What causes "container {container} does not exist" in microsoft/ailab?

Confirm the container exists in the target storage account and that the connection string points to the same account

microsoft/ailab · error · ApplicationException

container does not exist

Error message

container {container} does not exist

What it means

GetFile downloads a blob from an Azure Blob container and first verifies the container exists, throwing ApplicationException('container {container} does not exist') when the check fails. It then verifies the individual blob exists. This is the low-level file fetch used by GetPredictionAsync and other callers, so it surfaces whenever results are requested from a missing container.

Solutions

Confirm the container exists in the target storage account and that the connection string points to the same account
Re-run the analysis pipeline so results are saved before fetching files
Validate/normalize the container id from the request before calling GetFile
Check lifecycle management or cleanup jobs that might have removed the container
Handle ApplicationException in callers to return a clear 'results expired or not found' response

Example fix

// before
var bytes = await service.GetFile(folderId, "original.png");
// after
var c = cloudBlobClient.GetContainerReference(folderId);
if (!await c.ExistsAsync()) throw new ApplicationException($"Prediction {folderId} expired; re-run the analysis");
var bytes = await service.GetFile(folderId, "original.png");

Defensive patterns

Strategy: try-catch

Validate before calling

var c = cloudBlobClient.GetContainerReference(container);
if (!await c.ExistsAsync())
    throw new ApplicationException($"Container {container} does not exist");

Try / catch

try
{
    var bytes = await service.GetFile(container, file);
}
catch (ApplicationException ex) when (ex.Message.StartsWith("container "))
{
    logger.LogWarning(ex, "Missing blob container {Container}", container);
    return NotFound($"Results for {container} are unavailable.");
}

Prevention

Validate container ids from user input (format, existence) before fetching
Translate ApplicationException into meaningful HTTP responses
Verify connection string parity between write and read services
Check cleanup jobs and retention policies against expected result lifetime

When it happens

Trigger: Calling GetFile(container, file) with a container name that has no matching container in the storage account — stale/typo folder id, wrong storage account, or deleted container — or invoking it as part of GetPredictionAsync/data/content flows against a nonexistent folder.

Common situations: Expired or cleaned-up prediction containers; mismatched storage connection string between save and read paths; user-supplied container id containing invalid characters or typos; reading results before the writing run completed.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of microsoft/ailab@89fe2fc620 (2026-09-13). Data as JSON: /api/errors/826d2cecbaa7063a. Report an issue: GitHub.

Appendix: source

Thrown at Sketch2Code/Sketch2Code.Core/Services/ObjectDetectionAppService.cs:292

            detail.OriginalImage = await this.GetFile(folderId, "original.png");
            detail.PredictionImage = await this.GetFile(folderId, "predicted.png");
            detail.PredictedObjects = await this.GetFile<IList<PredictedObject>>(folderId, "results.json");
            var groupBox = await this.GetFile<GroupBox>(folderId, "groups.json");
            detail.GroupBox = new List<GroupBox> { groupBox };

            return detail;
        }
        public async Task<IList<CloudBlobContainer>> GetPredictionsAsync()
        {
            return await Task.Run(() => _cloudBlobClient.ListContainers().Where(l => l.Name != "azure-webjobs-hosts")
                .OrderByDescending(c => c.Properties.LastModified).ToList());
        }
        public async Task<byte[]> GetFile(string container, string file)
        {
            var blobcontainer = _cloudBlobClient.GetContainerReference(container);
            if (!await blobcontainer.ExistsAsync())
            {
                throw new ApplicationException($"container {container} does not exist");
            }
            var blob = blobcontainer.GetBlobReference(file);
            if (!await blob.ExistsAsync())
            {
                throw new ApplicationException($"file {file} does not exist in container {container}");
            }
            using (var ms = new MemoryStream())
            {
                await blob.DownloadToStreamAsync(ms);
                return ms.ToArray();
            }
        }
        public async Task<T> GetFile<T>(string container, string file)
        {
            var data = await this.GetFile(container, file);
            if (data == null) return default(T);
            return JsonConvert.DeserializeObject<T>(Encoding.UTF8.GetString(data));
        }

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