orcchg’s gists

orcchg / suspend_next_coroutines.kt

Created October 21, 2023 18:22

Next coroutine suspends at the very beginning

	suspend fun <T> synchronized(block: suspend () -> T): T {
	val thisJobId = id.getAndIncrement()
	while (isInsideCriticalSection) {
	suspendCoroutine { cont -> // <-- suspending call
	suspendedJobs[thisJobId] = cont
	}
	suspendedJobs.remove(thisJobId)
	}
	...
	}

orcchg / obtain_and_refresh_token_in_a_single_thread.kt

Created October 21, 2023 18:04

Run obtain and refresh token login in a single thread

	fun obtainAccessToken(): String {
	val kCriticalSection = DI.get<KCriticalSection>(qualifier = "shared")
	val singleThread = DI.get<CoroutineDispatcher>(qualifier = "shared")

	return runBlocking(singleThread) {
	kCriticalSection.synchronized {
	val accessToken = readAccessTokenFromStorageOrMemory() // might be a suspending call

	if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
	return@synchronized accessToken.toString() // access token is valid

orcchg / check_token_exist_or_expired.kt

Created October 21, 2023 17:51

Check for token existence and expiration

	if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
	return@synchronized accessToken.toString() // access token is valid
	}

orcchg / shared_critical_section_for_coroutines.kt

Created October 21, 2023 10:47

Shared critical section for true synchronization

	suspend fun obtainAccessToken(): String {
	val kCriticalSection = DI.get<KCriticalSection>(qualifier = "shared")

	return kCriticalSection.synchronized {
	val accessToken = readAccessTokenFromStorageOrMemory() // might be a suspending call

	if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
	return@synchronized accessToken.toString() // access token is valid
	}

orcchg / critical_section_for_coroutines.kt

Last active October 21, 2023 17:29

Critical section for coroutines

	import java.util.concurrent.ConcurrentHashMap
	import kotlin.coroutines.Continuation
	import kotlin.coroutines.resume
	import kotlin.coroutines.suspendCoroutine

	class KCriticalSection {
	private val suspendedJobs = ConcurrentHashMap<Int, Continuation<Boolean>>()
	private var id = AtomicInteger(1000)
	@Volatile private var isInsideCriticalSection = false

orcchg / get_and_refresh_token_in_a_critical_section.kt

Created October 21, 2023 10:12

Wrap token obtain and refresh logic in a critical section

	suspend fun obtainAccessToken(): String =
	KCriticalSection().synchronized {
	val accessToken = readAccessTokenFromStorageOrMemory() // might be a suspending call

	if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
	return@synchronized accessToken.toString() // access token is valid
	}

	val refreshToken = readRefreshTokenFromSecureStorage() // normally a suspending call

orcchg / token_refresh_logic.kt

Last active October 21, 2023 10:05

Check existing access token for expiration and refresh if need

	suspend fun obtainAccessToken(): String {
	val accessToken = readAccessTokenFromStorageOrMemory() // might be a suspending call

	if (accessToken != null && System.currentTimeMillis() < accessToken.createdAt + accessToken.expiresIn) {
	return accessToken.toString() // access token is valid
	}

	val refreshToken = readRefreshTokenFromSecureStorage() // normally a suspending call

	// normally suspending as it makes another API call

orcchg / obtain_access_token.kt

Created October 21, 2023 08:56

Obtaining access token is normally an asynchronous operation

	suspend fun obtainAccessToken(): String {
	// do the real job to obtain access token
	return "access token"
	}

orcchg / auth_interceptor_with_async_access_token.kt

Created October 21, 2023 08:51

Interceptor with Authorization header and asynchronously obtained access token

	import kotlinx.coroutines.runBlocking
	import okhttp3.Interceptor
	import okhttp3.Response
	class AuthInterceptor : Interceptor {
	override fun intercept(chain: Interceptor.Chain): Response {
	val accessToken = runBlocking { obtainAccessToken() }

	val request = chain.request()
	val newRequest = request.newBuilder()
	.addHeader("Authorization", accessToken)

orcchg / authorization_interceptor.kt

Created October 21, 2023 08:41

Interceptor with Authorization header

	import okhttp3.Interceptor
	import okhttp3.Response

	class AuthInterceptor : Interceptor {
	override fun intercept(chain: Interceptor.Chain): Response {
	val accessToken = obtainAccessToken() // <-- how to get token? This might be a suspending call

	val request = chain.request()
	val newRequest = request.newBuilder()
	.addHeader("Authorization", accessToken)

Max Alov orcchg