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283 lines
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283 lines
13 KiB
Markdown
Cloudgizer: An introduction to a new open source web development tool
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======
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[Cloudgizer][1] is a free open source tool for building web applications. It combines the ease of scripting languages with the performance of [C][2], helping manage the development effort and run-time resources for cloud applications.
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Cloudgizer works on [Red Hat][3]/[CentOS][4] Linux with the [Apache web server][5] and [MariaDB database][6]. It is licensed under [Apache License version 2][7].
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### Hello World
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In this example, we output an [HTTP][8] header and Hello World, followed by a horizontal line:
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```
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#include "cld.h"
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void home()
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{
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/*<
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output-http-header
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Hello World!
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<hr/>
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>*/
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}
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```
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Cloudgizer code is written as a C comment with `/*<` and `>*/` at the beginning and ending, respectively.
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Writing output to the web client is as simple as directly writing [HTML][9] code in your source. There are no API calls or special markups for that—simplicity is good because HTML (or [JavaScript][10], [CSS][11], etc.) will probably comprise a good chunk of your code.
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### How it works
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Cloudgizer source files (with a `.v` extension) are translated into C code by the `cld` command-line tool. C code is then compiled and linked with the web server and your application is ready to be used. For instance, generated code for the source file named `home.v` would be `__home.c`, if you'd like to examine it.
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Much of your code will be written as "markups," small snippets of intuitive and descriptive code that let you easily do things like the following:
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* database queries
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* web programming
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* encoding and encryption
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* executing programs
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* safe string manipulation
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* file operations
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* sending emails
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and other common tasks. For less common tasks, there is an API that covers broader functionality. And ultimately, you can write any C code and use any libraries you wish to complete your task.
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The `main()` function is generated by Cloudgizer and is a part of the framework, which provides Apache and database integration and other services. One such service is tracing and debugging (including memory garbage collection, underwrite/overwrite detection, run-time HTML linting, etc.). A program crash produces a full stack, including the source code lines, and the crash report is emailed to you the moment it happens.
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A Cloudgizer application is linked with the Apache server as an Apache module in a pre-fork configuration. This means the Apache web server will pre-fork a number of processes and direct incoming requests to them. The Apache module mechanism provides high-performance request handling for applications.
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All Cloudgizer applications run under the same Linux user, with each application separated under its own application directory. This user is also the Apache user; i.e., the user running the web server.
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Each application has its own database with the name matching that of the application. Cloudgizer establishes and maintains database connections across requests, increasing performance.
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### Development process
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The process of compiling your source code and building an installation file is automated. By using the `cldpackapp` script, you’ll transform your code into pure C code and create an installation file (a [.tar.gz file][12]). The end user will install this file with the help of a configuration file called `appinfo`, producing a working web application. This process is straightforward:
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The deployment process is designed to be automated if needed, with configurable parameters.
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### Getting started
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The development starts with installing [the Example application][13]. This sets up the development environment; you start with a Hello World and build up your application from there.
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The Example application also serves as a smoke test because it has a number of code snippets that test various Cloudgizer features. It also gives you a good amount of example code (hence the name).
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There are two files to be aware of as you start:
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* `cld_handle_request.v` is where incoming requests (such as `GET`, `POST`, or a command-line execution) are processed.
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* `sourcelist` lists all your source code so that Cloudgizer can make your application.
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In addition to `cld_handle_request.v`, `oops.v` implements an error handler, and `file_too_large.v` implements a response to an upload that's too large. These are already implemented in the Example application, and you can keep them as they are or tweak them.
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Use `cldbuild` to recompile source-file (`.v`) changes, and `cldpackapp` to create an installer file for testing or release delivery via `cldgoapp`:
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Deployment via `cldgoapp` lets you install an application from scratch or update from one version to another.
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### Example
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Here's a stock-ticker application that updates and reports on ticker prices. It is included in the Example application.
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#### The code
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The request handler checks the URL query parameter page, and if it's `stock`, it calls `function stock()`:
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```
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#include "cld.h"
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void cld_handle_request()
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{
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/*<
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input-param page
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if-string page="stock"
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c stock ();
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else
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report-error "Unrecognized page %s", page
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end-if
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>*/
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}
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```
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The implementation of function `stock()` would be in file `stock.v`. The code adds a stock ticker if the URL query parameter action is `add` or shows all stock tickers if it is `show`.
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```
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#include "cld.h"
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void stock()
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{
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/*<
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output-http-header
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<html>
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<body>
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input-param action
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if-string action="add"
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input-param stock_name
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input-param stock_price
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run-query#add_data = "insert into stock \
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(stock_name, stock_price) values \
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(<?stock_name?>, <?stock_price?>) \
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on duplicate key update \
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stock_price=<?stock_price?>"
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query-result#add_data, error as \
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define err
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if atoi(err) != 0
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report-error "Cannot update \
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stock price, error [%s]",err
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end-if
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end-query
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<div>
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Stock price updated!
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</div>
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else-if-string action="show"
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<table>
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<tr>
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<td>Stock name</td>
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<td>Stock price</td>
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</tr>
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run-query#show_data = "select stock_name, \
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stock_price from stock"
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<tr>
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<td>
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query-result#show_data, stock_name
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</td>
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<td>
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query-result#show_data, stock_price
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</td>
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</tr>
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end-query
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</table>
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else
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<div>Unrecognized request!</div>
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end-if
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</body>
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</html>
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>*/
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}
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```
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#### The database table
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The SQL table used would be:
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```
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create table stock (stock_name varchar(100) primary key, stock_price bigint);
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```
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#### Making and packaging
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To include `stock.v` in your Cloudgizer application, simply add it to the sourcelist file:
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```
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SOURCE_FILES=stock.v ....
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...
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stock.o : stock.v $(CLDINCLUDE)/cld.h $(HEADER_FILES)
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...
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```
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To recompile changes to your code, use:
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```
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cldbuild
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```
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To package your application for deployment, use:
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```
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cldpackapp
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```
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When packaging an application, all additional objects you create (other than source code files), should be included in the `create.sh` file. This file sets up anything that the Cloudgizer application installer doesn't do; in this case, create the above SQL table. For example, the following code in your `create.sh` might suffice:
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```
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echo -e "drop table if exists stock;\ncreate table stock (stock_name varchar(100) primary key, stock_price bigint);" | mysql -u root -p$CLD_DB_ROOT_PWD -D $CLD_APP_NAME
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```
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In `create.sh`, you can use any variables from the `appinfo` file (an installation configuration file). Those variables always include `CLD_DB_ROOT_PWD` (the root password database, which is always automatically cleared after installation for security), `CLD_APP_NAME` (the application and database name), `CLD_SERVER` (the URL of the installation server), `CLD_EMAIL` (the administration and notification email address), and others. You also have `CLD_APP_HOME_DIR` (the application's home directory) and `CLD_APP_INSTALL_DIR` (the location where the installation .tar.gz file had been unzipped so you can copy files from it). You can include any other variables in the `appinfo` file that you find useful.
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#### Using the application
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If your application name is 'myapp' running on myserver.com, then the URL to update a stock ticker would be this:
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```
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https://myserver.com/go.myapp?page=stock&action=add&stock_name=RHT&stock_price=500
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```
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and the URL to show all stock tickers would be this:
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```
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https://myserver.com/go.myapp?page=stock&action=show
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```
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(The URL path for all Cloudgizer applications always starts with `go.`; in this case, `go.myapp`.)
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### Download and more examples
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For more examples or download and installation details, visit [Zigguro.org/cloudgizer][14]. You'll also find the above example included in the installation (see [the Example application source code][15]).
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For a much larger real-world example, check out the [source code][16] for [Rentomy][17], a free open source cloud application for rental property managers, written entirely in Cloudgizer and consisting of over 32,000 lines of code.
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### Why use Cloudgizer?
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Here's why Rentomy is written in Cloudgizer:
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Originally, the goal was to use one of the popular [scripting languages][18] or [process virtual machines][19] like [Java][20], and to host Rentomy as a [Software-as-a-Service][21] (Saas) free of charge.
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Since there are nearly 50 million rental units in the US alone, a free service like this needs superior software performance.
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So squeezing more power from CPUs and using less RAM became very important. And with [Moore's Law slowing down][22], the bloat of popular web languages is costing more computing resources—we're talking about process-virtual machines, interpreters, [p-code generators][23], etc.
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Debugging can be a pain because more layers of abstraction exist between you and what's really going on. Not every library can be easily used, so some functional and interoperability limitations remain.
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On the other hand, in terms of big performance and a small footprint, there is no match for C. Most libraries are written in C for the same reason, so virtually any library you need is available, and debugging is straightforward.
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However, C has issues with memory and overall safety (overwrites, underwrites, garbage collection, etc.), usability (it is low-level), application packaging, etc. And equally important, much of the development cost lies in the ease of writing and debugging the code and in its accessibility to novices.
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From this perspective, Cloudgizer was born. Greater performance and a smaller footprint mean cheaper computing power. Easy, stable coding brings Zen to the development process, as does the ability to manage it better.
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In hindsight, using Cloudgizer to build Rentomy was like using a popular scripting language without the issues.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/18/8/cloudgizer-intro
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作者：[Sergio Mijares][a]
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选题：[lujun9972](https://github.com/lujun9972)
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://opensource.com/users/sergio-mijares
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[1]:https://zigguro.org/cloudgizer/
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[2]:https://en.wikipedia.org/wiki/C_%28programming_language%29
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[3]:https://www.redhat.com/en
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[4]:https://www.centos.org/
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[5]:http://httpd.apache.org/
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[6]:https://mariadb.com/
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[7]:http://www.apache.org/licenses/LICENSE-2.0
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[8]:https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol
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[9]:https://en.wikipedia.org/wiki/HTML
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[10]:https://en.wikipedia.org/wiki/JavaScript
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[11]:https://en.wikipedia.org/wiki/Cascading_Style_Sheets
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[12]:https://opensource.com/article/17/7/how-unzip-targz-file
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[13]:https://zigguro.org/cloudgizer/#install
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[14]:https://zigguro.org/cloudgizer
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[15]:https://bitbucket.org/zigguro/cloudgizer_example/src
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[16]:https://bitbucket.org/zigguro/rentomy/src
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[17]:https://zigguro.org/rentomy/
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[18]:https://en.wikipedia.org/wiki/Scripting_language
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[19]:https://en.wikipedia.org/wiki/Virtual_machine
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[20]:https://www.java.com/en/
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[21]:https://en.wikipedia.org/wiki/Software_as_a_service
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[22]:https://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/17209/DARPAs-100-Million-Programs-for-a-Silicon-Compiler-and-a-New-Open-Hardware-Ecosystem.aspx
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[23]:https://en.wikipedia.org/wiki/P-code_machine
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