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ktor websocket flow retry mechanism
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| @Serialized | |
| data class MessageDto( | |
| @SerialName(value = "id") | |
| val id: String, | |
| @SerialName(value = "message") | |
| val message: String | |
| ) | |
| class MessageService constructor( | |
| private val httpClient: HttpClient | |
| ) { | |
| private val sendMessageFlow: Flow<MessageDto> = MutableSharedFlow() | |
| fun sendMessage(messageDto) { | |
| sendMessageFlow.emit(messageDto) | |
| } | |
| fun messages(): Flow<MessageDto> = flow { | |
| httpClient.wss( | |
| method = HttpMethod.Get, | |
| host = getHostname(), | |
| port = getPort(), | |
| path = "/v1/messages" | |
| ) { | |
| coroutineScope { | |
| sendMessageFlow | |
| .conflate() | |
| .map(::sendSerialized) | |
| .launchIn(this) | |
| while (true) { | |
| emit(receiveDeserialized<MessageDto>()) | |
| } | |
| } | |
| } | |
| }.retryWithBackoff() | |
| .flowOn(coroutineDispatcher) | |
| } |
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| inline val defaultExceptions: Set<Class<out Exception>> | |
| get() = setOf( | |
| ClosedReceiveChannelException::class.java, | |
| ConnectException::class.java, | |
| UnresolvedAddressException::class.java | |
| ) | |
| /** | |
| * Retries a `Flow<T>` indefinitely with exponential backoff | |
| * | |
| * @param delay -- delay in seconds between retries | |
| * @param delayAtMost -- maximum delay in seconds after which this value is used to delay | |
| */ | |
| public fun <T> Flow<T>.retryWithBackoff( | |
| delay: Int = 1, | |
| delayAtMost: Int = 10, | |
| exceptions: Set<Class<out Exception>> = defaultExceptions | |
| ): Flow<T> { | |
| var _delay = delay | |
| return retryWhen { cause, attempt -> | |
| val shouldRetry = exceptions.any { (cause::class.java == it) } | |
| if (shouldRetry) { | |
| delay(_delay.seconds.inWholeMilliseconds) | |
| val next = _delay * 2 | |
| _delay = if (next < delayAtMost) { | |
| next | |
| } else delayAtMost | |
| true | |
| } else false | |
| } | |
| } |
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