feat(client): add latency histogram (#3099)

* add latency histogram command, tests (##1955)

packages/client/lib/commands/LATENCY_HISTOGRAM.spec.ts

@@ -0,0 +1,93 @@
+import assert from "node:assert/strict";
+import testUtils, { GLOBAL } from "../test-utils";
+import LATENCY_HISTOGRAM from "./LATENCY_HISTOGRAM";
+import { parseArgs } from "./generic-transformers";
+
+describe("LATENCY HISTOGRAM", () => {
+  describe("transformArguments", () => {
+    it("filtered by command set", () => {
+      assert.deepEqual(parseArgs(LATENCY_HISTOGRAM, "set"), [
+        "LATENCY",
+        "HISTOGRAM",
+        "set",
+      ]);
+    });
+
+    it("unfiltered", () => {
+      assert.deepEqual(parseArgs(LATENCY_HISTOGRAM), [
+        "LATENCY",
+        "HISTOGRAM",
+      ]);
+    });
+  });
+
+  describe("RESP 2", () => {
+    testUtils.testWithClient(
+      "unfiltered list",
+      async (client) => {
+        await client.configResetStat();
+        await Promise.all([
+          client.lPush("push-key", "hello "),
+          client.set("set-key", "world!"),
+        ]);
+        const histogram = await client.latencyHistogram();
+        const commands = ["config|resetstat", "set", "lpush"];
+        for (const command of commands) {
+          assert.ok(typeof histogram[command]["calls"], "number");
+        }
+      },
+      GLOBAL.SERVERS.OPEN,
+    );
+
+    testUtils.testWithClient(
+      "filtered by a command list",
+      async (client) => {
+        await client.configSet("latency-monitor-threshold", "100");
+        await client.set("set-key", "hello");
+        const histogram = await client.latencyHistogram("set");
+        assert.ok(typeof histogram.set["calls"], "number");
+      },
+      GLOBAL.SERVERS.OPEN,
+    );
+  });
+
+  describe("RESP 3", () => {
+    testUtils.testWithClient(
+      "unfiltered list",
+      async (client) => {
+        await client.configResetStat();
+        await Promise.all([
+          client.lPush("push-key", "hello "),
+          client.set("set-key", "world!"),
+        ]);
+        const histogram = await client.latencyHistogram();
+        const commands = ["config|resetstat", "set", "lpush"];
+        for (const command of commands) {
+          assert.ok(typeof histogram[command]["calls"], "number");
+        }
+      },
+      {
+        ...GLOBAL.SERVERS.OPEN,
+        clientOptions: {
+          RESP: 3,
+        },
+      },
+    );
+
+    testUtils.testWithClient(
+      "filtered by a command list",
+      async (client) => {
+        await client.configSet("latency-monitor-threshold", "100");
+        await client.set("set-key", "hello");
+        const histogram = await client.latencyHistogram("set");
+        assert.ok(typeof histogram.set["calls"], "number");
+      },
+      {
+        ...GLOBAL.SERVERS.OPEN,
+        clientOptions: {
+          RESP: 3,
+        },
+      },
+    );
+  });
+});

packages/client/lib/commands/LATENCY_HISTOGRAM.ts

@@ -0,0 +1,46 @@
+import { CommandParser } from '../client/parser';
+import { Command } from '../RESP/types';
+import { transformTuplesToMap } from './generic-transformers';
+
+type RawHistogram = [string, number, string, number[]];
+
+type Histogram = Record<string, {
+  calls: number;
+  histogram_usec: Record<string, number>;
+}>;
+
+const id = (n: number) => n;
+
+export default {
+  CACHEABLE: false,
+  IS_READ_ONLY: true,
+  /**
+   * Constructs the LATENCY HISTOGRAM command
+   *
+   * @param parser - The command parser
+   * @param commands - The list of redis commands to get histogram for
+   * @see https://redis.io/docs/latest/commands/latency-histogram/
+   */
+  parseCommand(parser: CommandParser, ...commands: string[]) {
+    const args = ['LATENCY', 'HISTOGRAM'];
+    if (commands.length !== 0) {
+      args.push(...commands);
+    }
+    parser.push(...args);
+  },
+  transformReply: {
+    2: (reply: (string | RawHistogram)[]): Histogram => {
+      const result: Histogram = {};
+      if (reply.length === 0) return result;
+      for (let i = 1; i < reply.length; i += 2) {
+        const histogram = reply[i] as RawHistogram;
+        result[reply[i - 1] as string] = {
+          calls: histogram[1],
+          histogram_usec: transformTuplesToMap(histogram[3], id),
+        };
+      }
+      return result;
+    },
+    3: undefined as unknown as () => Histogram,
+  }
+} as const satisfies Command;

packages/client/lib/commands/index.ts

@@ -364,6 +364,7 @@ import VREM from './VREM';
 import VSETATTR from './VSETATTR';
 import VSIM from './VSIM';
 import VSIM_WITHSCORES from './VSIM_WITHSCORES';
+import LATENCY_HISTOGRAM from './LATENCY_HISTOGRAM';
 
 export {
   CLIENT_KILL_FILTERS,
@@ -722,6 +723,8 @@ export default {
   latencyGraph: LATENCY_GRAPH,
   LATENCY_HISTORY,
   latencyHistory: LATENCY_HISTORY,
+  LATENCY_HISTOGRAM,
+  latencyHistogram: LATENCY_HISTOGRAM,
   LATENCY_LATEST,
   latencyLatest: LATENCY_LATEST,
   LATENCY_RESET,