_counters not set MongoCheckpointStore about eventuous HOT 5 CLOSED

Hmm, have you got a specific case when it fails? The normal sequence is GetLastChecpoint (unconditionally), then StoreCheckpoint. The _counters[checkpointId] entry is initialised in GetLastCheckpoint, so I assumed it will always work.

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@alexeyzimarev - I copied your Checkpoint and built my own (I didn't want to use Mongo)

readonly ConcurrentDictionary<string, int> _counters = new();

And the first occurance of this being used, as you said is GetLastCheckpoint:

_counters[checkpointId] = 0;

I couldn't see any place where the key was initialised, i.e.:

_counters.Add(checkpointId,0);

As soon as I ran my code, I got an exception when GetLastCheckpoint attempted to update the counter which did not exist.

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@alexeyzimarev - clearly you are not seeing the same issue, so could it be a version problem? But a later version of this ConcurrentDictionary creates a new entry in the Dictionary rather than throw an Exception?

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_counters[checkpointId] = 0; is equivalent to Add if the dictionary entry doesn't exist. That's how dictionaries always worked. I am not sure what the issue is in your case. I've never seen it fail.

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@alexeyzimarev - yeah, can't argue with that. I have tried replicating the issue and no luck. My checkpoint was slightly different, and I am wondering if I had somehow managed to try and use the key before the GetLastCheckpoint init.
Insider my GetLastCheckpoint, I called another method which loaded my checkpoint from a file.
From there, I must have assumed it was what i thought was a lack of .Add being called.

Every day's a school day...

Thanks for taking the time to look at this.

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