Skip to main content

Angular 2–Angular CLI

With the availability of Angular 2, I started experimenting with Angular CLI, a CLI for Angular 2 applications based on the ember-cli project. The project is still young and I encountered a lot of issues along the way.

Here are some tips and lesssons I learned:

  • Update Node to the latest LTS version(you need at least version 4 or later).
  • Run ng in a command prompt with Admin permissions
  • Be patient. The initial installation as well as ng new take a looooong time.
  • On Windows you need to run the build and serve commands with Admin permissions, otherwise the performance is awful.

Some errors I got:

  • “ng is not recognized as an internal or external command”
    • Check that %AppData%\npm is added to the PATH variable.
  • “SyntaxError: Use of const in strict mode.”
    • You are still using an older Node version that doesn’t support some of the new ES2015 features
  • “Error: Cannot find module 'exists-sync'”
    • For an unknown reason NPM still couldn’t find some packages. I installed them manually using the following command
      • npm install --save exists-sync
  • “The Broccoli Plugin: [BroccoliTypeScriptCompiler] failed with:Error: EMFILE: too many open files”
    • This happened when I tried to run ng test. As a workaround you can run ng build first and then run ng test –-watch false. This will run ng test without watching for file changes.
Labels:

Popular posts from this blog

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME         ...
Read more

Cache stampede: when our cache turned against us

While investigating some performance issues, we ran into an ASP.NET Core API that cached a fairly expensive aggregation query for 60 seconds. Under normal load, that was fine: one request rebuilds the cache, everyone else reads from it. Under peak load, dozens of requests would arrive in that same expiry window, all see a cache miss, and all fire the same expensive query in parallel. The database didn't like that. That was the moment when our caching layer stopped helping and started hurting. A burst of requests comes in at the same time, all miss the cache, and all go hammer the database or the downstream API at once. That's a cache stampede . The cache was supposed to protect our backend, and for a few hundred milliseconds it did the opposite. Why this happens IMemoryCache.GetOrCreate (and its async sibling) looks like it protects you, but it doesn't add any locking on its own. Look at the naive version: public async Task<Report> GetReportAsync(string key) ...
Read more

The role of ActivitySource in OpenTelemetry for .NET

While doing some pair programming to integrate OpenTelemetry tracing to a .NET application, we had a discussion on how to use the ActivitySource . It looks simple. You new one up, give it a name, start an activity, done. The discussion started when we added a second ActivitySource with the exact same name in a different class. This made us wonder: "Are we duplicating traces now? Is this a memory leak? Do we need a singleton?" So we decided to dig deeper. This post is what we learned… What ActivitySource actually is ActivitySource is part of System.Diagnostics , not part of the OpenTelemetry NuGet packages. Microsoft built tracing primitives directly into the BCL, and OpenTelemetry's .NET SDK simply listens to them. This is why you can add distributed tracing to a library without taking a dependency on OpenTelemetry at all. An ActivitySource is a factory for Activity objects, and an Activity is .NET's name for what OpenTelemetry calls a span.(don’t ask m...
Read more