Changing the Set internals makes a lot of sense as it saves doing
conversions in multiple places and gives a central place to alter
the key when a item is computed.
This will have no side effects other then that the ordering is now
based on strings instead on integers, so the order will be different.
This will however have no effect on existing configs as these will
use the individual codes/keys and not the ordering to determine if
there is a diff or not.
Lastly (but I think also most importantly) there is a fix in this PR
that makes diffing sets extremely more performand. Before a full diff
required reading the complete Set for every single parameter/attribute
you wanted to diff, while now it only gets that specific parameter.
We have a use case where we have a Set that has 18 parameters and the
set consist of about 600 items (don't ask 😉). So when doing a diff
it would take 100% CPU of all cores and stay that way for almost an
hour before being able to complete the diff.
Debugging this we learned that for retrieving every single parameter
it made over 52.000 calls to `func (c *ResourceConfig) get(..)`. In
this function a slice is created and used only for the duration of the
call, so the time needed to create all needed slices and on the other
hand the time the garbage collector needed to clean them up again caused
the system to cripple itself. Next to that there are also some expensive
reflect calls in this function which also claimed a fair amount of CPU
time.
After this fix the number of calls needed to get a single parameter
dropped from 52.000+ to only 2! 😃
This was actually quite nasty as the first bug covered the second one…
The first bug is with HasChange. This function uses reflect.DeepEqual
to check if two instances are the same/have the same content. This
works fine for all types except for Set’s as they contain a function.
And reflect.DeepEqual will only say the functions are equal if they are
both nil (which they aren’t in a Set). So in effect it means that
currently HasChange will always say true for Set’s, even when they are
actually being equal.
As soon as you fix this problem, you will notice the second one (which
the added test is written for). Without saying you want the exact diff,
you will end up with a merged value which will (in most cases) be the
same.
Run all unit tests and a good part of the acc tests to verify this
works as expected and all look good.
/cc @svanharmelen - I think some logic changed after my refactor. I now
return Exists: true when Computed: true but the value might be blank to
note that the FieldReader FOUND a value, its just unknown. I think
before it didn't do that so the logic for GetOk has to be "does it exist
and is it _not_ computed"
Seems weird because I just realized there is no way to get the OLD value
of something if it is being computed now, but I looked and there are
tests that verify this and they're like... test #5 of Get. So, they're
not new meaning that must've been expected behavior? Hm. Let me know if
you find any other issues from acceptance tests
This is a refactored solution for PR #616. Functionally this is still
the same change, but it’s implemented a lot cleaner with less code and
less changes to existing parts of TF.
Prior to this, the diff only contained changed set elements. The issue
with this is that `getSet`, the internal function that reads a set from
the ResourceData, expects that each level (state, config, diff, etc.)
has the _full set_ information. This change was done to fix merging
issues.
Because of this, we need to make sure the full set is visible in the
diff.
I know it’s very unlikely that a user will notice the difference, but
why range through the list, generate the set and calculate the
hashcode, only to find out that indexMap == nil (e.g. don’t do anything
with the generated hashcode).
As indexMap is only needed when len(parts) > 0, why not only create and
fill it (in one go) when len(parts) > 0?
This fixes a seemingly minor issue (GH-255) around plans showing changes
when in fact there are none. But in reality this turned out to uncover a
really terrible bug.
The effect of what was happening was that multiple items in a set were
being merged. Now, they were being merged in the right order, so if you
didn't have rich types (lists in a set) then you never saw the effect
since the later value would overwrite the earlier. But with lists (such
as in security groups), you would end up with the lists merging. So, if
you had one ingress rule with CIDR blocks and one with SGs, then after
the merge both ingress rules would have BOTH CIDR and SGs, resulting in
an incorrect plan (GH-255).
This fixes the issue by introducing a `getSourceExact` bitflag to the
ResourceData source. When this is set, ALL data must come from this
level, instead of merging lower levels. In the case of sets and diffs,
this is exactly what you want: "Get me the set 'foo' from the config and
the config ONLY (not the state or diff or w/e)".
Andddddd its fixed.
GH-255
Sander van Harmelen