feat(webconnectivity): try all the available THs (#980)

Browse source

We introduce a fork of internal/httpx, named internal/httpapi, where there is a clear split between the concept of an API endpoint (such as https://0.th.ooni.org/) and of an API descriptor (such as using `GET` to access /api/v1/test-list/url).

Additionally, httpapi allows to create a SequenceCaller that tries to call a given API descriptor using multiple API endpoints. The SequenceCaller will stop once an endpoint works or when all the available endpoints have been tried unsuccessfully.

The definition of "success" is the following: we consider "failure" any error that occurs during the HTTP round trip or when reading the response body. We DO NOT consider "failure" errors (1) when parsing the input URL; (2) when the server returns >= 400; (3) when the server returns a string that does not parse as valid JSON. The idea of this classification of failures is that we ONLY want to retry when we see what looks like a network error that may be caused by (collateral or targeted) censorship.

We take advantage of the availability of this new package and we refactor web_connectivity@v0.4 and web_connectivity@v0.5 to use a SequenceCaller for calling the web connectivity TH API. This means that we will now try all the available THs advertised by the backend rather than just selecting and using the first one provided by the backend.

Because this diff is designed to be backported to the `release/3.16` branch, we have omitted additional changes to always use httpapi where we are currently using httpx. Yet, to remind ourselves about the need to do that, we have deprecated the httpx package. We will rewrite all the code currently using httpx to use httpapi as part of future work.

It is also worth noting that httpapi will allow us to refactor the backend code such that (1) we remove code to select a backend URL endpoint at the beginning and (2) we try several endpoints. The design of the code is such that we can add to the mix some endpoints using as `http.Client` a special client using a tunnel. This will allow us to automatically fallback backend queries.

Closes https://github.com/ooni/probe/issues/2353.

Related to https://github.com/ooni/probe/issues/1519.

...

This commit is contained in:

Simone Basso 2022-11-21 16:28:53 +01:00 • committed by GitHub

parent 28aabe0947

commit c2ea0b4704

No known key found for this signature in database

GPG key ID: 4AEE18F83AFDEB23

19 changed files with 2444 additions and 65 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

1163

internal/httpapi/call_test.go Normal file

View file

File diff suppressed because it is too large Load diff