Update sampling config to use the JSON format (#31247)

GitOrigin-RevId: 1898424d22a71be0ace1a24f0e7f24d227a049e7
get-convex · Nov 7, 2024 · e6d9941 · e6d9941
1 parent 51f3774
commit e6d9941
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Showing 2 changed files with 26 additions and 23 deletions.
diff --git a/crates/common/src/knobs.rs b/crates/common/src/knobs.rs
@@ -1100,35 +1100,38 @@ pub static MAX_PUSH_BYTES: LazyLock<usize> =
     LazyLock::new(|| env_config("MAX_PUSH_BYTES", 100_000_000));
 
 /// Percentage of request traces that should sampled.
-/// Can set a global value, as well as per-route values
 ///
-/// Note that the regexes can't contain commas.
+/// Sampling config is a JSON object with the following format:
+/// {
+///     instanceOverrides: {
+///         instanceName1: [{routeRegexp1: fraction1}, {routeRegexp2:
+/// fraction2}, ...],         instanceName2: [{routeRegexp1: fraction1},
+/// {routeRegexp2: fraction2}, ...],         ...
+///     },
+///     routeOverrides: [{routeRegexp: fraction}, ...],
+///     defaultFraction: fraction
+/// }
 ///
-/// Enable sampling for 10% of /api/push_config and 0.001% of all requests
-/// Use knobs to enable to higher limits for individual instances.
+/// (see also the doc comment on SamplingConfigJson).
 ///
-/// You can also enable sampling for individual instance_names if applicable,
-/// e.g. in Usher.
+/// These apply in order -- the instance overrides take precedence over route
+/// overrides, which take precedence over the default fraction.
 ///
+/// When in doubt, write out a test case to verify the behavior in
+/// minitrace_helpers.rs.
 ///
-/// Examples:
-///   REQUEST_TRACE_SAMPLE_CONFIG=0.01
-///   REQUEST_TRACE_SAMPLE_CONFIG=/route1=0.50,0.01
-///   REQUEST_TRACE_SAMPLE_CONFIG=/route1=0.50,route2=0.50,0.01
-///   REQUEST_TRACE_SAMPLE_CONFIG=/http/.*=0.50
+/// It's often easiest to craft the JSON in a repl (e.g. node, browser console),
+/// and then stringify it at the end.
 ///
-///   REQUEST_TRACE_SAMPLE_CONFIG=carnitas:/route1=0.5,alpastor:1.0,0.01
-///   This configures:
-///   - sampling for "/route1" for instance name "carnitas" to 0.5
-///   - sampling for all methods for instance name "alpastor" to 1.0
-///   - sampling for anything else to 0.01
-
+/// See `minitrace_helpers.rs` for more examples
 pub static REQUEST_TRACE_SAMPLE_CONFIG: LazyLock<SamplingConfig> = LazyLock::new(|| {
     env_config(
         "REQUEST_TRACE_SAMPLE_CONFIG",
         prod_override(
             SamplingConfig::default(),
-            "/api/push_config=0.1,0.00001".parse().unwrap(),
+            r#"{"defaultFraction":0.00001,"routeOverrides":[{"routeRegexp":"/api/push_config","fraction":0.1}]}"#
+                .parse()
+                .unwrap(),
         ),
     )
 });

diff --git a/crates/common/src/minitrace_helpers.rs b/crates/common/src/minitrace_helpers.rs
@@ -339,7 +339,6 @@ mod tests {
             "defaultFraction": 0.01
         }"#
         .parse()?;
-        assert_eq!(config.by_regex.len(), 3);
         assert_eq!(config.sample_ratio("carnitas", "a"), 0.5);
         assert_eq!(config.sample_ratio("carnitas", "b"), 0.15);
         assert_eq!(config.sample_ratio("carnitas", "c"), 0.01);
@@ -351,15 +350,17 @@ mod tests {
             "defaultFraction": 0.0
         }"#
         .parse()?;
-        assert_eq!(config.by_regex.len(), 2);
         assert_eq!(config.sample_ratio("carnitas", "/f/a"), 0.5);
         assert_eq!(config.sample_ratio("carnitas", "/f/b"), 0.5);
         assert_eq!(config.sample_ratio("carnitas", "c"), 0.0);
 
         // Instance overrides.
         let config: SamplingConfig = r#"{
             "instanceOverrides": {
-                "alpastor": [ { "routeRegexp": "a", "fraction": 0.5 } ],
+                "alpastor": [ 
+                    { "routeRegexp": "a", "fraction": 0.5 }, 
+                    { "routeRegexp": "c", "fraction": 0.5 } 
+                ],
                 "carnitas": [ { "routeRegexp": ".*", "fraction": 0.01 } ]
             },
             "routeOverrides": [
@@ -368,13 +369,12 @@ mod tests {
             "defaultFraction": 1.0
         }"#
         .parse()?;
-        assert_eq!(config.by_regex.len(), 4);
         assert_eq!(config.sample_ratio("carnitas", "a"), 0.01);
         assert_eq!(config.sample_ratio("carnitas", "b"), 0.01);
         assert_eq!(config.sample_ratio("carnitas", "c"), 0.01);
         assert_eq!(config.sample_ratio("alpastor", "a"), 0.5);
         assert_eq!(config.sample_ratio("alpastor", "b"), 0.15);
-        assert_eq!(config.sample_ratio("alpastor", "c"), 1.0);
+        assert_eq!(config.sample_ratio("alpastor", "c"), 0.5);
         assert_eq!(config.sample_ratio("chorizo", "a"), 1.0);
         assert_eq!(config.sample_ratio("chorizo", "b"), 0.15);
         assert_eq!(config.sample_ratio("chorizo", "c"), 1.0);