sure ! So being able to traverse a zero length list would fix yours issue and avoid the need for my workaround
Phil 2014-05-01 21:44 GMT+02:00 kesten broughton <[email protected]>: > ah, thanks phillippe. > > I think in my case this won't work since i DO care about doing it one more > time. > The thing i'm doing is creating vms. But i don't want to create 1 more if > i already have my desired N. > > k > > > On Thu, May 1, 2014 at 2:17 PM, Philippe Eveque <[email protected] > > wrote: > >> The link references a previous exchange similar to yours >> >> The specific case was about using the lineinfile module and with_sequence >> to add a parameter to all the kernel liles in grub.conf >> >> here is a copy of what I wrote: >> >> " >> tasks 1: count the number of lines to replace (via shell module using and >> grep -E <regexp> | wc -l ) >> using register to remember the linecounted >> >> task 2: using lineinfile and with_sequence: linecounted >> >> one caveat is that with sequence does not accept a 0 count ( a potential >> future improvement ?) >> >> so just add 1 to the count (you do not care about doing it one more time) >> >> then you can run those 2 tasks multiples times >> >> works for me on grub.conf >> " >> >> >> Phil >> >> >> 2014-05-01 15:34 GMT+02:00 kesten broughton <[email protected]>: >> >>> Phil, the link doesn't work for me. >>> >>> >>> On Thursday, May 1, 2014 2:32:23 AM UTC-5, Philippe Eveque wrote: >>> >>>> In similar case A workaround I used is to add 1 to your sequence count >>>> see https://mail.google.com/mail/#search/label%3Aansible+with_ >>>> sequence/1435e13b34e3a0e1 >>>> >>>> Phil >>>> >>>> >>>> 2014-04-30 23:51 GMT+02:00 kesten broughton <[email protected]>: >>>> >>>>> The error is >>>>> fatal: [localhost] => can't count backwards >>>>> >>>>> This occurs whenever count=0 or start=M end=M >>>>> >>>>> If with_sequence is used for the purpose of bringing a system to a >>>>> state = HAS N of something >>>>> then there should be a way of running the playbook twice and not >>>>> having anything new created. >>>>> That's what i meant by idempotent. >>>>> >>>>> "with sequence can't traverse a zero length list" accurately >>>>> describes my concern >>>>> >>>>> kesten >>>>> >>>>> On Wednesday, April 30, 2014 3:03:56 PM UTC-5, Michael DeHaan wrote: >>>>> >>>>>> You are throwing two words together that have nothing to do with each >>>>>> other. >>>>>> >>>>>> with_sequence is a loop. >>>>>> >>>>>> Idempotency is a mathematical statement that says "F(X) = F(F(X))" >>>>>> for how many times X is applied. >>>>>> >>>>>> "This will work if M is strictly less than N, but if M=N (the >>>>>> idempotent case) then ansible gives an error." >>>>>> >>>>>> What you have here is Ansible giving an error. It has nothing to do >>>>>> with idempotency. >>>>>> >>>>>> It may imply "with sequence can't traverse a zero length list", which >>>>>> more accurately describes the problem. >>>>>> >>>>>> So, the best thing to do here is to share what the error is and we >>>>>> can go from there. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Wed, Apr 30, 2014 at 9:34 AM, Kesten Broughton < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> >>>>>>> I recently had a need for with_sequence, but it doesn't seem >>>>>>> possible to do a zero count of actions. >>>>>>> >>>>>>> Suppose i have a local action to create N things, perhaps vms or >>>>>>> floating ips. Some number M < N may already be present. >>>>>>> >>>>>>> I'd like to do >>>>>>> >>>>>>> hosts: localhost >>>>>>> vars: >>>>>>> expected_foo_count: 10 >>>>>>> >>>>>>> - name: Get the number of foos >>>>>>> shell: echo M >>>>>>> register: foo_count >>>>>>> >>>>>>> - name: Create the missing number of foos >>>>>>> shell: make_new_foos >>>>>>> with_sequence: start=0 end="{{expected_foo_count >>>>>>> -foo_count.stdout }}" >>>>>>> >>>>>>> or with_sequence: count="{{expected_foo_count - foo_count.stdout}}" >>>>>>> >>>>>>> This will work if M is strictly less than N, but if M=N (the >>>>>>> idempotent case) then ansible gives an error. >>>>>>> >>>>>>> fatal: [localhost] => can't count backwards >>>>>>> I tried putting a "when" guard such as >>>>>>> when: "{{ expected_foo_count - foo_count.stdout > 0 }}" >>>>>>> >>>>>>> But it appears "when" gets evaluated after the with_sequence >>>>>>> conditional. That in itself poses problems, since in branching code the >>>>>>> register variables may not be defined and you have to litter code with >>>>>>> when: "{{ (register_var or '') | conditional }}". >>>>>>> >>>>>>> The problem with the with_sequence is in the >>>>>>> lib/ansible/runner/lookup_plugins/sequence.py >>>>>>> >>>>>>> def generate_sequence(self): >>>>>>> numbers = xrange(self.start, self.end+1, self.stride) >>>>>>> >>>>>>> which means that contrary to conventional python such as >>>>>>> range(a,b) which gives a sequence starting at 'a' and ending at >>>>>>> 'b-1', ie. [a,b) >>>>>>> >>>>>>> with_sequence: start=n end=m >>>>>>> >>>>>>> runs over the sequence [n,m]. If n=m with_sequence still executes >>>>>>> once, so there is no possible way to have a with_sequence that runs zero >>>>>>> times. >>>>>>> >>>>>>> changing the generate_sequence code to >>>>>>> >>>>>>> def generate_sequence(self): >>>>>>> numbers = xrange(self.start, self.end, self.stride) >>>>>>> >>>>>>> Fixes the problem. >>>>>>> >>>>>>> Is there a design reason behind not allowing for zero count >>>>>>> sequences? If so, how can a playbook including with_sequence be made >>>>>>> idempotent? >>>>>>> >>>>>>> kesten >>>>>>> >>>>>>> -- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "Ansible Project" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>>> send an email to [email protected]. >>>>>>> To post to this group, send email to [email protected]. >>>>>>> >>>>>>> To view this discussion on the web visit >>>>>>> https://groups.google.com/d/msgid/ansible-project/CAO2fFsVLw >>>>>>> C6qoVKReu--zjyfOwUA1KUJQWy2cG36nmHRietk0g%40mail.gmail.com<https://groups.google.com/d/msgid/ansible-project/CAO2fFsVLwC6qoVKReu--zjyfOwUA1KUJQWy2cG36nmHRietk0g%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>>> . >>>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>>> >>>>>> >>>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Ansible Project" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to [email protected]. >>>>> To post to this group, send email to [email protected]. >>>>> To view this discussion on the web visit https://groups.google.com/d/ >>>>> msgid/ansible-project/263df645-0b20-419b-ae3f- >>>>> 2cdff75280f5%40googlegroups.com<https://groups.google.com/d/msgid/ansible-project/263df645-0b20-419b-ae3f-2cdff75280f5%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Ansible Project" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> >>> To post to this group, send email to [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/ansible-project/361bfbdc-5ba1-4bcc-bde5-603c633cf4fa%40googlegroups.com<https://groups.google.com/d/msgid/ansible-project/361bfbdc-5ba1-4bcc-bde5-603c633cf4fa%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "Ansible Project" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/ansible-project/swkbKGLio1g/unsubscribe >> . >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> >> To post to this group, send email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/ansible-project/CAB1FMuSeAVaMDXKUfNRPz6pphRKNE8LV-PaXhqUGhK92ORTX8A%40mail.gmail.com<https://groups.google.com/d/msgid/ansible-project/CAB1FMuSeAVaMDXKUfNRPz6pphRKNE8LV-PaXhqUGhK92ORTX8A%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> For more options, visit https://groups.google.com/d/optout. >> > > -- > You received this message because you are subscribed to the Google Groups > "Ansible Project" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/ansible-project/CAK5UeTt_rLuB6gKkJooXwZL0O%3DtMrLRb-Kou%2BpPLMSdZT6fXkQ%40mail.gmail.com<https://groups.google.com/d/msgid/ansible-project/CAK5UeTt_rLuB6gKkJooXwZL0O%3DtMrLRb-Kou%2BpPLMSdZT6fXkQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Ansible Project" group. 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