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2. How Heroku Works - Heroku: Up and Running. At the time of writing, Heroku has had over three million separate applications deployed on its infrastructure, and this number grows day by day. Running a large number of applications day to day requires a substantially different approach than running just a handful, and this is one of the reasons that the Heroku architecture is markedly different from what you or I might develop if we were setting up our own environment on our own hardware for a single application.

Heroku’s task is to support the running of all of these applications at the same time, managing the deployments that users are requesting, as well as scaling applications’ needs. In order to achieve this, the Heroku platform is broken up into several key segments; the most important among these are: In addition to these, there are a number of extra components, such as the Logplex and the various add-ons and services available to your applications (see Figure 2-1). So, let’s walk through all of these parts in turn.

Figure 2-2. HTTP Routing. Last updated 10 November 2015 The Heroku platform automatically routes HTTP requests sent to your app’s hostname(s) to your web dynos. The entry point for all applications on the Cedar stack is the domain which offers a direct routing path to your web dynos. This article provides a detailed reference of how the router behaves, and how it conforms to the HTTP specification. Routing Inbound requests are received by a load balancer that offers SSL termination. From here they are passed directly to a set of routers. The routers are responsible for determining the location of your application’s web dynos and forwarding the HTTP request to one of these dynos. A request’s unobfuscated path from the end-client through the Heroku infrastructure to your application allows for full support of HTTP 1.1 features such as chunked responses, long polling, websockets, and using an async webserver to handle multiple responses from a single web process.

Request distribution Request queueing Caching. Warming Up a Java Process. Last updated 04 November 2015 The first request made to a Java or JVM web application is often substantially slower than the average response time over the life of the process. This warm-up period can usually be attributed to lazy class loading and just-in-time compilation, which optimize the runtime for subsequent requests that execute identical code. As a result, many users find it beneficial to submit a few artificial requests into the JVM process before using it to handle real traffic. Even a simple set of no-op requests to your application can warm-up the networking and messaging parts of the stack, which usually constitute a large portion of the request overhead.

This article describes one strategy for implementing such behavior on Heroku. Prebooting an application In order to do anything with a process before the router starts sending it requests, you must enable Heroku’s Preboot feature. Creating a warm-up script To send the requests, add this code next: Enabling the warm-up script. Development and Configuration Principles. Last updated 13 October 2015 Using Heroku as your deployment environment not only impacts the runtime aspects of your application, but also its development process.

Included here are several principles of application development and configuration central to the development experience on Heroku. These development and configuration principles are one of several categories of best-practices when developing for Heroku. Please review all the principles of architecting applications to gain a complete understanding of properly developing apps on Heroku. Applications & codebases When developing an app most of the work is done on the application’s codebase which is stored in some form of version control system (VCS) like Git, Subversion, Mercurial etc… The VCS keeps track of the many revisions of the codebase and coordinates the modifications to the source code amongst development teams of all sizes.

On deployment to Heroku your app will be transmitted via the Git VCS. Dependencies Configuration. Managing Multiple Environments for an App. Last updated 30 May 2018 Your Heroku app runs in at least two environments: On your local machine (i.e., development).Deployed to the Heroku platform (i.e., production) Ideally, your app should run in two additional environments: Test, for running the app’s test suite safely in isolationStaging, for running a new build of the app in a production-like setting before promoting it You can help prevent buggy code from being deployed to production by maintaining these separate environments as different Heroku apps, and by using each environment only for its intended purpose.

This strategy is particularly important because Heroku’s Linux stacks likely differ from your development machine’s operating system. Heroku provides helpful tools (namely pipelines, Heroku CI, and review apps) for creating and maintaining your app’s staging and test environments. Creating a staging environment Let’s say you have an application running on your local (development) machine and you’re ready to push it to Heroku. Heroku Postgres. Last updated 30 October 2015 Heroku Postgres is the SQL database service run by Heroku that is provisioned and managed as an add-on.

Heroku Postgres is accessible from any language with a PostgreSQL driver including all languages and frameworks supported by Heroku: Java, Ruby, Python, Scala, Play, Node.js, PHP, Go, and Clojure. In addition to a variety of management commands available via the Heroku CLI, Heroku Postgres features a web dashboard, the ability to create dataclips and several additional services on top of a fully managed database service. Provisioning the add-on Many buildpacks (what compiles your application into a runnable entity on Heroku) automatically provision a Heroku Postgres instance for you.

. $ heroku addons | grep POSTGRES heroku-postgresql:hobby-dev HEROKU_POSTGRESQL_RED In order for Heroku to manage this add-on for you and respond to a variety of operational situations, the value of this config var may change at any time. Create a new database Establish primary DB !


AddOn. 1. Getting Started with Heroku - Heroku: Up and Running. Chapter 1. Getting Started with Heroku All day, every day, the Internet gets larger and larger, and recent estimates show simply phenomenal growth. Every minute, the Web is growing at a rate of over 500 new sites, while popular video hosting service YouTube is said to be receiving over 48 hours of new video content. Twitter users create over 100,000 new tweets, while Facebook users share over 600,000 new posts. To the common observer, these numbers are amazing. However, to the developer, these numbers are simply incredible, not only because of the sheer size of the applications required to support this growth, but also the infrastructure in the form of servers and bandwidth required to keep these services ticking over happily 24/7.

The Dawn of Virtual Servers Now fast-forward a few years. The first decade of this century brought the concept of cloud computing. Because the vendor is in complete control of the capacity and the ancillary services, new possibilities are available. Shared state.