The imperative part of that code appears to be analogous to templating. The actual work done under the covers is not imperative, but is based on the difference between the result of the template execution and the current state of the system. That's what makes it declarative.
It really depends on the interaction between the user's Pulumi script and the Pulumi engine.
If there is more than one back and forth, you become declarative, even if you imperatively generate a "declarative" intermediate representation (not really sure what state file at a point in time could ever be imperative), you then would get back some data from the engine, then make choices about what to send off to the engine in the next request.
It's important to understand that with Pulumi, you can end up in either situation. You have to be careful to not become imperative overall is probably the better way to consider this.
Another way this can break down is if the user writes code to call the same APIs in the middle of a Pulumi script. I meant to try this myself to verify it works, but I would assume that Pulumi is not stopping me from doing something like this.
In general maybe, but in the specific context above, I think calling that loop declarative is accurate, and laughing at that classification is a poor response rooted in a deep misunderstanding.
import pulumi
from pulumi_gcp import storage
bucket = "hof-io--develop-internal"
name = "pulumi/hack/condition.txt"
cond = False
msg = "running"
cnt = 0
while not cond:
cnt += 1
key = storage.get_bucket_object_content(name=name, bucket=bucket)
print(cnt, key.content)
if key.content == "exit":
msg = "hallo!"
break
pulumi.export('msg', msg)
pulumi.export('cnt', cnt)
---
769 exit
770 exit
771 exit
772 exit
773 exit
774 exit
775 exit
Outputs:
cnt: 775
msg: "hallo!"
Resources:
+ 1 to create
info: There are no resources in your stack (other than the stack resource).
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Of note, all but the last exit had a newline, until I `echo -n` the file I copied up
TF might be susceptible to the same file contents manipulation between plan & apply as well, but then again, you can save a plan to a file and then run it later, so maybe not? Another experiment seems to be in order
I think this is an advantage of Pulumi, here are two use cases:
1. Creating a resource where created is not the same as ready. This is extraordinarily common with compute resources (a virtual machine, a container, an HTTP server, a process) where attempting to create follow-up resources can result in costly retry-back-off loops. Even when creating Kubernetes resources, Pulumi will stand up an internet-connected deployment more quickly than many other tools because you can ensure the image is published before a pod references it, the pod is up before a service references it, and so on. (The Kubernetes provider bakes some of these awaits in by default.)
2. Resources graphs that are dynamic, reflecting external data sources at the moment of creation. Whether you want to write a Kubernetes operator, synchronize an LDAP directory to a SaaS product, or one of my favorite examples. When I set up demos, I often configure the authorized public IPs dynamically:
import * as publicIp from 'public-ip';
new someProvider.Kubernetes.Cluster('cluster',
{
apiServerAccessProfile: {
authorizedIPRanges: [await publicIp.v4()],
enablePrivateCluster: false,
},
}
Of course you think it is an advantage, you work for Pulumi
I'm telling you this is not how a potential user sees the same situation, that it is a disadvantage and was one of the reasons we are not making the switch.
This example above is exactly the kind of code we don't want in ops, it depends on the user environment and physical location at the time they run the command, bad practice. Thanks for an extra talking point though
The claim above is that Pulumi uses an imperative interface and that it is quite easy to slip past the declarative guardrails, so in most cases Pulumi is imperative, not declarative. The fact that Pulumi makes this separation opaque can be discussed, as can the clear separation be shown an alternative with benefits
The claim I keep seeing from Pulumi folks is that Pulumi is declarative, which is is not, as shown in multiple posts by many people. Please stop calling it such, it demonstrates dishonesty towards users
When someone tries to make a sophisticated argument that up is down and white is black, dismissive and shallow is the right response.
> The actual work done under the covers is not imperative
Having a declarative layer somewhere in the stack doesn't make something declarative, if that's not the layer you actually use to work on and reason about the system. See the famous "the C language is purely functional" post.
you can have loops and still be declarative, CUE has loops, though they are considered comprehensions more technically, but there is no assignment or stack in CUE
One of the interesting aspects of CUE is that it gives us many of the programming constructs we are used to, but remains Turing incomplete, so no general recursion or user defined functions. There is a scripting layer where you can get more real world stuff done too
The CUE language is super interesting, has a very unique take on things and comes from the same heritage as Go, containers, and Kubernetes
The imperative part of that code appears to be analogous to templating. The actual work done under the covers is not imperative, but is based on the difference between the result of the template execution and the current state of the system. That's what makes it declarative.