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zeitlinger merged 4 commits into from
Aug 19, 2026
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docs: document scrape query limits in request API #2391

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3519167
docs: document scrape query limits
zeitlinger Aug 18, 2026
5c2b6b8
docs: clarify scrape query limit configuration
zeitlinger Aug 18, 2026
1a68d61
style: format query limit documentation
zeitlinger Aug 18, 2026
7785168
docs: clarify scrape query limits are fixed
zeitlinger Aug 19, 2026
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3 changes: 2 additions & 1 deletion docs/content/exporters/filter.md
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Expand Up @@ -23,7 +23,8 @@ params:

For safety, exporters limit the query string to 65,536 characters and accept at most 1,024
query parameters. The parameter limit counts every `&`-separated pair, including repeated
parameters and empty pairs.
parameters and empty pairs. These are fixed implementation limits and cannot be changed through
runtime configuration.

If a request exceeds either limit or contains invalid percent-encoding, the `/metrics` endpoint
returns HTTP `400 Bad Request` with the plain-text response `Invalid query parameters`.
10 changes: 9 additions & 1 deletion ...ter-common/src/main/java/io/prometheus/metrics/exporter/common/PrometheusHttpRequest.java
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Expand Up @@ -41,7 +41,15 @@ default String getParameter(String name) {
}
}

/** See {@code jakarta.servlet.ServletRequest.getParameterValues(String)} */
/**
* See {@code jakarta.servlet.ServletRequest.getParameterValues(String)}.
*
* <p>For safety, the default implementation applies two fixed limits: {@code maxQueryStringLength
* = 64 * 1024} (65,536 characters) and {@code maxQueryParameterCount = 1024} ({@code &}-separated
* parameter pairs). These implementation values are not exposed as runtime configuration.
* Requests that exceed either limit or contain invalid percent-encoding are rejected by the
* scrape handler with HTTP {@code 400 Bad Request}.
*/
@Override
@Nullable
// decode with Charset is only available in Java 10+, but we want to support Java 8
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