Bitcoin And Stuck Transactions?

One problem of filling blocks is that transactions with too-low fees will get “stuck”; I’ve read about such things happening on Reddit.  Then one of my coworkers told me that those he looked at were simply never broadcast properly, and broadcasting them manually fixed it.  Which lead both of us to wonder how often it’s really happening…

My approach is to look at the last 2 years of block data, and make a simple model:

  1. I assume the tx is not a priority tx (some miners reserve space for these; default 50k).
  2. I judge the “minimum feerate to get into a block” as the smallest feerate for any transaction after the first 50k beyond the coinbase (this is an artifact of how bitcoin core builds transactions; priority area first).
  3. I assume the tx won’t be included in “empty” blocks with only a coinbase or a single non-coinbase tx (SPV mining); their feerate is “infinite”.

Now, what feerate do we assume?  The default “dumb wallet” fee is 10000 satoshi per kilobyte: bitcoin-core doesn’t do this pro-rata, so a median 300-byte transaction still pays 10000 satoshi by default (fee-per-byte 33.33).  The worse case is a transaction of exactly 1000 bytes (or, a wallet which does pro-rata fees), which would have a fee-per-byte of 10.

So let’s consider the last two years (since block 277918).  How many blocks in a row we see with a fee-per-byte > 33.33, and how many we see with a feerate of > 10:


In the last two years you would never have experienced a delay of more than 10 blocks for a median-size transaction with a 10,000 satoshi fee.

For a 1000-byte transaction paying the same fee, you would have experienced a 10 block delay 0.7% of the time, with a 20+ block delay on eight occasions: the worse being a 26 block delay at block 382918 (just under 5 hours).  But note that this fee is insufficient to be included in 40% of blocks during the last two years, too; if your wallet is generating such things without warning you, it’s time to switch wallets!

Stuck low-fee transactions are not a real user problem yet.  It’s good to see adoption of smarter wallets, though, because it’s expected that they will be in the near future…

6 replies on “Bitcoin And Stuck Transactions?”

  1. The reason for all the stuck transactions was the the careless raising of the min relay fee in core v0.11 that changed from 10 satoshi to 50 satoshi. This change was implemented without warning to end users. As a result many transactions failed to propagate properly and caused a host of resulting issues.

    This changed caused people who actually USE bitcoin for their day-to-day livelyhood endless headaches. The disregard for end users by the blockstream devs destroyed a lot of faith in bitcoin. Imagine doing an in person transaction with a stranger for hundreds of dollars and having the transaction fail to propagate… NOT FUN!

    I agree that the problems have dissipated now that wallets have had a chance to be changed, but the hubris of the current core devs is apparent. It’s almost as if they think bitcoin is their personal project to tweak with without even actually using it.

    There is far more to this issue as well. Claiming 10000 satoshis is a low fee is bogus… thats $0.04! Which is more than what a whole bitcoin cost when it first started being used. We will never see the same type of adoption with such OUTRAGEOUS fees. Say goodbye to the next 6 billion people using bitcoin with these type of inane fees being imposed on the people of the world.

    1. There’s no evidence that increasing the default relay fee did anything but cut the flood of spam; no wallet hit that relay limit AFAIK. On the contrary, the value was chosen to avoid that.
      Please provide some data that there really are stuck transactions.

  2. >There’s no evidence that increasing the default relay fee did anything but cut the
    >flood of spam; no wallet hit that relay limit AFAIK. On the contrary, the value was
    >chosen to avoid that.
    >Please provide some data that there really are stuck transactions.

    C’mon man this is exactly the type of hubris I’m talking about. Reddit was filled with people who had sent tx’s with 1000 fees that never confirmed but were included subsequent tx’s that were marked as double spends. Bitcointalk had numerous threads with app devs having to scramble to figure out why their transactions stopped working and why the new min tx size was 37 bits and how to properly calculate the new tx fees.

    We all know which core dev was advertising to code the spam attack for $500 just 3 days before it occurred. One can only assume the $12k/day required was funded by a blockstream investor. No one else has the motivation, but i am willing to concede lack of proof on that speculation. All in all extremely suspicious behavior whoever is responsible… not to mention all the censorship regarding the changes.

    1. I’m approving these only as an archive of the unsubstantiated rubbish which passes for knowledge in the bitcoin/reddit world. One popular online wallet was failing to relay transactions which got stuck, but that’s nothing to do with fee levels. Peter Todd did offer to do a stress test for payment, but he says he didn’t; and there were multiple such “stress tests” over a range of time.

      Much of your post isn’t coherent, but your belief that the core devs and/or Blockstream are sabotaging Bitcoin without some extraordinary proof is the hallmark of a conspiracy nut, and I’ll be trashing all your comments from now on.

  3. > The core wallet itself issued double spends using inputs from semi-propagated tx’s that never confirmed due to the min realy fee increase. It was an issue for all wallets.

    Strange, I can’t see a bug report? On #bitcoin-dev the devs assure me that core by default won’t double spend (an unreleased version prior to 0.12 had a bug though), so I’m not sure if you’re ignorant, lying, or just repeating things you heard on reddit as fact.

    Either way, this is not a platform for you to spread misinformation.

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