implement prometheus fast-api-instrumentor for http service metrics

[daniel-salib]

track http level metrics such as requests counts by route/status code, request duration and request size using prometheus fast-api-instrumentor

benchmark serving results:

BEFORE:

Successful requests:                     32741     
Benchmark duration (s):                  651.08    
Total input tokens:                      7238749   
Total generated tokens:                  5967511   
Request throughput (req/s):              50.29     
Output token throughput (tok/s):         9165.57   
Total Token throughput (tok/s):          20283.64  
---------------Time to First Token----------------
Mean TTFT (ms):                          391076.36 
Median TTFT (ms):                        383066.19 
P99 TTFT (ms):                           582484.00 
-----Time per Output Token (excl. 1st token)------
Mean TPOT (ms):                          70.28     
Median TPOT (ms):                        74.56     
P99 TPOT (ms):                           142.45    
---------------Inter-token Latency----------------
Mean ITL (ms):                           69.30     
Median ITL (ms):                         64.55     
P99 ITL (ms):                            102.58    

AFTER:

Successful requests:                     32740     
Benchmark duration (s):                  649.47    
Total input tokens:                      7238464   
Total generated tokens:                  5969746   
Request throughput (req/s):              50.41     
Output token throughput (tok/s):         9191.73   
Total Token throughput (tok/s):          20336.92  
---------------Time to First Token----------------
Mean TTFT (ms):                          402654.72 
Median TTFT (ms):                        402136.79 
P99 TTFT (ms):                           585043.95 
-----Time per Output Token (excl. 1st token)------
Mean TPOT (ms):                          68.99     
Median TPOT (ms):                        63.16     
P99 TPOT (ms):                           142.45    
---------------Inter-token Latency----------------
Mean ITL (ms):                           66.58     
Median ITL (ms):                         56.28     
P99 ITL (ms):                            98.87     

[github-actions]

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[youngkent]

LGTM. Thanks!

[simon-mo]

• Please add this to requirements txt
• Please run load test

[daniel-salib]

@simon-mo the package is actually already included requirements/common.txt I think

will share load test results in PR description shortly

[daniel-salib]

@simon-mo @youngkent benchmark comparison added to PR description