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from typing import Callable, Optional, Sequence, Union
from fastapi import FastAPI
from prometheus_client import REGISTRY, CollectorRegistry, Counter, Histogram, Summary
from prometheus_fastapi_instrumentator import Instrumentator
from prometheus_fastapi_instrumentator.metrics import Info
PING_TOTAL = Counter("ping", "Number of pings calls.")
def my_metrics(
latency_highr_buckets: Sequence[Union[float, str]] = (
0.01,
0.025,
0.05,
0.075,
0.1,
0.25,
0.5,
0.75,
1,
1.5,
2,
2.5,
3,
3.5,
4,
4.5,
5,
7.5,
10,
30,
60,
),
latency_lowr_buckets: Sequence[Union[float, str]] = (0.1, 0.5, 1),
registry: CollectorRegistry = REGISTRY,
) -> Optional[Callable[[Info], None]]:
def is_duplicated_time_series(error: ValueError) -> bool:
return any(
map(
error.args[0].__contains__,
[
"Duplicated timeseries in CollectorRegistry:",
"Duplicated time series in CollectorRegistry:",
],
)
)
if latency_highr_buckets[-1] != float("inf"):
latency_highr_buckets = [*latency_highr_buckets, float("inf")]
if latency_lowr_buckets[-1] != float("inf"):
latency_lowr_buckets = [*latency_lowr_buckets, float("inf")]
# Starlette will call app.build_middleware_stack() with every new middleware
# added, which will call all this again, which will make the registry
# complain about duplicated metrics.
#
# The Python Prometheus client currently doesn't seem to have a way to
# verify if adding a metric will cause errors or not, so the only way to
# handle it seems to be with this try block.
try:
TOTAL = Counter(
name="http_requests_total",
documentation="Total number of requests by method, status and handler.",
labelnames=(
"my_method",
"my_status",
"my_handler",
),
registry=registry,
)
IN_SIZE = Summary(
name="http_request_size_bytes",
documentation=(
"Content length of incoming requests by handler. "
"Only value of header is respected. Otherwise ignored. "
"No percentile calculated. "
),
labelnames=("my_handler",),
registry=registry,
)
OUT_SIZE = Summary(
name="http_response_size_bytes",
documentation=(
"Content length of outgoing responses by handler. "
"Only value of header is respected. Otherwise ignored. "
"No percentile calculated. "
),
labelnames=("my_handler",),
registry=registry,
)
LATENCY_HIGHR = Histogram(
name="http_request_duration_highr_seconds",
documentation=(
"Latency with many buckets but no API specific labels. "
"Made for more accurate percentile calculations. "
),
buckets=latency_highr_buckets,
registry=registry,
)
LATENCY_LOWR = Histogram(
name="http_request_duration_seconds",
documentation=(
"Latency with only few buckets by handler. "
"Made to be only used if aggregation by handler is important. "
),
buckets=latency_lowr_buckets,
labelnames=(
"my_method",
"my_handler",
),
registry=registry,
)
def instrumentation(info: Info) -> None:
TOTAL.labels(info.method, info.modified_status, info.modified_handler).inc()
IN_SIZE.labels(info.modified_handler).observe(
int(info.request.headers.get("Content-Length", 0))
)
if info.response and hasattr(info.response, "headers"):
OUT_SIZE.labels(info.modified_handler).observe(
int(info.response.headers.get("Content-Length", 0))
)
else:
OUT_SIZE.labels(info.modified_handler).observe(0)
if info.modified_status.startswith("2"):
LATENCY_HIGHR.observe(info.modified_duration)
LATENCY_LOWR.labels(info.modified_handler, info.method).observe(
info.modified_duration
)
return instrumentation
except ValueError as e:
if not is_duplicated_time_series(e):
raise e
return None
app = FastAPI()
Instrumentator().instrument(app).add(my_metrics()).expose(app)
@app.get("/ping")
def get_ping():
PING_TOTAL.inc()
return "pong"
|
