176 lines
5.0 KiB
ReStructuredText
176 lines
5.0 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 must be able to check if the** ``Internal Host``
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**is alive on an ongoing basis.**
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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 ``External Host`` to
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anybody.
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2. We **don't want** to manage VPNs or any similar solutions to access
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``Internal Host`` from the Internet.
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3. We **want to limit the actions** that a user can perform in our intranet
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while it is checking if ``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 with our goal in mind, we conclude that it
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is enough to use a simple :program:`ping` to ``Internal Host``.
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So, the next step is to analyze how to perform the :program:`ping`.
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Accessing via SSH to ``External Host``
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++++++++++++++++++++++++++++++++++++++
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If we choose this option, then, for every person that needs to check the status
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of ``Internal host``, we need to create a user in the ``External Host`` and
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grant them ``SSH`` access.
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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 :program:`ping` options the user can use to ping ``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
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to waste time**.
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3. By using *Kapow!* we can run any command in the ``External Host``
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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
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**we don't need to grant login access to** ``External Host`` **to
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anybody**.
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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
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to follow the steps below.
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Install Kapow!
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++++++++++++++
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Follow the :doc:`Installing Kapow! <install_and_configure>` instructions.
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Write a :file:`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. ``kapow route add /ping`` - adds a new `HTTP API` endpoint at ``/ping``
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path in the *Kapow!* server. You have to use ``GET`` method to invoke the
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endpoint.
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2. ``-c`` - after this parameter we write the system command that *Kapow!*
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will run each time the endpoint is invoked.
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3. ``ping -c 1 10.10.10.100`` - sends 1 ping packet to the host
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*10.10.10.100*, i.e. ``Internal Host``.
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4. ``| kapow set /response/body`` - writes the output of :program:`ping` to the body
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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 :program:`kapow` with our :file:`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 :program:`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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