Wire extended heartbeat interval through sidecar

[khanayan123]

Description

The libdatadog telemetry worker already supports telemetry_extended_heartbeat_interval
in its Config (added in libdatadog PR #1824), but the sidecar's SessionConfig and
FFI layer did not expose it. This meant PHP (and any other sidecar consumer) could not
configure the extended heartbeat interval, preventing app-extended-heartbeat events
from being emitted at the desired cadence.

Changes:

• libdatadog sidecar SessionConfig (datadog-sidecar/src/service/mod.rs):
  add telemetry_extended_heartbeat_interval: Duration field

• libdatadog sidecar server (datadog-sidecar/src/service/sidecar_server.rs):
  propagate the new field into the telemetry Config inside modify_telemetry_config

• libdatadog sidecar FFI (datadog-sidecar-ffi/src/lib.rs):
  add telemetry_extended_heartbeat_interval_millis: u64 parameter to
  ddog_sidecar_session_set_config and wire it into SessionConfig

• PHP C header (components-rs/sidecar.h):
  update ddog_sidecar_session_set_config signature with the new parameter

• PHP configuration (ext/configuration.h):
  add DD_TELEMETRY_EXTENDED_HEARTBEAT_INTERVAL config (default 86400 s = 24 hours),
  matching the default in libdd-telemetry

• PHP sidecar call (ext/sidecar.c):
  pass DD_TELEMETRY_EXTENDED_HEARTBEAT_INTERVAL through the FFI call

Note: The libdatadog submodule is pointed at branch
ayan.khan/wire-extended-heartbeat-sidecar which contains the Rust-side changes.
A companion libdatadog PR will be needed to merge those changes to main first,
then the submodule pointer can be updated to the merged commit.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[datadog-datadog-prod-us1-2]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 60.64% (-0.01%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: c038e78 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}

[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-04-15 19:33:06

Comparing candidate commit c038e78 in PR branch ayan.khan/wire-extended-heartbeat-sidecar with baseline commit ad5a7e6 in branch master.

Found 1 performance improvements and 3 performance regressions! Performance is the same for 190 metrics, 0 unstable metrics.

scenario:MessagePackSerializationBench/benchMessagePackSerialization-opcache

• 🟩 execution_time [-5.931µs; -4.209µs] or [-5.504%; -3.906%]

scenario:PDOBench/benchPDOOverhead-opcache

• 🟥 execution_time [+7.131µs; +9.381µs] or [+2.968%; +3.904%]

scenario:PDOBench/benchPDOOverheadWithDBM-opcache

• 🟥 execution_time [+7.248µs; +9.276µs] or [+3.022%; +3.868%]

scenario:PHPRedisBench/benchRedisOverhead

• 🟥 execution_time [+38.859µs; +50.949µs] or [+4.092%; +5.365%]