Running `make unit` in a fresh cloned repo fails on `test_compute_elasticsearch`

[lvaylet]

Steps to reproduce (with Python 3.9.12):

$ git clone git@github.com:google/slo-generator.git
$ cd slo-generator
$ python -m venv venv/
$ source venv/bin/activate
$ make develop
$ make unit

[...]

======================================================================
ERROR: test_compute_elasticsearch (tests.unit.test_compute.TestCompute)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/venv/lib/python3.9/site-packages/mock/mock.py", line 1346, in patched
    return func(*newargs, **newkeywargs)
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/tests/unit/test_compute.py", line 104, in test_compute_elasticsearch
    compute(config, CONFIG)
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/slo_generator/compute.py", line 68, in compute
    report = SLOReport(config=slo_config,
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/slo_generator/report.py", line 114, in __init__
    data = self.run_backend(config, backend, client=client, delete=delete)
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/slo_generator/report.py", line 206, in run_backend
    instance = cls(client=client, **backend_cfg)
  File "/usr/local/google/home/lvaylet/workspace/github/google/slo-generator/slo_generator/backends/elasticsearch.py", line 41, in __init__
    self.client = Elasticsearch(**es_config)
TypeError: __init__() got an unexpected keyword argument 'url'

[...]

Ran 42 tests in 2.785s

FAILED (errors=1)
make: *** [Makefile:69: unit] Error 1

[lvaylet]

The test suite completes successfully after pinning elasticsearch to version 7.17.1. The latest 8.x.x release (8.1.1 at the time of writing) probably introduces a breaking change in how the ElasticSearch client is created and configured.

The release notes do not provide any specific migration instructions. However, the Overview pages of versions 7.17 and 8.1 show clear differences in how the client is created and configured:

Overview 7.17

>>> from elasticsearch import Elasticsearch

# By default we connect to localhost:9200
>>> es = Elasticsearch()

Overview 8.1

>>> from elasticsearch import Elasticsearch

# Connect to 'http://localhost:9200'
>>> es = Elasticsearch("http://localhost:9200")

[lvaylet]

@ocervell Passing the url entry of the es_config dictionary to the Elasticsearch client (instead of the whole dictionary) is a simple fix for this bug. However I am not sure about the impact on current deployments.

class ElasticsearchBackend:
    def __init__(self, client=None, **es_config):
        self.client = client
        if self.client is None:
+            self.client = Elasticsearch(es_config['url'])
-            self.client = Elasticsearch(**es_config)

The Elasticsearch client documentation states that:

Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of Elasticsearch. Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.

WDYT?