added retry policy to gbcs-client

build.gradle

@@ -46,6 +46,12 @@ allprojects { subproject ->
             }
         }
 
+        dependencies {
+            testImplementation catalog.junit.jupiter.api
+            testImplementation catalog.junit.jupiter.params
+            testRuntimeOnly catalog.junit.jupiter.engine
+        }
+
         test {
             useJUnitPlatform()
         }

gbcs-client/build.gradle

@@ -10,6 +10,8 @@ dependencies {
     implementation catalog.slf4j.api
     implementation catalog.netty.buffer
     implementation catalog.netty.codec.http
+
+    testRuntimeOnly catalog.logback.classic
 }
 
 

gbcs-client/src/main/kotlin/net/woggioni/gbcs/client/Client.kt

@@ -66,11 +66,18 @@ class GradleBuildCacheClient(private val profile: Configuration.Profile) : AutoC
             data class BasicAuthenticationCredentials(val username: String, val password: String) : Authentication()
         }
 
+        class RetryPolicy(
+            val maxAttempts: Int,
+            val initialDelayMillis: Long,
+            val exp: Double
+        )
+
         data class Profile(
             val serverURI: URI,
             val authentication: Authentication?,
-            val connectionTimeout : Duration?,
-            val maxConnections : Int
+            val connectionTimeout: Duration?,
+            val maxConnections: Int,
+            val retryPolicy: RetryPolicy?,
         )
 
         companion object {
@@ -161,28 +168,76 @@ class GradleBuildCacheClient(private val profile: Configuration.Profile) : AutoC
         pool = FixedChannelPool(bootstrap, channelPoolHandler, profile.maxConnections)
     }
 
-    fun get(key: String): CompletableFuture<ByteArray?> {
-        return sendRequest(profile.serverURI.resolve(key), HttpMethod.GET, null)
-            .thenApply {
-                val status = it.status()
-                if (it.status() == HttpResponseStatus.NOT_FOUND) {
-                    null
-                } else if (it.status() != HttpResponseStatus.OK) {
-                    throw HttpException(status)
-                } else {
-                    it.content()
-                }
-            }.thenApply { maybeByteBuf ->
-                maybeByteBuf?.let {
-                    val result = ByteArray(it.readableBytes())
-                    it.getBytes(0, result)
-                    result
+    private fun executeWithRetry(operation: () -> CompletableFuture<FullHttpResponse>): CompletableFuture<FullHttpResponse> {
+        val retryPolicy = profile.retryPolicy
+        return if (retryPolicy != null) {
+            val outcomeHandler = OutcomeHandler<FullHttpResponse> { outcome ->
+                when (outcome) {
+                    is OperationOutcome.Success -> {
+                        val response = outcome.result
+                        val status = response.status()
+                        when (status) {
+                            HttpResponseStatus.TOO_MANY_REQUESTS -> {
+                                val retryAfter = response.headers()[HttpHeaderNames.RETRY_AFTER]?.let { headerValue ->
+                                    try {
+                                        headerValue.toLong() * 1000
+                                    } catch (nfe: NumberFormatException) {
+                                        null
+                                    }
+                                }
+                                OutcomeHandlerResult.Retry(retryAfter)
+                            }
+
+                            HttpResponseStatus.INTERNAL_SERVER_ERROR, HttpResponseStatus.SERVICE_UNAVAILABLE ->
+                                OutcomeHandlerResult.Retry()
+
+                            else -> OutcomeHandlerResult.DoNotRetry()
+                        }
+                    }
+
+                    is OperationOutcome.Failure -> {
+                        OutcomeHandlerResult.Retry()
+                    }
                 }
             }
+            executeWithRetry(
+                group,
+                retryPolicy.maxAttempts,
+                retryPolicy.initialDelayMillis.toDouble(),
+                retryPolicy.exp,
+                outcomeHandler,
+                operation
+            )
+        } else {
+            operation()
+        }
+    }
+
+    fun get(key: String): CompletableFuture<ByteArray?> {
+        return executeWithRetry {
+            sendRequest(profile.serverURI.resolve(key), HttpMethod.GET, null)
+        }.thenApply {
+            val status = it.status()
+            if (it.status() == HttpResponseStatus.NOT_FOUND) {
+                null
+            } else if (it.status() != HttpResponseStatus.OK) {
+                throw HttpException(status)
+            } else {
+                it.content()
+            }
+        }.thenApply { maybeByteBuf ->
+            maybeByteBuf?.let {
+                val result = ByteArray(it.readableBytes())
+                it.getBytes(0, result)
+                result
+            }
+        }
     }
 
     fun put(key: String, content: ByteArray): CompletableFuture<Unit> {
-        return sendRequest(profile.serverURI.resolve(key), HttpMethod.PUT, content).thenApply {
+        return executeWithRetry {
+            sendRequest(profile.serverURI.resolve(key), HttpMethod.PUT, content)
+        }.thenApply {
             val status = it.status()
             if (it.status() != HttpResponseStatus.CREATED && it.status() != HttpResponseStatus.OK) {
                 throw HttpException(status)

gbcs-client/src/main/kotlin/net/woggioni/gbcs/client/impl/Parser.kt

@@ -17,16 +17,18 @@ object Parser {
 
     fun parse(document: Document): GradleBuildCacheClient.Configuration {
         val root = document.documentElement
-
         val profiles = mutableMapOf<String, GradleBuildCacheClient.Configuration.Profile>()
 
         for (child in root.asIterable()) {
             val tagName = child.localName
             when (tagName) {
                 "profile" -> {
-                    val name = child.renderAttribute("name") ?: throw ConfigurationException("name attribute is required")
-                    val uri = child.renderAttribute("base-url")?.let(::URI) ?: throw ConfigurationException("base-url attribute is required")
+                    val name =
+                        child.renderAttribute("name") ?: throw ConfigurationException("name attribute is required")
+                    val uri = child.renderAttribute("base-url")?.let(::URI)
+                        ?: throw ConfigurationException("base-url attribute is required")
                     var authentication: GradleBuildCacheClient.Configuration.Authentication? = null
+                    var retryPolicy: GradleBuildCacheClient.Configuration.RetryPolicy? = null
                     for (gchild in child.asIterable()) {
                         when (gchild.localName) {
                             "tls-client-auth" -> {
@@ -47,14 +49,42 @@ object Parser {
                                     .toList()
                                     .toTypedArray()
                                 authentication =
-                                    GradleBuildCacheClient.Configuration.Authentication.TlsClientAuthenticationCredentials(key, certChain)
+                                    GradleBuildCacheClient.Configuration.Authentication.TlsClientAuthenticationCredentials(
+                                        key,
+                                        certChain
+                                    )
                             }
 
                             "basic-auth" -> {
-                                val username = gchild.renderAttribute("user") ?: throw ConfigurationException("username attribute is required")
-                                val password = gchild.renderAttribute("password") ?: throw ConfigurationException("password attribute is required")
+                                val username = gchild.renderAttribute("user")
+                                    ?: throw ConfigurationException("username attribute is required")
+                                val password = gchild.renderAttribute("password")
+                                    ?: throw ConfigurationException("password attribute is required")
                                 authentication =
-                                    GradleBuildCacheClient.Configuration.Authentication.BasicAuthenticationCredentials(username, password)
+                                    GradleBuildCacheClient.Configuration.Authentication.BasicAuthenticationCredentials(
+                                        username,
+                                        password
+                                    )
+                            }
+
+                            "retry-policy" -> {
+                                val maxAttempts =
+                                    gchild.renderAttribute("max-attempts")
+                                        ?.let(String::toInt)
+                                        ?: throw ConfigurationException("max-attempts attribute is required")
+                                val initialDelay =
+                                    gchild.renderAttribute("initial-delay")
+                                        ?.let(Duration::parse)
+                                        ?: Duration.ofSeconds(1)
+                                val exp =
+                                    gchild.renderAttribute("exp")
+                                        ?.let(String::toDouble)
+                                        ?: 2.0f
+                                retryPolicy = GradleBuildCacheClient.Configuration.RetryPolicy(
+                                    maxAttempts,
+                                    initialDelay.toMillis(),
+                                    exp.toDouble()
+                                )
                             }
                         }
                     }
@@ -63,7 +93,13 @@ object Parser {
                         ?: 50
                     val connectionTimeout = child.renderAttribute("connection-timeout")
                         ?.let(Duration::parse)
-                    profiles[name] = GradleBuildCacheClient.Configuration.Profile(uri, authentication, connectionTimeout, maxConnections)
+                    profiles[name] = GradleBuildCacheClient.Configuration.Profile(
+                        uri,
+                        authentication,
+                        connectionTimeout,
+                        maxConnections,
+                        retryPolicy
+                    )
                 }
             }
         }

gbcs-client/src/main/kotlin/net/woggioni/gbcs/client/retry.kt

@@ -0,0 +1,75 @@
+package net.woggioni.gbcs.client
+
+import io.netty.util.concurrent.EventExecutorGroup
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.TimeUnit
+
+sealed class OperationOutcome<T> {
+    class Success<T>(val result: T) : OperationOutcome<T>()
+    class Failure<T>(val ex: Throwable) : OperationOutcome<T>()
+}
+
+sealed class OutcomeHandlerResult {
+    class Retry(val suggestedDelayMillis: Long? = null) : OutcomeHandlerResult()
+    class DoNotRetry : OutcomeHandlerResult()
+}
+
+fun interface OutcomeHandler<T> {
+    fun shouldRetry(result: OperationOutcome<T>): OutcomeHandlerResult
+}
+
+fun <T> executeWithRetry(
+    eventExecutorGroup: EventExecutorGroup,
+    maxAttempts: Int,
+    initialDelay: Double,
+    exp: Double,
+    outcomeHandler: OutcomeHandler<T>,
+    cb: () -> CompletableFuture<T>
+): CompletableFuture<T> {
+    val finalResult = cb()
+    var future = finalResult
+    var shortCircuit = false
+    for (i in 1 until maxAttempts) {
+        future = future.handle { result, ex ->
+            val operationOutcome = if (ex == null) {
+                OperationOutcome.Success(result)
+            } else {
+                OperationOutcome.Failure(ex.cause ?: ex)
+            }
+            if (shortCircuit) {
+                when(operationOutcome) {
+                    is OperationOutcome.Failure -> throw operationOutcome.ex
+                    is OperationOutcome.Success -> CompletableFuture.completedFuture(operationOutcome.result)
+                }
+            } else {
+                when(val outcomeHandlerResult = outcomeHandler.shouldRetry(operationOutcome)) {
+                    is OutcomeHandlerResult.Retry -> {
+                        val res = CompletableFuture<T>()
+                        val delay = run {
+                            val scheduledDelay = (initialDelay * Math.pow(exp, i.toDouble())).toLong()
+                            outcomeHandlerResult.suggestedDelayMillis?.coerceAtMost(scheduledDelay) ?: scheduledDelay
+                        }
+                        eventExecutorGroup.schedule({
+                            cb().handle { result, ex ->
+                                if (ex == null) {
+                                    res.complete(result)
+                                } else {
+                                    res.completeExceptionally(ex)
+                                }
+                            }
+                        }, delay, TimeUnit.MILLISECONDS)
+                        res
+                    }
+                    is OutcomeHandlerResult.DoNotRetry -> {
+                        shortCircuit = true
+                        when(operationOutcome) {
+                            is OperationOutcome.Failure -> throw operationOutcome.ex
+                            is OperationOutcome.Success -> CompletableFuture.completedFuture(operationOutcome.result)
+                        }
+                    }
+                }
+            }
+        }.thenCompose { it }
+    }
+    return future
+}

gbcs-client/src/main/resources/net/woggioni/gbcs/client/schema/gbcs-client.xsd

@@ -13,11 +13,14 @@
     </xs:complexType>
 
     <xs:complexType name="profileType">
-        <xs:choice>
-            <xs:element name="no-auth" type="gbcs-client:noAuthType"/>
-            <xs:element name="basic-auth" type="gbcs-client:basicAuthType"/>
-            <xs:element name="tls-client-auth" type="gbcs-client:tlsClientAuthType"/>
-        </xs:choice>
+        <xs:sequence>
+            <xs:choice>
+                <xs:element name="no-auth" type="gbcs-client:noAuthType"/>
+                <xs:element name="basic-auth" type="gbcs-client:basicAuthType"/>
+                <xs:element name="tls-client-auth" type="gbcs-client:tlsClientAuthType"/>
+            </xs:choice>
+            <xs:element name="retry-policy" type="gbcs-client:retryType" minOccurs="0"/>
+        </xs:sequence>
         <xs:attribute name="name" type="xs:token" use="required"/>
         <xs:attribute name="base-url" type="xs:anyURI" use="required"/>
         <xs:attribute name="max-connections" type="xs:positiveInteger" default="50"/>
@@ -38,4 +41,10 @@
         <xs:attribute name="key-password" type="xs:string" use="optional"/>
     </xs:complexType>
 
+    <xs:complexType name="retryType">
+        <xs:attribute name="max-attempts" type="xs:positiveInteger" use="required"/>
+        <xs:attribute name="initial-delay" type="xs:duration" default="PT1S"/>
+        <xs:attribute name="exp" type="xs:double" default="2.0"/>
+    </xs:complexType>
+
 </xs:schema>

gbcs-client/src/test/kotlin/net/woggioni/gbcs/client/RetryTest.kt

@@ -0,0 +1,149 @@
+package net.woggioni.gbcs.client
+
+import io.netty.util.concurrent.DefaultEventExecutorGroup
+import io.netty.util.concurrent.EventExecutorGroup
+import net.woggioni.gbcs.common.contextLogger
+import org.junit.jupiter.api.Assertions
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtensionContext
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.ArgumentsProvider
+import org.junit.jupiter.params.provider.ArgumentsSource
+import java.util.concurrent.CompletableFuture
+import java.util.stream.Stream
+import kotlin.random.Random
+
+class RetryTest {
+
+    data class TestArgs(
+        val seed: Int,
+        val maxAttempt: Int,
+        val initialDelay: Double,
+        val exp: Double,
+    )
+
+    class TestArguments : ArgumentsProvider {
+        override fun provideArguments(context: ExtensionContext): Stream<out Arguments> {
+            return Stream.of(
+                TestArgs(
+                    seed = 101325,
+                    maxAttempt = 5,
+                    initialDelay = 50.0,
+                    exp = 2.0,
+                ),
+                TestArgs(
+                    seed = 101325,
+                    maxAttempt = 20,
+                    initialDelay = 100.0,
+                    exp = 1.1,
+                ),
+                TestArgs(
+                    seed = 123487,
+                    maxAttempt = 20,
+                    initialDelay = 100.0,
+                    exp = 2.0,
+                ),
+                TestArgs(
+                    seed = 20082024,
+                    maxAttempt = 10,
+                    initialDelay = 100.0,
+                    exp = 2.0,
+                )
+            ).map {
+                object: Arguments {
+                    override fun get() = arrayOf(it)
+                }
+            }
+        }
+    }
+
+    @ArgumentsSource(TestArguments::class)
+    @ParameterizedTest
+    fun test(testArgs: TestArgs) {
+        val log = contextLogger()
+        log.debug("Start")
+        val executor: EventExecutorGroup = DefaultEventExecutorGroup(1)
+        val attempts = mutableListOf<Pair<Long, OperationOutcome<Int>>>()
+        val outcomeHandler = OutcomeHandler<Int> { outcome ->
+            when(outcome) {
+                is OperationOutcome.Success -> {
+                    if(outcome.result % 10 == 0) {
+                        OutcomeHandlerResult.DoNotRetry()
+                    } else {
+                        OutcomeHandlerResult.Retry(null)
+                    }
+                }
+                is OperationOutcome.Failure -> {
+                    when(outcome.ex) {
+                        is IllegalStateException -> {
+                            log.debug(outcome.ex.message, outcome.ex)
+                            OutcomeHandlerResult.Retry(null)
+                        }
+                        else -> {
+                            OutcomeHandlerResult.DoNotRetry()
+                        }
+                    }
+                }
+            }
+        }
+        val random = Random(testArgs.seed)
+
+        val future =
+            executeWithRetry(executor, testArgs.maxAttempt, testArgs.initialDelay, testArgs.exp, outcomeHandler) {
+                val now = System.nanoTime()
+                val result = CompletableFuture<Int>()
+                executor.submit {
+                    val n = random.nextInt(0, Integer.MAX_VALUE)
+                    log.debug("Got new number: {}", n)
+                    if(n % 3 == 0) {
+                        val ex = IllegalStateException("Value $n can be divided by 3")
+                        result.completeExceptionally(ex)
+                        attempts += now to OperationOutcome.Failure(ex)
+                    } else if(n % 7 == 0) {
+                        val ex = RuntimeException("Value $n can be divided by 7")
+                        result.completeExceptionally(ex)
+                        attempts += now to OperationOutcome.Failure(ex)
+                    } else {
+                        result.complete(n)
+                        attempts += now to OperationOutcome.Success(n)
+                    }
+                }
+                result
+            }
+        Assertions.assertTrue(attempts.size <= testArgs.maxAttempt)
+        val result = future.handle { res, ex ->
+            if(ex != null) {
+                val err = ex.cause ?: ex
+                log.debug(err.message, err)
+                OperationOutcome.Failure(err)
+            } else {
+                OperationOutcome.Success(res)
+            }
+        }.get()
+        for ((index, attempt) in attempts.withIndex()) {
+            val (timestamp, value) = attempt
+            if (index > 0) {
+                /* Check the delay for subsequent attempts is correct */
+                val previousAttempt = attempts[index - 1]
+                val expectedTimestamp =
+                    previousAttempt.first + testArgs.initialDelay * Math.pow(testArgs.exp, index.toDouble()) * 1e6
+                val actualTimestamp = timestamp
+                val err = Math.abs(expectedTimestamp - actualTimestamp) / expectedTimestamp
+                Assertions.assertTrue(err < 1e-3)
+            }
+            if (index == attempts.size - 1 && index < testArgs.maxAttempt - 1) {
+                /*
+                 * If the last attempt index is lower than the maximum number of attempts, then
+                 * check the outcome handler returns DoNotRetry
+                 */
+                Assertions.assertTrue(outcomeHandler.shouldRetry(value) is OutcomeHandlerResult.DoNotRetry)
+            } else if (index < attempts.size - 1) {
+                /*
+                 * If the attempt is not the last attempt check the outcome handler returns Retry
+                 */
+                Assertions.assertTrue(outcomeHandler.shouldRetry(value) is OutcomeHandlerResult.Retry)
+            }
+        }
+    }
+}

gbcs-client/src/test/resources/logback.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE configuration>
+
+<configuration>
+    <import class="ch.qos.logback.classic.encoder.PatternLayoutEncoder"/>
+    <import class="ch.qos.logback.core.ConsoleAppender"/>
+
+    <appender name="console" class="ConsoleAppender">
+        <target>System.err</target>
+        <encoder class="PatternLayoutEncoder">
+            <pattern>%d [%highlight(%-5level)] \(%thread\) %logger{36} -%kvp- %msg %n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="info">
+        <appender-ref ref="console"/>
+    </root>
+    <logger name="io.netty" level="info"/>
+    <logger name="com.google.code.yanf4j" level="warn"/>
+    <logger name="net.rubyeye.xmemcached" level="warn"/>
+</configuration>

gbcs-server/build.gradle

@@ -18,9 +18,6 @@ dependencies {
 
     testImplementation catalog.bcprov.jdk18on
     testImplementation catalog.bcpkix.jdk18on
-    testImplementation catalog.junit.jupiter.api
-    testImplementation catalog.junit.jupiter.params
-    testRuntimeOnly catalog.junit.jupiter.engine
 
     testRuntimeOnly project(":gbcs-server-memcached")
 }