> ## Documentation Index > Fetch the complete documentation index at: https://launchdarkly-preview.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Flushing events > This topic explains how to use the flush feature. > For the complete documentation index, see [llms.txt](/llms.txt). For the full documentation snapshot, see [llms-full.txt](/llms-full.txt). ## Overview This topic explains how to use the flush feature. The flush feature is available in server-side, client-side, and edge SDKs. Server-side, client-side, and edge SDKs automatically flush pending analytics events to LaunchDarkly at regular intervals. This prevents the SDK from having to send constant network requests. The time between intervals varies by SDK, and is configurable. To learn how to configure your SDK's flush interval, read [Configuration](/sdk/features/config). You can manually call flush to send events immediately without waiting for the next interval. Most customers do not need to use the flush feature because SDKs automatically flush their pending analytics events on a periodic frequency. However, it can be useful if you are using the SDK in a short-lived serverless process or a test application, rather than in a long-running application. To learn more, read [Analytics events](/sdk/concepts/events). ## About the flush feature The flush feature tells the client to send all of an SDK's pending analytics events to LaunchDarkly as soon as possible. All SDKs support asynchronous flushing, which tells the SDK to start delivering events, but returns control to the application before delivery is complete. Some SDKs also support synchronous flushing, which tells the SDK to deliver the events and not return control until delivery is complete. Details about each SDK's configuration are available in the SDK-specific sections below. * [Client-side SDKs](#client-side-sdks) * [Server-side SDKs](#server-side-sdks) * [Edge SDKs](#edge-sdks) ## Client-side SDKs This feature is available in the following client-side SDKs: * [.NET (client-side)](#net-client-side) * [Android](#android) * [C++ (client-side)](#c-client-side) * [Flutter](#flutter) * [iOS](#ios) * [JavaScript](#javascript) * [Node.js (client-side)](#nodejs-client-side) * [React Native](#react-native) * [Roku](#roku) ### .NET (client-side) Internally, the client-side .NET SDK keeps an event buffer for `Track` and `Identify` calls. These are flushed periodically in a background thread. If you test the SDK in a REPL, you may want to manually call `Flush` to process events immediately. The flush interval is configurable. If you need to change the interval, you can do so with the `Configuration` class. To call `flush`: ```csharp title="C#" theme={null} client.Flush(); ``` ### Android The Android SDK keeps an internal event buffer for analytics calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. This call is non-blocking, so it returns before the events are sent. Here's how: ```java title="Java" theme={null} client.flush(); ``` ```kotlin title="Kotlin" theme={null} client.flush() ``` The flush interval is configurable. ### C++ (client-side) The LaunchDarkly SDK keeps an internal event buffer for analytics events. These are flushed periodically in a background thread. In some situations, for example if you're testing the SDK in a simulator, you may want to manually call flush to process events immediately. ```cpp title="C++ SDK v3.0 (native)" theme={null} client.FlushAsync(); ``` ```c title="C++ SDK v3.0 (C binding)" theme={null} LDClientSDK_Flush(client, LD_NONBLOCKING); ``` ```c title="C SDK v2.x" theme={null} LDClientFlush(client); ``` You can also examine the result to determine if the flush succeeded. Here's how: ```cpp title="C++ SDK v3.0 (native)" theme={null} auto flush_result = client.FlushAsync(context); auto status = flush_result.wait_for(maxwait); if (status == std::future_status::ready) { /* The client's attempt to flush succeeded or failed in the specified amount of time. */ if (flush_result.get()) { /* Flush succeeded */ } else { /* Flush failed */ } } else { /* The specified timeout was reached, but the client is still attempting to flush. */ } ``` ```cpp title="C++ SDK v3.0 (C binding)" theme={null} bool flushed_successfully; if (LDClientSDK_Flush(client, context, maxwait, &flushed_successfully)) { /* The client's attempt to flush succeeded or failed in the specified amount of time. */ if (flushed_successfully) { /* Flush succeeded. */ else { /* Flush failed. */ } } else { /* The specified timeout was reached, but the client is still attempting to flush. */ } ``` The flush interval is configurable. If you need to change the interval, you can do so using the configuration. To learn more, read [`FlushAsync`](https://launchdarkly.github.io/cpp-sdks/libs/client-sdk/docs/html/classlaunchdarkly_1_1client__side_1_1Client.html#ad19e6199bff8c0c0caa94e28f44ded3f) and [`FlushInterval`](https://launchdarkly.github.io/cpp-sdks/libs/client-sdk/docs/html/classlaunchdarkly_1_1config_1_1shared_1_1builders_1_1EventsBuilder.html#a999ee341dcf36b412e14ec5c923cceff). ### Flutter Internally, the Flutter SDK keeps an event buffer for `track` calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. This call is non-blocking, so it returns before the events are sent. To call `flush`: ```dart title="Dart" theme={null} await client.flush(); ``` To learn more, read [`flush`](https://pub.dev/documentation/launchdarkly_flutter_client_sdk/latest/launchdarkly_flutter_client_sdk/LDClient/flush.html). ### iOS Internally, the iOS SDK keeps an event buffer for `track` calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. This call is non-blocking, so it returns before the events are sent. To call `flush`: ```swift title="Swift" theme={null} LDClient.get()!.flush() ``` ```objectivec title="Objective-C" theme={null} [[LDClient get] flush]; ``` ### Java Script Internally, the JavaScript SDK keeps an event buffer for `track` calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. This call is non-blocking, so it returns before the events are sent. This method is asynchronous. You can pass a callback or wait for the returned `Promise` to determine when all events have been flushed. To call `flush`: ```js title="JavaScript" theme={null} client.flush(); ``` ### Node.js (client-side) Internally, the LaunchDarkly SDK keeps an analytics event buffer. These events are flushed periodically. In some situations, you may want to manually call `flush` to process events immediately. This method is asynchronous. You can pass a callback or wait for the returned `Promise` to determine when all events have been flushed. To call `flush`: ```js title="JavaScript" theme={null} client.flush(); // or, with a callback: client.flush(() => { console.log('flush complete'); }); // or, with a Promise: client.flush().then(() => { console.log('flush complete'); }); ``` ### React Native Internally, the React Native SDK keeps an event buffer for `track` calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. To call `flush`: ```js title="React Native SDK, v10" theme={null} const { result, error } = await client.flush(); ``` `flush` is asynchronous and can be awaited. It returns a promise that resolves to an object containing an error, if there is one, and a boolean result. To learn more, read [`flush`](https://launchdarkly.github.io/js-core/packages/sdk/react-native/docs/classes/LDClientImpl.html#flush). ### Roku Internally, the Roku SDK keeps an event buffer for `track` calls. These are flushed periodically in a background thread. You can configure the flush interval if needed. In some situations, such as when you're testing the SDK in a simulator, you may want to manually call `flush` to request any queued events to be sent immediately. This call is non-blocking, so it returns before the events are sent. To call `flush`: ```brightscript title="BrightScript" theme={null} launchDarkly.flush() ``` ## Server-side SDKs This feature is available in the following server-side SDKs: * [.NET (server-side)](#net-server-side) * [C++ (server-side)](#c-server-side) * [Go](#go) * [Haskell](#haskell) * [Java](#java) * [Lua](#lua) * [Node.js (server-side)](#nodejs-server-side) * [PHP](#php) * [Python](#python) * [Ruby](#ruby) * [Rust](#rust) ### .NET (server-side) The .NET (server-side) SDK supports asynchronous flushing with the [`Flush`](https://launchdarkly.github.io/dotnet-core/pkgs/sdk/server/api/LaunchDarkly.Sdk.Server.LdClient.html#LaunchDarkly_Sdk_Server_LdClient_Flush_) method. To call `flush`: ```csharp title="C#" theme={null} client.Flush(); ``` Starting in version 7.0.0, the SDK also supports synchronous flushing with the [`FlushAndWait`](https://launchdarkly.github.io/dotnet-core/pkgs/sdk/server/api/LaunchDarkly.Sdk.Server.LdClient.html#LaunchDarkly_Sdk_Server_LdClient_FlushAndWait_System_TimeSpan_) method. In this example, the `TimeSpan.FromSeconds(2)` value means that the application is willing to wait no more than two seconds for event delivery. ```csharp title="C#" theme={null} client.FlushAndWait(TimeSpan.FromSeconds(2)); ``` The flush interval is configurable. If you need to change the interval, you can do so with the `Configuration` class. Here's how: ```csharp title="C#" theme={null} var config = Configuration.Builder("YOUR_SDK_KEY") .Events( Components.SendEvents().FlushInterval(TimeSpan.FromSeconds(10)) ) .Build(); var client = new LdClient(config); ``` ### C++ (server-side) The LaunchDarkly SDK keeps an internal event buffer for analytics events. These are flushed periodically in a background thread. If you test the SDK in a simulator, you may want to manually call flush to process events immediately. This function will not block, but instead initiate a flush operation in the background. The flush interval is configurable. If you need to change the interval, you can do so with the configuration. Here's how: ```cpp title="C++ SDK v3.0 (native)" theme={null} client.FlushAsync(); ``` ```c title="C++ SDK v3.0 (C binding)" theme={null} LDServerSDK_Flush(client, LD_NONBLOCKING); ``` ```c title="C SDK v2.x (native)" theme={null} LDClientFlush(client); ``` The flush interval is configurable. If you need to change the interval, you can do so using the configuration. To learn more, read about `FlushAsync()` in [`Client`](https://launchdarkly.github.io/cpp-sdks/libs/server-sdk/docs/html/classlaunchdarkly_1_1server__side_1_1Client.html) and about `FlushInterval()` in [`EventsBuilder`](https://launchdarkly.github.io/cpp-sdks/libs/server-sdk/docs/html/classlaunchdarkly_1_1config_1_1shared_1_1builders_1_1EventsBuilder.html). ### Go The Go SDK supports asynchronous flushing with the [`Flush`](https://pkg.go.dev/github.com/launchdarkly/go-server-sdk/v7#LDClient.Flush) method. ```go title="Go" theme={null} client.Flush(); ``` Starting in version 6.0.0, the SDK also supports synchronous flushing with the [`FlushAndWait`](https://pkg.go.dev/github.com/launchdarkly/go-server-sdk/v7#LDClient.FlushAndWait) method. In this example, the `time.Second*2` value means that the application is willing to wait no more than two seconds for event delivery. ```go title="Go" theme={null} client.FlushAndWait(time.Second*2); ``` The interval for automatic event flushing is configurable. If you need to change the interval, you can do so by making a custom client configuration. Here's how: ```go title="Go" theme={null} config := ld.Config{ Events: ldcomponents.SendEvents().FlushInterval(time.Second*10), } ``` ### Haskell The LaunchDarkly SDK keeps an internal event buffer for analytics events. These events are flushed periodically in a background thread. If you test the SDK in a simulator, you may want to manually call flush to process events immediately. This function will not block, but instead initiate a flush operation in the background. The flush interval is configurable. If you need to change the interval, you can do so with the configuration. Here's how: ```haskell title="Haskell" theme={null} flushEvents client ``` ### Java Internally, the LaunchDarkly SDK keeps an event buffer for `track` and `identify` calls. These are flushed periodically in a background thread. If you test the SDK in a REPL, you may want to manually call [`flush`](https://launchdarkly.github.io/java-core/lib/sdk/server/com/launchdarkly/sdk/server/LDClient.html#flush--) to process events immediately. Here's how: ```java title="Java" theme={null} client.flush(); ``` The flush interval is configurable. If you need to change the interval, you can do so with [`LDConfig.Builder`](https://launchdarkly.github.io/java-core/lib/sdk/server/com/launchdarkly/sdk/server/LDConfig.Builder.html) and [`Components.sendEvents()`](https://launchdarkly.github.io/java-core/lib/sdk/server/com/launchdarkly/sdk/server/Components.html#sendEvents--). ### Lua The LaunchDarkly SDK keeps an internal event buffer for analytics events. These are flushed periodically in a background thread. If you test the SDK in a simulator, you may want to manually call flush to process events immediately. This function will not block, but instead initiate a flush operation in the background. The flush interval is configurable. If you need to change the interval, you can do so with the configuration. Here's how: ```lua title="Lua" theme={null} client:flush() ``` To learn more, read [`flush`](https://launchdarkly.github.io/lua-server-sdk/modules/launchdarkly-server-sdk.html#flush). ### Node.js (server-side) Internally, the LaunchDarkly SDK keeps an event buffer for `track` and `identify` calls. These are flushed periodically in a background thread. If you test the SDK in a REPL, you may want to manually call `flush` to process events immediately. The flush interval is configurable. If you need to change the interval, you can do so when configuring your client instance. Here's how: ```js title="JavaScript" theme={null} client.flush(); ``` ### PHP Internally, the LaunchDarkly SDK keeps an event buffer for `variation`, `track`, and `identify` calls. These are automatically flushed when the LDClient is destroyed. PHP's shared-nothing architecture means manual invocation of this method is typically not needed. Developers may do so if they wish to flush events prior to teardown. Here's how: ```php title="PHP" theme={null} ldclient->flush(); ``` ### Python Internally, the LaunchDarkly SDK keeps an event buffer for `variation`, `track`, and `identify` calls. These are flushed periodically in a background thread. If you test the SDK in a REPL, you may want to manually call `flush` to process events immediately. Otherwise, Python may close before flushing the event buffer and your user changes and tracks will be lost. The flush interval is configurable. If you need to change the interval, you can do so when you configure your client instance. Here's how: ```python title="Python" theme={null} ldclient.get().flush() ``` ### Ruby Internally, the LaunchDarkly SDK keeps an event buffer for `track` and `identify` calls. These are flushed periodically in a background thread. If you test the SDK in a REPL, you may want to manually call `flush` to process events immediately. The flush interval is configurable. If you need to change the interval, you can do so when you configure your client instance. Here's how: ```ruby title="Ruby" theme={null} client.flush ``` ### Rust Internally, the LaunchDarkly SDK keeps an event buffer for the analytics events that are produced by calling the `variation` or `variation_detail` methods, the `track` methods, or `identify`. These are flushed periodically in a background thread. In some situations, you may want to manually call [`flush`](https://docs.rs/launchdarkly-server-sdk/latest/launchdarkly_server_sdk/struct.Client.html#method.flush) to process events immediately. The Rust SDK supports asynchronous flushing with the `flush` method: ```rust title="Rust" theme={null} let result = client.flush(); ``` Starting in version 3.0, the SDK also supports synchronous flushing with the `flush_blocking` method. This method triggers a flush of events currently in the outbox and blocks until that flush completes or the specified timeout expires. It returns `true` if the flush completed, or `false` if the timeout was reached. In this example, the `Duration::from_secs(5)` value means that the application is willing to wait no more than five seconds for the flush to complete. ```rust title="Rust SDK v3.0" theme={null} use std::time::Duration; let success = client.flush_blocking(Duration::from_secs(5)); if !success { eprintln!("Event flush timed out"); } ``` The flush interval is configurable. If you need to change the interval, you can do so by making a custom client configuration. ## Edge SDKs Most edge SDKs support sending events directly. The [Akamai SDK](/sdk/edge/akamai) does not. When you [configure an edge SDK to send events](/sdk/features/config#edge-sdks), you must also flush those events to ensure that they are sent back to LaunchDarkly. This feature is available in the following edge SDKs: * [Cloudflare](#cloudflare) * [Fastly](#fastly) * [Vercel](#vercel) ### Cloudflare Flushing events is available in Cloudflare SDK version 2.3.0 and later. If you send [events](/sdk/features/events#cloudflare), you must also flush those events before your worker exits to ensure that they are sent back to LaunchDarkly. If you call `flush` inside the `waitUntil` method, then flushing events will not impact the handler's response time. To learn more, read the [Cloudflare documentation on `waitUntil`](https://developers.cloudflare.com/workers/runtime-apis/fetch-event/#waituntil). Here's how: ```ts title="Cloudflare SDK v2.3.0+ (TypeScript)" theme={null} // executionContext is the Cloudflare worker handler context // https://github.com/cloudflare/workers-types/blob/master/index.d.ts#L567 executionContext.waitUntil( client.flush((err, res) => { console.log(`flushed events result: ${res}, error: ${err}`); }), ); ``` If you do not call `flush`, the events will not be sent to LaunchDarkly servers, due to the ephemeral nature of edge workers. ### Fastly If you send [events](/sdk/features/events#fastly), you must also flush those events before your worker exits to ensure that they are sent back to LaunchDarkly. If you call `flush` inside the `waitUntil` method, then flushing events will not impact the handler's response time. To learn more, read the [Fastly Compute documentation on `waitUntil`](https://js-compute-reference-docs.edgecompute.app/docs/globals/FetchEvent/prototype/waitUntil). Here's how: ```ts title="TypeScript" theme={null} async function handleRequest(event: FetchEvent) { ... event.waitUntil( client.flush((err, res) => { console.log(`flushed events result: ${res}, error: ${err}`); }), ); ... } ``` If you do not call `flush`, the events will not be sent to LaunchDarkly servers, due to the ephemeral nature of edge workers. To learn more, read [`flush`](https://launchdarkly.github.io/js-core/packages/sdk/fastly/docs/classes/LDClient.html#flush). ### Vercel Flushing events is available in Vercel SDK v1.2.0 and later. If you send [events](/sdk/features/events#vercel), you must also flush those events before your worker exits to ensure that they are sent back to LaunchDarkly. If you call `flush` inside the `waitUntil` method, then flushing events will not impact the handler's response time. To learn more, read the [Vercel documentation on `waitUntil`](https://vercel.com/docs/functions/edge-functions/edge-functions-api#waituntil). Here's how: ```ts title="Vercel SDK v1.2.0+ (TypeScript)" theme={null} context.waitUntil( client.flush((err, res) => { console.log(`flushed events result: ${res}, error: ${err}`); }), ); ``` If you do not call `flush`, the events will not be sent to LaunchDarkly servers, due to the ephemeral nature of edge workers.