leveldb: show non-default options during init #31644

To help with to debugging and traceability (in alignment with displaying other non-default args such as Command-line arg: dbcache="10000") we can extend the LevelDB opening log with an additional debug message for the used non-default settings.

To avoid showing booleans as e.g. create_if_missing=1, I've added a local ToString lambda for bool. I wanted to use util::Join at the end, but couldn't find any way that I liked.

Example output after the change:

2025-10-15T02:39:45Z Opened LevelDB successfully
2025-10-15T02:39:45Z [leveldb] startup options: options.compression=NoCompression, options.create_if_missing=true, options.max_file_size=33554432, options.paranoid_checks=true, options.write_buffer_size=524288, readoptions.fill_cache=false, readoptions.verify_checksums=true, writeoptions.sync=true

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31644.

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Conflicts

No conflicts as of last run.

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🚧 At least one of the CI tasks failed. _{Debug: https://github.com/bitcoin/bitcoin/runs/35494695770}

<details><summary>Hints</summary>

Try to run the tests locally, according to the documentation. However, a CI failure may still happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

</details>

How is this useful?

How is this useful?

I've extended the description with more details.

<details> <summary>Details</summary>

2025-01-16T10:47:35Z Opening LevelDB in /Users/lorinc/Library/Application Support/Bitcoin/blocks/index
2025-01-16T10:47:35Z Opened LevelDB successfully with options: options.compression=NoCompression, options.create_if_missing=true, options.max_file_size=33554432, options.paranoid_checks=true, options.write_buffer_size=524288, readoptions.fill_cache=false, readoptions.verify_checksums=true, writeoptions.sync=true
...
2025-01-16T10:47:51Z Opening LevelDB in /Users/lorinc/Library/Application Support/Bitcoin/chainstate
2025-01-16T10:47:51Z Opened LevelDB successfully with options: options.compression=NoCompression, options.create_if_missing=true, options.max_file_size=33554432, options.paranoid_checks=true, options.write_buffer_size=2097152, readoptions.fill_cache=false, readoptions.verify_checksums=true, writeoptions.sync=true

E.g. dbwrapper_tests/dbwrapper shows

options.compression=NoCompression, options.create_if_missing=true, options.max_file_size=33554432, options.paranoid_checks=true, options.write_buffer_size=262144, readoptions.fill_cache=false, readoptions.verify_checksums=true, writeoptions.sync=true

</details>

Logging the non-default LevelDB options during initialization makes it easier to understand and debug database behavior. For example, the blocks/index and chainstate databases already use different write_buffer_size values (512KiB vs. 2MiB) - optimized for their specific workloads (which are expected to diverge further the more we fine-tune them).

Logging these differences helps trace configuration changes, especially when command-line arguments (such as -dbcache or -dbbatchsize) can influence the settings.

Concept ACK

Perhaps the legend "with options: ..." could be debug log? Ideally in the same line but I don't think we support it actually. As an alternative (haven't tested it) maybe:

const bool log_options = LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug);

LogInfo("Opened LevelDB successfully%s", 
    log_options
        ? tfm::format(" with options: %s", GetChangedOptions(DBContext()))
        : "");

Thanks for the hint @pablomartin4btc, I kept the original line and added and extra debug log, when starting with -debug=leveldb.

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🚧 At least one of the CI tasks failed. _{Task lint: https://github.com/bitcoin/bitcoin/actions/runs/21794054901/job/62880530991} _{LLM reason (✨ experimental): Lint failure: duplicate #include lines in src/dbwrapper.cpp triggered lint-includes.py, causing the lint-all step to fail.}

<details><summary>Hints</summary>

Try to run the tests locally, according to the documentation. However, a CI failure may still happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

</details>

For the simple change that this is, it has not received significant review in a while. Maybe interest in this change is not strong enough?