fix request head timeout

[robjtede]

PR Type

Fix and Docs

PR Checklist

• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.
• A changelog entry has been made for the appropriate packages.
• Format code with the latest stable rustfmt.
• (Team) Label with affected crates and semver status.

Overview

TODO:

• perf testing
• unboxing can come later given the perf testing

closes #1269

[robjtede]

not seeing any big difference in perf:

# before
 › vegeta attack -targets=target.list -duration=40s -rate=100/s | tee results.bin | vegeta report
Requests      [total, rate, throughput]         4000, 100.02, 100.02
Duration      [total, attack, wait]             39.99s, 39.99s, 237.958µs
Latencies     [min, mean, 50, 90, 95, 99, max]  71.75µs, 700.113µs, 539.2µs, 1.137ms, 1.681ms, 4.469ms, 10.014ms
Bytes In      [total, mean]                     7432000, 1858.00
Bytes Out     [total, mean]                     0, 0.00
Success       [ratio]                           100.00%
Status Codes  [code:count]                      200:4000
Error Set:

# after
 › vegeta attack -targets=target.list -duration=40s -rate=100/s | tee results.bin | vegeta report
Requests      [total, rate, throughput]         4000, 100.02, 100.02
Duration      [total, attack, wait]             39.991s, 39.99s, 338.791µs
Latencies     [min, mean, 50, 90, 95, 99, max]  87µs, 689.905µs, 521.139µs, 1.174ms, 1.731ms, 4.375ms, 10.126ms
Bytes In      [total, mean]                     7432000, 1858.00
Bytes Out     [total, mean]                     0, 0.00
Success       [ratio]                           100.00%
Status Codes  [code:count]                      200:4000
Error Set: