162 lines
4.9 KiB
ReStructuredText
162 lines
4.9 KiB
ReStructuredText
Quick Start Guide
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=================
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We'll explain a simple example to help you understand what **Kapow!** can do and
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why it is so awesome :-).
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Scenario
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--------
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In this example we'll consider that our scenario is a corporate network like
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this:
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.. _quickstart_image:
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.. image:: /_static/network.png
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:align: center
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:width: 80%
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Our organization has an external host that acts as a bridge between our intranet
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an the public Internet.
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**Our goal: Our team needs to check if the** :samp:`Internal Host` **is alive.**
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Limitations and Constraints
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---------------------------
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1. We **don't want** to **grant access** to the :samp:`*External Host*` to anybody.
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2. We **don't want** to manage VPNs or any similar solutions to access :samp:`Internal Host` from the Internet.
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3. We **want to limit the actions** that a user can perform in our intranet while it is checking if :samp:`Internal Host` is alive.
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4. We **want** to use the most standard mechanism. Easy to use and automate.
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5. We **don't have a budget** to invest in a custom solution.
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The Desired Solution
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--------------------
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After analyzing the problem and our with our goal in mind, we conclude that it
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is enough **to use a simple** :samp:`ping` **to** :samp:`Internal Host`.
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So, the next step is to **analyze how to perform the ping.**
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Accessing via SSH to :samp:`External Host`
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++++++++++++++++++++++++++++++++++++++++++
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If we choose this option then we need to create a user in the host and grant
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them access via :samp:`SSH` to :samp:`External Host` for every person that needs
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to check the :samp:status of `Internal host`.
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Conclusion: **Not a good idea.**
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Reasons:
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1. We need to manage users (violates a constraint.)
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2. We need to grant usesrs access to a host (violates a constraint.)
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3. We can't control what :samp:`ping` options the user can use to ping :samp:`Internal Host` (violates a constraint.)
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Develop and Deploy a Custom Solution
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++++++++++++++++++++++++++++++++++++
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Ok, this approach could be the best choice for our organization, but:
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1. We'll need to start a new project, develop, test, manage and maintain it.
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2. We need to wait for for the development to be production ready.
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3. We need a budget. Even if we have developers in our organization, their time
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it's not free.
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Conclusion: **Not a good idea.**
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Reasons:
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1. Need to spend money (violates a constraint.)
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2. Need to spend time (and time is money, see reason #1)
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Using Kapow! (spoiler: it's the winner!)
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++++++++++++++++++++++++++++++++++++++++
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Ok, let's analyze **Kapow!** and check if it is compatible with our constraints:
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1. **Kapow!** is Open Source, so **it's also free as in beer**.
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2. By using kapow! we don't need to code our own solution, so we **don't have to waste time**.
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3. By using Kapow! we can run any command in the :samp:`External Host` limiting the command parameters, so **it's safe**.
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4. By using Kapow! we can launch any system command as an HTTP API easily, so **we don't need to grant login access to anybody to** :samp:`External Host`.
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Conclusion: **Kapow! is the best choice.**
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Reasons: It satisfies all of our requirements.
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Using Kapow!
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------------
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In order to get our example :ref:`Scenario <quickstart_image>` working we need to follow the below steps.
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Install Kapow!
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++++++++++++++
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Follow :doc:`Install Kapow! <install_and_configure>` instructions.
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Write a ``ping.pow`` File
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+++++++++++++++++++++++++
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Kapow! uses plain text files (called ``POW`` files) so you can define the
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endpoints you want to expose the system command with. For our example we need a
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file like this:
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.. code-block:: console
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$ cat ping.pow
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kapow route add /ping -c 'ping -c 1 10.10.10.100 | kapow set /response/body'
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Explanation:
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1. :samp:`kapow route add /ping` - adds a new HTTP API endpoint at :samp:`/ping` path in the Kapow! server. You have to use `GET` method to invoke the endpoint.
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2. :samp:`-c` - after this parameter we write the system command that **Kapow!** will run each time the endpoint is invoked.
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3. :samp:`ping -c 1 10.10.10.100` - sends 1 ping package to the host *10.10.10.100*, i.e. :samp:`Internal Host`.
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4. :samp:`| kapow set /response/body` - writes the output of `ping` to the body of the response, so you can see it.
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Launch the Service
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++++++++++++++++++
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At this point we only need to launch `kapow` with our :samp:`ping.pow`:
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.. code-block:: console
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$ kapow server ping.pow
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Consume the Service
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+++++++++++++++++++
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Now we can call our newly created endpoint by using our favorite HTTP client.
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In this example we're using :samp:`curl`:
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.. code-block:: console
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$ curl http://external.host/ping
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PING 10.10.100 (10.10.100): 56 data bytes
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64 bytes from 10.10.100: icmp_seq=0 ttl=55 time=1.425 ms
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et voilà !
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Under the Hood
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++++++++++++++
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To understand what's happening under the hood with **Kapow!** let's see the
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following diagram:
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.. image:: /_static/sequence.png
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:align: center
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:width: 80%
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As you can see, **Kapow!** provides the necessary *magic* to turn a **system
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command** into an ``HTTP API``.
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