From 05198eb93aa1f1ba0179cdf08c490ec8e4fdb036 Mon Sep 17 00:00:00 2001
From: Alex Butler <alexheretic@gmail.com>
Date: Sat, 06 Jan 2024 01:00:35 +0000
Subject: [PATCH] Fetch crate metadata concurrently (#68)

* Fetch crate metadata concurrently

Handle missing invalid metadata more gracefully

* Update PAT_URL

* Rename PARALLEL_METADATA_FETCHES const---
 CHANGELOG.md       |   5 +++++
 Cargo.lock         | 448 +++++++++++++++++++++++++++++++++++++++++++++++++++-----------------------------
 src/main.rs        |  85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---------------
 test/create_pat.py |   2 +-
 4 files changed, 312 insertions(+), 228 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f467f6..9280d70 100644
--- a/CHANGELOG.md
+++ a/CHANGELOG.md
@@ -1,3 +1,8 @@
+# Unreleased
+
+- Fetch crate metadata concurrently.
+- Handle missing invalid metadata non-fatally.
+
 # v0.1.4
 
 - Add optional `metadata-format` config. Options: `json` (default) & `json.zst`.
diff --git a/Cargo.lock b/Cargo.lock
index 755d09f..4278a13 100644
--- a/Cargo.lock
+++ a/Cargo.lock
@@ -32,9 +32,9 @@
 
 [[package]]
 name = "ahash"
-version = "0.8.6"
+version = "0.8.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "91429305e9f0a25f6205c5b8e0d2db09e0708a7a6df0f42212bb56c32c8ac97a"
+checksum = "77c3a9648d43b9cd48db467b3f87fdd6e146bcc88ab0180006cef2179fe11d01"
 dependencies = [
  "cfg-if",
  "getrandom",
@@ -54,9 +54,9 @@
 
 [[package]]
 name = "anstream"
-version = "0.6.4"
+version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2ab91ebe16eb252986481c5b62f6098f3b698a45e34b5b98200cf20dd2484a44"
+checksum = "d664a92ecae85fd0a7392615844904654d1d5f5514837f471ddef4a057aba1b6"
 dependencies = [
  "anstyle",
  "anstyle-parse",
@@ -74,37 +74,37 @@
 
 [[package]]
 name = "anstyle-parse"
-version = "0.2.2"
+version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "317b9a89c1868f5ea6ff1d9539a69f45dffc21ce321ac1fd1160dfa48c8e2140"
+checksum = "c75ac65da39e5fe5ab759307499ddad880d724eed2f6ce5b5e8a26f4f387928c"
 dependencies = [
  "utf8parse",
 ]
 
 [[package]]
 name = "anstyle-query"
-version = "1.0.0"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ca11d4be1bab0c8bc8734a9aa7bf4ee8316d462a08c6ac5052f888fef5b494b"
+checksum = "e28923312444cdd728e4738b3f9c9cac739500909bb3d3c94b43551b16517648"
 dependencies = [
- "windows-sys",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "anstyle-wincon"
-version = "3.0.1"
+version = "3.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0699d10d2f4d628a98ee7b57b289abbc98ff3bad977cb3152709d4bf2330628"
+checksum = "1cd54b81ec8d6180e24654d0b371ad22fc3dd083b6ff8ba325b72e00c87660a7"
 dependencies = [
  "anstyle",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "anyhow"
-version = "1.0.75"
+version = "1.0.79"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
+checksum = "080e9890a082662b09c1ad45f567faeeb47f22b5fb23895fbe1e651e718e25ca"
 
 [[package]]
 name = "arrayvec"
@@ -114,9 +114,9 @@
 
 [[package]]
 name = "async-trait"
-version = "0.1.74"
+version = "0.1.77"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a66537f1bb974b254c98ed142ff995236e81b9d0fe4db0575f46612cb15eb0f9"
+checksum = "c980ee35e870bd1a4d2c8294d4c04d0499e67bca1e4b5cefcc693c2fa00caea9"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -258,9 +258,9 @@
 
 [[package]]
 name = "cargo-platform"
-version = "0.1.5"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e34637b3140142bdf929fb439e8aa4ebad7651ebf7b1080b3930aa16ac1459ff"
+checksum = "ceed8ef69d8518a5dda55c07425450b58a4e1946f4951eab6d7191ee86c2443d"
 dependencies = [
  "serde",
 ]
@@ -281,10 +281,11 @@
 
 [[package]]
 name = "cc"
-version = "1.0.84"
+version = "1.0.83"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f8e7c90afad890484a21653d08b6e209ae34770fb5ee298f9c699fcc1e5c856"
+checksum = "f1174fb0b6ec23863f8b971027804a42614e347eafb0a95bf0b12cdae21fc4d0"
 dependencies = [
+ "jobserver",
  "libc",
 ]
 
@@ -315,9 +316,9 @@
 
 [[package]]
 name = "clap"
-version = "4.4.8"
+version = "4.4.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2275f18819641850fa26c89acc84d465c1bf91ce57bc2748b28c420473352f64"
+checksum = "52bdc885e4cacc7f7c9eedc1ef6da641603180c783c41a15c264944deeaab642"
 dependencies = [
  "clap_builder",
  "clap_derive",
@@ -325,9 +326,9 @@
 
 [[package]]
 name = "clap_builder"
-version = "4.4.8"
+version = "4.4.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "07cdf1b148b25c1e1f7a42225e30a0d99a615cd4637eae7365548dd4529b95bc"
+checksum = "fb7fb5e4e979aec3be7791562fcba452f94ad85e954da024396433e0e25a79e9"
 dependencies = [
  "anstream",
  "anstyle",
@@ -362,9 +363,9 @@
 
 [[package]]
 name = "core-foundation"
-version = "0.9.3"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "194a7a9e6de53fa55116934067c844d9d749312f75c6f6d0980e8c252f8c2146"
+checksum = "91e195e091a93c46f7102ec7818a2aa394e1e1771c3ab4825963fa03e45afb8f"
 dependencies = [
  "core-foundation-sys",
  "libc",
@@ -372,15 +373,15 @@
 
 [[package]]
 name = "core-foundation-sys"
-version = "0.8.4"
+version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e496a50fda8aacccc86d7529e2c1e0892dbd0f898a6b5645b5561b89c3210efa"
+checksum = "06ea2b9bc92be3c2baa9334a323ebca2d6f074ff852cd1d7b11064035cd3868f"
 
 [[package]]
 name = "cpufeatures"
-version = "0.2.11"
+version = "0.2.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ce420fe07aecd3e67c5f910618fe65e94158f6dcc0adf44e00d69ce2bdfe0fd0"
+checksum = "53fe5e26ff1b7aef8bca9c6080520cfb8d9333c7568e1829cef191a9723e5504"
 dependencies = [
  "libc",
 ]
@@ -435,15 +436,15 @@
 
 [[package]]
 name = "data-encoding"
-version = "2.4.0"
+version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2e66c9d817f1720209181c316d28635c050fa304f9c79e47a520882661b7308"
+checksum = "7e962a19be5cfc3f3bf6dd8f61eb50107f356ad6270fbb3ed41476571db78be5"
 
 [[package]]
 name = "deranged"
-version = "0.3.9"
+version = "0.3.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f32d04922c60427da6f9fef14d042d9edddef64cb9d4ce0d64d0685fbeb1fd3"
+checksum = "b42b6fa04a440b495c8b04d0e71b707c585f83cb9cb28cf8cd0d976c315e31b4"
 dependencies = [
  "powerfmt",
  "serde",
@@ -506,12 +507,12 @@
 
 [[package]]
 name = "errno"
-version = "0.3.6"
+version = "0.3.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7c18ee0ed65a5f1f81cac6b1d213b69c35fa47d4252ad41f1486dbd8226fe36e"
+checksum = "a258e46cdc063eb8519c00b9fc845fc47bcfca4130e2f08e88665ceda8474245"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -532,18 +533,18 @@
 
 [[package]]
 name = "form_urlencoded"
-version = "1.2.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a62bc1cf6f830c2ec14a513a9fb124d0a213a629668a4186f329db21fe045652"
+checksum = "e13624c2627564efccf4934284bdd98cbaa14e79b0b5a141218e507b3a823456"
 dependencies = [
  "percent-encoding",
 ]
 
 [[package]]
 name = "futures"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da0290714b38af9b4a7b094b8a37086d1b4e61f2df9122c3cad2577669145335"
+checksum = "645c6916888f6cb6350d2550b80fb63e734897a8498abe35cfb732b6487804b0"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -556,9 +557,9 @@
 
 [[package]]
 name = "futures-channel"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ff4dd66668b557604244583e3e1e1eada8c5c2e96a6d0d6653ede395b78bbacb"
+checksum = "eac8f7d7865dcb88bd4373ab671c8cf4508703796caa2b1985a9ca867b3fcb78"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -566,15 +567,15 @@
 
 [[package]]
 name = "futures-core"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eb1d22c66e66d9d72e1758f0bd7d4fd0bee04cad842ee34587d68c07e45d088c"
+checksum = "dfc6580bb841c5a68e9ef15c77ccc837b40a7504914d52e47b8b0e9bbda25a1d"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f4fb8693db0cf099eadcca0efe2a5a22e4550f98ed16aba6c48700da29597bc"
+checksum = "a576fc72ae164fca6b9db127eaa9a9dda0d61316034f33a0a0d4eda41f02b01d"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -583,15 +584,15 @@
 
 [[package]]
 name = "futures-io"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8bf34a163b5c4c52d0478a4d757da8fb65cabef42ba90515efee0f6f9fa45aaa"
+checksum = "a44623e20b9681a318efdd71c299b6b222ed6f231972bfe2f224ebad6311f0c1"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "53b153fd91e4b0147f4aced87be237c98248656bb01050b96bf3ee89220a8ddb"
+checksum = "87750cf4b7a4c0625b1529e4c543c2182106e4dedc60a2a6455e00d212c489ac"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -600,21 +601,21 @@
 
 [[package]]
 name = "futures-sink"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e36d3378ee38c2a36ad710c5d30c2911d752cb941c00c72dbabfb786a7970817"
+checksum = "9fb8e00e87438d937621c1c6269e53f536c14d3fbd6a042bb24879e57d474fb5"
 
 [[package]]
 name = "futures-task"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "efd193069b0ddadc69c46389b740bbccdd97203899b48d09c5f7969591d6bae2"
+checksum = "38d84fa142264698cdce1a9f9172cf383a0c82de1bddcf3092901442c4097004"
 
 [[package]]
 name = "futures-util"
-version = "0.3.29"
+version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a19526d624e703a3179b3d322efec918b6246ea0fa51d41124525f00f1cc8104"
+checksum = "3d6401deb83407ab3da39eba7e33987a73c3df0c82b4bb5813ee871c19c41d48"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -651,9 +652,9 @@
 
 [[package]]
 name = "gimli"
-version = "0.28.0"
+version = "0.28.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6fb8d784f27acf97159b40fc4db5ecd8aa23b9ad5ef69cdd136d3bc80665f0c0"
+checksum = "4271d37baee1b8c7e4b708028c57d816cf9d2434acb33a549475f78c181f6253"
 
 [[package]]
 name = "gitlab-cargo-shim"
@@ -668,7 +669,7 @@
  "clap",
  "futures",
  "hex",
- "indexmap 2.1.0",
+ "indexmap",
  "indoc",
  "itoa",
  "packfile",
@@ -698,9 +699,9 @@
 
 [[package]]
 name = "h2"
-version = "0.3.21"
+version = "0.3.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "91fc23aa11be92976ef4729127f1a74adf36d8436f7816b185d18df956790833"
+checksum = "4d6250322ef6e60f93f9a2162799302cd6f68f79f6e5d85c8c16f14d1d958178"
 dependencies = [
  "bytes",
  "fnv",
@@ -708,24 +709,18 @@
  "futures-sink",
  "futures-util",
  "http",
- "indexmap 1.9.3",
+ "indexmap",
  "slab",
  "tokio",
  "tokio-util",
  "tracing",
 ]
-
-[[package]]
-name = "hashbrown"
-version = "0.12.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
 
 [[package]]
 name = "hashbrown"
-version = "0.14.2"
+version = "0.14.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f93e7192158dbcda357bdec5fb5788eebf8bbac027f3f33e719d29135ae84156"
+checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
 
 [[package]]
 name = "heck"
@@ -768,9 +763,9 @@
 
 [[package]]
 name = "http-body"
-version = "0.4.5"
+version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d5f38f16d184e36f2408a55281cd658ecbd3ca05cce6d6510a176eca393e26d1"
+checksum = "7ceab25649e9960c0311ea418d17bee82c0dcec1bd053b5f9a66e265a693bed2"
 dependencies = [
  "bytes",
  "http",
@@ -791,9 +786,9 @@
 
 [[package]]
 name = "hyper"
-version = "0.14.27"
+version = "0.14.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ffb1cfd654a8219eaef89881fdb3bb3b1cdc5fa75ded05d6933b2b382e395468"
+checksum = "bf96e135eb83a2a8ddf766e426a841d8ddd7449d5f00d34ea02b41d2f19eef80"
 dependencies = [
  "bytes",
  "futures-channel",
@@ -806,7 +801,7 @@
  "httpdate",
  "itoa",
  "pin-project-lite",
- "socket2 0.4.10",
+ "socket2",
  "tokio",
  "tower-service",
  "tracing",
@@ -829,22 +824,12 @@
 
 [[package]]
 name = "idna"
-version = "0.4.0"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7d20d6b07bfbc108882d88ed8e37d39636dcc260e15e30c45e6ba089610b917c"
+checksum = "634d9b1461af396cad843f47fdba5597a4f9e6ddd4bfb6ff5d85028c25cb12f6"
 dependencies = [
  "unicode-bidi",
  "unicode-normalization",
-]
-
-[[package]]
-name = "indexmap"
-version = "1.9.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bd070e393353796e801d209ad339e89596eb4c8d430d18ede6a1cced8fafbd99"
-dependencies = [
- "autocfg",
- "hashbrown 0.12.3",
 ]
 
 [[package]]
@@ -854,7 +839,7 @@
 checksum = "d530e1a18b1cb4c484e6e34556a0d948706958449fca0cab753d649f2bce3d1f"
 dependencies = [
  "equivalent",
- "hashbrown 0.14.2",
+ "hashbrown",
 ]
 
 [[package]]
@@ -880,15 +865,24 @@
 
 [[package]]
 name = "itoa"
-version = "1.0.9"
+version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af150ab688ff2122fcef229be89cb50dd66af9e01a4ff320cc137eecc9bacc38"
+checksum = "b1a46d1a171d865aa5f83f92695765caa047a9b4cbae2cbf37dbd613a793fd4c"
 
 [[package]]
+name = "jobserver"
+version = "0.1.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c37f63953c4c63420ed5fd3d6d398c719489b9f872b9fa683262f8edd363c7d"
+dependencies = [
+ "libc",
+]
+
+[[package]]
 name = "js-sys"
-version = "0.3.65"
+version = "0.3.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "54c0c35952f67de54bb584e9fd912b3023117cbafc0a77d8f3dee1fb5f572fe8"
+checksum = "cee9c64da59eae3b50095c18d3e74f8b73c0b86d2792824ff01bbce68ba229ca"
 dependencies = [
  "wasm-bindgen",
 ]
@@ -901,9 +895,9 @@
 
 [[package]]
 name = "libc"
-version = "0.2.150"
+version = "0.2.151"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89d92a4743f9a61002fae18374ed11e7973f530cb3a3255fb354818118b2203c"
+checksum = "302d7ab3130588088d277783b1e2d2e10c9e9e4a16dd9050e6ec93fb3e7048f4"
 
 [[package]]
 name = "libredox"
@@ -930,9 +924,9 @@
 
 [[package]]
 name = "linux-raw-sys"
-version = "0.4.11"
+version = "0.4.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "969488b55f8ac402214f3f5fd243ebb7206cf82de60d3172994707a4bcc2b829"
+checksum = "c4cd1a83af159aa67994778be9070f0ae1bd732942279cabb14f86f986a21456"
 
 [[package]]
 name = "lock_api"
@@ -958,9 +952,9 @@
 
 [[package]]
 name = "memchr"
-version = "2.6.4"
+version = "2.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
+checksum = "523dc4f511e55ab87b694dc30d0f820d60906ef06413f93d4d7a1385599cc149"
 
 [[package]]
 name = "mime"
@@ -979,13 +973,13 @@
 
 [[package]]
 name = "mio"
-version = "0.8.9"
+version = "0.8.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3dce281c5e46beae905d4de1870d8b1509a9142b62eedf18b443b011ca8343d0"
+checksum = "8f3d0b296e374a4e6f3c7b0a1f5a51d748a0d34c85e7dc48fc3fa9a87657fe09"
 dependencies = [
  "libc",
  "wasi",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1040,18 +1034,18 @@
 
 [[package]]
 name = "object"
-version = "0.32.1"
+version = "0.32.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9cf5f9dd3933bd50a9e1f149ec995f39ae2c496d31fd772c1fd45ebc27e902b0"
+checksum = "a6a622008b6e321afc04970976f62ee297fdbaa6f95318ca343e3eebb9648441"
 dependencies = [
  "memchr",
 ]
 
 [[package]]
 name = "once_cell"
-version = "1.18.0"
+version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dd8b5dd2ae5ed71462c540258bedcb51965123ad7e7ccf4b9a8cafaa4a63576d"
+checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
 [[package]]
 name = "opaque-debug"
@@ -1074,7 +1068,7 @@
  "bytes",
  "flate2",
  "hex",
- "indexmap 2.1.0",
+ "indexmap",
  "itoa",
  "sha1",
  "thiserror",
@@ -1103,7 +1097,7 @@
  "libc",
  "redox_syscall",
  "smallvec",
- "windows-targets",
+ "windows-targets 0.48.5",
 ]
 
 [[package]]
@@ -1152,9 +1146,9 @@
 
 [[package]]
 name = "percent-encoding"
-version = "2.3.0"
+version = "2.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b2a4787296e9989611394c33f193f676704af1686e70b8f8033ab5ba9a35a94"
+checksum = "e3148f5046208a5d56bcfc03053e3ca6334e51da8dfb19b6cdc8b306fae3283e"
 
 [[package]]
 name = "pin-project-lite"
@@ -1170,9 +1164,9 @@
 
 [[package]]
 name = "pkg-config"
-version = "0.3.27"
+version = "0.3.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26072860ba924cbfa98ea39c8c19b4dd6a4a25423dbdf219c1eca91aa0cf6964"
+checksum = "69d3587f8a9e599cc7ec2c00e331f71c4e69a5f9a4b8a6efd5b07466b9736f9a"
 
 [[package]]
 name = "powerfmt"
@@ -1188,18 +1182,18 @@
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.69"
+version = "1.0.75"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "134c189feb4956b20f6f547d2cf727d4c0fe06722b20a0eec87ed445a97f92da"
+checksum = "907a61bd0f64c2f29cd1cf1dc34d05176426a3f504a78010f08416ddb7b13708"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.33"
+version = "1.0.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
 dependencies = [
  "proc-macro2",
 ]
@@ -1285,9 +1279,9 @@
 
 [[package]]
 name = "reqwest"
-version = "0.11.22"
+version = "0.11.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "046cd98826c46c2ac8ddecae268eb5c2e58628688a5fc7a2643704a73faba95b"
+checksum = "37b1ae8d9ac08420c66222fb9096fc5de435c3c48542bc5336c51892cffafb41"
 dependencies = [
  "base64",
  "bytes",
@@ -1325,16 +1319,16 @@
 
 [[package]]
 name = "ring"
-version = "0.17.5"
+version = "0.17.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb0205304757e5d899b9c2e448b867ffd03ae7f988002e47cd24954391394d0b"
+checksum = "688c63d65483050968b2a8937f7995f443e27041a0f7700aa59b0822aedebb74"
 dependencies = [
  "cc",
  "getrandom",
  "libc",
  "spin",
  "untrusted",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1345,22 +1339,22 @@
 
 [[package]]
 name = "rustix"
-version = "0.38.21"
+version = "0.38.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2b426b0506e5d50a7d8dafcf2e81471400deb602392c7dd110815afb4eaf02a3"
+checksum = "72e572a5e8ca657d7366229cdde4bd14c4eb5499a9573d4d366fe1b599daa316"
 dependencies = [
  "bitflags 2.4.1",
  "errno",
  "libc",
  "linux-raw-sys",
- "windows-sys",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "rustls"
-version = "0.21.8"
+version = "0.21.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "446e14c5cda4f3f30fe71863c34ec70f5ac79d6087097ad0bb433e1be5edf04c"
+checksum = "f9d5a6813c0759e4609cd494e8e725babae6a2ca7b62a5536a13daaec6fcb7ba"
 dependencies = [
  "log",
  "ring",
@@ -1389,9 +1383,9 @@
 
 [[package]]
 name = "ryu"
-version = "1.0.15"
+version = "1.0.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ad4cc8da4ef723ed60bced201181d83791ad433213d8c24efffda1eec85d741"
+checksum = "f98d2aa92eebf49b69786be48e4477826b256916e84a57ff2a4f21923b48eb4c"
 
 [[package]]
 name = "same-file"
@@ -1420,27 +1414,27 @@
 
 [[package]]
 name = "semver"
-version = "1.0.20"
+version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "836fa6a3e1e547f9a2c4040802ec865b5d85f4014efe00555d7090a3dcaa1090"
+checksum = "b97ed7a9823b74f99c7742f5336af7be5ecd3eeafcb1507d1fa93347b1d589b0"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "serde"
-version = "1.0.193"
+version = "1.0.194"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "25dd9975e68d0cb5aa1120c288333fc98731bd1dd12f561e468ea4728c042b89"
+checksum = "0b114498256798c94a0689e1a15fec6005dee8ac1f41de56404b67afc2a4b773"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.193"
+version = "1.0.194"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "43576ca501357b9b071ac53cdc7da8ef0cbd9493d8df094cd821777ea6e894d3"
+checksum = "a3385e45322e8f9931410f01b3031ec534c3947d0e94c18049af4d9f9907d4e0"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1449,9 +1443,9 @@
 
 [[package]]
 name = "serde_json"
-version = "1.0.108"
+version = "1.0.111"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3d1c7e3eac408d115102c4c24ad393e0821bb3a5df4d506a80f85f7a742a526b"
+checksum = "176e46fa42316f18edd598015a5166857fc835ec732f5215eac6b7bdbf0a84f4"
 dependencies = [
  "itoa",
  "ryu",
@@ -1543,16 +1537,6 @@
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 checksum = "4dccd0940a2dcdf68d092b8cbab7dc0ad8fa938bf95787e1b916b0e3d0e8e970"
-
-[[package]]
-name = "socket2"
-version = "0.4.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9f7916fc008ca5542385b89a3d3ce689953c143e9304a9bf8beec1de48994c0d"
-dependencies = [
- "libc",
- "winapi",
-]
 
 [[package]]
 name = "socket2"
@@ -1561,7 +1545,7 @@
 checksum = "7b5fac59a5cb5dd637972e5fca70daf0523c9067fcdc4842f053dae04a18f8e9"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1584,9 +1568,9 @@
 
 [[package]]
 name = "syn"
-version = "2.0.39"
+version = "2.0.48"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "23e78b90f2fcf45d3e842032ce32e3f2d1545ba6636271dcbf24fa306d87be7a"
+checksum = "0f3531638e407dfc0814761abb7c00a5b54992b849452a0646b7f65c9f770f3f"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1621,23 +1605,23 @@
 checksum = "21bebf2b7c9e0a515f6e0f8c51dc0f8e4696391e6f1ff30379559f8365fb0df7"
 dependencies = [
  "rustix",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
 name = "thiserror"
-version = "1.0.50"
+version = "1.0.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f9a7210f5c9a7156bb50aa36aed4c95afb51df0df00713949448cf9e97d382d2"
+checksum = "d54378c645627613241d077a3a79db965db602882668f9136ac42af9ecb730ad"
 dependencies = [
  "thiserror-impl",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.50"
+version = "1.0.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "266b2e40bc00e5a6c09c3584011e08b06f123c00362c92b975ba9843aaaa14b8"
+checksum = "fa0faa943b50f3db30a20aa7e265dbc66076993efed8463e8de414e5d06d3471"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1723,9 +1707,9 @@
 
 [[package]]
 name = "time"
-version = "0.3.30"
+version = "0.3.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c4a34ab300f2dee6e562c10a046fc05e358b29f9bf92277f30c3c8d82275f6f5"
+checksum = "f657ba42c3f86e7680e53c8cd3af8abbe56b5491790b46e22e19c0d57463583e"
 dependencies = [
  "deranged",
  "powerfmt",
@@ -1742,9 +1726,9 @@
 
 [[package]]
 name = "time-macros"
-version = "0.2.15"
+version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4ad70d68dba9e1f8aceda7aa6711965dfec1cac869f311a51bd08b3a2ccbce20"
+checksum = "26197e33420244aeb70c3e8c78376ca46571bc4e701e4791c2cd9f57dcb3a43f"
 dependencies = [
  "time-core",
 ]
@@ -1766,9 +1750,9 @@
 
 [[package]]
 name = "tokio"
-version = "1.34.0"
+version = "1.35.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d0c014766411e834f7af5b8f4cf46257aab4036ca95e9d2c144a10f59ad6f5b9"
+checksum = "c89b4efa943be685f629b149f53829423f8f5531ea21249408e8e2f8671ec104"
 dependencies = [
  "backtrace",
  "bytes",
@@ -1778,9 +1762,9 @@
  "parking_lot",
  "pin-project-lite",
  "signal-hook-registry",
- "socket2 0.5.5",
+ "socket2",
  "tokio-macros",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -1903,9 +1887,9 @@
 
 [[package]]
 name = "try-lock"
-version = "0.2.4"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3528ecfd12c466c6f163363caf2d02a71161dd5e1cc6ae7b34207ea2d42d81ed"
+checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
 [[package]]
 name = "typenum"
@@ -1915,9 +1899,9 @@
 
 [[package]]
 name = "unicode-bidi"
-version = "0.3.13"
+version = "0.3.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "92888ba5573ff080736b3648696b70cafad7d250551175acbaa4e0385b3e1460"
+checksum = "6f2528f27a9eb2b21e69c95319b30bd0efd85d09c379741b0f78ea1d86be2416"
 
 [[package]]
 name = "unicode-ident"
@@ -1942,9 +1926,9 @@
 
 [[package]]
 name = "url"
-version = "2.4.1"
+version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "143b538f18257fac9cad154828a57c6bf5157e1aa604d4816b5995bf6de87ae5"
+checksum = "31e6302e3bb753d46e83516cae55ae196fc0c309407cf11ab35cc51a4c2a4633"
 dependencies = [
  "form_urlencoded",
  "idna",
@@ -1978,9 +1962,9 @@
 
 [[package]]
 name = "uuid"
-version = "1.5.0"
+version = "1.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "88ad59a7560b41a70d191093a945f0b87bc1deeda46fb237479708a1d6b6cdfc"
+checksum = "5e395fcf16a7a3d8127ec99782007af141946b4795001f876d54fb0d55978560"
 dependencies = [
  "getrandom",
 ]
@@ -2030,9 +2014,9 @@
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.88"
+version = "0.2.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7daec296f25a1bae309c0cd5c29c4b260e510e6d813c286b19eaadf409d40fce"
+checksum = "0ed0d4f68a3015cc185aff4db9506a015f4b96f95303897bfa23f846db54064e"
 dependencies = [
  "cfg-if",
  "wasm-bindgen-macro",
@@ -2040,9 +2024,9 @@
 
 [[package]]
 name = "wasm-bindgen-backend"
-version = "0.2.88"
+version = "0.2.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e397f4664c0e4e428e8313a469aaa58310d302159845980fd23b0f22a847f217"
+checksum = "1b56f625e64f3a1084ded111c4d5f477df9f8c92df113852fa5a374dbda78826"
 dependencies = [
  "bumpalo",
  "log",
@@ -2055,9 +2039,9 @@
 
 [[package]]
 name = "wasm-bindgen-futures"
-version = "0.4.38"
+version = "0.4.39"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9afec9963e3d0994cac82455b2b3502b81a7f40f9a0d32181f7528d9f4b43e02"
+checksum = "ac36a15a220124ac510204aec1c3e5db8a22ab06fd6706d881dc6149f8ed9a12"
 dependencies = [
  "cfg-if",
  "js-sys",
@@ -2067,9 +2051,9 @@
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.88"
+version = "0.2.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5961017b3b08ad5f3fe39f1e79877f8ee7c23c5e5fd5eb80de95abc41f1f16b2"
+checksum = "0162dbf37223cd2afce98f3d0785506dcb8d266223983e4b5b525859e6e182b2"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -2077,9 +2061,9 @@
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.88"
+version = "0.2.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c5353b8dab669f5e10f5bd76df26a9360c748f054f862ff5f3f8aae0c7fb3907"
+checksum = "f0eb82fcb7930ae6219a7ecfd55b217f5f0893484b7a13022ebb2b2bf20b5283"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2090,15 +2074,15 @@
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.88"
+version = "0.2.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d046c5d029ba91a1ed14da14dca44b68bf2f124cfbaf741c54151fdb3e0750b"
+checksum = "7ab9b36309365056cd639da3134bf87fa8f3d86008abf99e612384a6eecd459f"
 
 [[package]]
 name = "web-sys"
-version = "0.3.65"
+version = "0.3.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5db499c5f66323272151db0e666cd34f78617522fb0c1604d31a27c50c206a85"
+checksum = "50c24a44ec86bb68fbecd1b3efed7e85ea5621b39b35ef2766b66cd984f8010f"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -2106,9 +2090,9 @@
 
 [[package]]
 name = "webpki-roots"
-version = "0.25.2"
+version = "0.25.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "14247bb57be4f377dfb94c72830b8ce8fc6beac03cf4bf7b9732eadd414123fc"
+checksum = "1778a42e8b3b90bff8d0f5032bf22250792889a5cdc752aa0020c84abe3aaf10"
 
 [[package]]
 name = "winapi"
@@ -2146,8 +2130,17 @@
 version = "0.48.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
+dependencies = [
+ "windows-targets 0.48.5",
+]
+
+[[package]]
+name = "windows-sys"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.52.0",
 ]
 
 [[package]]
@@ -2155,14 +2148,29 @@
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a2fa6e2155d7247be68c096456083145c183cbbbc2764150dda45a87197940c"
+dependencies = [
+ "windows_aarch64_gnullvm 0.48.5",
+ "windows_aarch64_msvc 0.48.5",
+ "windows_i686_gnu 0.48.5",
+ "windows_i686_msvc 0.48.5",
+ "windows_x86_64_gnu 0.48.5",
+ "windows_x86_64_gnullvm 0.48.5",
+ "windows_x86_64_msvc 0.48.5",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a18201040b24831fbb9e4eb208f8892e1f50a37feb53cc7ff887feb8f50e7cd"
 dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.52.0",
+ "windows_aarch64_msvc 0.52.0",
+ "windows_i686_gnu 0.52.0",
+ "windows_i686_msvc 0.52.0",
+ "windows_x86_64_gnu 0.52.0",
+ "windows_x86_64_gnullvm 0.52.0",
+ "windows_x86_64_msvc 0.52.0",
 ]
 
 [[package]]
@@ -2170,42 +2178,84 @@
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb7764e35d4db8a7921e09562a0304bf2f93e0a51bfccee0bd0bb0b666b015ea"
 
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbaa0368d4f1d2aaefc55b6fcfee13f41544ddf36801e793edbbfd7d7df075ef"
 
 [[package]]
 name = "windows_i686_gnu"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a28637cb1fa3560a16915793afb20081aba2c92ee8af57b4d5f28e4b3e7df313"
 
 [[package]]
 name = "windows_i686_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ffe5e8e31046ce6230cc7215707b816e339ff4d4d67c65dffa206fd0f7aa7b9a"
 
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d6fa32db2bc4a2f5abeacf2b69f7992cd09dca97498da74a151a3132c26befd"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a657e1e9d3f514745a572a6846d3c7aa7dbe1658c056ed9c3344c4109a6949e"
 
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.48.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dff9641d1cd4be8d1a070daf9e3773c5f67e78b4d9d42263020c057706765c04"
 
 [[package]]
 name = "winreg"
@@ -2214,7 +2264,7 @@
 checksum = "524e57b2c537c0f9b1e69f1965311ec12182b4122e45035b1508cd24d2adadb1"
 dependencies = [
  "cfg-if",
- "windows-sys",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
@@ -2229,18 +2279,18 @@
 
 [[package]]
 name = "zerocopy"
-version = "0.7.25"
+version = "0.7.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8cd369a67c0edfef15010f980c3cbe45d7f651deac2cd67ce097cd801de16557"
+checksum = "74d4d3961e53fa4c9a25a8637fc2bfaf2595b3d3ae34875568a5cf64787716be"
 dependencies = [
  "zerocopy-derive",
 ]
 
 [[package]]
 name = "zerocopy-derive"
-version = "0.7.25"
+version = "0.7.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2f140bda219a26ccc0cdb03dba58af72590c53b22642577d88a927bc5c87d6b"
+checksum = "9ce1b18ccd8e73a9321186f97e46f9f04b778851177567b1975109d26a08d2a6"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/src/main.rs b/src/main.rs
index bbb7da7..c2cf727 100644
--- a/src/main.rs
+++ a/src/main.rs
@@ -16,7 +16,7 @@
 use anyhow::anyhow;
 use bytes::{BufMut, Bytes, BytesMut};
 use clap::Parser;
-use futures::Future;
+use futures::{stream::FuturesOrdered, Future, StreamExt};
 use indexmap::IndexMap;
 use packfile::{
     codec::{Encoder, GitCodec},
@@ -39,6 +39,7 @@
     ChannelId, CryptoVec,
 };
 use thrussh_keys::key::PublicKey;
+use tokio::sync::Semaphore;
 use tokio_util::codec::{Decoder, Encoder as CodecEncoder};
 use tracing::{debug, error, info, info_span, instrument, Instrument, Span};
 use uuid::Uuid;
@@ -50,6 +51,8 @@
     env!("CARGO_PKG_VERSION"),
     "\n"
 );
+/// Number of metadata GETs to do in parallel.
+const PARALLEL_METADATA_FETCHES: usize = 6;
 
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
@@ -222,13 +225,14 @@
     /// globally cache-able since it's immutable, to get to this call
     /// the user must've already fetched the crate path from the provider
     /// and hence verified they have permission to read it.
-    #[instrument(skip(self), err)]
     async fn fetch_metadata(
-        &self,
+        gitlab: &U,
+        cache: &MetadataCache,
         path: &U::CratePath,
         checksum: &str,
         crate_name: &str,
         crate_version: &str,
+        do_as: &User,
     ) -> anyhow::Result<Arc<CargoIndexCrateMetadata>> {
         let key = MetadataCacheKey {
             checksum: checksum.into(),
@@ -239,15 +243,15 @@
         // check if the crate metadata already exists in our cache, if it does
         // we'll just return that
         {
-            let reader = self.metadata_cache.read();
+            let reader = cache.read();
             if let Some(cache) = reader.get(&key) {
                 return Ok(Arc::clone(cache));
             }
         }
 
         // fetch metadata from the provider
-        let metadata = Arc::clone(&self.gitlab)
-            .fetch_metadata_for_release(path, crate_version, self.user()?)
+        let metadata = gitlab
+            .fetch_metadata_for_release(path, crate_version, do_as)
             .await?;
 
         // transform the `cargo metadata` output to the cargo index
@@ -260,7 +264,7 @@
         // cache the transformed value so the next user to pull it
         // doesn't have to wait for _yet another_ gitlab call
         {
-            let mut writer = self.metadata_cache.write();
+            let mut writer = cache.write();
             writer.insert(key.into_owned(), Arc::clone(&metadata));
         }
 
@@ -291,8 +295,9 @@
 
         // fetch the impersonation token for the user we'll embed
         // the `dl` string.
-        let token = match &self.user()?.token {
-            None => self.gitlab.fetch_token_for_user(self.user()?).await?,
+        let user = self.user()?;
+        let token = match &user.token {
+            None => self.gitlab.fetch_token_for_user(user).await?,
             Some(token) => token.clone(),
         };
 
@@ -307,35 +312,59 @@
 
         // fetch the releases for every project within the given project
         let releases_by_crate = self.fetch_releases_by_crate().await?;
+
+        // fetch metadata concurrently
+        // parses the `cargo metadata` stored in the release, which
+        // should be stored according to MetadataFormat.
+        let fetch_concurrency = Semaphore::new(PARALLEL_METADATA_FETCHES);
+        let mut metadata_fetches = FuturesOrdered::new();
+        for ((crate_path, crate_name), releases) in &releases_by_crate {
+            for release in releases {
+                metadata_fetches.push_back({
+                    let user = Arc::clone(user);
+                    let gitlab = &self.gitlab;
+                    let cache = &self.metadata_cache;
+                    let fetch_concurrency = &fetch_concurrency;
+                    let checksum = &release.checksum;
+                    let version = &release.version;
+                    async move {
+                        let _guard = fetch_concurrency.acquire().await?;
+                        debug!("Fetching metadata for {crate_name}-{version}");
+                        Self::fetch_metadata(
+                            gitlab, cache, crate_path, checksum, crate_name, version, &user,
+                        )
+                        .await
+                    }
+                });
+            }
+        }
 
         // a reusable buffer for writing the metadata json blobs out to
         // for each package
-        let mut buffer = BytesMut::new();
-
-        for ((crate_path, crate_name), releases) in &releases_by_crate {
+        let mut buffer = BytesMut::new().writer();
+        for ((_, crate_name), releases) in &releases_by_crate {
             for release in releases {
-                let checksum = &release.checksum;
-                let version = &release.version;
-
-                debug!("Fetching metadata for {}-{}", crate_name, version);
-
-                // parses the `cargo metadata` stored in the release, which
-                // should be stored under `metadata.json`.
-                let meta = self
-                    .fetch_metadata(crate_path, checksum, crate_name, version)
-                    .await?;
-
-                // each crates file in the index is a metadata blob for
-                // each version separated by a newline
-                buffer.extend_from_slice(&serde_json::to_vec(&*meta)?);
-                buffer.put_u8(b'\n');
+                match metadata_fetches
+                    .next()
+                    .await
+                    .expect("invalid metadata_fetches")
+                {
+                    Ok(meta) => {
+                        // each crates file in the index is a metadata blob for
+                        // each version separated by a newline
+                        serde_json::to_writer(&mut buffer, &*meta)?;
+                        buffer.get_mut().put_u8(b'\n');
+                    }
+                    // continue after errors, metadata files may be missing etc
+                    Err(error) => error!(%error, ?release, "fetch_metadata failed"),
+                }
             }
 
             // insert the crate version metadata into the packfile
             packfile.insert(
                 &get_crate_folder(crate_name),
                 Arc::clone(crate_name),
-                buffer.split().freeze(),
+                buffer.get_mut().split().freeze(),
             )?;
         }
 
diff --git a/test/create_pat.py b/test/create_pat.py
index 4ee3234..1266ecb 100644
--- a/test/create_pat.py
+++ a/test/create_pat.py
@@ -12,7 +12,7 @@
 
 BASE_URL = "http://127.0.0.1"
 SIGN_IN_URL = BASE_URL + "/users/sign_in"
-PAT_URL = BASE_URL + "/-/profile/personal_access_tokens"
+PAT_URL = BASE_URL + "/-/user_settings/personal_access_tokens"
 
 session = requests.Session()
 
--
rgit 0.1.3