`Service Time` measurement Trail_Approach_1

[saimedhi]

Description

• Service time is calculated within the perform_request function of the Connection class ( This draft uses RequestsHttpConnection) at the point where the server call is made.

• The calculated service time is added to the response or data in the connection.

• I understand that this method is not ideal for returning service time and am exploring alternative options for improvement.

Issues Resolved

Related to #678

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[saimedhi]

Sample usage

host = 'localhost'
port = 9200
auth = ('admin', 'admin') # For testing only. Don't store credentials in code.

client = OpenSearch(
    hosts = [{'host': host, 'port': port}],
    http_auth = auth,
    use_ssl = True,
    verify_certs = False,
    connection_class = RequestsHttpConnection,
    calculate_service_time = True,
)

client.info()

{'name': 'c3b344c0372b', 'cluster_name': 'docker-cluster', 'cluster_uuid': 'f6p2z4YRQvGW8nknOPgPeg', 'version': {'distribution': 'opensearch', 'number': '2.11.1', 'build_type': 'tar', 'build_hash': '6b1986e964d440be9137eba1413015c31c5a7752', 'build_date': '2023-11-29T21:45:35.524809067Z', 'build_snapshot': False, 'lucene_version': '9.7.0', 'minimum_wire_compatibility_version': '7.10.0', 'minimum_index_compatibility_version': '7.0.0'}, 'tagline': 'The OpenSearch Project: https://opensearch.org/', '__client': {'Service_Time': '0.43622279167175293'}}

[codecov[bot]]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (4b69c09) 72.14% compared to head (921cd55) 72.13%.

Files	Patch %	Lines
opensearchpy/connection/http_requests.py	62.50%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #679 +/- ## ========================================== - Coverage 72.14% 72.13% -0.02% ========================================== Files 89 89 Lines 7945 7952 +7 ========================================== + Hits 5732 5736 +4 - Misses 2213 2216 +3 ```

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[dblock]

This is a good start and shows what we're trying to achieve.

What do you think about an idea where we first expose "events", then add "metrics"? Googling I found https://stackoverflow.com/questions/443885/python-callbacks-delegates-what-is-common and https://pypi.org/project/Events/ that could be a start. The client could expose events such as "request started", "finished", "errored", etc., and then another class called Metrics or Measurements could collect time information using this event system.