disable-last-modified-behaviour-ipns-routes

[cong-or]

7968 Webgateway: sets 'last-modified' header to now()

@RubenKelevra @Stebalien

As per the documentation:

If modtime is not zero time, ServeContent includes it in the Last-Modified header in the response. If the request includes an If-Modified-Since header, ServeContent uses modtime to determine whether the content needs to be sent at all.

To disable this behaviour, pass a "zero" date to ServeContent.

This change only effects ipns routes not ipfs routes.

[RubenKelevra]

Question: Don't we already cache the ipns record and "know" when we last updated it? 🤔

Shouldn't we use this value instead of sending a "0"?

[cong-or]

@RubenKelevra

Do you know where the ipns record is cached?

If so, it would make sense to use this value instead of "0".

However, if it's hard to extract, it might be best to just omit the header with "0" to avoid confusion.

[RubenKelevra]

@mycorrhizas nope. I only remember the setting in the config to specify the size. Would have to look it up where the value is used.

[lidel]

I've added sharness tests for HTTP headers related to caching but think this PR needs more work before can be safely merged.

Namely, I am worried that removal of Last-Modified without replacing it with an explicit Cache-Control will introduce performance regression around HTTP caching. See my comment about browsers using Last-Modified as weak signal for how long to cache page: https://github.com/ipfs/go-ipfs/issues/1818#issuecomment-450866591

Cache-Control based on /ipns/ TTL

Ideally, /ipns/* should return Cache-Control based on TTL from IPNS record or DNSLink (TTL of a TXT record on DNS).

@aschmahmann to resolve this, we need to extend the namesys interface to return TTL of both record types in addition to Path.

I think we decided that is out of scope for #8068, so we may want to park this PR until 0.9 ships and aim at 0.10+, but we need to do this at some point: otherwise every IPNS website will be a bit slower due to unnecessary requests than it should.

UPDATE: now tracked in https://github.com/ipfs/go-ipfs/issues/1818#issuecomment-1015849462

Related:

• https://github.com/ipfs/go-ipfs/issues/1818
• Add TTL to /api/v0/dns #5884
• IPNS record TTL/caching improvements #7564

[BigLep]

This is blocked until TTLs are respected in DNSLink and IPNS. (https://github.com/ipfs/go-ipfs/issues/1818#issuecomment-1015849462)

[cong-or]

This is blocked until TTLs are respected in DNSLink and IPNS.

👍