Sometimes download from azure blob storage is very slow

Question

When download file from blob storage sometimes it can take more than 10 minutes. What's can be the problem?

STORAGE:
Performance:Premium
Replication:Locally-redundant storage (LRS)
Account kind:BlockBlobStorage
Location:Switzerland North

FILES:
from 4mb to 60mb

CLIENT:
cordova application using "@azure/storage-blob": "12.9.0",
from Italy
connection check: done is always good (>100mb/s)

CODE:
const containerClient = await this.blobServiceClient.getContainerClient(containerParentName);
let blobs = await containerClient.listBlobsByHierarchy("/", { prefix: containerName + "/" });
for await (const blob of blobs) {
const blobClient = await containerClient.getBlobClient(blob.name);
const blobProp = await blobClient.getProperties();
const downloadBlockBlobResponse = await blobClient.download(null, null, {
onProgress: (ev) => {
........
}

METRICS :
E2E Latency very high
Server Latency normal

})

Answer 1

Hello @Mattia Fravezzi

Welcome to Microsoft Q&A Platform.

End-to-end (E2E) latency measures the interval from when Azure Storage receives the first packet of the request until Azure Storage receives a client acknowledgment on the last packet of the response.

There are many different factors that can be related, like operation size, client configuration, client CPU/memory or network path:
https://learn.microsoft.com/en-us/azure/storage/blobs/storage-blobs-latency#factors-influencing-latency

I would recommend checking the article below as starting point:
https://learn.microsoft.com/en-us/azure/storage/common/troubleshoot-latency-storage-analytics-logs

A network capture taken at the time of the issue should help, you can look for retransmits and high response times
If the issue requires remote assistance & collection of logs for further assistance, I request you file a support ticket if you have a support plan

I hope this helps!

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Answer 2

I followed all points in those link, but I didn't solve my problem.
I solved problem adding CDN at Azure storage and connecting there from my mobile application.