Implements Connection Pool Destroy Delay

[waahm7]

Description of changes: Problem: If the user makes requests serially, we destroy the connection pool between each request, which impacts performance.

Solution: Add a 3-second delay before destroying the connection pool, unless the Client is also being destroyed. If the user makes another request within those 3 seconds, the connection pool is not destroyed.

Benchmark: Downloading 1000 64Kb files in serial on c5n.18xlarge

Main Branch:
Run:1 Secs:33.994031 Gb/s:0.015423
Run:2 Secs:34.439879 Gb/s:0.015223
Run:3 Secs:35.191540 Gb/s:0.014898
Run:4 Secs:34.023091 Gb/s:0.015410
Run:5 Secs:34.815079 Gb/s:0.015059
Run:6 Secs:35.207595 Gb/s:0.014891
Run:7 Secs:36.181037 Gb/s:0.014491
Run:8 Secs:35.388686 Gb/s:0.014815
Run:9 Secs:35.315042 Gb/s:0.014846
Run:10 Secs:37.175047 Gb/s:0.014103
Overall Throughput (Gb/s) Median:0.014895 Mean:0.014916 Min:0.014103 Max:0.015423 Variance:0.000000 StdDev:0.000384
Overall Duration (Secs) Median:35.199567 Mean:35.173103 Min:33.994031 Max:37.175047 Variance:0.847040 StdDev:0.920348
Peak RSS:20.632812 MiB

This PR:
Run:1 Secs:21.822355 Gb/s:0.024025
Run:2 Secs:18.661068 Gb/s:0.028095
Run:3 Secs:16.470886 Gb/s:0.031831
Run:4 Secs:16.819767 Gb/s:0.031171
Run:5 Secs:15.395681 Gb/s:0.034054
Run:6 Secs:16.630556 Gb/s:0.031526
Run:7 Secs:16.218798 Gb/s:0.032326
Run:8 Secs:16.514378 Gb/s:0.031747
Run:9 Secs:17.100299 Gb/s:0.030660
Run:10 Secs:16.876424 Gb/s:0.031066
Overall Throughput (Gb/s) Median:0.031348 Mean:0.030650 Min:0.024025 Max:0.034054 Variance:0.000007 StdDev:0.002620
Overall Duration (Secs) Median:16.725162 Mean:17.251021 Min:15.395681 Max:21.822355 Variance:2.927835 StdDev:1.711092
Peak RSS:20.628906 MiB

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.45%. Comparing base (e91577e) to head (4c45503).

Additional details and impacted files

[](https://app.codecov.io/gh/awslabs/aws-c-s3/pull/412?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs) ```diff @@ Coverage Diff @@ ## main #412 +/- ## ========================================== + Coverage 89.37% 89.45% +0.08% ========================================== Files 20 20 Lines 5854 5900 +46 ========================================== + Hits 5232 5278 +46 Misses 622 622 ``` | [Files](https://app.codecov.io/gh/awslabs/aws-c-s3/pull/412?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs) | Coverage Δ | | |---|---|---| | [source/s3\_client.c](https://app.codecov.io/gh/awslabs/aws-c-s3/pull/412?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-c291cmNlL3MzX2NsaWVudC5j) | `88.40% <100.00%> (+0.23%)` | :arrow_up: | | [source/s3\_endpoint.c](https://app.codecov.io/gh/awslabs/aws-c-s3/pull/412?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-c291cmNlL3MzX2VuZHBvaW50LmM=) | `91.87% <100.00%> (+1.50%)` | :arrow_up: |