Spurious network errors for serde -> serde_derive -> syn

[workingjubilee]

I hate to raise an issue based on what I consider to be mere speculation. However, unfortunately, "network issues" are very hard to pinpoint, so sometimes mere speculation is what we have. I have noticed that during my recent round of reviews for backtrace, which also offers serialization of a backtrace through serde, the network consistently chokes on this chain of errors:

 warning: spurious network error (1 tries remaining): [28] Timeout was reached (Operation too slow. Less than 10 bytes/sec transferred the last 30 seconds)
error: failed to get `syn` as a dependency of package `serde_derive v1.0.183`
    ... which satisfies dependency `serde_derive = "=1.0.183"` of package `serde v1.0.183`
    ... which satisfies dependency `serde = "^1.0"` of package `backtrace v0.3.69 (D:\a\backtrace-rs\backtrace-rs)`
    ... which satisfies path dependency `backtrace` of package `cpp_smoke_test v0.1.0 (D:\a\backtrace-rs\backtrace-rs\crates\cpp_smoke_test)`

It is always on this dependency chain. I have noticed random buggy network errors before, but they were always, well... fairly random. I have never noticed such a consistent error here before. Most crates are quite small after being gzipped for transfer, so I have to ask: Have you done something to significantly increase the amount of network traffic these dependencies incur?

[dtolnay]

I don't know of any relevant change from my end.

I run thousands of CI jobs per day across my various repos, with a wide range of rustc versions, and have observed this failure too.

1. It only happens on syn. It can happen even if serde_derive is not the thing depending on syn.
2. It only ever occurs with 1.71 and 1.70. Not 1.69 or any older release. Not 1.72-beta. Not 1.73-nightly. So I infer that it was just a cargo bug (or bug in dependency of cargo) that is already fixed.
3. Approximately 1/600 builds are impacted (<0.2%).

So probably just disable 1.71 CI for now, or wait 6 days for the next stable Cargo release.

[workingjubilee]

Fair enough. Weird!

[dtolnay]

Concrete example of a definitely non-serde occurrence just now: https://github.com/dtolnay/dtoa/actions/runs/5921067888/job/16053158600.

The entire lockfile for dtoa is as follows, with no serde in sight:

# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 3

[[package]]
name = "dtoa"
version = "1.0.9"
dependencies = [
 "no-panic",
]

[[package]]
name = "no-panic"
version = "0.1.26"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "71a6d126424f5ce0bb4587ff4561421d44aeede520541cc66f1bb912506ae46a"
dependencies = [
 "proc-macro2",
 "quote",
 "syn",
]

[[package]]
name = "proc-macro2"
version = "1.0.66"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "18fb31db3f9bddb2ea821cde30a9f70117e3f119938b5ee630b7403aa6e2ead9"
dependencies = [
 "unicode-ident",
]

[[package]]
name = "quote"
version = "1.0.33"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
dependencies = [
 "proc-macro2",
]

[[package]]
name = "syn"
version = "2.0.29"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "c324c494eba9d92503e6f1ef2e6df781e78f6a7705a0202d9801b198807d518a"
dependencies = [
 "proc-macro2",
 "quote",
 "unicode-ident",
]

[[package]]
name = "unicode-ident"
version = "1.0.11"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "301abaae475aa91687eb82514b328ab47a211a533026cb25fc3e519b86adfc3c"