows: Fulcrum (Read 1423 times)

You need to wait for flushing to finish. Painful and long, but it will pass. [1]

[1] https://bitcoin.stackexchange.com/questions/116776/why-is-there-a-need-to-flush-the-utxo-set-when-you-prune-blk-dat-and-rev-dat-f

You need to wait for flushing to finish. Painful and long, but it will pass. [1]

[1] https://bitcoin.stackexchange.com/questions/116776/why-is-there-a-need-to-flush-the-utxo-set-when-you-prune-blk-dat-and-rev-dat-f

I’ve been considering setting up Fulcrum, but it looks like the initial sync and hardware requirements are something to plan for. Might stick with Electrs for now since it works fine for my needs

If one wants to have an Electrum server, one of the options is Fulcrum.

I already have an Electrum server (Electrs), which I use and for which I've made a more complete tutorial in the past, but at some point I've made tests with Fulcrum too and it would be a shame to remove it without providing a tutorial for the others who want it.

So... one major advantage of Fulcrum comes on Windows: the user can just get compiled binaries for Bitcoin Core, Fulcrum and Electrum, configure and run them all, without the need of stepping into Windows Subsystem for Linux (WSL). Another good thing is it's performance: it's processing the requests significantly faster than Electrs. Just in my experience (HDD, infrequent use for rather short tasks) Fulcrum gets in the state I can access it significantly slower than Electrs.

But, tbh, I don't like Fulcrum as much as the other option I have (Electrs)
* Fulcrum is made by somebody with BCH ties and it may be much better optimized for BCH (to say the least)
* As I said, Fulcrum starts/syncs slower than Electrs and that's not OK for my use case

Something more about this tutorial. This is made for a Fulcrum as I use it: me, for myself. No discussions with other servers, not announcing my server, also no SSL. I've kept it simple. If one wants to expand the tutorial with that, be my guest.

Since an Electrum server works on top of a Bitcoin Core node, I'll handle Bitcoin Core first, but shortly.

Bitcoin Core is with pretty much the same as in my other tutorial, but with some tiny bit of change in config:
* already in that topic, later on, I've switched for use with rpc user and password instead of cookie. If you want to keep using cookie, that's fine too, just pay attention to the config files (both of them)
* Bitcoin core's config needs one more line: zmqpubhashblock=tcp://127.0.0.1:8433

So, I will not insist with Bitcoin Core, it's in the other tutorial, I'll just put here my config:

Fulcrum (https://github.com/cculianu/Fulcrum)

You download Fulcrum from https://github.com/cculianu/Fulcrum/releases ; you will get something like Fulcrum-1.9.0-win64.zip
It would be nice to verify your download, which is done with the correcponding *.asc file, like for Electrum.

Unpack the zip into a new folder, maybe FulcrumBinaries. We won't touch that folder from now on.
Now we create a file called Fulcrum.conf with the content:

Some details:
* The username and password has to match with the one from Bitcoin
* x:\FulcrumData_MainNet is a folder you create, preferably somewhere fast (SSD), since this is where Fulcrum will keep its data; mine has now ~113 GB, but it may be safe to have some more space there, especially at start
* that fast-sync line should be commented (put a # in front of it) after the initial sync finishes
* the server is set to not discuss with other servers, not announce itself for other clients and so on; also no SSL

I've made a batch file for start and one for stop, but this stop works only after the sync is done. Else you better press the good old CRTL-C.
The content of the batch file is not very useful as it is, maybe as example, because it contains the path to the exe and, as parameter, the path to the config.
In my case it's:

Same goes for the stop.

After starting Fulcrum (start.bat) it might take an awful lot of time until everything is sync-ed. You may want to look for lines like:

or


Then you can start Electrum. As I wrote in the other tutorial I'm lazy and I'm using the portable Electrum. For me the command line is:

So I synced Fulcrum from scratch and now it's stuck like this (for three hours now):


Looking at the task manager it's not using disk space apparently, and just some memory (RAM) so I think it's safe to stay it's not doing anything? Also the Processed height: 606000, 68.8% makes me think that Fulcrum is aware that my Bitcoin node was stopped at a specific block height that's missing a lot of recent blocks. Not sure what to do with this thing now really, I'd be happy to have it work correctly with up toblock height 606,010 (which is where I have turned connect=0 for my node), but I don't know if that's doable.

I could not say 100% what is the problem, but one thing I can see is that the console doesn't say anything about the tcp server on port 50001 being started.
So it's not matching with what I've written back then:

After starting Fulcrum (start.bat) it might take an awful lot of time until everything is sync-ed. You may want to look for lines like:

or

Unfortunately, it will take some time, so be prepared with patience.
After doing that, you should be ok, but feel free to post here again, after finishing the re-indexing process.

Thanks for looking, I am proceeding with that; hopefully it won't take long, it took me a whole week to sync it :s

I think you 'll need to re-index Bitcoin Core.
Make sure to stop fulcrum before doing it.
I don't run fulcrum, unfortunately, but the error seems straightforward. Especially since it reads some blocks but it fails on the rest.

I had deleted the data dir for Fulcrum and still the same issue. Here's my Fulcrum.conf:

I didn't encounter this error, but I've looked up on the internet.
The answer from here ( https://bitcoin.stackexchange.com/a/79749 ) tells that you probably need a reindex in your bitcoind.

Probably your databasei is broken and you need a rescan.

Before you do it, can you post your fulcrum.conf please? Omit anything you don't wanna share.

My Bitcoin node is now fully synced; however, I keep getting errors on Fulcrum, related to the latest block (while it was syncing at just 5%):

<...>

Can someone please advise? I have txindex enabled, and pruning is disabled, and I do have enough diskspace where Bitcoin data and Fulcrum data is stored. I am not sure what's wrong.

Block not found on disk

I didn't use Fulcrum with a block explorer so I can't confirm that. But it should work.
After giving up WSL (including electrs and BTC RPC Explorer) I no longer reinstalled a block explorer. I am no longer that much active and I also had much less transactions (hence less to check). So what I'll tell are just theories:

* there's a good chance may not be able to connect as long as Bitcoin Core and Fulcrum are not fully synced; I'd expect you get data only after you see the lines I wrote about in the topic start post

* tcp://localhost:50001 looks good to me, I also use 127.0.0.1:50001:t for my electrum when I connect to Fulcrum


* I did use BTC RPC Explorer with Electrs (see this) for quite a lot of time, but sadly last time I've tried something from my steps no longer worked and I gave up. But I think that since then the Electrs doc is more complete and I've avoided Docker for personal reasons and that may be the easy way.

* I recommend Bitcoin core's blocks\index, chainstate, indexes\txindex and Fulcrum's data folder to be on SSD, else it'll be slow

I've used Fulcrum but can't remember why I it didn't work so I gave up. It could've been down to my SSD or OS config so you'll have to troubleshoot until it's working. Did you locate alternatives ?

TL;DR
Local instances of BTC RPC Explorer and mempool.space work nicely with Fulcrum.

I'll have to dig out how it's configured as I've used it with RaspiBlitz where you simply install it (ok, switching from electrs to Fulcrum needs a tweak or two in earlier versions of RaspiBlitz).

I've used Fulcrum in my RaspiBlitz node setup instead of electrs and had local instances of blockchain explorers like BTC RPC Explorer aka bitcoinexplorer.org and mempool.space. It has worked like a charm until I ran out of space on the 1TB storage media (Fulcrum takes considerably more space than electrs).

From my own experience electrs is significantly slower for large address histories than Fulcrum and this was for me the main driver to switch from electrs to Fulcrum.

Why am I talking of past stuff? Well, I've been a bit lazy to upgrade my RaspiBlitz node and setup a more recent version of it. I also wanted to see how RaspiBlitz evolves (I started with v1.7.0 upgraded a few versions from there and tweaked it here and there to my liking... until it broke). As I've another node with electrs as Electrum server and BTC RPC Explorer and local instance of mempool.space there wasn't much pressure to fix my RaspiBlitz as soon as possible, so I procrastinated...

As far as I can tell from syncing my Fulcrum: it took a while and syncing it is more time consuming than with electrs. But my Bitcoin Core was in sync back then. Fulcrum definitely won't respond to queries as long as it isn't fully synced and as long as the Bitcoin Core it talks to isn't synced either.



The issue might not be your internet connection but additionally maybe too small value for dbcache due to not enough free RAM available. On what kind of storage media is your blocks and chainstate directories located, hopefully a SSD?

Yes, I have Bitcoin Core running with txindex=1, so no pruning; however, my connection is so slow so I am still only at blockheight 462,528.