Cargo tries to resolve an incorrect host name to download crates

[ksqsf]

Problem

Cargo sometimes tries to resolve an incorrect host name to download crates. This problem is intermittent.

warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
warning: spurious network error (1 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates)
error: failed to download from `https://crates-io.proxy.ustclug.org/api/v1/crates/tokio-core/0.1.17/download`

Caused by:
  [6] Couldn't resolve host name (Could not resolve host: crates)

... while curl can indeed download data.

Steps

1. Enable USTCLUG reverse proxy service for crates.io
2. cargo build and it automatically downloads crates from that site
3. Fail: error: failed to download from https://crates-io.proxy.ustclug.org/api/v1/crates/xml-rs/0.7.0/download Caused by: [6] Couldn't resolve host name (Could not resolve host: crates)`

Possible Solution(s)

I'm not familiar with cargo, so I don't know why this happens. This might be a problem with our reverse proxy set-up, but I'd like a pointer on how to figure out the root cause. :-)

Notes

Output of cargo version: cargo 1.37.0 (9edd089 2019-08-02)

Another report

[alexcrichton]

Thanks for the report! Can you try setting http.debug in .cargo/config and gist the output of the result? You may want to try it on a smaller project as well which only attempts to download one crate to avoid lots of interleaved output.

[http]
# This setting can be used to help debug what's going on with HTTP requests made
# by Cargo. When set to `true` then Cargo's normal debug logging will be filled
# in with HTTP information, which you can extract with
# `CARGO_LOG=cargo::ops::registry=debug` (and `trace` may print more).
#
# Be wary when posting these logs elsewhere though, it may be the case that a
# header has an authentication token in it you don't want leaked! Be sure to
# briefly review logs before posting them.
debug = false

[ksqsf]

http debug trace

(Attempted to obtain a smaller trace but the problem suddenly is gone...)

[ksqsf]

Thanks for the hint! So here's the problem.

[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < HTTP/2 302 
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < server: nginx
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < date: Fri, 18 Oct 2019 07:18:23 GMT
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < content-type: text/html
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < content-length: 154
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < location: https:///crates/unicase/unicase-2.5.1.crate
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: < 
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: * Ignoring the response-body
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: * Issue another request to this URL: 'https:///crates/unicase/unicase-2.5.1.crate'
[2019-10-18T07:18:23Z DEBUG cargo::ops::registry] http-debug: * Unwillingly accepted illegal URL using 3 slashes!

The request is incorrectly redirected. Likely a mistake in our setup. Closing.

[JavierLiu]

Hello, I have encountered the same problem as you. May I know your solution?
Thanks in advance!

[s977120]

Hello, I have encountered the same problem as you. May I know your solution?
Thanks in advance!

+1

[fengerzh]

It's caused by too many connections. Add following command before any of your cargo command:

CARGO_HTTP_MULTIPLEXING=false

For example:

CARGO_HTTP_MULTIPLEXING=false cargo install cargo-generate

Or, just add this env setting in your .bash_profile:

export CARGO_HTTP_MULTIPLEXING=false

[passiondu]

It's caused by too many connections. Add following command before any of your cargo command:

CARGO_HTTP_MULTIPLEXING=false

For example:

CARGO_HTTP_MULTIPLEXING=false cargo install cargo-generate

Or, just add this env setting in your .bash_profile:

export CARGO_HTTP_MULTIPLEXING=false

thank you ,

[dmartin]

I am seeing a similar issue intermittently in CI when building a crate using maturin:

It's similar to the original report, though the hostname appears to be crates.io rather than crates.

out: #24 38.66 💥 maturin failed
out: #24 38.66   Caused by: Cargo metadata failed. Does your crate compile with `cargo build`?
out: #24 38.66   Caused by: `cargo metadata` exited with an error:     Updating crates.io index
out: #24 38.66  Downloading crates ...
out: #24 38.66 warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
out: #24 38.66 warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
out: #24 38.66 warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
out: #24 38.66 warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)
out: #24 38.66 warning: spurious network error (2 tries remaining): [6] Couldn't resolve host name (Could not resolve host: crates.io)

Is this truly caused by too many connections, as mentioned above? If so, some sort of throttling would be preferable to failing the build. Adding the CARGO_HTTP_MULTIPLEXING=false flag as mentioned above doesn't seem ideal as this only happens intermittently and seemingly only on certain hosts.

[DelSkayn]

I encountered a similar issue in github CI with a different hostname: static.crates.iocrates

Downloading crates ...
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
warning: spurious network error (3 tries remaining): [6] Couldn't resolve host name (Could not resolve host: static.crates.iocrates)
...

Trying to build resulted in these error twice before suddenly working the third time.

[Eh2406]

crates.io was having an outage see https://status.crates.io/incidents/qtcxln295f0n and https://blog.rust-lang.org/inside-rust/2023/07/21/crates-io-postmortem.html

[balqaasem]

My solution is:

git config --global http.proxy http://127.0.0.1:4780

It worked for me.