"UnsatisfiedLinkError: no netty ..." error when connecting to TypeDB Server

TypeDB
1

When connecting to TypeDB in my Spring Boot application, I get an UnsatisfiedLinkError that talks about netty:

22:24:40.506 [main] DEBUG io.netty.util.internal.NativeLibraryLoader - Unable to load the library 'netty_transport_native_epoll_x86_64', trying other loading mechanism.
java.lang.UnsatisfiedLinkError: no netty_transport_native_epoll_x86_64 in java.library.path: [/usr/java/packages/lib, /usr/lib64, /lib64, /lib, /usr/lib]
	at java.base/java.lang.ClassLoader.loadLibrary(ClassLoader.java:2670)
	at java.base/java.lang.Runtime.loadLibrary0(Runtime.java:830)
	at java.base/java.lang.System.loadLibrary(System.java:1873)
	at io.netty.util.internal.NativeLibraryUtil.loadLibrary(NativeLibraryUtil.java:38)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at io.netty.util.internal.NativeLibraryLoader$1.run(NativeLibraryLoader.java:336)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at io.netty.util.internal.NativeLibraryLoader.loadLibraryByHelper(NativeLibraryLoader.java:328)
	at io.netty.util.internal.NativeLibraryLoader.loadLibrary(NativeLibraryLoader.java:306)
	at io.netty.util.internal.NativeLibraryLoader.load(NativeLibraryLoader.java:136)
	at io.netty.channel.epoll.Native.loadNativeLibrary(Native.java:198)
	at io.netty.channel.epoll.Native.<clinit>(Native.java:61)
	at io.netty.channel.epoll.Epoll.<clinit>(Epoll.java:38)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:315)
	at io.grpc.netty.Utils.isEpollAvailable(Utils.java:295)
	at io.grpc.netty.Utils.<clinit>(Utils.java:113)
	at io.grpc.netty.NettyChannelBuilder.<clinit>(NettyChannelBuilder.java:82)
	at com.vaticle.typedb.client.connection.core.CoreClient.<init>(CoreClient.java:40)
	at com.vaticle.typedb.client.connection.core.CoreClient.<init>(CoreClient.java:35)
	at com.vaticle.typedb.client.TypeDB.coreClient(TypeDB.java:38)

UnsatisfiedLinkError suggests that a dependency of typedb-client failed to load - why would that happen? My Gradle build file is:

buildscript {
    ext {
        springBootVersion = '2.1.2.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'com.graphql-java.tutorial'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenCentral()
    maven {
        url "https://repo.vaticle.com/repository/maven/"
    }
}

dependencies {
    implementation 'com.graphql-java:graphql-java:11.0'
    implementation 'com.graphql-java:graphql-java-spring-boot-starter-webmvc:1.0'
    implementation 'com.google.guava:guava:26.0-jre'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'com.vaticle.typedb:typedb-client:2.8.0'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
2

This kind of error typically occurs when you have conflicting dependencies, for example, two different libraries in your application pull in conflicting versions of a dependency.

In this case, it looks like Spring Boot has pulled in a version of Netty that isn’t compatible with TypeDB.

To resolve the conflict, add an explicit dependency on Netty, setting the version to whatever typedb-client wants. You can find this in typedb-client's pom.xml (It is 4.1.63Final as of version 2.8.0 of typedb-client).