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From Sebastien Goasguen <>
Subject Re: Blameless post mortem
Date Mon, 28 Sep 2015 11:29:19 GMT

> On Sep 28, 2015, at 1:14 PM, Remi Bergsma <> wrote:
> Hi Bharat,
> There is only one way to prove a feature works: with tests. That’s why I say actually
_running_ the tests we have today on any new PR, is the most important thing. Having no documentation
is a problem, I agree, but it is not more important IMHO. If we had the documentation, we
still would have issues if nobody runs the tests and verifies pull requests. Documentation
that is perfect does not automatically lead to perfect implementation. So we need tests to
> If we don’t agree that is also fine. We need to do both anyway and I think we do agree
on that.

Also we need to move forward. We should have a live chat once 4.6 is out to discuss all issues/problems
and iron out the process.

But reverting the VR refactor is not going to happen. There was ample discussions on the PR
when it was submitted, there was time to review and raise concerns at that time. It went through
quite a few reviews, tests etc…Maybe the documentation is not good, but the time to raise
this concern I am afraid was six months ago. We can learn from it, but we are not going to
revert it, this would not go cleanly as David mentioned.

So let’s get back to blockers for 4.6, are there still VR related issues with master ?

> Regards,
> Remi
> On 28/09/15 12:15, "Bharat Kumar" <> wrote:
>> Hi Remi,
>> i do not agree with “There is no bigger problem”  part of your reply. so I had
to repeat myself to make it more clear, Not because i am not aware of what this thread is
supposed to do.
>> Regards,
>> Bharat.
>> On 28-Sep-2015, at 2:51 pm, Remi Bergsma <> wrote:
>>> Hi Bharat,
>>> I understand your frustrations but we already agreed on this so no need to repeat.
This thread is supposed to list some improvements and learn from it. Your point has been taken
so let’s move on.
>>> We need documentation first, then do a change after which all tests should pass.
Even better is we write (missing) tests before changing stuff so you know they pass before
and after the fact. 
>>> When doing reviews, feel free to ask for design documentation if you feel it
is needed.
>>> Regards, Remi
>>> On 28/09/15 11:02, "Bharat Kumar" <> wrote:
>>>> Hi Remi,
>>>> I never intended to say that we should not run tests, but even before tests
we should have proper documentation. My concern was if a major change is being introduced
it should be properly documented. All the issues which we are trying to fix are majorly due
to VR refactor. If there was a proper documentation for this we could
>>>> have fixed this in a better way.  Even to add tests we need to understand
how a particular thing works and what data dose it expect. I think while fixing the python
based code changes this is where most of the people are facing issues. A proper documentation
will help in understanding these in a better way.
>>>> Thanks,
>>>> Bharat.
>>>> On 28-Sep-2015, at 1:57 pm, Remi Bergsma <>
>>>>> Hi Bharat,
>>>>> There is no bigger problem. We should always run the tests and if we
find a case that isn’t currently covered by the tests we should simply add tests for it.
There’s no way we’ll get a stable master without them. The fact that they may not cover
everything, is no reason to not rely on them. If a feature is not important enough to write
a test for, then the feature is probably not important anyway. And if it is, then add a test
>>>>> I do agree on the design documentation requirement for any (major?) change.
I found some design documentations on the subject you mention, but it should have been more
>>>>> Regards,
>>>>> Remi
>>>>> On 28/09/15 09:58, "Bharat Kumar" <> wrote:
>>>>>> Hi Remi,
>>>>>> Thank you for the Blame less postmortem. 
>>>>>> I think there is a bigger problem here than just the review process
and running tests. Even if we run the tests we cannot be sure that every thing will work as
intended. The tests will only give some level of confidence. The tests may not cover all the
use cases.
>>>>>> I think the problem here is that the way major changes to the code
base are dealt with. For example,  VR refactoring was done without discussing the design implications
and the amount of changes it would bring in. I could not find any design document. The vr
refactor changed a lot of code and the way VR used to work and in my opinion it was incomplete-vpn,
isolated networks, basic networks, iptable rules and rvr in isolated case etc were not implemented.
Most of us are still in the process of understanding this. Even before reaching this state
we had to spend a lot of time fixing issues mentioned in the thread [Blocker/Critical] VR
related Issues.  
>>>>>> When a change of this magnitude is being made, we should call out
all the changes and document them properly. This will help people to create better fixes.
Currently when we attempt to fix the isolated vr case it is effecting the vpc and vice versa.
for example pr 738 fixed it for vpc networks but broke it for isolated case. I believe it
is not too late to at least start documenting the changes now.
>>>>>> Thanks,
>>>>>> Bharat.
>>>>>> On 28-Sep-2015, at 10:52 am, Sanjeev N <>
>>>>>>> I have a concern here. Some of us are actively involved in reviewing
>>>>>>> PRs related to marvin tests(Enhancing existing tests/Adding new
tests). If
>>>>>>> we have to test a PR it requires an environment to be created
with actual
>>>>>>> resources and this is going to take lot of time. Some of the
tests can run
>>>>>>> on simulator but most of the tests require real hardware to test.
>>>>>>> submitter is already testing and submitting the test results
along with the
>>>>>>> PR. So is it require to test these PRs by reviewers?
>>>>>>> On Sat, Sep 26, 2015 at 1:49 PM, sebgoa <>
>>>>>>>> Remi, thanks for the detailed post-mortem, it's a good read
and great
>>>>>>>> learning.
>>>>>>>> I hope everyone reads it.
>>>>>>>> The one thing to emphasize is that we now have a very visible
way to get
>>>>>>>> code into master, we have folks investing time to provide
review (great),
>>>>>>>> we need the submitters to make due diligence and answer all
comments in the
>>>>>>>> reviews.
>>>>>>>> In another project i work on, nothing can be added to the
code without
>>>>>>>> unit tests. I think we could go down the route of asking
for new
>>>>>>>> integration tests and unit tests for anything. If not, the
PR does not get
>>>>>>>> merged. But let's digest your post-mortem and we can discuss
after 4.6.0.
>>>>>>>> I see that you reverted one commit that was not made by you,
that's great.
>>>>>>>> Let's focus on the blockers now, everything else can wait.
>>>>>>>> The big bonus of doing what we are doing is that once 4.6.0
is out, we can
>>>>>>>> merge PRs again (assuming they are properly rebased and tested)
and we can
>>>>>>>> release 4.6.1 really quickly after.
>>>>>>>> -sebastien
>>>>>>>> On Sep 25, 2015, at 9:51 PM, Remi Bergsma <>
>>>>>>>> wrote:
>>>>>>>>> Hi all,
>>>>>>>>> This mail is intended to be blameless. We need to learn
something from
>>>>>>>> it. That's why I left out who exactly did what because it’s
not relevant.
>>>>>>>> There are multiple examples but it's about the why. Let's
learn from this
>>>>>>>> without blaming anyone.
>>>>>>>>> We know we need automated testing. We have integration
tests, but we are
>>>>>>>> unable to run all of them on any Pull Request we receive.
If we would have
>>>>>>>> that in place, it'd be much easier to spot errors, regression
and so on.
>>>>>>>> It'd also be more rewarding to write more tests.
>>>>>>>>> Unfortunately we're not there yet. So, we need to do
something else
>>>>>>>> instead until we get there. If we do nothing, we know we
have many issues
>>>>>>>> because a master that breaks on a regular basis is the most
>>>>>>>> things. We said we'd use Pull Requests with at least two
humans to review
>>>>>>>> and give their OK for a Pull Request. In the form of LGTM:
Looks Good To
>>>>>>>> Me. Ok, so the LGTMs are there because we have no automated
testing. Keep
>>>>>>>> that in mind. You are supposed to replace automated testing
until it's
>>>>>>>> there.
>>>>>>>>> Since we do this, master got a lot more stable. But every
now and then
>>>>>>>> we still have issues. Let's look at how we do manual reviews.
Again, this
>>>>>>>> is not to blame anyone. It's to open our eyes and make us
realise what
>>>>>>>> we're doing and what results we get out of that.
>>>>>>>>> Example Pull Request #784:
>>>>>>>>> Title: CLOUDSTACK-8799 fixed the default routes
>>>>>>>>> That's nice, it has a Jira id and a short description
(as it should be).
>>>>>>>>> The first person comes along and makes a comment:
>>>>>>>>> "There was also an issue with VPC VRs" ... "Have you
seen this issue?
>>>>>>>> Does your change affects the VPC VR (single/redundant)?"
>>>>>>>>> Actually a good question. Unfortunaly there comes no
answer. After a
>>>>>>>> reminder, it was promised to do tests against VPC networks.
>>>>>>>>> The Jenkins builds both succeed and also Travis is green.
But how much
>>>>>>>> value does this have? They have the impression to do automated
testing, and
>>>>>>>> although you could argue they do, it's far from complete.
If it breaks, you
>>>>>>>> know you have an issue. But it doesn’t work the other way
>>>>>>>>> Back to our example PR. In the mean time, another commit
gets pushed to
>>>>>>>> it: "CLOUDSTACK-8799 fixed for vpc networks." But if you
look at the Jira
>>>>>>>> issue, you see it is about redundant virtual routers. The
non-VPC ones. So
>>>>>>>> this is vague at best. But a reviewer gives a LGTM because
the person could
>>>>>>>> create a VPC. That doesn't have anything to do with the problem
being fixed
>>>>>>>> in this PR nor with the comments made earlier. But, at least
the person
>>>>>>>> said what he did and we should all do that. What nobody knew
back then, was
>>>>>>>> that this broke the default route on VPCs.
>>>>>>>>> Then something strange happens: the two commits from
the PR end up on
>>>>>>>> master as direct commits. With just one LGTM and no verification
from the
>>>>>>>> person commenting about the linked issue. This happened on
Friday September
>>>>>>>> 11th.
>>>>>>>>> That day 21 commits came in, from 7 Pull Request and
unfortunately also
>>>>>>>> from some direct commits. We noticed the direct commits and
notified the
>>>>>>>> list (
As a lot
>>>>>>>> came in at the same time, it was decided not to revert them.
Looking back,
>>>>>>>> we should have done it.
>>>>>>>>> From this point on, VPCs were broken as they wouldn't
get a default
>>>>>>>> route. So, no public internet access from VMs in VPC tiers,
no VPNs
>>>>>>>> working, etc. This was mentioned to the list on Thursday
September 15th,
>>>>>>>> after some chats and debugging going on over the weekend
>>>>>>>>> Here we are, master is broken functionality wise and
new Pull Requests
>>>>>>>> come in to fix blockers. But we cannot ever test their proper
>>>>>>>> because VPCs are broken in master and so also in the PRs
branched off of
>>>>>>>> it. With or without change in the PR.
>>>>>>>>> It starts to escalate as the days go by.
>>>>>>>>> I’ll leave out the bit on how this frustrated people.
Although it’s good
>>>>>>>> to know we do not want to be in this situation.
>>>>>>>>> Eventually Wilder and I spent an evening and a day working
on a branch
>>>>>>>> where we loaded 7 PRs on top of each other (all VR related)
only to find
>>>>>>>> the VPC is still broken. It allowed us to zoom in and find
the default
>>>>>>>> route was missing again. We said it worked 3 weeks before,
because the same
>>>>>>>> tests that succeeded then, now were broken. We had already
fixed this in PR
>>>>>>>> #738 on August 25 so were sure about it.
>>>>>>>>> After some digging we could trace it back to Pull Request
#784. Imagine
>>>>>>>> the feeling seeing your own comment there mentioning the
previous issue on
>>>>>>>> the default gateways. Fair to say our human review process
clearly failed
>>>>>>>> here. Many many hours were spent on this problem over the
past two weeks.
>>>>>>>> Could we have prevented this from happening? I think so,
>>>>>>>>> This example clearly shows why:
>>>>>>>>> - we should use Pull Requests
>>>>>>>>> It made the change visible: Great!
>>>>>>>>> - we do reviews and ask for feedback
>>>>>>>>> We got feedback and questions: Also great!
>>>>>>>>> - we should always respond to feedback and verify it
is resolved, before
>>>>>>>> merging
>>>>>>>>> We need to improve here. Even with two reviewers that
say LGTM, we
>>>>>>>> should still address any feedback before merging.
>>>>>>>>> - we should have two humans doing a review
>>>>>>>>> We need to improve here as well. Not one reviewer, we
need two. Really.
>>>>>>>>> - we need to document why we say LGTM.
>>>>>>>>> Another improvement. It’s nice to say LGTM, but a review
of only 4
>>>>>>>> characters and nothing more is useless. We need to know what
was tested and
>>>>>>>> how. Test results, screen shots or anything that shows what's
>>>>>>>> verified. If you only reviewed the code, also fine but at
least say that.
>>>>>>>> Then the next reviewer should do another type of review to
get the comlete
>>>>>>>> picture. Remember you're replacing automated testing!
>>>>>>>>> - we should always merge Pull Requests
>>>>>>>>> We made it easy, merging is the de facto standard, and
it has even more
>>>>>>>> benefits. You can trace commits back to their Pull Request
(and find all
>>>>>>>> comments and discussion there: saves time, trust me). It
also allows for
>>>>>>>> easier reverting of a Pull Request. We’ll see even more
benefits once 4.7
>>>>>>>> is there. Although the intentions to merge the Pull Request
were there, it
>>>>>>>> still didn't happen. We should always check before we push.
As a committer
>>>>>>>> we just need to be sure.
>>>>>>>>> - we need automated testing!
>>>>>>>>> The sooner the better. It’s all about the missing automated
>>>>>>>> After 4.6, we all need to focus on this. Saves a lot of time.
>>>>>>>> frustrations.
>>>>>>>>> We're doing final testing on PR #887 and will merge it
soon. From that
>>>>>>>> point on we can look into new issues. Be aware that any PR
out there that
>>>>>>>> was created after September 10 needs to be rebased with current
>>>>>>>> (when #887 is merged). Without that, no serious testing can
be done.
>>>>>>>>> Let's be careful what to land on master. I'll only be
merging Pull
>>>>>>>> Requests that have had proper reviews with information on
what was tested.
>>>>>>>> At least one reviewer needs to actually verify it works (and
show the rest
>>>>>>>> of us). We simply cannot assume it will work.
>>>>>>>>> If we do this, I think we can start resolving the remaining
>>>>>>>> one-by-one and go into the first RC round. Please help out
where you can so
>>>>>>>> we can make this a success together. Thanks!
>>>>>>>>> Looking forward to the day we have our automated testing
in place ;-)
>>>>>>>>> Regards,
>>>>>>>>> Remi

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