[serve] Replace uuid.uuid4() with getrandbits

[edoakes]

Why are these changes needed?

Reduces CPU overhead (particularly on the proxy). This is less cryptographically secure but should be OK for our use case.

App:

from ray import serve

@serve.deployment(
    max_ongoing_requests=100,
    num_replicas=16,
    ray_actor_options={"num_cpus": 0},
)
class A:
    def __call__(self):
        return b"hi"

app = A.bind()

Benchmark:

ab -n 10000 -c 100 http://127.0.0.1:8000/

Before (~780 qps):

Concurrency Level:      100
Time taken for tests:   12.747 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      1910000 bytes
HTML transferred:       120000 bytes
Requests per second:    784.47 [#/sec] (mean)
Time per request:       127.475 [ms] (mean)
Time per request:       1.275 [ms] (mean, across all concurrent requests)
Transfer rate:          146.32 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.6      0      21
Processing:     5  127  35.7    127     305
Waiting:        3  125  35.8    126     304
Total:          5  127  35.6    128     306

Percentage of the requests served within a certain time (ms)
  50%    128
  66%    138
  75%    147
  80%    153
  90%    170
  95%    188
  98%    210
  99%    224
 100%    306 (longest request)

After (~820 qps):

Concurrency Level:      100
Time taken for tests:   12.130 seconds
Complete requests:      10000
Failed requests:        0
Total transferred:      1910000 bytes
HTML transferred:       120000 bytes
Requests per second:    824.44 [#/sec] (mean)
Time per request:       121.295 [ms] (mean)
Time per request:       1.213 [ms] (mean, across all concurrent requests)
Transfer rate:          153.78 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.5      0       4
Processing:     6  121  30.1    124     230
Waiting:        4  119  30.2    123     228
Total:          7  121  30.0    124     230

Percentage of the requests served within a certain time (ms)
  50%    124
  66%    132
  75%    138
  80%    144
  90%    157
  95%    167
  98%    181
  99%    189
 100%    230 (longest request)

Related issue number

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[GeneDer]