fix(appconfig): #1009 rewrite to not use deprecated appconfig getConfiguration command

[mju-spyrosoft]

#1009

Rewrites parts of appconfig middleware to no longer use deprecated GetConfigurationCommand and use GetLatestConfigurationCommand instead. Basically uses new way of getting appconfig.

• Calls start session configuration once per lambda initialization. See why

This token should only be used once in your first call to GetLatestConfiguration. You must use the new token in the GetLatestConfiguration response (NextPollConfigurationToken) in each subsequent call to GetLatestConfiguration ......

• On subsequent calls will use NextPollConfigurationToken returned by previous api call
• NextConfigurationToken is stored internally in middleware
• Note that fetchData object keys have changed

 key: {
  ApplicationIdentifier: '...',
  ConfigurationProfileIdentifier: '...',
  EnvironmentIdentifier: '...'
 }

@willfarrell I run into case where i'm not sure how it should be handled.
When calling GetLatestConfigurationCommand it may return null value for config if it hasn't change last poll . Its problematic since middy already removed configuration from cache.

You can see this specific case in failing test It should keep previous configuration value if getLatestConfiguration returns null configuration

How to handle this? It could be kept in internal middleware cache in the same way configurationTokens are in this PR but not sure if that's good apporach.

TODO

• change @aws-sdk/client-appconfig to @aws-sdk/client-appconfig-data and update middleware logic
• update skipped tests
• store configuration token in middleware cache
• uninstall @aws-sdk/client-appconfig
• update index.d.ts, index.test.-d.ts
• Move StartConfigurationSessionCommand to cold start part of lambda
• Add test for when mime type is not application/json
• Add test for when StartConfigurationSessionCommand fails
• Run it against real AWS account.
  • feature flag configuration
  • freeform configuration - Appconfig hosted configuration
  • freeform configuration - ssm
• add test for when fetching multiple paramters

[willfarrell]

Thanks for putting this together.

Calls start session configuration once per lambda initialization.

It would make sense to request this as part (StartConfigurationSessionCommand) during the cold start (before precache). This should allow you to combine fetchLatestConfiguration and fetch together and simplify the logic.

Note that fetchData object keys have changed

Because the options will need changing, this will have to be a breaking change and wait for v5. I hope to have an alpha out in the early summer.

When calling GetLatestConfigurationCommand it may return null value for config if it hasn't change last poll . Its problematic since middy already removed configuration from cache.

Storing the previous value as a fallback when the response is null is fine.

[mju-spyrosoft]

It would make sense to request this as part (StartConfigurationSessionCommand) during the cold start (before precache). This should allow you to combine fetchLatestConfiguration and fetch together and simplify the logic.

Sorry not sure if i get it. I can move StartConfigurationSessionCommand to be part of cold start but this would mean that appconfig client creation needs to be part of cold start as well, right?

From what im seeing in all middlewares AWS client are initialized with await createClient(options, request) in before unless they are passed into middleware or are created by prefetch

function startConfigurationSession() {
    for (const internalKey of Object.keys(options.fetchData)) {
      client
      .send(
        new StartConfigurationSessionCommand(options.fetchData[internalKey])
      )
      // put config tokens into token cache
  }

//Cold start stuff
  let prefetch, client
  if (canPrefetch(options)) {
    client = createPrefetchClient(options)
    prefetch = processCache(options, fetch)
  }

  if (!client) {
    client = await createClient(options, request) //No request here. 
  }
  startConfigurationSession()

[willfarrell]

Ah yes, it can't be included always during the cold start because if X-Ray is attached it will break. Super annoying. Don't worry about it. If you can finish off the typings I can merge it in.

Thanks for you help on this.

[mju-spyrosoft]

@willfarrell I think this is almost ready for review. I need to read last time through code and see if workflows are passing. Will try to find time for it today's as soon as possible

[willfarrell]

Haven't forgotten about this, just been busy.

[mju-spyrosoft]

No problem at all. I moved it for ready to review, updated todos in PR description to better reflect changes.

[naorpeled]

LGTM!

[willfarrell]

Didn't mean to close this, give me a few