Quick question on aws_retry_token_record_success

[quinnj]

In the docs, it says:

/**
 * Records a successful retry. This is used for making future decisions to open up token buckets, AIMD breakers etc...
 * some strategies such as exponential backoff will ignore this, but you should always call it after a successful
 * operation or your system will never recover during an outage.
 */
AWS_IO_API int aws_retry_token_record_success(struct aws_retry_token *token);

but in the s3_client.c implementation, it seems that even if we didn't have to call aws_retry_strategy_schedule_retry, it calls aws_retry_token_record_success.

My question is then if the usage is to always call aws_retry_token_record_success, even if no actual retry was required (this is assuming a similar workflow to the s3_client.c where a retry_token is acquired for every request before the request is first attempted).

[graebm]

The idea behind an aws_retry_token, is that you should be holding one when you perform any HTTP request, even if it's your first try. Then you need to inform the system whether or not the token was used successfully (by calling aws_retry_token_record_success() to indicate success, or aws_retry_strategy_schedule_retry() to indicate failure). Finally, after you are 100% done with the token, you call aws_retry_token_release() to decrement its ref-count and allow its memory to be cleaned up.

The flow should be like:

1. you have an HTTP request you want to execute...
2. you call aws_retry_strategy_acquire_retry_token():
   • if that fails immediately, or the callback informs you it failed, then you permanently fail the HTTP request: GOTO FAIL
3. else you successfully receive your aws_retry_token...
4. you execute your HTTP request...
5. if the HTTP request succeeds:
   • you call aws_retry_token_record_success() then aws_retry_token_release(): GOTO SUCCESS
6. else the HTTP request failed, so you want to retry...
7. you call aws_retry_strategy_schedule_retry()
   • if that fails immediately, or the callback informs you it failed, then you call aws_retry_token_release() and then permanently fail the HTTP request: GOTO FAIL
8. else you successfully got permission to retry: GOTO step 4 (executing your HTTP request again)

[quinnj]

Excellent clarification. Thanks @graebm. And I'm assuming the answer is yes, but aws_retry_strategy_schedule_retry will fail once the max number of retries has been attempted?

[graebm]

yes

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.