Flink job with CassandrSink fails with Error writing - cassandra

Question

I have two simple Flink streaming jobs that read from Kafka do some transformations and put the result into a Cassandra Sink. They read from different Kafka topics and save into different Cassandra tables.
When I run any one of the two jobs alone everything works fine. Checkpoints are triggered and completed and data is saved to Cassandra.
But when ever I run both jobs (or one of them twice) the second job fails at start up with this exception:
com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: localhost/127.0.0.1:9042 (com.datastax.driver.core.exceptions.TransportException: [localhost/127.0.0.1] Error writing)).
I could not find much info about this error, it may be caused by any one of the following:
Flink (v 1.10.0-scala_2.12),
Flink Cassandra Connector (flink-connector-cassandra_2.11:jar:1.10.2, also tried with flink-connector-cassandra_2.12:jar:1.10.0),
Datastax underlying driver (v 3.10.2),
Cassandra v4.0 (same with v3.0),
Netty transport (v 4.1.51.Final).
I also use packages that may have collisions with the first ones:
mysql-connector-java (v 8.0.19),
cassandra-driver-extras (v 3.10.2)
Finally this is my code for the cluster builder:
ClusterBuilder builder = new ClusterBuilder() {
#Override
protected Cluster buildCluster(Cluster.Builder builder) {
Cluster cluster = null;
try {
cluster = builder
.addContactPoint("localhost")
.withPort(9042)
.withClusterName("Test Cluster")
.withoutJMXReporting()
.withProtocolVersion(ProtocolVersion.V4)
.withoutMetrics()
.build();
// register codecs from datastax extras.
cluster.getConfiguration().getCodecRegistry()
.register(LocalTimeCodec.instance);
} catch (ConfigurationException e) {
e.printStackTrace();
} catch (NoHostAvailableException nhae) {
nhae.printStackTrace();
}
return cluster;
}
};
I tried with different PoolingOptions and SocketOptions settings but no success.
Cassandra Sink:
CassandraSink.addSink(dataRows)
.setQuery("insert into table_name_(16 columns names) " +
"values (16 placeholders);")
.enableWriteAheadLog()
.setClusterBuilder(builder)
.setFailureHandler(new CassandraFailureHandler() {
#Override
public void onFailure(Throwable throwable) {
LOG.error("A {} occurred.", "Cassandra Failure", throwable);
}
})
.build()
.setParallelism(1)
.name("Cassandra Sink For Unique Count every N minutes.");
The full trace log from flink job manager:
com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: localhost/127.0.0.1:9042 (com.datastax.driver.core.exceptions.TransportException: [localhost/127.0.0.1] Error writing))
at com.datastax.driver.core.ControlConnection.reconnectInternal(ControlConnection.java:231)
at com.datastax.driver.core.ControlConnection.connect(ControlConnection.java:77)
at com.datastax.driver.core.Cluster$Manager.init(Cluster.java:1414)
at com.datastax.driver.core.Cluster.init(Cluster.java:162)
at com.datastax.driver.core.Cluster.connectAsync(Cluster.java:333)
at com.datastax.driver.core.Cluster.connectAsync(Cluster.java:308)
at com.datastax.driver.core.Cluster.connect(Cluster.java:250)
at org.apache.flink.streaming.connectors.cassandra.CassandraSinkBase.createSession(CassandraSinkBase.java:143)
at org.apache.flink.streaming.connectors.cassandra.CassandraSinkBase.open(CassandraSinkBase.java:87)
at org.apache.flink.streaming.connectors.cassandra.AbstractCassandraTupleSink.open(AbstractCassandraTupleSink.java:49)
at org.apache.flink.api.common.functions.util.FunctionUtils.openFunction(FunctionUtils.java:36)
at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.open(AbstractUdfStreamOperator.java:102)
at org.apache.flink.streaming.api.operators.StreamSink.open(StreamSink.java:48)
at org.apache.flink.streaming.runtime.tasks.StreamTask.initializeStateAndOpen(StreamTask.java:1007)
at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$beforeInvoke$0(StreamTask.java:454)
at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$SynchronizedStreamTaskActionExecutor.runThrowing(StreamTaskActionExecutor.java:94)
at org.apache.flink.streaming.runtime.tasks.StreamTask.beforeInvoke(StreamTask.java:449)
at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:461)
at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:707)
at org.apache.flink.runtime.taskmanager.Task.run(Task.java:532)
at java.base/java.lang.Thread.run(Thread.java:834)
Any help is appreciated.
Edit:
I just tried using two Cassandra separate instances (different machines and different clusters). I then pointed one job to an instance and the other job to the other instance. Nothing has changed, I still get the same error.
Tried to reduce dependencies, here is the new pom file:
<!--
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or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
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Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied. See the License for the
specific language governing permissions and limitations
under the License.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.abcde.ai</groupId>
<artifactId>analytics-etl</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Flink Quickstart Job</name>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<flink.version>1.10.2</flink.version>
<java.version>1.8</java.version>
<scala.binary.version>2.11</scala.binary.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
</properties>
<repositories>
<repository>
<id>apache.snapshots</id>
<name>Apache Development Snapshot Repository</name>
<url>https://repository.apache.org/content/repositories/snapshots/</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>
<dependencies>
<!-- Apache Flink dependencies -->
<!-- These dependencies are provided, because they should not be packaged into the JAR file. -->
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-java</artifactId>
<version>${flink.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-streaming-java_${scala.binary.version}</artifactId>
<version>${flink.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-streaming-scala_${scala.binary.version}</artifactId>
<version>${flink.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.6</version>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-connector-kafka_${scala.binary.version}</artifactId>
<version>${flink.version}</version>
</dependency>
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-connector-cassandra_${scala.binary.version}</artifactId>
<version>${flink.version}</version>
</dependency>
<dependency>
<groupId>commons-configuration</groupId>
<artifactId>commons-configuration</artifactId>
<version>1.10</version>
</dependency>
<!-- Add logging framework, to produce console output when running in the IDE. -->
<!-- These dependencies are excluded from the application JAR by default. -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.7</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<plugins>
<!-- Java Compiler -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>${java.version}</source>
<target>${java.version}</target>
</configuration>
</plugin>
<!-- We use the maven-shade plugin to create a fat jar that contains all necessary dependencies. -->
<!-- Change the value of <mainClass>...</mainClass> if your program entry point changes. -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.1.1</version>
<executions>
<!-- Run shade goal on package phase -->
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<artifactSet>
<excludes>
<exclude>org.apache.flink:force-shading</exclude>
<exclude>com.google.code.findbugs:jsr305</exclude>
<exclude>org.slf4j:*</exclude>
<exclude>log4j:*</exclude>
</excludes>
</artifactSet>
<filters>
<filter>
<!-- Do not copy the signatures in the META-INF folder.
Otherwise, this might cause SecurityExceptions when using the JAR. -->
<artifact>*:*</artifact>
<excludes>
<exclude>META-INF/*.SF</exclude>
<exclude>META-INF/*.DSA</exclude>
<exclude>META-INF/*.RSA</exclude>
</excludes>
</filter>
</filters>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>com.abcde.analytics.etl.KafkaUniqueCountsStreamingJob</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
<pluginManagement>
<plugins>
<!-- This improves the out-of-the-box experience in Eclipse by resolving some warnings. -->
<plugin>
<groupId>org.eclipse.m2e</groupId>
<artifactId>lifecycle-mapping</artifactId>
<version>1.0.0</version>
<configuration>
<lifecycleMappingMetadata>
<pluginExecutions>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<versionRange>[3.1.1,)</versionRange>
<goals>
<goal>shade</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore/>
</action>
</pluginExecution>
<pluginExecution>
<pluginExecutionFilter>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<versionRange>[3.1,)</versionRange>
<goals>
<goal>testCompile</goal>
<goal>compile</goal>
</goals>
</pluginExecutionFilter>
<action>
<ignore/>
</action>
</pluginExecution>
</pluginExecutions>
</lifecycleMappingMetadata>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
Edit:
I managed to narrow down the problem. The error gets fixed when I mark the dependency flink-connector-cassandra as provided and I simply copy the jar file from my local maven repository (~/.m2/repository/org/apache/flink/flink-connector-cassandra_2.11/1.10.2/flink-connector-cassandra_2.11-1.10.2.jar) to Flink lib folder. My problem is solved but the root cause is still a mystery.

Answer 1

I might be wrong, but most likely the issue is caused by netty client version conflict. The error states NoHostAvailableException, however the underlying error is TransportException with Error writing error message. Cassandra s definetely operating well.
There is a kind of similar stackoverflow case - Cassandra - error writing, with a very similar symptoms - a single project running well and AllNodesFailedException with TransportException with Error writing message as a root cause when adding one more. The author was able to solve it by unifying the netty client.
In your case, I'm not sure why there are so many dependencies, so I would try to get rid of all extras and libraries and would just leave Flink (v 1.10.0-scala_2.12) and Flink Cassandra Connector (flink-connector-cassandra_2.12:jar:1.10.0) libraries. They must already include necessary drivers, netty, etc. All other drivers should be skipped (at least for initial iteration to ensure that this solves the issue and it's library conflict).

Answer 2

To fix the error I marked the dependency flink-connector-cassandra as provided and I simply copy the jar file from my local maven repository (~/.m2/repository/org/apache/flink/flink-connector-cassandra_2.11/1.10.2/flink-connector-cassandra_2.11-1.10.2.jar) to Flink lib folder and restarted Flink, here is my new pom.xml file:
<dependency>
<groupId>org.apache.flink</groupId>
<artifactId>flink-connector-cassandra_${scala.binary.version}</artifactId>
<version>${flink.version}</version>
<scope>provided</scope>
</dependency>
How I found this? I was about to try to compile the connector from source with a more recent driver version. First I tried to reproduce the error with the unchanged sources. So I compiled it without changing anything, put the jar into Flink lib folder, Hooray it works! I then suspected that the jar from maven had something different. I copied it into the lib folder and at my surprise it also worked.
My problem is solved but the root cause remains a mystery.
My last attempt was to check if any packages are in conflict with Cassandra connector so I run dependency:tree -Dverbose there was one conflict with org.apache.flink:flink-metrics-dropwizard about metrics-core:
[INFO] +- org.apache.flink:flink-connector-cassandra_2.12:jar:1.10.0:provided
[INFO] | +- (io.dropwizard.metrics:metrics-core:jar:3.1.2:provided - omitted for conflict with 3.1.5)
[INFO] | \- (org.apache.flink:force-shading:jar:1.10.0:provided - omitted for duplicate)
I removed this dependency from my project but the error remains if the connector is not marked as provided and also put in the lib folder.