Issue Details

Number: 31373
Title: RFC: support for writing UTXO set dump (`dumptxoutset` RPC) to a named pipe
Description: ### Please describe the feature you'd like to see added. While the primary obvious use-case for the `dumptxoutset` RPC is to create AssumeUTXO snapshots (to be distributed and loaded on newly created nodes via the `loadtxoutset` RPC later), it can also be useful as input for external tooling like converters to other UTXO set formats, e.g. https://github.com/bitcoin/bitcoin/pull/27432. For those, the intermediate step of writing a >10GB file to disk and then reading it again is wasteful and annoying, as it consumes both more time and space than necessary. By supporting writing to a [named pipe](https://en.wikipedia.org/wiki/Named_pipe#In_Unix), the output data could be fed directly into another process instead. Thanks to the UNIX "everything is a file" philosophy, no logic changes in the tooling are even needed -- the reader only sees an input stream and doesn't notice or care if the input file represents an actual physical file on disk or if the data is generated on-the-fly from another process. Currently needed steps for external tools: 1. call `dumptxoutset` to create utxo.dump (>10GB on mainnet) 2. call external tool with utxo.dump as input (run only after step 1 is finished) 3. delete utxo.dump Needed steps for external tools with named pipe support: 1. create a named pipe utxo.pipe (e.g. via https://linux.die.net/man/3/mkfifo) 2. call `dumptxoutset` to write to utxo.pipe 3. call external tool with utxo.pipe as input (run in *parallel* to step 2) 4. delete utxo.pipe I've tried this yesterday and it works as expected with minimal changes (see proposed solution below). Will push the branch later with concrete instructions, if people feel that this is worthwhile to support. ### Is your feature related to a problem, if so please describe it. _No response_ ### Describe the solution you'd like The `dumptxoutset` call only needs two minor behaviour modificiations. If the passed `path` is a named pipe (trivially detectable via C++ standard library routine [std::filesystem::is_fifo](https://en.cppreference.com/w/cpp/filesystem/is_fifo)), then: * don't error if the file already exists * don't create a temporary file with `.incomplete` suffix, but write directly into the specified path ### Describe any alternatives you've considered _No response_ ### Please leave any additional context _No response_
URL: https://github.com/bitcoin/bitcoin/issue/31373
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