Building from current `main` branch fails

[tbrockman]

While poking around and following the install instructions:

rustup install nightly-2025-08-01
cargo +nightly-2025-08-01 install --git https://github.com/facebook/buck2.git buck2

I encountered the following error:

Compiling buck2_cmd_completion_client v0.1.0 (/Users/theo/.cargo/git/checkouts/buck2-d175d02358baf776/c89c58f/app/buck2_cmd_completion_client)
error[E0599]: no method named `blocking_queue_depth` found for struct `RuntimeMetrics` in the current scope
  --> app/buck2_server/src/snapshot.rs:74:55
   |
74 |         snapshot.tokio_blocking_queue_depth = metrics.blocking_queue_depth() as u64;
   |                                                       ^^^^^^^^^^^^^^^^^^^^
   |
help: there is a method `global_queue_depth` with a similar name
   |
74 -         snapshot.tokio_blocking_queue_depth = metrics.blocking_queue_depth() as u64;
74 +         snapshot.tokio_blocking_queue_depth = metrics.global_queue_depth() as u64;
   |

error[E0599]: no method named `num_idle_blocking_threads` found for struct `RuntimeMetrics` in the current scope
  --> app/buck2_server/src/snapshot.rs:75:60
   |
75 |         snapshot.tokio_num_idle_blocking_threads = metrics.num_idle_blocking_threads() as u64;
   |                                                            ^^^^^^^^^^^^^^^^^^^^^^^^^ method not found in `RuntimeMetrics`

error[E0599]: no method named `num_blocking_threads` found for struct `RuntimeMetrics` in the current scope
  --> app/buck2_server/src/snapshot.rs:76:55
   |
76 |         snapshot.tokio_num_blocking_threads = metrics.num_blocking_threads() as u64;
   |                                                       ^^^^^^^^^^^^^^^^^^^^ method not found in `RuntimeMetrics`

   Compiling buck2_cmd_debug_client v0.1.0 (/Users/theo/.cargo/git/checkouts/buck2-d175d02358baf776/c89c58f/app/buck2_cmd_debug_client)
For more information about this error, try `rustc --explain E0599`.
error: could not compile `buck2_server` (lib) due to 3 previous errors
warning: build failed, waiting for other jobs to finish...
error: failed to compile `buck2 v0.1.0 (https://github.com/facebook/buck2.git#c89c58f8)`, intermediate artifacts can be found at `/var/folders/zh/jqg80dw961j_k5634kv_qhd00000gn/T/cargo-installvV93bz`.
To reuse those artifacts with a future compilation, set the environment variable `CARGO_TARGET_DIR` to that path.

Didn't dig into the why too much, but choosing a commit before these calls were added leads to a successful build:

cargo +nightly-2025-08-01 install --git https://github.com/facebook/buck2.git --rev c6bfcc629378a00921aa04597551442c9e2ea2eb buck2
...
    Finished `release` profile [optimized] target(s) in 3m 06s
  Installing /Users/theo/.cargo/bin/buck2
   Installed package `buck2 v0.1.0 (https://github.com/facebook/buck2.git?rev=c6bfcc629378a00921aa04597551442c9e2ea2eb#c6bfcc62)` (executable `buck2`)

[A248]

Can confirm the same error.

Maybe Buck2's executable installation should be based on fixed version releases to crates.io

[cormacrelf]

It's the instructions that should change, not the release process. It seems to recommend building from the tip of a megamonorepo, which is a bad idea. Their CI cannot be expected to slow down just to run GitHub Actions and cargo check. So it will very often contain breakage for the OSS build. Also, buck's binaries will not be published on crates.io because it's something like 75 separate crates and there is not a single API among them that should appear to be public or be depended on by anyone.

The binaries on the releases page are proof enough that something builds. The docs should recommend building from a release tag like latest, which cargo install can do.