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<div>An honest question,</div>
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<div>U are mentioning what appears to be the basis for a full programming language (variables, calling other workflows - similar to functions) but then u mention this is being stuffed into yaml. </div>
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<div>Why? </div>
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<div>It appears like u might as well spend the effort and define a grammar and simplistic language that is not stuffed inside yaml. Shoving one into yaml syntax seems like it gets u none of the benefits of syntax checking, parsing, validation (highlighting...)
and all the pain of yaml. </div>
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<div>Something doesn't seem right about the approach of creating languages inside the yaml format (in a way it becomes like xsl, yet xsl at least has a spec and is well defined). </div>
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<div>My 2 cents....<br>
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Sent from my really tiny device...</div>
<div><br>
On Feb 14, 2014, at 7:22 PM, "Alexander Tivelkov" <<a href="mailto:ativelkov@mirantis.com">ativelkov@mirantis.com</a>> wrote:<br>
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<div class="gmail_default"><span id="docs-internal-guid-161e6d58-3354-17b8-4338-c031171bb4d7">
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Hi folks,</span></p>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Murano matures, and we are getting more and more feedback from our early adopters. The overall reception is very positive,
but at the same time there are some complaints as well. By now the most significant complaint is is hard to write workflows for application deployment and maintenance.</span></p>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Current version of workflow definition markup really have some design drawbacks which limit its potential adoption. They
are caused by the fact that it was never intended for use for Application Catalog use-cases.</span></p>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">I'll briefly touch these drawbacks first:</span></p>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="margin-top:0pt;margin-bottom:0pt"></p>
<ol>
<li style="font-size:small;line-height:1.15"><span style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:15px;white-space:pre-wrap;line-height:1.15">Murano's workflow engine is actually a state machine, however the workflow markup
does not explicitly define the states and transitions.</span> </li><li><span style="background-color:transparent"><font color="#000000" face="Arial"><span style="font-size:15px;line-height:1.15;white-space:pre-wrap">There is no data isolation within any environment, which causes both potential security vulnerabilities and
unpredictable workflow </span><span style="font-size:15px;line-height:17px;white-space:pre-wrap">behaviours</span><span style="font-size:15px;line-height:1.15;white-space:pre-wrap">.</span></font></span>
</li><li style="font-size:small;line-height:1.15"><span style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:15px;white-space:pre-wrap;line-height:1.15">There is no easy way to reuse the workflows and their related procedures between
several applications.</span> </li><li style="font-size:small;line-height:1.15"><span style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:15px;white-space:pre-wrap;line-height:1.15">The markup uses JSONPath, which relies on Python’s 'eval' function. This is insecure
and has to be avoided. </span> </li><li style="font-size:small;line-height:1.15"><span style="background-color:transparent;color:rgb(0,0,0);font-family:Arial;font-size:15px;white-space:pre-wrap;line-height:1.15">5. The workflow markup is XML-based, which is not a common practice in the OpenStack
community.</span> </li></ol>
<p></p>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">So, it turns out that we have to design and implement a new workflow definition notation, which will not have any of the
issues mentioned above.</span></p>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">At the same time, it should still allow to fully specify the configuration of any third-party Application, its dependencies
with other Applications and define specific actions which are required for Application deployment, configuration and life cycle management.</span></p>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">This new notation should allow to do the following:
</span></p>
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<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<ul style="font-size:small;margin-top:0pt;margin-bottom:0pt">
<li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">List all the required configuration parameters and dependencies for a given application</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Validate user input and match it to the defined parameters</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Define specific deployment actions and their execution order</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Define behaviors to handle the events of changes in application’s environment</span></p>
</li></ul>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Also, it should satisfy the following requirements:</span></p>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<ul style="font-size:small;margin-top:0pt;margin-bottom:0pt">
<li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Minimize the amount of configuration for common application parts, i.e. reuse existing configuration
parts and add only difference specific to the application.</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Allow to use different deployment tools with using the same markup constructs. i.e. provide a high-level
abstraction on the underlying tools (heat, shell, chef, puppet etc)</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">For security reasons it should NOT allow to execute arbitrary operations - i.e. should allow to run
only predefined set of meaningful configuration actions. </span></p>
</li></ul>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span><br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">So, I would suggest to introduce a simple and domain specific notation which would satisfy these needs:</span></p>
<ul style="font-size:small;margin-top:0pt;margin-bottom:0pt">
<li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Application dependencies and configuration properties are defined declaratively, in a way similar
to how it is done in Heat templates.</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Each property has special constraints and rules, allowing to validate the input and applications relationship
within the environment.</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">The workflows are defined in imperative way: as a sequence of actions or method calls. This may include
assigning data variables or calling the workflows of other applications.</span></p>
</li><li dir="ltr" style="list-style-type:disc;font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline">
<p dir="ltr" style="line-height:1.15;margin-top:0pt;margin-bottom:0pt"><span style="background-color:transparent;vertical-align:baseline;white-space:pre-wrap">All of these may be packaged in a YAML format. The example may look something like this [1]</span></p>
</li></ul>
<br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">The final version may become a bit more complicated, but as the starting point this should look fine. I suggest to cover
this in more details on our next IRC meeting on Tuesday.</span></p>
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<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Any feedback or suggestions are appreciated.</span></p>
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<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span><br>
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span>
<p dir="ltr" style="font-size:small;line-height:1.15;margin-top:0pt;margin-bottom:0pt">
<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">[1]
<a href="https://etherpad.openstack.org/p/murano-new-dsl-example">https://etherpad.openstack.org/p/murano-new-dsl-example</a></span></p>
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<span style="font-size:15px;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"></span></span></div>
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<div dir="ltr"><font>--<br>
</font>
<div dir="ltr"><font>Regards,<br>
Alexander Tivelkov</font></div>
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