Category Archives: Coding

Fixing ASPNET Production Issues by adding custom data to App Insights logs

Debugging issues in production is hard. Things vary – seemingly identical requests to the same URL could be made but one succeed and the other fail.

Without information about the context and configuration it’s hard to isolate issue, here is a quick way to get more of that context.

The key is having the data to understand the cause of the failures. One of the things we do to help that is creating our own ITelemetryInitializer for application insights.

In this we track which environment the request was made in, the cloud instance handling the request, code version, UserId and lots more.

This means, if an issue occurs, we have a wealth of data to understand and debug the issue. It’s embedded in every telemetry event tracked.

Here is an example of a Telemetry Initializer which adds the UserID and Azure WebApps Instance Id to tracked events, if a user is signed in. You’ll find, once you start using this you’ll add more information over time.

To get it setup register it, like this, in your Startup.cs:


Go do it now, seriously you’ll need it later!

Running Redis in a Service Fabric cluster

I’m working on a project where we’re in need of a cache inside Service Fabric. Now the cache doesn’t need to be durable just nice, quick and easy to use.

So I came up with the idea of running a Redis cache inside the cluster as a stateless service fabric service. The problem with this is that when the cluster re-balances the services between nodes I will lose the inmemory data in Redis (all of it). What I can do is set the movement cost set to ‘high’, to discourage the cluster from reallocating the service between nodes regularly and causing unnecessary loss of the cache. Great read on how and why the Resource Manager allocations services between nodes here, if you’d like to know more.

It’s worth noting that, if I wanted a durable cache, I could look at using Redis Clustering/Redis as a Service in Azure to prevent this occurring but for what we need it’s overkill.

Either way, I got this up and running and have shared the code here with a ReadMe going into more detail for others that are interested in having a play. Hope it’s useful!

Lawrence Gripper


Build & Push a Docker Image using Visual Studio Online Build vNext

So I’ve got a nice and simple NodeJs app and I want to have a CI build which builds my Docker image and pushes it to my docker hub ready for deployment. I’ll look at deployment in a future post, this time round we’ll focus on the build process.

To get this setup we’ll need to go through two bits, basically VSO uses agents (machines used to execute builds) and a build, which defines some steps that output an artifact (in this case a docker image). So we’ll setup a build agent, where the docker build can run, and then setup the build itself.

Setup the Build Agent

We’re going to need a linux based build agent to build out our docker image and push it to docker hub, as we’re hosting on the linux version of docker. We could also look at using the Windows implementation of Docker, which is available in the most recently Window Server Preview, but I’ll leave this for another day.

To do this we can use the ARM templates from the Azure Marketplace in the new portal to spin up an ubuntu VM then install all the bits we need. One the machine is up and running connect up to it via SSH to start install stuff, if you don’t have a client puttys a good bet.

First up let’s install docker on the agent. (full guide )

sudo curl -sSL | sh

After the docker install I found I had to reboot the machine to get things to behave.

After the reboot, check docker is up and running on the box. Easy way to do this is to type “docker info” at command line and you should get an overview of the Docker install, like so.

Next let’s install the VSO agent so it can pick up and do the builds. (full guide here )

To do this we have to setup apt-get for Ubuntu to install Nodejs:

curl -sL | sudo -E bash -

Then install Nodejs:

sudo apt-get install –yes nodejs

So hopefully that went well and now if you type ‘node –v’ you see it all installed! (This may change over time, install docs for npm are here)

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