Transports: remove api_version

[p-datadog]

What does this PR do?

Removes api_version from transports.

There are actually four different meanings of "api version";

1. The one that this PR is removing. I think this concept dates back to before we had the current API::Map and Endpoint classes, and this is how different endpoints were selected. In master this api version is never passed in explicitly and is always defaulted to nil. As far as I can tell it doesn't do anything.
2. Telemetry has a parameter called "api version". This is actually sent in the payloads, and is presently set to v2 in telemetry itself as a default. External to telemetry callers never provide a different api version. Given our transport architecture I don't think it would work to change the endpoint by just providing a different version externally to a component like telemetry.
3. Tracing has a parameter called "api version". I think it's conceptually the same thing as the first type of "api version" and may be the precursor to "api version" being in core component code. This one is in the public API, therefore I retained the transport_options argument in one place and added notes that it's now ignored. The transport code in master already does not use transport_options or the api version provided therein, as far as I can tell.
4. There are one or two places that refer to our existing endpoints as "api versions". I think this conceptually goes with the first usage again but now "api version" is an Endpoint/Instance(?) object instead of a string, I am very confused what the actual type of value is supposed to be passed in. Luckily as far as I can tell thus parameter is never actually used so it doesn't matter.

Motivation:
Continuing cleanup of transport code

Change log entry
None

Additional Notes:

How to test the change?

Existing CI

[github-actions]

Typing analysis

Note: Ignored files are excluded from the next sections.

Untyped methods

This PR introduces 5 untyped methods and 4 partially typed methods, and clears 4 untyped methods and 5 partially typed methods.

Untyped methods (+5-4)

❌ Introduced:

sig/datadog/core/telemetry/transport/http/telemetry.rbs:23
└── def headers: (request_type: untyped, api_key: untyped) -> untyped
sig/datadog/core/telemetry/transport/http.rbs:6
└── def self?.agentless_telemetry: (agent_settings: untyped, logger: untyped, ?api_key: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/telemetry/transport/http.rbs:7
└── def self?.agent_telemetry: (agent_settings: untyped, logger: untyped, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/di/transport/http.rbs:5
└── def self.diagnostics: (agent_settings: untyped, logger: untyped, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/di/transport/http.rbs:6
└── def self.input: (agent_settings: untyped, logger: untyped, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped

✅ Cleared:

sig/datadog/core/telemetry/transport/http.rbs:6
└── def self?.agentless_telemetry: (agent_settings: untyped, logger: untyped, ?api_key: untyped?, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/telemetry/transport/http.rbs:7
└── def self?.agent_telemetry: (agent_settings: untyped, logger: untyped, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/di/transport/http.rbs:5
└── def self.diagnostics: (agent_settings: untyped, logger: untyped, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/di/transport/http.rbs:6
└── def self.input: (agent_settings: untyped, logger: untyped, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped

Partially typed methods (+4-5)

❌ Introduced:

sig/datadog/core/remote/transport/http.rbs:6
└── def self?.root: (agent_settings: untyped, logger: Core::Logger, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/remote/transport/http.rbs:7
└── def self?.v7: (agent_settings: untyped, logger: Core::Logger, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/telemetry/request.rbs:5
└── def self.build_payload: (Event::Base event, int seq_id, ?debug: bool) -> ::Hash[Symbol, untyped]
sig/datadog/core/transport/http.rbs:5
└── def self?.build: (agent_settings: untyped, ?logger: untyped, ?headers: untyped?) { (untyped) -> untyped } -> HTTP::Builder

✅ Cleared:

sig/datadog/core/remote/transport/http.rbs:6
└── def self?.root: (agent_settings: untyped, logger: Core::Logger, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/remote/transport/http.rbs:7
└── def self?.v7: (agent_settings: untyped, logger: Core::Logger, ?api_version: untyped?, ?headers: untyped?) ?{ (untyped) -> untyped } -> untyped
sig/datadog/core/telemetry/request.rbs:5
└── def self.build_payload: (Event::Base event, int seq_id, ?api_version: String, ?debug: bool) -> ::Hash[Symbol, untyped]
sig/datadog/core/telemetry/transport/http/telemetry.rbs:23
└── def headers: (request_type: untyped, api_key: untyped, ?api_version: ::String) -> untyped
sig/datadog/core/transport/http.rbs:5
└── def self?.build: (agent_settings: untyped, ?logger: untyped, ?api_version: untyped?, ?headers: untyped?) { (untyped) -> untyped } -> HTTP::Builder

If you believe a method or an attribute is rightfully untyped or partially typed, you can add # untyped:accept to the end of the line to remove it from the stats.

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 94.23%
• Overall Coverage: 95.22% (+0.01%)

View detailed report

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: d9cb568 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-12-31 18:05:45

Comparing candidate commit 78855c2 in PR branch transport-api-version with baseline commit 1efce15 in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 43 metrics, 2 unstable metrics.

scenario:profiling - hold / resume

• 🟥 throughput [-134859.389op/s; -131641.926op/s] or [-7.808%; -7.621%]

[vpellan]

LGTM

[p-datadog]

Following up on discussion with @marco I have done a manual test passing headers via transport_options and this seems to work in master, despite having no test coverage in our library:

as=Datadog::Core::Configuration::AgentSettingsResolver.call(Datadog.configuration)
writer=Datadog::Tracing::Writer.new(agent_settings:as,transport_options:{headers:{foo: 'bar'}})
writer.transport

#<Datadog::Tracing::Transport::Traces::Transport:0x00007afc1b36b1d0
 @apis=
  {"v0.4"=>
    #<Datadog::Core::Transport::HTTP::API::Instance:0x00007afc1bd2a7e8
     @adapter=
      #<Datadog::Core::Transport::HTTP::Adapters::Net:0x00007afc1b36b310
       @hostname="127.0.0.1",
       @port=8126,
       @ssl=false,
       @timeout=30>,
     @endpoint=
      #<Datadog::Tracing::Transport::HTTP::Traces::API::Endpoint:0x00007afc1b36b2c0
       @encoder=Datadog::Core::Encoding::MsgpackEncoder,
       @path="/v0.4/traces",
       @service_rates=true,
       @verb=:post>,
     @headers=
      {"Datadog-Client-Computed-Top-Level"=>"1",
       "Datadog-Meta-Lang"=>"ruby",
       "Datadog-Meta-Lang-Version"=>"3.3.4",
       "Datadog-Meta-Lang-Interpreter"=>"ruby-x86_64-linux",
       "Datadog-Meta-Lang-Interpreter-Vendor"=>"ruby",
       "Datadog-Meta-Tracer-Version"=>"2.24.0",
       :foo=>"bar"}>,
   "v0.3"=>
    #<Datadog::Core::Transport::HTTP::API::Instance:0x00007afc1bd2a798
     @adapter=
      #<Datadog::Core::Transport::HTTP::Adapters::Net:0x00007afc1b36b310
       @hostname="127.0.0.1",
       @port=8126,
       @ssl=false,
       @timeout=30>,
     @endpoint=
      #<Datadog::Tracing::Transport::HTTP::Traces::API::Endpoint:0x00007afc1b36b220
       @encoder=Datadog::Core::Encoding::MsgpackEncoder,
:

I will reinstate transport_options and add a test passing headers through it.

[p-datadog]

We identified https://github.com/DataDog/datadog-lambda-rb/blob/main/lib/datadog/lambda.rb as a consumer of our tracing Writer classes. This consumer does not pass transport_options at all and should thus not be affected by the changes in this PR.