184 lines
5.1 KiB
ReStructuredText
184 lines
5.1 KiB
ReStructuredText
.. _quickstart:
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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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.. admonition:: Goal
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:class: hint
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Our team must be able to check if the **Internal Host** is alive on an
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ongoing basis.
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Limitations and Constraints
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---------------------------
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#. We don't want to grant access to the **External Host** to anybody.
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#. 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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#. 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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#. We want to use the most standard mechanism. Easy to use and automate.
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#. 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 :command:`ping` to **Internal Host**.
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So, the next step is to analyze how to perform the :command:`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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.. admonition:: Verdict
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This is **not a good idea**, because:
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#. We'd need to manage users (violates a constraint).
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#. We'd need to grant users access to a host (violates a constraint).
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#. We would not be able to control what options the user could provide to
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:command:`ping` (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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#. We'd need to start a new project, develop, test, manage and maintain it.
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#. We'd need to wait for for the development to be production ready.
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#. We'd 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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.. admonition:: Verdict
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This is **not a good idea**, because:
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#. We'd need to spend money (violates a constraint).
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#. We'd 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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#. *Kapow!* is Open Source, so it's also **free as in beer**.
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#. 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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#. 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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#. 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 anybody**.
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.. admonition:: Verdict
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*Kapow!* is the **best** choice, because it satisfies all of our
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requirements.
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Using *Kapow!*
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--------------
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In order to get our :ref:`example 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 :ref:`installation instructions <installation>`.
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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) where the endpoints you want
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to expose are defined.
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For each endpoint, you can decide which commands get executed.
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For our example we need a 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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Let's dissect this beast piece by piece:
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#. ``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 the ``GET`` method to invoke
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the endpoint.
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#. ``-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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#. ``ping -c 1 10.10.10.100`` - sends one `ICMP ping packet` to the **Internal
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Host**.
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#. ``| kapow set /response/body`` - writes the output of :command:`ping` to the
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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 :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 *mojo* to turn a **system
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command** into an `HTTP API`.
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