Crucible dependencies on oximeter-producer doubling build times for several packages

[smklein]

I believe this is the root cause of #1481 , but the issue also impacts build times. Filed as a separate issue to track reduction of duplicate dependencies in addition to the build flake.

The following command:

RUSTDOCFLAGS="-Dwarnings" cargo doc --workspace

Returns the following output:

warning: output filename collision.
The lib target `nexus-client` in package `nexus-client v0.1.0 (https://github.com/oxidecomputer/omicron?branch=main#c458fddc)` has the same output filename as the lib target `nexus-client` in package `nexus-client v0.1.0 (/home/smklein/repos/oxide/omicron/nexus-client)`.
Colliding filename is: /home/smklein/repos/oxide/omicron/target/doc/nexus_client/index.html                          
The targets should have unique names.                     
This is a known bug where multiple crates with the same name use                                                     
the same path; see <https://github.com/rust-lang/cargo/issues/6313>.                                                   
warning: output filename collision.                                                                                  
The lib target `omicron-common` in package `omicron-common v0.1.0 (https://github.com/oxidecomputer/omicron?branch=main#c458fddc)` has the same output filename as the lib target `omicron-common` in package `omicron-common v0.1.0 (/home/smklein/repos/oxide/omicron/common)`.
Colliding filename is: /home/smklein/repos/oxide/omicron/target/doc/omicron_common/index.html                          
The targets should have unique names.                                                                                
This is a known bug where multiple crates with the same name use                                                     
the same path; see <https://github.com/rust-lang/cargo/issues/6313>.                                                   
warning: output filename collision.                                                                                  
The lib target `oximeter` in package `oximeter v0.1.0 (https://github.com/oxidecomputer/omicron?branch=main#c458fddc)` has the same output filename as the lib target `oximeter` in package `oximeter v0.1.0 (/home/smklein/repos/oxide/omicron/oximeter/oximeter)`.
Colliding filename is: /home/smklein/repos/oxide/omicron/target/doc/oximeter/index.html                              
The targets should have unique names.                                                                                
This is a known bug where multiple crates with the same name use                                                       
the same path; see <https://github.com/rust-lang/cargo/issues/6313>.                                                 
warning: output filename collision.                                                                                  
The bin target `oximeter` in package `oximeter-collector v0.1.0 (/home/smklein/repos/oxide/omicron/oximeter/collector)` has the same output filename as the lib target `oximeter` in package `oximeter v0.1.0 (https://github.com/oxidecomputer/omicron?branch=main#c458fddc)`.
Colliding filename is: /home/smklein/repos/oxide/omicron/target/doc/oximeter/index.html                              
The targets should have unique names.
This is a known bug where multiple crates with the same name use                                                     
the same path; see <https://github.com/rust-lang/cargo/issues/6313>.                                                 
warning: output filename collision.
The lib target `oximeter-producer` in package `oximeter-producer v0.1.0 (https://github.com/oxidecomputer/omicron?branch=main#c458fddc)` has the same output filename as the lib target `oximeter-producer` in package `oximeter-producer v0.1.0 (/home/smklein/repos/oxide/omicron/oximeter/producer)`.
Colliding filename is: /home/smklein/repos/oxide/omicron/target/doc/oximeter_producer/index.html                     
The targets should have unique names.                                                                                  
This is a known bug where multiple crates with the same name use                                                       
the same path; see <https://github.com/rust-lang/cargo/issues/6313>.   

Inspecting the Cargo.lock file, we can see this is a valid complaint, tracing back to oximeter-producer.

In Cargo.lock, there are two [[package]]s for oximeter-producer:

• One is pulled directly from the current tree, as 0.1.0. This is used by most of Omicron.
• Another is pinned to the main branch. This appears to be used by crucible, which itself is used by propolis-client and the simulated sled agent.

The other mentioned targets also have duplicate [[package]]s, but I think that's because they're dependencies of oximeter-producer.

[smklein]

This is the current dependency tree. Arrows mean "depends on".

The problem here is that we are building Crucible, and all transitive dependencies of Crucible within Omicron, just to use a couple structs.

If we clear out the dependencies on crucible in omicron (which transitively depend on oximeter-producer), I think we can solve this issue.

• omicron-sled-agent depends on crucible::VolumeConstructionRequest in the simulated sled agent, to emulate a server.
• propolis-client also depends on crucible::VolumeConstructionRequest

If we could pull these structures out of the main Crucible repo, we could produce the following:

This would no longer require Omicron to build Crucible, and would fix the warning from the docs generator.

@leftwo , @jgallagher , WDYT?

[leftwo]

I'm just about to dig into the volume layer, so doing something like this (assuming it would work) would be good in term of timing for me.

[jgallagher]

Yes, I'd vote for doing this. @andrewjstone and I ran into some issues when writing sprockets related to the current dependency tree, and suggested splitting out a lighter-weight crucible crate at the time (https://matrix.to/#/!sHZivBWjdefFxgKtLU:oxide.computer/$8ccUIZiqOZZJTqLhHgyy2aDfFiiCzsYkcWAMwTyWfyM?via=oxide.computer&via=unix.house&via=timecube.club is the beginning of that conversation). IIRC we worked around the issue we were having by tweaking some dependency versions instead of pursuing this, though.