php.compilation.total_time_ms reports microseconds instead of milliseconds since v0.98.0

[dortort]

Description

Since PR #2230 (v0.98.0), the span metric php.compilation.total_time_ms reports values in microseconds rather than milliseconds, inflating reported values by 1000x.

Root cause

PR #2230 replaced the _get_microseconds() helper (which used clock_gettime and returned microseconds) with zend_hrtime() (which returns nanoseconds) in ext/engine_hooks.c, but did not update the accumulator or the serializer divisor:

// Before (correct): _get_microseconds() returned microseconds
DDTRACE_G(compile_time_microseconds) += (int64_t)(_get_microseconds() - start);

// After (incorrect): zend_hrtime() returns nanoseconds, stored as-is
DDTRACE_G(compile_time_microseconds) += (int64_t)(zend_hrtime() - start);

The serializer in ext/serializer.c divides by 1000. expecting microseconds → milliseconds, but now receives nanoseconds, producing microseconds labeled as milliseconds.

Notably, the same PR correctly handled this conversion in circuit_breaker.c:

return zend_hrtime() / 1000;  // correctly converts nanoseconds → microseconds

Evidence

A request with a total duration of ~4,350 ms reported php.compilation.total_time_ms of ~28,346 — impossible if in milliseconds (exceeds request duration), but perfectly reasonable as ~28.3 ms in microseconds.

PHP version

All versions (the bug is in the tracer, not PHP)

Tracer version

>= 0.98.0

Installed extensions

N/A — affects the tracer itself

Output of phpinfo()

N/A