Add if_match support

[Xuanwo]

If-Match is part of HTTP standards. And many storage service support it for conditional requests.

To support If-Match for services, we need to:

• Load if_match from OpRead / OpStat, for example: https://opendal.apache.org/docs/rust/opendal/ops/struct.OpRead.html#method.if_match
• Set If-Match header for request, for example

https://github.com/apache/incubator-opendal/blob/92e0aefe0f7eceae11a6f45c6b8088764c5c780c/core/src/services/obs/core.rs#L96-L98

Tasks

• core: Add if-match support in OpRead/OpWrite/OpStat #1966
• azblob: Add if-match support #1967
• gcs: Add if-match support #1968
• http: Add if-match support #1969
• obs: Add if-match support #1970
• oss: Add if-match support #1971
• s3: Add if-match support #1972

[tobehardest]

Or maybe I can try it, can you assign it to me?

[Xuanwo]

I have assigned this issue to you. Have fun!

[Xuanwo]

Hello, @tobehardest. Do you need help with this issue? I'm available to answer any questions you may have.

[STRRL]

Hi @Xuanwo , I want to take a try. Could you assign it to me?

IIUC, what I need to do is just like OpRead.with_range, append a field like called like if_match in OpRead, then resolve it in different backends.

Another other thing to concern?

One of my other questions is how to write integration tests for this case?

[Xuanwo]

IIUC, what I need to do is just like OpRead.with_range, append a field like called like if_match in OpRead, then resolve it in different backends.

Yes!

One of my other questions is how to write integration tests for this case?

Good question. To write integration test for this feature, we need #1752 first. In strict mode, backend should return NotSupported for unsupported feature. So we can write test by adding a new case with send if_match and ignore the unsupported error.

[STRRL]

One of my other questions is how to write integration tests for this case?

Good question. To write integration test for this feature, we need #1752 first. In strict mode, backend should return NotSupported for unsupported feature. So we can write test by adding a new case with send if_match and ignore the unsupported error.

OK. Great, Strict Mode would help a lot for different backend services with/without the support of If-Match.

But even without "Strict Mode", I could still write some integration tests, right? I want to know how to write integration tests with for the If-Match implementation backend service. Maybe just write test cases under core/tests/behavior?

[Xuanwo]

I want to know how to write integration tests with for the If-Match implementation backend service.

Sadly, we can't write this test without strict mode. The behavior for services that doesn't support If-Match is unknown.