Introduce config parameter limit label expansion - #261
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In the previous versions, there is no mechanism to limit label expansion. That causes a possibility of cardinality OOM DoS. To mitigate such situation, introduced the following parameters: * max_label_value_length: The maximum length of a label value. * max_series_per_metric: The maximum number of label sets a metric can hold. The above parameter is configurable for filter_prometheus and out_prometheus. For example, if about 8 million records are loaded without cardinality limitation, RSS increased from 64MB to 582MB. It might cause OOM DoS. In contrast to that case with cardinality limitation, RSS increased from 64MB to 84 MB in similar case. Then warning message is logged like this: 2026-08-06 14:06:04 +0900 [warn]: prometheus: dropped a label set because the metric reached max_series_per_metric. name="access_requests_total" max_series_per_metric=10000 Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>
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Seems that once a record has raised an exception, valid records sent afterwards no longer show up in the metric.
Please try attached file to reproduce.
repro-261.tar.gz
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In the previous versions, there is no mechanism to limit label expansion. That causes a possibility of cardinality OOM DoS.
To mitigate such situation, introduced the following parameters:
The above parameter is configurable for filter_prometheus and out_prometheus.