Short version: What reasons could there be for a sudden, dramatic, and seemingly permanent increase in the rate of timing-out Azure queue requests?
It's going to be difficult to provide all of the details that could possibly be relevant here, but here's a start:
This is an Azure application (SDK v2.0) with a WCF service placing work requests on a queue (roughly 100k calls a day) and a couple of worker roles which process the queue. We've got New Relic monitoring with the latest .NET agent (3.3.38).
We've run into an issue in our latest release, deployed a few days ago -- after it ran normally for about 24 hours, all of a sudden we started seeing a greatly increased rate of timeouts when our worker roles fetch messages from the queue, along with a catastrophic drop in throughput (our application can now barely keep up with its own queue using 40 workers, whereas it usually gets by with just 2!) Ever since the timeouts started, they show no signs of letting up, keeping up at the same rate since it started happening.
A couple images from New Relic to illustrate:
While this isn't nearly enough information to provide a good answer, I'm just trying to figure out where I might start looking. I've got support tickets open with New Relic and Microsoft, but we're trying to investigate on our own as well. Could this be throttling? Some kind of resource exhaustion in my queue processor worker role? We don't see increased load on the WCF service, and we haven't changed Azure client libraries or changed much of anything in the code that processes the queue.
I suggest you enable analytics on your storage account to determine if the bottleneck is server side or client side/network related. Specifically, you can look at Storage Analytics Metrics table - AverageE2ELatency and AverageServerLatency properties to check if the issue is server side or client side.
You can learn more about Azure storage analytics from links below
Overview:
http://msdn.microsoft.com/en-us/library/hh343270.aspx
How to enable in portal:
http://azure.microsoft.com/en-us/documentation/articles/storage-monitor-storage-account/
Metrics table Schema:
http://msdn.microsoft.com/en-us/library/hh343264.aspx
Blog post:
http://blogs.msdn.com/b/windowsazurestorage/archive/2011/08/03/windows-azure-storage-analytics.aspx
Related
We have a doubt about Azure because in some cases we have some dead times when we received requests in one of our AppServices or when a Service Bus triggers, for example, an Azure Functions.
If you see this image, you will see an example:
AppInsight Example Image
We execute a Request and at 5 seconds, but Azure delays more than 30 seconds to start the execution. We made a lot of optimizations in our apps, but we have no visibility about this delay.
Did someone face the same issue and found some solution? We believe it is a performance issue in the Workers, but, this happens also when the Workers are with a low load of memory and CPU. So we don't know how to scale horizontally automatically the resource if it is without load.
This happens also in our AZF, but we believe it's an issue between the Service Bus and the container of the AZF. In these cases we found the AZF has a higher consumption of CPU, but we don't why, because in the local environment we process a lot of messages with multithreading without any problem.
We use Application insights from Azure Functions, currently documenting outage scenarios for different Azure Components. What'll be the impact on Functions if Application Insights service goes down? I hope it doesn't impact Function executions and they continue to operate as normal.
Also when it comes back online, let's say half an hour after the outage, would all the logs done during that time will be lost?
What'll be the impact on Functions if Application Insights service goes down? I hope it doesn't impact Function executions and they continue to operate as normal.
It does not. Functions will continue to run as usual.Telemetry submitting is done in the background anyway.
Also when it comes back online, let's say half an hour after the outage, would all the logs done during that time will be lost?
It depends on what Channel is configured. The Application Insights .NET and .NET Core SDKs ship with two built-in channels:
InMemoryChannel: A lightweight channel that buffers items in memory until they're sent. Items are buffered in memory and flushed once every 30 seconds, or whenever 500 items are buffered. This channel offers minimal reliability guarantees because it doesn't retry sending telemetry after a failure. This channel also doesn't keep items on disk, so any unsent items are lost permanently upon application shutdown (graceful or not). This channel implements a Flush() method that can be used to force-flush any in-memory telemetry items synchronously.
ServerTelemetryChannel: A more advanced channel that has retry policies and the capability to store data on a local disk. This channel retries sending telemetry if transient errors occur. This channel also uses local disk storage to keep items on disk during network outages or high telemetry volumes.
When using the ServerTelemetryChannel you may need to configure the location where telemetry will be stored during the downtime. See also the docs regarding offline storage
I have a web app in production (.Net Core), I deployed it in Azure as App service which is in premium tier p2v2 4 instances. I am also using Azure Redis cache (Premium Tier) which my app is using it as cache. I have two app services (primary and secondary) configured Traffic Manager for load balancing.
Whenever I am trying to deploy my app into production using swap slot feature, Both the app service response time goes up to 20 secs and it is down for around 1 minute and my CPU utilization goes close to 90%. And I am seeing multiple exceptions from Redis client (For ex: No connection is available to service this operation: EVAL; It was not possible to connect to the Redis server(s). To create a disconnected multiplexer, disable AbortOnConnectFail. ConnectTimeout; IOCP: (Busy=0,Free=1000,Min=8,Max=1000), WORKER: (Busy=452,Free=32315,Min=8,Max=32767), Local-CPU: n/a) and my HttpQueue length goes above 10
I can infer from the above image is that worker thread has been overloaded, Donno why it is happening
I am using .Net StackExchange Redis client version 2.0.601, recently did an update from version 1.2.4
Note:
I didn't use slot specific app setting.
It keeps happening for every swap slots during deployment
I didn't find any app service restart in the logs.
I want to know any of you guys are facing this issue, if yes please suggest me where is the problem or how to debug and it would also better if you can share any of things you tried.
I tried to find any error logs in AZure Redis cache server but couldn't find any.
I am trying to figure out what is causing this issue, how to debug this kind of issues with azure, and whether anybody encountered the same and have implemented any resolution for the same?
Please let me know if you need any additional details.
Here is something which might be worth trying :
Cache metrics are reported using several reporting intervals, including Past hour, Today, Past week, and Custom. The Metric blade for each metrics chart displays the average, minimum, and maximum values for each metric in the chart, and some metrics display a total for the reporting interval.
Each metric includes two versions. One metric measures performance for the entire cache, and for caches that use clustering, a second version of the metric that includes (Shard 0-9) in the name measures performance for a single shard in a cache. For example if a cache has 4 shards, Cache Hits is the total amount of hits for the entire cache, and Cache Hits (Shard 3) is just the hits for that shard of the cache.
Try looking for the Error metric while monitoring.
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-how-to-monitor#available-metrics-and-reporting-intervals
Additionally , we need to retry for TimeoutException, RedisConnectionException or SocketException even which ensure it will try to connect in case of any exception, you can read about all the best practises arouns Redis Cache usage in below doc:
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-best-practices
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-best-practices#when-is-it-safe-to-retry
Hope it helps.
We have few of our internal business services hosted on an isolated ASE in Azure.
These services run on a medium app service plan with 2 instances.
This environment has been in production and use for little more than a month now and has been performing fairly well apart from the occasional sudden CPU spike to 100% in one of the instance which bring down the services.
We don't have auto scaling setup but have 2 instances running all the time.
The services are `aspnetcore` webapi and the runtime is dotnet core 2.0.
Every time I have come across this issue in the last couple of weeks I have not been lucky enough to login to kudu and get a process dump to investigate further. The business are literally behind my back to get the service up and running as quick as possible and the easiest route is to restart one of the faulting service or swap slots with a pre-prod environment.
Access to the ASE are also restricted from our network and makes it all the more difficult for me to switch to a WiFi and then go through jump boxes to login to kudu, I had asked our Ops engineer to get me the dump when this issue is reported but he has not been listening to me either, mostly for the same reasons as me not able to do it myself.
All exceptions I can see in Application Insights are due to the service themselves going down and there are no exceptions there which can cause the issue in the first place(at least I've not found it yet)
This lead me to take few guess and look for metrics, the only thing raising my
suspicions is garbage collection. I don't see any sudden spike in GC graphs as well, each time the service is re started the graph is fairly a straight line(24 hours) but increases day by day and ends up like below.
But the working memory is a sinusoid graph letting me think there are no memory leaks. But is the above graph over 3 days normal?
The drop is when I restart the service. But all services have a similar trajectory even the one that has not gone down.
I am not sure if this is a problem with an individual service or an environment configuration I have overlooked.
The API endpoints are simple CRUD operations and publish events to a service bus topic after each operation. There is a static `HttpClient` instance used to fetch data from another service. Apart from that there are no unmanaged resources and the DB connections are always wrapped in `using` statements.
I understand I would need a process dump to investigate further but my biggest concern is why is the application gateway(load balancer) not sending traffic to the healthy instance. Because of the gateway going unhealthy cloudflare returns a `502` response to clients using the api.
MS support haven't been able to help and have not answered if we have our load balancers working correctly.
The average number of requests is about 50-60 per minute.
CPU runs at less than 10% apart this sudden surge.
Thanks
It could be that the backend is pegged at 100% CPU and is unable to respond to Application Gateway health probes. When such an issue occurs, were you able to verify, using Backend health logs, the health state of your backends? If both backend instances were unhealthy, it would explain the 502s. If one of them was healthy and responding to probes, then new requests sent to Application Gateway would indeed flow to the healthy instance. If you suspect that is not the case then please reply back with subscription id, gateway name and approximate time window of incident for us to take a look.
I am relatively new to Azure. I have a website that has been running for a couple of months with not too much traffic...when users are on the system, the various dashboard monitors go up and then flat line the rest of the time. This week, the CPU time when way up when there were no requests and data going in or out of the site. Is there a way to determine the cause of this CPU activity when the site is not active? It doesn't make sense to me that I should have CPU activity being assigned to my site when there is to site activity.
If your website has significant processing at application start, it is possible your VM got rebooted or your app pool recycled and your onstart handler got executed again (which would cause CPU to spike without any request).
You can analyze this by adding application logs to your Application_Start event (but after initializing trace). There is another comment detailing how to enable logging, but you can also consult this link.
You need to collect data to understand what's going on. So first thing I would say is:
1. Go to Azure management portal -> your website (assuming you are using Azure websites) -> dashboard -> operation logs. Try to see whether there is any suspicious activity going on.
download the logs for your site using any ftp client and analyze what's happening. If there is not much data, I would suggest adding more logging in your application to see what is happening or which module is spinning.
A great way to detect CPU spikes and even determine slow running areas of your application is to use a profiler like New Relic. It's a free add on for Azure that collects data and provides you with a dashboard of data. You might find it useful to determine the exact cause of the CPU spike.
We regularly use it to monitor the performance of our applications. I would recommend it.