# Flush API in Mobile SDKs


This guide walks you through the `flush` API and the different event flushing policies supported by the RudderStack [Android (Kotlin)]({{< ref "sources/event-streams/sdks/kotlin-sdk/" >}}) and [iOS (Swift)]({{< ref "sources/event-streams/sdks/swift-sdk/" >}}) SDKs.

## Overview

The RudderStack Android (Kotlin) and iOS (Swift) SDKs provide a `flush` API that lets you manually flush any stored events irrespective of the configured [flush policies](#flush-policies).

You can trigger a `flush` API call as follows:

{{< tabs tabTotal="2" >}}
{{% tab tabName="Android (Kotlin)" %}}
```kotlin
analytics.flush()
```

The corresponding Java snippet is shown below:

```java
analytics.flush();
```
{{% /tab %}}
{{% tab tabName="iOS (Swift)" %}}
```swift
analytics.flush()
```

The corresponding Objective-C snippet is shown below:

```objectivec
[analytics flush];
```
{{% /tab %}}
{{< /tabs >}}

{{< warning >}}
If you have added a mobile device mode integration plugin, then a `flush` API call will also trigger the integration’s `flush` API, if it is supported.
{{< /warning >}}

## Flush policies

RudderStack supports three configurable flush policies. By default, all three policies are enabled.

### Count flush policy

The `CountFlushPolicy` triggers a `flush` call when a predefined threshold for the event count is reached.

| Flush policies | Data type | Notes |
| :----| :----- | :-----|
| `flushAt` | Integer | The value of this parameter must be within the range of `1` to `100` - the default value is `30`. |

### Frequency flush policy

The `FrequencyFlushPolicy` automatically triggers a flush at the specified intervals.

| Flush policies | Data type | Description |
| :----| :----- | :-----|
| `flushIntervalInMillis` | Long | Minimum allowed value is`1 millisecond` - the default value is `10 seconds`. |

### Startup flush policy

The `StartupFlushPolicy` automatically triggers a one-time `flush` API call after the Android (Kotlin) SDK is initialized.

## Set a flush policy

You can select and set a flush policy depending on your use case.

{{< warning >}}
Selecting a flush policy from the provided list overrides the default flush policy.
{{< /warning >}}

The following examples highlight how you can set the `FrequencyFlushPolicy` in Android (Kotlin) and iOS (Swift) SDKs:

### Android (Kotlin)

1. Import the flush policy as shown:

```kotlin
import com.rudderstack.sdk.kotlin.core.internals.policies.FrequencyFlushPolicy
```

2. Add `FrequencyFlushPolicy` during the SDK initialization, as shown below. Replace the `WRITE_KEY` and `DATA_PLANE_URL` parameters in the below snippet with the Android (Kotlin) source write key and your data plane URL.


```kotlin
analytics = Analytics(
    configuration = Configuration(
        writeKey = BuildConfig.WRITE_KEY,
        application = application,
        dataPlaneUrl = BuildConfig.DATA_PLANE_URL,
        flushPolicies = listOf(
            FrequencyFlushPolicy()
        )
    )
)
```

The corresponding Java snippet is shown below:

```java
FrequencyFlushPolicy frequencyFlushPolicy = new FrequencyFlushPolicy();
ArrayList<FlushPolicy> listOfFlushPolicies = new ArrayList<>();
listOfFlushPolicies.add(frequencyFlushPolicy);

Configuration configuration = new ConfigurationBuilder(this, "WRITE_KEY", "DATA_PLANE_URL")
        .setFlushPolicies(listOfFlushPolicies)
        .build();

analytics = new JavaAnalytics(configuration);
```

### iOS (Swift)

{{< tabs tabTotal="2" >}}
{{% tab tabName="Swift" %}}

1. Import the flush policy as shown:

```swift
import RudderStackAnalytics
```

2. Add `FrequencyFlushPolicy` during the SDK initialization. Replace the `WRITE_KEY` and `DATA_PLANE_URL` parameters in the below snippet with the iOS (Swift) source write key and your data plane URL.

```swift
self.analytics = Analytics(configuration: Configuration(
    writeKey: "<WRITE_KEY>",
    dataPlaneUrl: "<DATA_PLANE_URL>",
    flushPolicies: [
        FrequencyFlushPolicy()
    ]
))
```
{{% /tab %}}
{{% tab tabName="Objective-C" %}}

1. Import the flush policy as shown:

```objectivec
@import RudderStackAnalytics;
```

2. Add `FrequencyFlushPolicy` during the SDK initialization. Replace the `WRITE_KEY` and `DATA_PLANE_URL` parameters in the below snippet with the iOS (Swift) source write key and your data plane URL.

```objectivec
RSSConfigurationBuilder *builder = [[RSSConfigurationBuilder alloc]
    initWithWriteKey:@"<WRITE_KEY>"
       dataPlaneUrl:@"<DATA_PLANE_URL>"];

[builder setFlushPolicies:@[
    [RSSFrequencyFlushPolicy new]
]];

RSSAnalytics *analytics = [[RSSAnalytics alloc]
    initWithConfiguration:[builder build]];
```
{{% /tab %}}
{{< /tabs >}}