Implement rateLimit configuration (#84)

Very similar to throttle implementation in #66

The test timings need to account for GCRA buckets https://www.inngest.com/docs/guides/rate-limiting#how-rate-limiting-works

inngest-spring-boot-demo/src/main/java/com/inngest/springbootdemo/testfunctions/RateLimitedFunction.java

@@ -0,0 +1,28 @@
+package com.inngest.springbootdemo.testfunctions;
+
+import com.inngest.FunctionContext;
+import com.inngest.InngestFunction;
+import com.inngest.InngestFunctionConfigBuilder;
+import com.inngest.Step;
+import org.jetbrains.annotations.NotNull;
+
+import java.time.Duration;
+
+public class RateLimitedFunction extends InngestFunction {
+
+    @NotNull
+    @Override
+    public InngestFunctionConfigBuilder config(InngestFunctionConfigBuilder builder) {
+        return builder
+            .id("RateLimitedFunction")
+            .name("RateLimited Function")
+            .triggerEvent("test/rateLimit")
+            .rateLimit(2, Duration.ofSeconds(6));
+    }
+
+    @Override
+    public Integer execute(FunctionContext ctx, Step step) {
+        return step.run("result", () -> 42, Integer.class);
+    }
+}
+

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/DemoTestConfiguration.java

@@ -24,6 +24,7 @@ protected HashMap<String, InngestFunction> functions() {
         addInngestFunction(functions, new InvokeFailureFunction());
         addInngestFunction(functions, new TryCatchRunFunction());
         addInngestFunction(functions, new ThrottledFunction());
+        addInngestFunction(functions, new RateLimitedFunction());
         addInngestFunction(functions, new DebouncedFunction());
         addInngestFunction(functions, new PriorityFunction());
         addInngestFunction(functions, new IdempotentFunction());

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/RateLimitedFunctionIntegrationTest.java

@@ -0,0 +1,46 @@
+package com.inngest.springbootdemo;
+
+import com.inngest.Inngest;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.springframework.beans.factory.annotation.Autowired;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@IntegrationTest
+@Execution(ExecutionMode.CONCURRENT)
+class RateLimitedFunctionIntegrationTest {
+    @Autowired
+    private DevServerComponent devServer;
+
+    @Autowired
+    private Inngest client;
+
+    @Test
+    void testFunctionIsRateLimited() throws Exception {
+        String event1 = InngestFunctionTestHelpers.sendEvent(client, "test/rateLimit").getIds()[0];
+        // Rate limit test function is limited to 2 over 6 seconds. Based on the simplistic description of GCRA in
+        // https://www.inngest.com/docs/guides/rate-limiting#how-rate-limiting-works
+        // we need to sleep at least 3 seconds here for the second event not to get rate limited
+        Thread.sleep(3500);
+        String event2 = InngestFunctionTestHelpers.sendEvent(client, "test/rateLimit").getIds()[0];
+        Thread.sleep(1000);
+        String event3 = InngestFunctionTestHelpers.sendEvent(client, "test/rateLimit").getIds()[0];
+
+        // Sleep at least 6 seconds for the rate limit bucket to be completely cleared
+        Thread.sleep(6000);
+
+        // Rate limit should only allow the first 2 events to run
+        assertEquals("Completed", devServer.runsByEvent(event1).first().getStatus());
+        assertEquals("Completed", devServer.runsByEvent(event2).first().getStatus());
+        assertEquals(0, devServer.runsByEvent(event3).data.length);
+
+        // new event after the rate limit period will run, but the previously skipped event will stay skipped
+        String event4 = InngestFunctionTestHelpers.sendEvent(client, "test/rateLimit").getIds()[0];
+        Thread.sleep(4000);
+
+        assertEquals(0, devServer.runsByEvent(event3).data.length);
+        assertEquals("Completed", devServer.runsByEvent(event4).first().getStatus());
+    }
+}

inngest/src/main/kotlin/com/inngest/Function.kt

@@ -81,6 +81,8 @@ internal class InternalFunctionConfig
         @Json(serializeNull = false)
         val throttle: Throttle? = null,
         @Json(serializeNull = false)
+        val rateLimit: RateLimit? = null,
+        @Json(serializeNull = false)
         val debounce: Debounce? = null,
         @Json(serializeNull = false)
         val priority: Priority? = null,

inngest/src/main/kotlin/com/inngest/InngestFunctionConfigBuilder.kt

@@ -14,6 +14,7 @@ class InngestFunctionConfigBuilder {
     private var concurrency: MutableList<Concurrency>? = null
     private var retries = 3
     private var throttle: Throttle? = null
+    private var rateLimit: RateLimit? = null
     private var debounce: Debounce? = null
     private var priority: Priority? = null
     private var idempotency: String? = null
@@ -164,6 +165,21 @@ class InngestFunctionConfigBuilder {
         burst: Int? = null,
     ): InngestFunctionConfigBuilder = apply { this.throttle = Throttle(limit, period, key, burst) }
 
+    /**
+     * Configure function rate limit
+     *
+     * @param limit The number of times to allow the function to run per the given `period`.
+     * @param period The period of time to allow the function to run `limit` times. The period begins when the first matching event
+     * is received
+     * @param key An optional expression to use for rate limiting, similar to idempotency.
+     */
+    @JvmOverloads
+    fun rateLimit(
+        limit: Int,
+        period: Duration,
+        key: String? = null,
+    ): InngestFunctionConfigBuilder = apply { this.rateLimit = RateLimit(limit, period, key) }
+
     /**
      * Debounce delays functions for the `period` specified. If an event is sent,
      * the function will not run until at least `period` has elapsed.
@@ -241,6 +257,7 @@ class InngestFunctionConfigBuilder {
                 triggers,
                 concurrency,
                 throttle,
+                rateLimit,
                 debounce,
                 priority,
                 idempotency,
@@ -313,6 +330,16 @@ internal data class Throttle
         val burst: Int? = null,
     )
 
+internal data class RateLimit
+    @JvmOverloads
+    constructor(
+        val limit: Int,
+        @KlaxonDuration
+        val period: Duration,
+        @Json(serializeNull = false)
+        val key: String? = null,
+    )
+
 internal data class Debounce
     @JvmOverloads
     constructor(