Missing documentation on how to manage a 404 when querying Cosmos

In our program we perform LINQ queries with the SDKv3 with a helper method that looks something like the following example :

IQueryable<TEntity> cosmosQuery = _container.GetItemLinqQueryable<TEntity>(
    continuationToken: continuationToken,
    requestOptions: queryOptions
);

if (filter != null)
    cosmosQuery = cosmosQuery.Where(filter);

if (orderBy != null)
    cosmosQuery = cosmosQuery.OrderByDescending(orderBy);

var query = cosmosQuery.Select(select).ToFeedIterator();

var iterator = cosmosQuery.ToFeedIterator();
var items = new List<TEntity>();
while (iterator.HasMoreResults)
{
    var item = await iterator.ReadNextAsync();
    items.AddRange(item);
}
return items;

It happens occasionally that the ReadNextAsync raises a Cosmos Exception with StatusCode 404 and SubStatus 0. Message from ApplicationInsights:

Response status code does not indicate success: NotFound (404); Substatus: 0; ActivityId: ; Reason: ();

The documentation specifies that this is expected behavior and the reason is:

The collection is no longer a resource. For example, the resource may have been deleted.

What I can’t find anywhere is how to manage this exception. Could I simply get a new Iterator?

...
var query = cosmosQuery.Select(select).ToFeedIterator();
try {
    var iterator = cosmosQuery.ToFeedIterator();
    var items = new List<TEntity>();
    while (iterator.HasMoreResults)
    {
        var item = await iterator.ReadNextAsync();
        items.AddRange(item);
    }
    return items;
}
catch (CosmosException e) when (e.StatusCode == HttpStatusCode.NotFound)
{
    var iterator = cosmosQuery.ToFeedIterator();
    var items = new List<TEntity>();
    while (iterator.HasMoreResults)
    {
        var item = await iterator.ReadNextAsync();
        items.AddRange(item);
    }
    return items;
}

Or do I need to open a new IOrderedQueryable from the Container? I know that the code is really ugly but I hope that I pointed my needs.

Thank you all!

[Ettores88]

@j82w the exception.ToString() is the one that I already provided: “Response status code does not indicate success: NotFound (404); Substatus: 0; ActivityId: ; Reason: ();”

I cannot get the “ResponseMessage.Diagnostics.ToString()” 'cause a CosmosException is raised from the SDK when the Response is 404. But I see that CosmosException contains a Diagnostics property so with a HOTFIX we are going to trace that out.

[j82w]

@Ettores88 can you provide either the ResponseMessage.Diagnostics.ToString() or exception.ToString() of those 404?