Allow MongoDB to be unavailable

[myieye]

I don't love how I've implemented this.
But, LF classic is a seperate service so it seems reasonable to make it optional and have less development dependencies.
I'm not sure how to make it better.

If anyone thinks this is bad, silly or unnecessary that's fine with me.
Or is there a better way to do this?

[github-actions]

C# Unit Tests

71 tests  +14   71 ✅ +14   9s ⏱️ -1s
12 suites + 1    0 💤 ± 0 
 2 files   ± 0    0 ❌ ± 0 

Results for commit e889b07. ± Comparison against base commit 8c03571.

This pull request removes 3 and adds 17 tests. Note that renamed tests count towards both.

Testing.LexCore.CrdtCommitTests ‑ CanRoundTripCommitChanges
Testing.LexCore.CrdtCommitTests ‑ CanSaveCrdtCommit
Testing.LexCore.CrdtCommitTests ‑ TypePropertyShouldAlwaysBeFirst

Testing.LexCore.CrdtServerCommitTests ‑ CanRoundTripCommitChanges
Testing.LexCore.CrdtServerCommitTests ‑ CanSaveServerCommit
Testing.LexCore.CrdtServerCommitTests ‑ TypePropertyShouldAlwaysBeFirst
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "!")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "#")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "-not-start-with-dash")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "../hacker")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "/hacker")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "_____deleted_____")
Testing.LexCore.ProjectCodeTests ‑ InvalidCodesThrows(code: "_____temp_____")
…

♻️ This comment has been updated with latest results.

[hahn-kev]

there's some weird stuff going on in the IsAvailable call, though I might just rewrite it to use a long delay before checking again so we don't check every single time.

[hahn-kev]

Uh, I'm not sure what you're trying to do here, but I don't think this is what you want. This will attempt to run RunCommandAsync synchronously (via the Wait) and throw if it doesn't finish in time, meanwhile you're awaiting a task that runs that async code as sync. You might want to just do this:

Suggested change

	_isAvailable = await Task.Run(() =>
	{
	return _mongoDatabase.RunCommandAsync((Command<BsonDocument>)"{ping:1}").Wait(100);
	});
	_isAvailable = await _mongoDatabase.RunCommandAsync((Command<BsonDocument>)"{ping:1}")
	.WaitAsync(TimeSpan.FromMilliseconds(100));

this will throw if there's not a response within 100ms, so that still might not be what you want.

[myieye]

No, Wait(100) never throws. It returns a boolean indicating whether the command finished within the timeout:

// Returns:
// true if the System.Threading.Tasks.Task completed execution within the allotted
// time; otherwise, false.

[hahn-kev]

ahh ok, I forget some of them throw on timeout. It would still probably be better to catch exceptions and not use Wait as that's intended as a last resort when calling an Async method from a sync context. I'd use WaitAsync for that instead, although it throws a timeout exception when hitting the timeout.

[myieye]

This doesn't actually seem to work currently. I'm not sure what I did in my initial testing, maybe I set _isAvailable to false explicitly while I was testing or something. Anyway, if Mongo is not up then I just get:

2024-06-04 11:43:48       1 CompositeServerSelector{ Selectors = ReadPreferenceServerSelector{ ReadPreference = { Mode : Primary } }, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 }, OperationsCountServerSelector } 1 aggregate { ClusterId : "1", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "{ ClusterId : 1, EndPoint : "Unspecified/host.docker.internal:27017" }", EndPoint: "Unspecified/host.docker.internal:27017", ReasonChanged: "ServerInitialDescription", State: "Disconnected", ServerVersion: , TopologyVersion: , Type: "Unknown", LastHeartbeatTimestamp: null, LastUpdateTimestamp: "2024-06-04T09:43:47.9909070Z" }] } Waiting for suitable server to become available 29997

And it has nothing to do with my Ping/wait/etc.