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[Wallet] Add RPC call "rescanblockchain <startheight> <stopheight>" #7061

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merged 2 commits into from Oct 13, 2017

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jonasschnelli commented Nov 19, 2015

A RPC rescan command is much more flexible for the following reasons:

  • You can define the start and end-height
  • It can be called during runtime
  • It can work in multiwallet environment
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I'd rather have it that the API is such that an explicit rescan is never needed. Wasn't there some work on a multi-import w/ timestamps?

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laanwj commented Nov 19, 2015

I'd rather have it that the API is such that an explicit rescan is never needed. Wasn't there some work on a multi-import w/ timestamps?

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Yes. There is a PR (see PR description). I agree that it would be better to avoid rescans at all, although it might be complicated to catch all edge-cases and a manual trigger can help in situations where someone needs to deal with multiple/complex imports (you only want to do one rescan).

And I think some people will cancel a rescan because they want to do other stuff and/or had not considered that a rescan can take a long time. Afterward calling -rescan (from genesis) is a time consuming option.

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jonasschnelli commented Nov 19, 2015

Yes. There is a PR (see PR description). I agree that it would be better to avoid rescans at all, although it might be complicated to catch all edge-cases and a manual trigger can help in situations where someone needs to deal with multiple/complex imports (you only want to do one rescan).

And I think some people will cancel a rescan because they want to do other stuff and/or had not considered that a rescan can take a long time. Afterward calling -rescan (from genesis) is a time consuming option.

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But manually specifying a block # to rescan from is extremely fragile... it's very easy to get this wrong.

Also, rescanning doesn't interact with pruning which will be more and more common in the future.

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laanwj commented Nov 19, 2015

But manually specifying a block # to rescan from is extremely fragile... it's very easy to get this wrong.

Also, rescanning doesn't interact with pruning which will be more and more common in the future.

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@lannwj I thought thats part of what the height parameter here was for-- addressing pruning comparability?

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gmaxwell commented Nov 19, 2015

@lannwj I thought thats part of what the height parameter here was for-- addressing pruning comparability?

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How about we call this rescanfromheight instead, to make it possible to add a rescanfromtime later if users demand? Equally, some kind of RPC call that finds the first block with a nTime after a specific time might be useful here.

Do we have a way of querying what block # is the oldest non-pruned block?

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petertodd commented Nov 20, 2015

How about we call this rescanfromheight instead, to make it possible to add a rescanfromtime later if users demand? Equally, some kind of RPC call that finds the first block with a nTime after a specific time might be useful here.

Do we have a way of querying what block # is the oldest non-pruned block?

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It also occurs to me that for this usecase we might instead want to have pruning not happen automatically, but rather be an on-demand thing where the user specifies the oldest time they're interested in.

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petertodd commented Nov 20, 2015

It also occurs to me that for this usecase we might instead want to have pruning not happen automatically, but rather be an on-demand thing where the user specifies the oldest time they're interested in.

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So the biggest negative I personally see here is that it furthers this misunderstanding that rescan is some thing users generally need to be doing. Until we added these non-rescan imports a user initiated rescan is something that never should have been needed (and indicated a serious bug we'd like to know about if it was). As a result of the -rescan argument there is now this whole cargo cult of people that rescan every time they're scarred by a shadow. I hate to further that.

But I can't deny how really useful this will be.

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gmaxwell commented Nov 20, 2015

So the biggest negative I personally see here is that it furthers this misunderstanding that rescan is some thing users generally need to be doing. Until we added these non-rescan imports a user initiated rescan is something that never should have been needed (and indicated a serious bug we'd like to know about if it was). As a result of the -rescan argument there is now this whole cargo cult of people that rescan every time they're scarred by a shadow. I hate to further that.

But I can't deny how really useful this will be.

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@gmaxwell A possible way around that would be to make the rescan check if you have any addresses that haven't yet been scanned in that range and error out if not. (basically make it say "no rescan needed")

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petertodd commented Nov 21, 2015

@gmaxwell A possible way around that would be to make the rescan check if you have any addresses that haven't yet been scanned in that range and error out if not. (basically make it say "no rescan needed")

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Hm. this could also take a stop argument, allowing you to scan single blocks or avoid rescan overlap. Also, I think all the wallet re-scanning should traverse its interval backwards-- for more instant gratification; though this would dork with the wallet transaction ordering... actually import at all breaks that, I should go talk to luke-jr about that.

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gmaxwell commented Nov 22, 2015

Hm. this could also take a stop argument, allowing you to scan single blocks or avoid rescan overlap. Also, I think all the wallet re-scanning should traverse its interval backwards-- for more instant gratification; though this would dork with the wallet transaction ordering... actually import at all breaks that, I should go talk to luke-jr about that.

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agree with gmaxwell that this should scan a range of blocks

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pstratem commented Nov 24, 2015

agree with gmaxwell that this should scan a range of blocks

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Agree with the stop parameter. Working on a implementation....

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jonasschnelli commented Nov 24, 2015

Agree with the stop parameter. Working on a implementation....

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I would still prefer an approach that imports with birthdate instead of explicit rescanning.

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sipa commented Nov 24, 2015

I would still prefer an approach that imports with birthdate instead of explicit rescanning.

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Added a commit that allows providing a optional parameter with a height where the rescan should stop.

@sipa: I agree that rescan height over a key/address birthday would be nice to have (see #6570). But a explicit rescan RPC call can be useful IMO. It's trivial to maintain and it can save lots of rescan-time on the user side. But agree, it has to be considered as "experts" feature.

What about implementing a threshold for autodetecting wether the parameter is a blockheight or timestamp (similar to LOCKTIME_THRESHOLD)?

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jonasschnelli commented Nov 24, 2015

Added a commit that allows providing a optional parameter with a height where the rescan should stop.

@sipa: I agree that rescan height over a key/address birthday would be nice to have (see #6570). But a explicit rescan RPC call can be useful IMO. It's trivial to maintain and it can save lots of rescan-time on the user side. But agree, it has to be considered as "experts" feature.

What about implementing a threshold for autodetecting wether the parameter is a blockheight or timestamp (similar to LOCKTIME_THRESHOLD)?

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@jonasschnelli see #6570 (comment) regarding your last comment.

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promag commented Nov 24, 2015

@jonasschnelli see #6570 (comment) regarding your last comment.

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GIJensen commented Dec 7, 2015

ACK

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If this is still moving forward - I tested it a bit (including pruned mode) and it looks fine to me. One suggestion is to make the start-height a required parameter so that the user specifies "rescanblockchain 1" to scan from genesis. If the start-height is < 1 or higher than current height, throw an error.
Otherwise, ACK.

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mrbandrews commented Mar 14, 2016

If this is still moving forward - I tested it a bit (including pruned mode) and it looks fine to me. One suggestion is to make the start-height a required parameter so that the user specifies "rescanblockchain 1" to scan from genesis. If the start-height is < 1 or higher than current height, throw an error.
Otherwise, ACK.

Show outdated Hide outdated src/wallet/wallet.cpp

@laanwj laanwj added the Feature label Jun 16, 2016

luke-jr added a commit to bitcoinknots/bitcoin that referenced this pull request Jun 28, 2016

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Rebased.
I think there are still reasons to consider that PR. At the moment, it would really be useful. Even once we have #7551 (importmulti) it could see use cases for rescanblockchain.

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jonasschnelli commented Jul 20, 2016

Rebased.
I think there are still reasons to consider that PR. At the moment, it would really be useful. Even once we have #7551 (importmulti) it could see use cases for rescanblockchain.

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This seems better #7984, but I still prefer not furthering the usage of various rescans. We need APIs that don't require users to keep track of the concept of rescanning IMHO.

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sipa commented Aug 25, 2016

This seems better #7984, but I still prefer not furthering the usage of various rescans. We need APIs that don't require users to keep track of the concept of rescanning IMHO.

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I agree. Ideally, there will be no need to rescan. But in practice, rescans are sometimes required (I guess everyone who gave some users support has encountered that). IMO a rpc rescan commend with an optional hight is much more flexible then -rescan as a startup argument.

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jonasschnelli commented Aug 25, 2016

I agree. Ideally, there will be no need to rescan. But in practice, rescans are sometimes required (I guess everyone who gave some users support has encountered that). IMO a rpc rescan commend with an optional hight is much more flexible then -rescan as a startup argument.

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I think we should work on importmulti instead (or at least an importprivkey that takes a key birthdate as parameter), not on more ways to rescan.

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sipa commented Aug 25, 2016

I think we should work on importmulti instead (or at least an importprivkey that takes a key birthdate as parameter), not on more ways to rescan.

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I think we should work on importmulti instead (or at least an importprivkey that takes a key birthdate as parameter), not on more ways to rescan.

Yes. I can agree with that.

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jonasschnelli commented Aug 25, 2016

I think we should work on importmulti instead (or at least an importprivkey that takes a key birthdate as parameter), not on more ways to rescan.

Yes. I can agree with that.

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Concept ACK.
This seem like moving in the right direction, even if in the long term we want to avoid the need for rescans completely.

This now does replace the -rescan startup argument with a new RPC call rescanblockchain.

I don't see this in the code. Shouldn't we at least deprecate the startup argument at the same time? (I would not oppose to directly remove it as an exception to the general policy instead of waiting for 0.17).
Perhaps note in the release notes that this is also supposed to be temporary.

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jtimon commented Oct 5, 2017

Concept ACK.
This seem like moving in the right direction, even if in the long term we want to avoid the need for rescans completely.

This now does replace the -rescan startup argument with a new RPC call rescanblockchain.

I don't see this in the code. Shouldn't we at least deprecate the startup argument at the same time? (I would not oppose to directly remove it as an exception to the general policy instead of waiting for 0.17).
Perhaps note in the release notes that this is also supposed to be temporary.

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This now does replace the -rescan startup argument with a new RPC call rescanblockchain.

I don't see this in the code. Shouldn't we at least deprecate the startup argument at the same time? (I would not oppose to directly remove it as an exception to the general policy instead of waiting for 0.17).
Perhaps note in the release notes that this is also supposed to be temporary.

This was removed from the PRs description (but not from a later comment, now added a strike-through attr.)

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jonasschnelli commented Oct 5, 2017

This now does replace the -rescan startup argument with a new RPC call rescanblockchain.

I don't see this in the code. Shouldn't we at least deprecate the startup argument at the same time? (I would not oppose to directly remove it as an exception to the general policy instead of waiting for 0.17).
Perhaps note in the release notes that this is also supposed to be temporary.

This was removed from the PRs description (but not from a later comment, now added a strike-through attr.)

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IMO this is ready to merge even though there are some concerns that need to be addressed in follow ups:

  • Rescan continues even if a corrupted block is detected but the RPC fails to the caller;
  • rescanblockchain can be refactored a little to avoid the cs_main and cs_wallet locks;

I also would like to discuss the option to make this RPC asynchronous so the caller doesn't wait for the rescan to complete, it only asks for a rescan. There is a big chance the caller interrupts the call, but I believe in server side the rescan continues.

utACK 559542a.

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promag commented Oct 5, 2017

IMO this is ready to merge even though there are some concerns that need to be addressed in follow ups:

  • Rescan continues even if a corrupted block is detected but the RPC fails to the caller;
  • rescanblockchain can be refactored a little to avoid the cs_main and cs_wallet locks;

I also would like to discuss the option to make this RPC asynchronous so the caller doesn't wait for the rescan to complete, it only asks for a rescan. There is a big chance the caller interrupts the call, but I believe in server side the rescan continues.

utACK 559542a.

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re-utACK 559542a modulo comments above

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MeshCollider commented Oct 5, 2017

re-utACK 559542a modulo comments above

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jonasschnelli commented Oct 9, 2017

Fixed @MeshCollider nits.

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I still think it's worth it to handle

  1. Invalid Start Height: no negative heights
  2. Invalid Stop Height: No negative heights

and

  1. Invalid Start Height: Beyond what's been synced
  2. Invalid Stop Height: Beyond what's been synced

differently. Specifically, the latter calls could still be handled and processed.

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JeremyRubin commented Oct 9, 2017

I still think it's worth it to handle

  1. Invalid Start Height: no negative heights
  2. Invalid Stop Height: No negative heights

and

  1. Invalid Start Height: Beyond what's been synced
  2. Invalid Stop Height: Beyond what's been synced

differently. Specifically, the latter calls could still be handled and processed.

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Tested ACK 35e7fd1

I still think it's worth it to handle ... differently.

These already fail with Invalid start_height and Invalid stop_height. Yes, we can always provide more detailed error messages or logging, but lets not hold this PR up on that. It's already been very heavily reviewed.

I'll happily review follow-up PRs if you want to change error logging.

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jnewbery commented Oct 10, 2017

Tested ACK 35e7fd1

I still think it's worth it to handle ... differently.

These already fail with Invalid start_height and Invalid stop_height. Yes, we can always provide more detailed error messages or logging, but lets not hold this PR up on that. It's already been very heavily reviewed.

I'll happily review follow-up PRs if you want to change error logging.

"}\n"
"\nExamples:\n"
+ HelpExampleCli("rescanblockchain", "100000 120000")
+ HelpExampleRpc("rescanblockchain", "100000 120000")

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I think the HelpExampleRpc should have a comma between the arguments, i.e. a comma after 100000
Yeah would be good to get this merged, sorry for yet another nit :)

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I think the HelpExampleRpc should have a comma between the arguments, i.e. a comma after 100000
Yeah would be good to get this merged, sorry for yet another nit :)

@@ -3233,6 +3309,7 @@ static const CRPCCommand commands[] =
{ "wallet", "walletpassphrasechange", &walletpassphrasechange, {"oldpassphrase","newpassphrase"} },
{ "wallet", "walletpassphrase", &walletpassphrase, {"passphrase","timeout"} },
{ "wallet", "removeprunedfunds", &removeprunedfunds, {"txid"} },
{ "wallet", "rescanblockchain", &rescanblockchain, {"start_height", "stop_height"} },

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Very tiny nit, but every other place skips the space between words in argument list. I.e. {"start_height","stop_height"}.

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Very tiny nit, but every other place skips the space between words in argument list. I.e. {"start_height","stop_height"}.

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re-utACK 35e7fd1

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@jnewbery to be clear

  1. I don't think it's fair to say it was heavily reviewed and I'm needlessly holding it up, I found a major bug in the implementation which required a (imo) pretty significant change to the semantics of the return value.

  2. I'm not suggesting a change in error reporting, I am suggesting a functional change to the ranges which are handled by this call. Specifically, I would like for the cases where

    1. Invalid Start Height: Beyond what's been synced
    2. Invalid Stop Height: Beyond what's been synced

to not throw an error and return a successful scan range (if possible).

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JeremyRubin commented Oct 12, 2017

@jnewbery to be clear

  1. I don't think it's fair to say it was heavily reviewed and I'm needlessly holding it up, I found a major bug in the implementation which required a (imo) pretty significant change to the semantics of the return value.

  2. I'm not suggesting a change in error reporting, I am suggesting a functional change to the ranges which are handled by this call. Specifically, I would like for the cases where

    1. Invalid Start Height: Beyond what's been synced
    2. Invalid Stop Height: Beyond what's been synced

to not throw an error and return a successful scan range (if possible).

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@JeremyRubin - sorry if that came off as a personal criticism. That's not what I meant. This PR was re-opened in December last year and has been reviewed by 9 people so far. It's very useful functionality and it'd be great to see it merged. And yes - you did catch a subtle bug in your review which the rest of us missed. Thank you!

re: your suggested change to the interface - if start_height is beyond what's been sync'ed, then there's nothing to rescan and we should return an error to make it clear to the user that the call was a no-op. If stop_height is beyond the sync height, then it's safer to return an error and let the user call the method again with a valid stop_height. If the call succeeded then a user who's not paying close attention to the return value may incorrectly assume that the wallet is rescanned up to the requested stop_height.

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jnewbery commented Oct 12, 2017

@JeremyRubin - sorry if that came off as a personal criticism. That's not what I meant. This PR was re-opened in December last year and has been reviewed by 9 people so far. It's very useful functionality and it'd be great to see it merged. And yes - you did catch a subtle bug in your review which the rest of us missed. Thank you!

re: your suggested change to the interface - if start_height is beyond what's been sync'ed, then there's nothing to rescan and we should return an error to make it clear to the user that the call was a no-op. If stop_height is beyond the sync height, then it's safer to return an error and let the user call the method again with a valid stop_height. If the call succeeded then a user who's not paying close attention to the return value may incorrectly assume that the wallet is rescanned up to the requested stop_height.

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I haven't followed most of the review conversation, but would give light conditional utACK for 35e7fd1 if >= comment below is addressed.

I like @JeremyRubin's suggestion of avoiding errors when rescans are requested beyond the synced range, but it seems like that could easily be added in a followup.

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jonasschnelli added some commits Nov 19, 2015

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Fixed @ryanofsky points with the >= check.
Lets merge this now,... I think the ranges cleanup (if we want to do this) could be PRed by @JeremyRubin after this PR.

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jonasschnelli commented Oct 12, 2017

Fixed @ryanofsky points with the >= check.
Lets merge this now,... I think the ranges cleanup (if we want to do this) could be PRed by @JeremyRubin after this PR.

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utACK 7a91ceb. Only change since last review was >= fix

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ryanofsky commented Oct 12, 2017

utACK 7a91ceb. Only change since last review was >= fix

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jnewbery commented Oct 12, 2017

reACK 7a91ceb

@jonasschnelli jonasschnelli merged commit 7a91ceb into bitcoin:master Oct 13, 2017

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jonasschnelli added a commit that referenced this pull request Oct 13, 2017

Merge #7061: [Wallet] Add RPC call "rescanblockchain <startheight> <s…
…topheight>"

7a91ceb [QA] Add RPC based rescan test (Jonas Schnelli)
c77170f [Wallet] add rescanblockchain <start_height> <stop_height> RPC command (Jonas Schnelli)

Pull request description:

  A RPC rescan command is much more flexible for the following reasons:
  * You can define the start and end-height
  * It can be called during runtime
  * It can work in multiwallet environment

Tree-SHA512: df67177bad6ad1d08e5a621f095564524fa3eb87204c2048ef7265e77013e4b1b29f991708f807002329a507a254f35e79a4ed28a2d18d4b3da7a75d57ce0ea5
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🎉

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jnewbery commented Oct 13, 2017

🎉

jonasschnelli added a commit that referenced this pull request Oct 16, 2017

Merge #11496: [Trivial] Add missing comma from rescanblockchain example
43f76f6 Add missing comma from rescanblockchain (MeshCollider)

Pull request description:

  #7061 forgot a comma in the HelpExampleRpc() for the rescanblockchain RPC, giving an incorrect example command output:
  > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "rescanblockchain", "params": [100000 120000] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/

  Was just missed during nit-fixing. This is a trivial fix to add that comma in.

Tree-SHA512: b808f32674af585a1ddb78b25621dff0387dbad79c97d65ff61d8a9a12a94e4b8ecf03eda3f281fe439bddb6c0703c39104dbb279f1718949abd930faaa9042f

luke-jr added a commit to bitcoinknots/bitcoin that referenced this pull request Nov 6, 2017

luke-jr added a commit to bitcoinknots/bitcoin that referenced this pull request Nov 6, 2017

luke-jr added a commit to bitcoinknots/bitcoin that referenced this pull request Nov 6, 2017

[QA] Add RPC based rescan test
Github-Pull: #7061
Rebased-From: bea58bcc248fed84627142447b74d78e299c04e7
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