Mongod.start() fails on MongoDB version >= 6.1.0

[juho-workfellow]

Describe the bug
Starting MongoDB fails on versions later than 6.1.0 due to removal of ephemeralForTest engine: https://jira.mongodb.org/browse/SERVER-65151

To Reproduce
This works:

from pymongo_inmemory import MongoClient
import os

os.environ["PYMONGOIM__DOWNLOAD_URL"] = "https://fastdl.mongodb.org/windows/mongodb-windows-x86_64-6.0.0.zip"

client = MongoClient()  # No need to provide host
db = client['testdb']
collection = db['test-collection']
# etc., etc.
client.close()

This fails:

from pymongo_inmemory import MongoClient
import os

os.environ["PYMONGOIM__DOWNLOAD_URL"] = "https://fastdl.mongodb.org/windows/mongodb-windows-x86_64-7.0.3.zip"

client = MongoClient()  # No need to provide host
db = client['testdb']
collection = db['test-collection']
# etc., etc.
client.close()

Changing self.engine to "wiredTiger" here seems to fix the issue: https://github.com/kaizendorks/pymongo_inmemory/blob/master/pymongo_inmemory/mongod.py#L54

Expected behavior
Expected the example code from instructions to run without errors.

Logs

  File "C:\testmongo\minimal.py", line 6, in <module>
    client = MongoClient()  # No need to provide host
  File "C:\testmongo\.venv\lib\site-packages\pymongo_inmemory\_pim.py", line 15, in __init__
    self._mongod.start()
  File "C:\testmongo\.venv\lib\site-packages\pymongo_inmemory\mongod.py", line 144, in start
    while not self.is_healthy:
  File "C:\testmongo\.venv\lib\site-packages\pymongo_inmemory\mongod.py", line 184, in is_healthy
    status = db.command("serverStatus")
  File "C:\testmongo\.venv\lib\site-packages\pymongo\_csot.py", line 107, in csot_wrapper
    return func(self, *args, **kwargs)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\database.py", line 890, in command
    with self.__client._conn_for_reads(read_preference, session) as (
  File "C:\testmongo\.venv\lib\site-packages\pymongo\mongo_client.py", line 1346, in _conn_for_reads
    server = self._select_server(read_preference, session)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\mongo_client.py", line 1303, in _select_server
    server = topology.select_server(server_selector)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\topology.py", line 302, in select_server
    server = self._select_server(selector, server_selection_timeout, address)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\topology.py", line 286, in _select_server
    servers = self.select_servers(selector, server_selection_timeout, address)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\topology.py", line 237, in select_servers
    server_descriptions = self._select_servers_loop(selector, server_timeout, address)
  File "C:\testmongo\.venv\lib\site-packages\pymongo\topology.py", line 259, in _select_servers_loop
    raise ServerSelectionTimeoutError(
pymongo.errors.ServerSelectionTimeoutError: 127.0.0.1:27017: [WinError 10061] No connection could be made because the target machine actively refused it (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms), Timeout: 30s, Topology Description: <TopologyDescription id: 655f3dee8b6bb45d6b5a77e7, topology_type: Unknown, servers: [<ServerDescription ('127.0.0.1', 27017) server_type: Unknown, rtt: None, error=AutoReconnect('127.0.0.1:27017: [WinError 10061] No connection could be made because the target machine actively refused it (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms)')>]>

Context:

• OS: Windows 11
• Version of pymongo_inmemory: 0.4.0
• Version of mongo you are downloading: 6.1.0, 7.0.3

[ekarademir]

Hi @juho-workfellow thank you for the report. I am aware of this behaviour. However I didn't have time to investigate further. With this report I'll try to prioritize it. That being said, I don't have a clear answer to why this is happening. Probably I'm missing some start up configuration.

[juho-workfellow]

I think it's just that pymongo_inmemory tries to use ephemeralForTest engine, which was removed from the latest MongoDB versions.

[Guibod]

In fact you need to overwrite the PYMONGOIM__STORAGE_ENGINE env variable to wiredTiger.

os.environ['PYMONGOIM__STORAGE_ENGINE'] = 'wiredTiger'