fix: move object store read/write timer into inner

[dimbtp]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

#3622

What's changed and what's your intention?

Move timer from read/write function into PrometheusMetricWrapper and update data when dropping to get accurate metric.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[dimbtp]

Question:
In #3622, the inner method returns a writer which indicates that the actual write operation does not perform yet, but I don't find write function try to return a writer. It seems all the write jobs are awaited.

[evenyag]

Question: In #3622, the inner method returns a writer which indicates that the actual write operation does not perform yet, but I don't find write function try to return a writer. It seems all the write jobs are awaited.

The return value of that async method is (RpWrite, Self::Writer). So we only get a writer after await.

greptimedb/src/object-store/src/layers/prometheus.rs

Line 179 in bfd3257

async fn write(&self, path: &str, args: OpWrite) -> Result<(RpWrite, Self::Writer)> {

The operator writes to the writer later.
https://github.com/apache/opendal/blob/50791255c6ef3ed259c88dcc04a4295fa60fa443/core/src/types/operator/operator.rs#L1246-L1250

You could refer to the metrics layer in opendal v0.45.1
https://github.com/apache/opendal/blob/v0.45.1/core/src/layers/metrics.rs#L744-L752
https://github.com/apache/opendal/blob/v0.45.1/core/src/layers/metrics.rs#L765-L773

It observes the timer in drop()

impl<R> Drop for MetricWrapper<R> {
    fn drop(&mut self) {
        self.bytes_counter.increment(self.bytes);
        if let Some(instant) = self.start {
            let dur = instant.elapsed().as_secs_f64();
            self.requests_duration_seconds.record(dur);
        }
    }
}

This behavior changes in the main branch after apache/opendal#4381 but v0.45.1 is still the latest release we are using so we should follow its implementation. I have updated links in #3622

[codecov]

Codecov Report

Attention: Patch coverage is 65.51724% with 30 lines in your changes are missing coverage. Please review.

Project coverage is 84.81%. Comparing base (6c316d2) to head (1372e5d).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3627      +/-   ##
==========================================
- Coverage   85.36%   84.81%   -0.55%     
==========================================
  Files         935      943       +8     
  Lines      156348   156962     +614     
==========================================
- Hits       133463   133128     -335     
- Misses      22885    23834     +949     

[dimbtp]

@evenyag Thanks for your information. Please take a took.

[evenyag]

We should move the histogram timer to the PrometheusMetricWrapper. The timer will track the start time and duration for us.

[dimbtp]

@evenyag I leave some messages, please take a look.

[evenyag]

We can get rid of Option in this way.

[evenyag]

LGTM

[killme2008]

LGTM