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"""Record the latency of selected functions."""

from tokenspeed.runtime.metrics.utils import exponential_buckets

enable_metrics = False


def enable_func_timer():
    """Enable Prometheus-backed function latency metrics."""
    # We need to import prometheus_client after setting the env variable `PROMETHEUS_MULTIPROC_DIR`
    from prometheus_client import Histogram

    global enable_metrics, FUNC_LATENCY
    enable_metrics = True

    FUNC_LATENCY = Histogram(
        "tokenspeed:func_latency_seconds",
        "Function latency in seconds",
        # captures latency in range [50ms - ~50s]
        buckets=exponential_buckets(start=0.05, width=1.5, length=18),
        labelnames=["name"],
    )


FUNC_LATENCY = None