The readme of the <dynamo db adapter> states &gt; ...

# http4k

[Philipp Mayer]

The readme of the dynamo db adapter states

Note that there currently is no Fake implementation of the Dynamo adapter. You can use DynamoDB local instead.”

Although there is a fake implementation - is it a leftover? 🙂

[Philipp Mayer]

Seems to be that some guy named David Denton committed this in 2021..

[dave]

Yes. That's a leftover. There is a pretty fully featured fake dynamo now! 🙃

[Philipp Mayer]

That’s why I was surprised! I’ll create a PR.

I’m just having trouble getting it to work - can the fake break when there’s a reverse proxy in-between? Currently debugging..

[dave]

Don't worry about the docs - I'll update them to reflect what FakeDynamo does right now

[dave]

If you can repro it simply I can try to help. It should work very well (although some "SQL like" functions arent supported really - the main operations are)

[Philipp Mayer]

I’m quite sure the problem is 70cm away from the display.
I’m currently wrapping my head around “exploring the testing hyperpyramid”, I’m sure I just forgot to set something correctly.

[Philipp Mayer]

I have the following scenario:
Simple repository class that writes to dynamo db.

The test for wiring up the repository and sticking a fake in it works well: Github

Trying the same with wiring up the whole app fails with a 501: Github

it’s quite a lot of code, I’ll see if I can boil down the example.

[Philipp Mayer]

Running E2ETests gives me a 501 when calling DynamoDb, which is interesting

Looks like the reverse proxy can’t route to the dynamo fake

[dave]

The test fails with a 400 on my machine (from your repo). Is the table created?

[Philipp Mayer]

I’m doing something wrong here, I’m quite sure about it.
It fails with “No mapped host for: http://dynamo-db/“, which is the response by the reverse proxy

[dave]

When running the e2e tests - I get a response 400 from dynamo - it can't find the artists table. Is there another test to run on main?

[Philipp Mayer]

Trying it in the DB test directly works (ofc): https://github.com/p10r/pedro/blob/5212600d2693e8a6ffe6a97894b111ba157b2666/src/test/kotlin/de/p10r/DBTests.kt#L18

[Philipp Mayer]

It will always tries to create the table on instantiation here, which is failing.
The 400 gets raised when the test tries to read from the db.
So first a 501 (from the reverse proxy), then a 400.
Which makes me wonder: Is DynamoDB not set up when I try to create the table, but ready later on?

[dave]

how can i recreate your 501?

[Philipp Mayer]

If you run E2ETests, you’ll see in the logs:

{"timestamp":"2023-10-08T16:28:10.592291Z","event":"Outgoing","data":{"uri":"<http://dynamo-db/>","method":"POST","status":501,"latency":0,"xuriTemplate":""}}
could not create table
RemoteFailure(method=POST, uri=/, status=501 Not Implemented, message=No mapped host for: <http://dynamo-db/>)
{"timestamp":"2023-10-08T16:28:10.808905Z","event":"Outgoing","data":{"uri":"<http://dynamo-db/>","method":"POST","status":400,"latency":36,"xuriTemplate":""}}

I pushed some more debugging stuff

[dave]

this is a timing thing

[dave]

you are trying to create the table before the http has been set in the network access I think

[dave]

networkAccess.http = routes(
      reverseProxyRouting(
        env[DYNAMO_URI].authority to dynamoDb,
        env[TELEGRAM_URI].authority to telegram,
        env[RA_URI].authority to ra,
        Uri.of("<http://pedro>").authority to ProdApp(env, events, networkAccess.debug()),
      )
    )

[dave]

This code calls ProdApp and then once it's done it sets the http on networkaccess

[Philipp Mayer]

Yes, this is also my guess! I’m just trying to figure out how this happens.

[Philipp Mayer]

Ugh, this makes sense. I’m looking way too long on this already.

[dave]

yep - you create the table on the creation of ArtistRepository

[dave]

(which is done by creating your app)

[Philipp Mayer]

Ah yeah, looking in the presentation repo also shows this: https://github.com/http4k/exploring-the-testing-hyperpyramid/blob/f278db75576ba1eb48f567f7b38f74f2805ea5cd/e2e/src/testFixtures/kotlin/hyperpyramid/EcommerceSystem.kt#L31

[Philipp Mayer]

Back to the drawing board. Thanks a ton.

[dave]

np 🙂

[dave]

you should probably just move the creation of the table completely out - otherwise you'll be trying to create it everytime you start you app 🙂

[dave]

Ugh, this makes sense. I’m looking way too long on this already.

[Philipp Mayer]

Yes, this makes sense. 🙂
I think I went too deep into the pyramid, now it’s time to find a way out 😉

[Andrew O'Hara]

Did you solve the reverse-proxy to dynamodb issue? The host must be dynamodb and not dynamo-db. You need to use the same host found in the service interface. For example:

private val internet = reverseProxy(
    "dynamodb" to dynamo
)

And here's where you would find the host to use.
https://github.com/http4k/http4k-connect/blob/master/amazon/dynamodb/client/src/main/kotlin/org/http4k/connect/amazon/dynamodb/DynamoDb.kt#L15

[Philipp Mayer]

Thanks Andrew! I did resolve it - in the end it was exactly the problem David pointed out.