> On Feb 18, 2015, at 3:07 PM, Dmitri Zimine <dzim...@stackstorm.com> wrote:
>
>> Syntax options that we’d like to discuss further
>>
>> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is
>> too large symbol
>> <{1 + 1}> # pro - less spaces, con - no familiarity
>> <? 1 + 1 ?> # php familiarity, need spaces
>>
>> The primary criteria to select these 3 options is that they are YAML
>> compatible. Technically they all would solve our problems (primarily no
>> embracing quotes needed like in Ansible so no ambiguity on data types).
>>
>> The secondary criteria is syntax symmetry. After all I agree with Patrick's
>> point about better readability when we have opening and closing sequences
>> alike.
>
>
> To me, another critical criteria is familiarity: target users - openstack
> developers and devops, familiar with the delimiters.
>
> That is why of the three above I prefer <% %> .
>
> It is commonly used in Puppet/Chef [1], Ruby, Javascript. One won’t be
> surprised to see it and won’t need to change the muscle memory to type
> open/closed characters especially when working on say Puppet and Mistral at
> the same time (not unlikely).
>
>
> [1]
> https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
>
>
I have been lurking on this thread, and just wanted to toss in $0.02 as you all
deliberate. In truth, any of the options Renat highlights would be fine, and
the points made to arrive at the final choices are sound. The end result will
types will be explicit, and that is great. In light of this though, using the
<% %> syntax is still ideal if only for one reason: friction.
In a recent discussion with a colleague of mine, he told me that in his daily
job, he is so busy and slammed with operations tasks, his measure of a tool he
will use is whether it provides value within 30-60 minutes. Otherwise, there is
a fire somewhere else that needs to be put out and cannot be bothered.
To be frank, there is no way that this proposed syntax change and how it is
ultimately decorated is going to be a game changer to how future users will
evaluate Mistral. But, at 3am in the morning during a production outage where
an Ops admin is hotpatching a workflow to get things moving again... That
disparity does in fact matter. Eyes are already trained to look for <% %>, the
large amount of spacing draws the eyes, and it's a known function in other
existing ops toolkits. Less friction to adoption/less friction to
troubleshoot.I think these are all pluses. I want to be drawn to where things
are changing or dynamic in my templates to aid in troubleshooting.
Again, this is just another data point to throw out. While users are busy
trying to absorb all that is workflow creation/design... Having as many
likenesses and anchors to existing tools can certainly not hurt adoption.
Thank you all for your efforts!
>
>> On Feb 18, 2015, at 3:20 AM, Renat Akhmerov <rakhme...@mirantis.com> wrote:
>>
>> Hi again,
>>
>> Sorry, I started writing this email before Angus replied so I will shoot it
>> as is and then we can continue…
>>
>>
>> So after discussing all the options again with a small group of team members
>> we came to the following things:
>>
>> Syntax options that we’d like to discuss further
>>
>> <% 1 + 1 %> # pro- ruby/js/puppet/chef familiarity con - spaces, and % is
>> too large symbol
>> <{1 + 1}> # pro - less spaces, con - no familiarity
>> <? 1 + 1 ?> # php familiarity, need spaces
>>
>> The primary criteria to select these 3 options is that they are YAML
>> compatible. Technically they all would solve our problems (primarily no
>> embracing quotes needed like in Ansible so no ambiguity on data types).
>>
>> The secondary criteria is syntax symmetry. After all I agree with Patrick's
>> point about better readability when we have opening and closing sequences
>> alike.
>>
>> Some additional details can be found in [0]
>>
>>
>> [0] https://etherpad.openstack.org/p/mistral-YAQL-delimiters
>>
>> Renat Akhmerov
>> @ Mirantis Inc.
>>
>>
>>>> On 18 Feb 2015, at 07:37, Patrick Hoolboom <patr...@stackstorm.com> wrote:
>>>>
>>>> My main concern with the {} delimiters in YAQL is that the curly brace
>>>> already has a defined use within YAML. We most definitely will eventually
>>>> run in to parsing errors with whatever delimiter we choose but I don't
>>>> feel that it should conflict with the markup language it is directly
>>>> embedded in. It gets quite difficult to, at a glance, identify YAQL
>>>> expressions. <% %> may appear ugly to some but I feel that it works as a
>>>> clear delimiter of both the beginning AND the end of the YAQL query. The
>>>> options that only escape the beginning look fine in small examples like
>>>> this but the workflows that we have written or seen in the wild tend to
>>>> have some fairly large expressions. If the opening and closing delimiters
>>>> don't match, it gets quite difficult to read.
>>>>
>>>>> From: Anastasia Kuznetsova <akuznets...@mirantis.com>
>>>>> Subject: Re: [openstack-dev] [Mistral] Changing "expression" delimiters
>>>>> in Mistral DSL
>>>>> Date: February 17, 2015 at 8:28:27 AM PST
>>>>> To: "OpenStack Development Mailing List (not for usage questions)"
>>>>> <openstack-dev@lists.openstack.org>
>>>>> Reply-To: "OpenStack Development Mailing List \(not for usage
>>>>> questions\)" <openstack-dev@lists.openstack.org>
>>>>>
>>>>> As for me, I think that <% ... %> is not an elegant solution and looks
>>>>> massive because of '%' sign. Also I agree with Renat, that <% ... %>
>>>>> reminds HTML/Jinja2 syntax.
>>>>>
>>>>> I am not sure that similarity with something should be one of the main
>>>>> criteria, because we don't know who will use Mistral.
>>>>>
>>>>> I like:
>>>>> - <{1 + $.var}> Renat's example
>>>>> - variant with using some functions (item 2 in Dmitry's list): { yaql:
>>>>> “1+1+$.my.var < 100” } or <yaql: 'Hello' + $.name >
>>>>> - my two cents, maybe we can use something like: result: -< "Hello" +
>>>>> $.name >-
>>>>>
>>>>>
>>>>> Regards,
>>>>> Anastasia Kuznetsova
>>>>>
>>>>>> On Tue, Feb 17, 2015 at 1:17 PM, Nikolay Makhotkin
>>>>>> <nmakhot...@mirantis.com> wrote:
>>>>>> Some suggestions from me:
>>>>>>
>>>>>> 1. <y 1 + $.var > # (short from yaql).
>>>>>> 2. <{ 1 + $.var }> # as for me, looks more elegant than <% %>. And
>>>>>> visually it is more strong
>>>>>>
>>>>>> A also like p7 and p8 suggested by Renat.
>>>>>>
>>>>>> On Tue, Feb 17, 2015 at 11:43 AM, Renat Akhmerov
>>>>>> <rakhme...@mirantis.com> wrote:
>>>>>>> One more:
>>>>>>>
>>>>>>> p9: \{1 + $.var} # That’s pretty much what
>>>>>>> https://review.openstack.org/#/c/155348/ addresses but it’s not exactly
>>>>>>> that. Note that we don’t have to put it in quotes in this case to deal
>>>>>>> with YAML {} semantics, it’s just a string
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Renat Akhmerov
>>>>>>> @ Mirantis Inc.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> On 17 Feb 2015, at 13:37, Renat Akhmerov <rakhme...@mirantis.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>> Along with <% %> syntax here are some other alternatives that I
>>>>>>>> checked for YAML friendliness with my short comments:
>>>>>>>>
>>>>>>>> p1: ${1 + $.var} # Here it’s bad that $ sign is used for two
>>>>>>>> different things
>>>>>>>> p2: ~{1 + $.var} # ~ is easy to miss in a text
>>>>>>>> p3: ^{1 + $.var} # For someone may be associated with regular
>>>>>>>> expressions
>>>>>>>> p4: ?{1 + $.var}
>>>>>>>> p5: <{1 + $.var}> # This is kinda crazy
>>>>>>>> p6: e{1 + $.var} # That looks a pretty interesting option to me,
>>>>>>>> “e” could mean “expression” here.
>>>>>>>> p7: yaql{1 + $.var} # This is interesting because it would give a
>>>>>>>> clear and easy mechanism to plug in other expression languages, “yaql”
>>>>>>>> here is a used dialect for the following expression
>>>>>>>> p8: y{1 + $.var} # “y” here is just shortened “yaql"
>>>>>>>>
>>>>>>>>
>>>>>>>> Any ideas and thoughts would be really appreciated!
>>>>>>>>
>>>>>>>> Renat Akhmerov
>>>>>>>> @ Mirantis Inc.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> On 17 Feb 2015, at 12:53, Renat Akhmerov <rakhme...@mirantis.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>> Dmitri,
>>>>>>>>>
>>>>>>>>> I agree with all your reasonings and fully support the idea of
>>>>>>>>> changing the syntax now as well as changing system’s API a little bit
>>>>>>>>> due to recently found issues in the current engine design that don’t
>>>>>>>>> allow us, for example, to fully implement ‘with-items’ (although
>>>>>>>>> that’s a little bit different story).
>>>>>>>>>
>>>>>>>>> Just a general note about all changes happening now: Once we release
>>>>>>>>> kilo stable release our API, DSL of version 2 must be 100% stable. I
>>>>>>>>> was hoping to stabilize it much earlier but the start of production
>>>>>>>>> use revealed a number of things (I think this is normal) which we
>>>>>>>>> need to address, but not later than the end of Kilo.
>>>>>>>>>
>>>>>>>>> As far as <% %> syntax. I see that it would solve a number of
>>>>>>>>> problems (YAML friendliness, type ambiguity) but my only not strong
>>>>>>>>> argument is that it doesn’t look that elegant in YAML as it looks,
>>>>>>>>> for example, in ERB templates. It really reminds me XML/HTML and
>>>>>>>>> looks like a bear in a grocery store (tried to make it close to one
>>>>>>>>> old russian saying :) ). So just for this only reason I’d suggest we
>>>>>>>>> think about other alternatives, maybe not so familiar to
>>>>>>>>> Ruby/Chef/Puppet users but looking better with YAML and at the same
>>>>>>>>> time being YAML friendly.
>>>>>>>>>
>>>>>>>>> I would be good if we could here more feedback on this, especially
>>>>>>>>> from people who started using Mistral.
>>>>>>>>>
>>>>>>>>> Thanks
>>>>>>>>>
>>>>>>>>> Renat Akhmerov
>>>>>>>>> @ Mirantis Inc.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> On 17 Feb 2015, at 03:06, Dmitri Zimine <dzim...@stackstorm.com>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>> SUMMARY:
>>>>>>>>>> ----------------
>>>>>>>>>>
>>>>>>>>>> We are changing the syntax for inlining YAQL expressions in Mistral
>>>>>>>>>> YAML from {1+$.my.var} (or “{1+$.my.var}”) to <% 1+$.my.var %>
>>>>>>>>>>
>>>>>>>>>> Below I explain the rationale and the criteria for the choice.
>>>>>>>>>> Comments and suggestions welcome.
>>>>>>>>>>
>>>>>>>>>> DETAILS:
>>>>>>>>>> -------------
>>>>>>>>>>
>>>>>>>>>> We faced a number of problems with using YAQL expressions in Mistral
>>>>>>>>>> DSL: [1] must handle any YAQL, not only the ones started with $; [2]
>>>>>>>>>> must preserve types and [3] must comply with YAML. We fixed these
>>>>>>>>>> problems by applying Ansible style syntax, requiring quotes around
>>>>>>>>>> delimiters (e.g. “{1+$.my.yaql.var}”). However, it lead to
>>>>>>>>>> unbearable confusion in DSL readability, in regards to types:
>>>>>>>>>>
>>>>>>>>>> publish:
>>>>>>>>>> intvalue1: "{1+1}” # Confusing: you expect quotes to be
>>>>>>>>>> string.
>>>>>>>>>> intvalue2: "{int(1+1)}” # Even this doestn’ clean the
>>>>>>>>>> confusion
>>>>>>>>>> whatisthis:"{$.x + $.y}” # What type would this return?
>>>>>>>>>>
>>>>>>>>>> We got a very strong push back from users in the filed on this
>>>>>>>>>> syntax.
>>>>>>>>>>
>>>>>>>>>> The crux of the problem is using { } as delimiters YAML. It is plain
>>>>>>>>>> wrong to use the reserved character. The clean solution is to find a
>>>>>>>>>> delimiter that won’t conflict with YAML.
>>>>>>>>>>
>>>>>>>>>> Criteria for selecting best alternative are:
>>>>>>>>>> 1) Consistently applies to to all cases of using YAML in DSL
>>>>>>>>>> 2) Complies with YAML
>>>>>>>>>> 3) Familiar to target user audience - openstack and devops
>>>>>>>>>>
>>>>>>>>>> We prefer using two-char delimiters to avoid requiring extra
>>>>>>>>>> escaping within the expressions.
>>>>>>>>>>
>>>>>>>>>> The current winner is <% %>. It fits YAML well. It is familiar to
>>>>>>>>>> openstack/devops as this is used for embedding Ruby expressions in
>>>>>>>>>> Puppet and Chef (for instance, [4]). It plays relatively well across
>>>>>>>>>> all cases of using expressions in Mistral (see examples in [5]):
>>>>>>>>>>
>>>>>>>>>> ALTERNATIVES considered:
>>>>>>>>>> --------------------------------------------------
>>>>>>>>>>
>>>>>>>>>> 1) Use Ansible-like syntax:
>>>>>>>>>> http://docs.ansible.com/YAMLSyntax.html#gotchas
>>>>>>>>>> Rejected for confusion around types. See above.
>>>>>>>>>>
>>>>>>>>>> 2) Use functions, like Heat HOT or TOSCA:
>>>>>>>>>>
>>>>>>>>>> HOT templates and TOSCA doesn’t seem to have a concept of typed
>>>>>>>>>> variables to borrow from (please correct me if I missed it). But
>>>>>>>>>> they have functions: function: { function_name: {foo: [parameter1,
>>>>>>>>>> parameter 2], bar:"xxx”}}. Applied to Mistral, it would look like:
>>>>>>>>>>
>>>>>>>>>> publish:
>>>>>>>>>> - bool_var: { yaql: “1+1+$.my.var < 100” }
>>>>>>>>>>
>>>>>>>>>> Not bad, but currently rejected as it reads worse than
>>>>>>>>>> delimiter-based syntax, especially in simplified one-line action
>>>>>>>>>> invocation.
>>>>>>>>>>
>>>>>>>>>> 3) < > paired with other symbols: php-styoe <? ..?>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> REFERENCES:
>>>>>>>>>> ----------------------
>>>>>>>>>>
>>>>>>>>>> [1] Allow arbitrary YAQL expressions, not just ones started with $ :
>>>>>>>>>> https://github.com/stackforge/mistral/commit/5c10fb4b773cd60d81ed93aec33345c0bf8f58fd
>>>>>>>>>> [2] Use Ansible-like syntax to make YAQL expressions YAML complient
>>>>>>>>>> https://github.com/stackforge/mistral/commit/d9517333b1fc9697d4847df33d3b774f881a111b
>>>>>>>>>> [3] Preserving types in YAQL
>>>>>>>>>> https://github.com/stackforge/mistral/blob/d9517333b1fc9697d4847df33d3b774f881a111b/mistral/tests/unit/test_expressions.py#L152-L184
>>>>>>>>>> [4]Using <% %> in Puppet
>>>>>>>>>> https://docs.puppetlabs.com/guides/templating.html#erb-is-plain-text-with-embedded-ruby
>>>>>>>>>>
>>>>>>>>>> [5] Etherpad with discussion
>>>>>>>>>> https://etherpad.openstack.org/p/mistral-YAQL-delimiters
>>>>>>>>>> [6] Blueprint
>>>>>>>>>> https://blueprints.launchpad.net/mistral/+spec/yaql-delimiters
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> __________________________________________________________________________
>>>>>>> OpenStack Development Mailing List (not for usage questions)
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Best Regards,
>>>>>> Nikolay
>>>>>>
>>>>>> __________________________________________________________________________
>>>>>> OpenStack Development Mailing List (not for usage questions)
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