From 967a6745ba487edaff558e36fdc572c6ca066fea Mon Sep 17 00:00:00 2001
From: Maddie Zechar <mez2113@columbia.edu>
Date: Tue, 7 Feb 2023 00:26:39 +0000
Subject: SERVER-71882 Add serverStatus metric for the number of entries
 evicted from the telemetry store

---
 .../telemetry/telemetry_server_status_metrics.js   | 80 ++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 jstests/telemetry/telemetry_server_status_metrics.js

(limited to 'jstests')

diff --git a/jstests/telemetry/telemetry_server_status_metrics.js b/jstests/telemetry/telemetry_server_status_metrics.js
new file mode 100644
index 00000000000..2f31d4bd9ba
--- /dev/null
+++ b/jstests/telemetry/telemetry_server_status_metrics.js
@@ -0,0 +1,80 @@
+/**
+ * Test the telemetry related serverStatus metrics.
+ */
+load('jstests/libs/analyze_plan.js');
+load("jstests/libs/feature_flag_util.js");
+
+(function() {
+"use strict";
+
+if (!FeatureFlagUtil.isEnabled(db, "Telemetry")) {
+    return;
+}
+
+function runTestWithMongodOptions(options, test, resetCacheSize) {
+    const conn = MongoRunner.runMongod(options);
+    const testDB = conn.getDB('test');
+    const coll = testDB[jsTestName()];
+
+    test(conn, testDB, coll, resetCacheSize);
+
+    MongoRunner.stopMongod(conn);
+}
+
+// Test serverStatus metric which counts the number of evicted
+// entries.
+function evictionTest(conn, testDB, coll, resetCacheSize) {
+    const evictedBefore = testDB.serverStatus().metrics.telemetry.numEvicted;
+    assert.eq(evictedBefore, 0);
+    for (var i = 0; i < 100; i++) {
+        let query = {};
+        for (var j = 0; j < 25; ++j) {
+            query["foo.field.xyz." + i + "." + j] = 1;
+            query["bar.field.xyz." + i + "." + j] = 2;
+            query["baz.field.xyz." + i + "." + j] = 3;
+        }
+        coll.aggregate([{$match: query}]).itcount();
+    }
+    if (!resetCacheSize) {
+        const evictedAfter = testDB.serverStatus().metrics.telemetry.numEvicted;
+        assert.gt(evictedAfter, 0);
+        return;
+    }
+    // Make sure number of evicted entries increases when the cache size is reset, which forces out
+    // least recently used entries to meet the new, smaller size requirement.
+    assert.eq(testDB.serverStatus().metrics.telemetry.numEvicted, 0);
+    assert.commandWorked(
+        testDB.adminCommand({setParameter: 1, internalQueryConfigureTelemetryCacheSize: "2MB"}));
+    const evictedAfter = testDB.serverStatus().metrics.telemetry.numEvicted;
+    assert.gt(evictedAfter, 0);
+}
+
+/**
+ * In this configuration, every query is sampled. Each query has a key(~2200 - 2300 bytes) and
+ * value(208 bytes). With a cache size of 3MB, there are 1024 partitions, each of max size ~ 3072
+ * bytes. Each partition will only be able to fit one entry, eg a partition with one entry will be
+ * considered full. When a second query shape/key falls into an already full partition, it will have
+ * to evict the original entry.
+ *
+ * */
+runTestWithMongodOptions({
+    setParameter: {
+        internalQueryConfigureTelemetryCacheSize: "3MB",
+        internalQueryConfigureTelemetrySamplingRate: 2147483647
+    },
+},
+                         evictionTest,
+                         false);
+/**
+ * In this configuration, every query is sampled. Due to the large initial cache size, entries
+ * should only be evicted once the cache is reset after telemetry metric collecting, is finished.
+ * */
+runTestWithMongodOptions({
+    setParameter: {
+        internalQueryConfigureTelemetryCacheSize: "10MB",
+        internalQueryConfigureTelemetrySamplingRate: 2147483647
+    },
+},
+                         evictionTest,
+                         true);
+}());
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