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FAQ
Hi,

starting to use hiera in earnest now (still on puppet 2.6 but planning an
upgrade to 3.x this summer).

the heirarchy looks for fqdn, then network_eth0, then 'default'.

Some of our subnets don't want to set http_proxy environment variables, the
rest do.

so default.json has a 'http_proxy_url' key in it, but I want to exclude it
for 10.9.8.7.

Is there a 'special' hiera value I can set in 10.9.8.7.json to stop the
search falling down into default.json ?

At the minute we've set an empty string, but then templates etc. need to be
littered with

if ($url_from_hiera != "") {
   do_stuff()
}

which feels like the sort of 'magic variable' that will bite future me in
the ass in around 6 months.

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  • Jcbollinger at May 15, 2013 at 2:24 pm ⇧

    On Wednesday, May 15, 2013 6:29:14 AM UTC-5, Dick Davies wrote:
    Hi,

    starting to use hiera in earnest now (still on puppet 2.6 but planning an
    upgrade to 3.x this summer).

    the heirarchy looks for fqdn, then network_eth0, then 'default'.

    Some of our subnets don't want to set http_proxy environment variables,
    the rest do.

    so default.json has a 'http_proxy_url' key in it, but I want to exclude it
    for 10.9.8.7.

    Is there a 'special' hiera value I can set in 10.9.8.7.json to stop the
    search falling down into default.json ?

    Yes, and no. ANY value you set for that key in 10.9.8.7.json will prevent
    the search from consulting the next hierarchy level. But it will cause the
    lookup to return the given value. As far as I know, there is no value that
    represents "no value".


    At the minute we've set an empty string, but then templates etc. need to
    be littered with

    if ($url_from_hiera != "") {
    do_stuff()
    }

    which feels like the sort of 'magic variable' that will bite future me in
    the ass in around 6 months.
    So, what do you envision hiera returning instead? undef? How would that
    make things better for you? Wouldn't you still need similar conditional
    logic in all the same places?

    I don't see the magic variable problem in this case, in that the empty
    string is actually a pretty good representation of the meaning you want to
    convey. You might even find that setting the http_proxy environment
    variable to an empty string has the desired effect (of not trying to use a
    proxy), though that's speculative on my part. If that did work then the
    empty string wouldn't be magic at all.


    John

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  • Dick Davies at May 15, 2013 at 3:45 pm ⇧
    On 15 May 2013 15:24, jcbollinger wrote:
    On Wednesday, May 15, 2013 6:29:14 AM UTC-5, Dick Davies wrote:


    At the minute we've set an empty string, but then templates etc. need to
    be littered with

    if ($url_from_hiera != "") {
    do_stuff()
    }

    which feels like the sort of 'magic variable' that will bite future me in
    the ass in around 6 months.
    So, what do you envision hiera returning instead? undef? How would that
    make things better for you? Wouldn't you still need similar conditional
    logic in all the same places?
    I can get a bit closer to the ideal if I set the value as : false
    - then the templates look like this (the $yum_proxy_url gets unpacked out
    of hiera
    up in the module):

    <%- if yum_proxy_url != false %>
    # use proxy
    proxy=<%=yum_proxy_url %>
    <% end -%>

    which is a bit more readable. Not really clear why the : != false part is
    required, but
    feels cleaner to me.

    And no, annoyingly

    proxy=

    breaks yum :)


    I don't see the magic variable problem in this case, in that the empty
    string is actually a pretty good representation of the meaning you want to
    convey. You might even find that setting the http_proxy environment
    variable to an empty string has the desired effect (of not trying to use a
    proxy), though that's speculative on my part. If that did work then the
    empty string wouldn't be magic at all.
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  • Jcbollinger at May 15, 2013 at 6:33 pm ⇧

    On Wednesday, May 15, 2013 10:45:19 AM UTC-5, Dick Davies wrote:
    On 15 May 2013 15:24, jcbollinger <John.Bo...@stjude.org <javascript:>>wrote:
    On Wednesday, May 15, 2013 6:29:14 AM UTC-5, Dick Davies wrote:


    At the minute we've set an empty string, but then templates etc. need to
    be littered with

    if ($url_from_hiera != "") {
    do_stuff()
    }

    which feels like the sort of 'magic variable' that will bite future me
    in the ass in around 6 months.
    So, what do you envision hiera returning instead? undef? How would that
    make things better for you? Wouldn't you still need similar conditional
    logic in all the same places?
    I can get a bit closer to the ideal if I set the value as : false
    - then the templates look like this (the $yum_proxy_url gets unpacked out
    of hiera
    up in the module):

    <%- if yum_proxy_url != false %>
    # use proxy
    proxy=<%=yum_proxy_url %>
    <% end -%>

    which is a bit more readable. Not really clear why the : != false part is
    required, but
    feels cleaner to me.
    In other words, yes, you do need all the same logic in all the same
    places. In that case, your only real option is to choose the special value
    you like best. Personally, I find the empty string very appropriate, and
    whereas there could conceivably be a machine named "false", but there
    cannot be one named "". Still, it's a matter of taste.


    And no, annoyingly

    proxy=

    breaks yum :)
    Bummer.


    John


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  • Dick Davies at May 16, 2013 at 6:53 am ⇧
    On 15 May 2013 19:33, jcbollinger wrote:
    On Wednesday, May 15, 2013 10:45:19 AM UTC-5, Dick Davies wrote:


    <%- if yum_proxy_url != false %>
    # use proxy
    proxy=<%=yum_proxy_url %>
    <% end -%>

    which is a bit more readable. Not really clear why the : != false part is
    required, but
    feels cleaner to me.
    In other words, yes, you do need all the same logic in all the same
    places. In that case, your only real option is to choose the special value
    you like best. Personally, I find the empty string very appropriate, and
    whereas there could conceivably be a machine named "false", but there
    cannot be one named "". Still, it's a matter of taste.
    Absolutely - see your point - it looks to me like the template is treating
    literal false (not "false")
    as a string rather than a boolean.
    I might be wrong but my reading is that hiera can return booleans as well
    as strings,
    so maybe it's a template thing? Anyway, spent enough time on this for now -
    cheers.

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postedMay 15, '13 at 11:29a
activeMay 16, '13 at 6:53a
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