write dataframe to cassandra facing BusyPoolException - cassandra

Question

I am trying to write dataframe to cassandra using these line of code,was able to write to table for someday but suddenly the error came
alertdf
.write.format("org.apache.spark.sql.cassandra")
.options(Map("keyspace" -> "dummy", "table" -> "dummytable"))
.mode(SaveMode.Append)
.save()
I get this below error,not able to find out what is getting wrong
ERROR QueryExecutor: Failed to execute: com.datastax.spark.connector.writer.RichBoundStatement#7dba59e2
com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: **.**.**.**/**.**.**.**:9042 (com.datastax.driver.core.exceptions.BusyPoolException: [**.**.**.**/**.**.**.**] Pool is busy (no available connection and the queue has reached its max size 256)))
at com.datastax.driver.core.RequestHandler.reportNoMoreHosts(RequestHandler.java:211)
at com.datastax.driver.core.RequestHandler.access$1000(RequestHandler.java:46)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution.findNextHostAndQuery(RequestHandler.java:275)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution$1.onFailure(RequestHandler.java:338)
at shade.com.datastax.spark.connector.google.common.util.concurrent.Futures$6.run(Futures.java:1310)
at shade.com.datastax.spark.connector.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:457)
at shade.com.datastax.spark.connector.google.common.util.concurrent.Futures$ImmediateFuture.addListener(Futures.java:106)
at shade.com.datastax.spark.connector.google.common.util.concurrent.Futures.addCallback(Futures.java:1322)
at shade.com.datastax.spark.connector.google.common.util.concurrent.Futures.addCallback(Futures.java:1258)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution.query(RequestHandler.java:297)
at com.datastax.driver.core.RequestHandler$SpeculativeExecution.findNextHostAndQuery(RequestHandler.java:272)
at com.datastax.driver.core.RequestHandler.startNewExecution(RequestHandler.java:115)
at com.datastax.driver.core.RequestHandler.sendRequest(RequestHandler.java:95)
at com.datastax.driver.core.SessionManager.executeAsync(SessionManager.java:132)
at sun.reflect.GeneratedMethodAccessor34.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.datastax.spark.connector.cql.SessionProxy.invoke(SessionProxy.scala:40)
at com.sun.proxy.$Proxy14.executeAsync(Unknown Source)
at sun.reflect.GeneratedMethodAccessor34.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.datastax.spark.connector.cql.SessionProxy.invoke(SessionProxy.scala:40)
at com.sun.proxy.$Proxy15.executeAsync(Unknown Source)
at com.datastax.spark.connector.writer.QueryExecutor$$anonfun$$lessinit$greater$1.apply(QueryExecutor.scala:11)
at com.datastax.spark.connector.writer.QueryExecutor$$anonfun$$lessinit$greater$1.apply(QueryExecutor.scala:11)
at com.datastax.spark.connector.writer.AsyncExecutor.executeAsync(AsyncExecutor.scala:31)
at com.datastax.spark.connector.writer.TableWriter$$anonfun$writeInternal$1$$anonfun$apply$2.apply(TableWriter.scala:199)
at com.datastax.spark.connector.writer.TableWriter$$anonfun$writeInternal$1$$anonfun$apply$2.apply(TableWriter.scala:198)
at scala.collection.Iterator$class.foreach(Iterator.scala:893)
at com.datastax.spark.connector.writer.GroupingBatchBuilder.foreach(GroupingBatchBuilder.scala:31)
at com.datastax.spark.connector.writer.TableWriter$$anonfun$writeInternal$1.apply(TableWriter.scala:198)
at com.datastax.spark.connector.writer.TableWriter$$anonfun$writeInternal$1.apply(TableWriter.scala:175)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$withSessionDo$1.apply(CassandraConnector.scala:112)
at com.datastax.spark.connector.cql.CassandraConnector$$anonfun$withSessionDo$1.apply(CassandraConnector.scala:111)
at com.datastax.spark.connector.cql.CassandraConnector.closeResourceAfterUse(CassandraConnector.scala:145)
at com.datastax.spark.connector.cql.CassandraConnector.withSessionDo(CassandraConnector.scala:111)
at com.datastax.spark.connector.writer.TableWriter.writeInternal(TableWriter.scala:175)
at com.datastax.spark.connector.writer.TableWriter.insert(TableWriter.scala:162)
at com.datastax.spark.connector.writer.TableWriter.write(TableWriter.scala:149)
at com.datastax.spark.connector.RDDFunctions$$anonfun$saveToCassandra$1.apply(RDDFunctions.scala:36)
at com.datastax.spark.connector.RDDFunctions$$anonfun$saveToCassandra$1.apply(RDDFunctions.scala:36)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:70)
at org.apache.spark.scheduler.Task.run(Task.scala:86)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:274)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
can anyone help me with this issue?

Answer 1

It looks like that your servers are overloaded, and don't process your requests on time. I recommend to try to tune write-related configuration parameters, like, output.concurrent.writes, output.throughput_mb_per_sec and other, but I would start with first 2.