The Joy of JARs (and Other Flink SQL Troubleshooting Tales)

A presentation at Current in September 2024 in Austin, TX, USA by Robin Moffatt

Could not execute SQL statement. Reason: java.lang.ClassNotFoundException

S m Could not find a file system plementation for scheme ‘s3’ m i org.apache.flink.core.fs. UnsupportedFileSyste chemeException:

m i Could not find any factory for identifier ‘hive’ that plements ‘org.apache.flink.table.factories. CatalogFactory’ in the classpath. 🏭

@decodableco Troubleshooting @rmoff / #current24

@decodableco @rmoff / #current24 “…now I ll jiggle things rando y until they unbreak” is not acceptable —Linus Torvalds l m i libquotes.com/linus-torvalds/quote/lbr1k4j w / / https:

@decodableco @rmoff / #current24 Troubleshooting Flink SQL • What is the root error? • Java loves stack traces! • SQL Client often only gives you the top level view • W ere is the error co ng from? • Is what you’re doing supported? • e.g. JDBC Catalog is read- i m E T h only, some table formats don’t support UPDA , etc.

@decodableco @rmoff / #current24 Things to a • Versions • Flink vs libraries • Dependencies, e.g. • Required JARs w l • Java version ays check

@decodableco @rmoff / #current24 What Runs Where?

@decodableco @rmoff / #current24 apache flink is a distributed system it’s not being difficult entirely for the sake of it ;)

@decodableco nightlies.apache.org/flink/flink-docs-master/docs/deployment/overview/ / / Ref: https: @rmoff / #current24

@decodableco @rmoff / #current24 Flink SQL> CREA DATABASE ‘db0l’; m i m E T [ERROR] Could not execute SQL statement. Reason: MetaException( essage:java.lang.Runt eException: java.lang.ClassNotFoundException: Class org.apache.hadoop.fs.s3a.S3AFileSystem not found)

@decodableco @rmoff / #current24 Flink SQL> INSERT INTO foo VALUES (‘a’,42); tted . . i . m i m [INFO] Sub tting SQL update statement to the cluster [INFO] SQL update statement has been successfully sub to the cluster: Job ID: cc43d32a6bb0e2faab5270e542c70499

@decodableco @rmoff / #current24 Flink SQL> INSERT INTO foo VALUES (‘a’,42); [INFO] Sub tting SQL update statement to the cluster [INFO] SQL update statement has been successfully sub to the cluster: Job ID: cc43d32a6bb0e2faab5270e542c70499 tted . . i . m i m Flink SQL> SHOW JOBS; +—————————————————+—————————-+—————+——| job id | job name | status | +—————————————————+—————————-+—————+——| cc43d32a6bb0e2faab5270e542c70499 | insert-into_table | FAILED | 2024 | 0b7f3f8cca2322de2366a1fd059fe5d9 | collect | FINISHED | 2024

@decodableco Flink Dashboard @rmoff / #current24

@decodableco @rmoff / #current24 The truth is the log m f queue.ac .org/detail.c m / / h/t Pat Helland https: ?id=2884038

@decodableco @rmoff / #current24 The truth is the log flink-1.20.0 └── log ├── flink-rmoff-sql-client-asgard08.log ├── flink-rmoff-standalonesession-1-asgard08.log ├── flink-rmoff-taskexecutor-1-asgard08.log └── flink-rmoff-taskexecutor-2-asgard08.log

@decodableco @rmoff / #current24 i m Na ng things is hard (apparently)

@rmoff / #current24 Log file names Configured through the log variable in the launch scripts • SQL Client (sq -c flink- e t.s ): LINK_IDEN RING-sql-client- HO • Job Manager / Task Manager ( flink- LINK_IDEN RING- DA NA .log k-dae o .s ) ON- d- HO NA USER if not already set .log h n E E M m M T T S S $ n $ i i l $ f M E h $ w n t i w i l T T S S _ _ T T l F F $ the instance of the component (e.g. for task managers this be 0 and 1) the command used to launch the Flink Component: standalonesession or taskexecutor $ $ @decodableco o ll

@decodableco Putting Flink in the ./bin @rmoff / #current24

@decodableco @rmoff / #current24 Logging configuration (Log4j 2) Which configuration file?

@decodableco @rmoff / #current24 Log level • Pre-1.19 Update each log4j configuration directly: rootLogger.level = TRACE • >= 1.19: Set as a central configuration option in Flink’s config.ya l m env.log.level: TRACE :

@decodableco @rmoff / #current24 Custo sing log level for specific components logger.<id>.name = <logger name> logger.<id>.level = <ERROR|WARN|INFO|TRACE|DEBUG> e.g. logger.catalog.name = org.apache.flink.table.catalog i m logger.catalog.level = TRACE

@decodableco @rmoff / #current24 Log format • Default is PatternLayout • Others available including JSON, CSV, YA { “instant” : { “epochSecond” : 1725463441, “nanoOfSecond” : 471575000 }, “thread” : “flink-rest-client-netty-thread-1”, “level” : “DEBUG”, “loggerName” : “org.apache.flink.runt e.rest.RestClient”, “message” : “Received response {“properties”:{“flink.hadoop.fs.s3a.secret.key”:”hunter2” “endOfBatch” : false, “loggerFqcn” : “org.apache.logging.slf4j.Log4jLogger”, “threadId” : 19, “threadPriority” : 5 L M m i }

@decodableco MOAR data plz / / / / / Creating endpoint configuration for “” Using default endpoint -no need to generate a c fs.s3a.endpoint.region=”us-east-1” Using default endpoint; setting region to us-ea Creating endpoint configuration for “http: loc Endpoint http: localhost:9000 is not the defau Endpoint URI = http: localhost:9000 Region for endpoint http: localhost:9000, URI / [] [] [] [] [] [] [] [] / org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory / BUG BUG BUG BUG BUG BUG BUG BUG @rmoff / #current24

@decodableco @rmoff / #current24 I can haz more data? BUG BUG BUG BUG BUG BUG BUG BUG org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory org.apache.hadoop.fs.s3a.DefaultS3ClientFactory [] [] [] [] [] [] [] [] Creating endpoint configuration for “” Using default endpoint -no need to generate a c fs.s3a.endpoint.region=”us-east-1” Using default endpoint; setting region to us-ea Creating endpoint configuration for “http: Endpoint http: Endpoint URI = http: Region for endpoint http: / / / % appender.

@decodableco @rmoff / #current24 MOAR data! tory tory tory tory tory tory tory tory [] [] [] [] [] [] [] [] tid:79 tid:79 tid:79 tid:79 tid:80 tid:80 tid:80 tid:80 [t_foo[2]: [t_foo[2]: [t_foo[2]: [t_foo[2]: [t_foo[2]: [t_foo[2]: [t_foo[2]: [t_foo[2]: Writer Writer Writer Writer Global Global Global Global -> t_foo[2]: Com -> t_foo[2]: Com -> t_foo[2]: Com -> t_foo[2]: Com Com tter (1/1) 0 Com tter (1/1) 0 Com tter (1/1) 0 Com tter (1/1) 0 tter tter tter tter (1/1) (1/1) (1/1) (1/1) 0 0 0 0 ] ] ] ] ] ] ] ]
Creating endpoint configuration for Using default endpoint -no need to fs.s3a.endpoint.region=”us-east-1” Using default endpoint; setting reg Creating endpoint configuration for Endpoint http: localhost:9000 is n Endpoint URI = http: localhost:900 Region for endpoint http: localhos i i i i m m m m
i i i i m m m m % appender.

@decodableco @rmoff / #current24 $ jps 84163 SqlClient 83671 StandaloneSessionClusterEntrypoint 83944 TaskManagerRunner

@decodableco $ jinfo 84163 @rmoff / #current24

@decodableco @rmoff / #current24 $ $ jinfo (pgrep -f SqlClient)

@decodableco @rmoff / #current24 $ jinfo (pgrep -f SqlClient) m W L / T / S m t w F T w l m $ m v t w Java System Properties: #Thu Sep 05 11:18:14 B 2024 gopherProxySet=false log4j.configuration=file:/Users/rmoff/flink/flink-1.18.1/conf/log4jcli.properties a .toolkit=sun. a . acosx. CToolkit java.specification.version=11 sun.cpu.isalist= sun.jnu.encoding=U -8 java. .vendor=Eclipse Adoptium sun.arch.data. odel=64 java.vendor.url=https: adoptiu .net/

@decodableco @rmoff / #current24 $ jinfo (pgrep -f SqlClient) S w T t $ i M […] VM Flags: -XX:CICompilerCount=4 -XX:ConcGCThreads=2 -XX:G1ConcRefinemen hreads=9 -XX:G1HeapRegionSize=4194304 -XX:GCDrainStackTargetSize=64 -XX:+IgnoreUnrecognizedVMOptions -XX:InitialHeapSize=1073741824 -XX:MarkStackSize=4194304 -XX:MaxHeapSize=17179869184 -XX:MaxNe ize=10305404928 -XX: nHeapDeltaBytes=4194304 -XX:NonNMethodCodeHeapSize=5836492 -XX:NonProfiledCodeHeapSize=122910874 -XX :ProfiledCodeHeapSize=122910874 -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:-UseAOT -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC

@decodableco @rmoff / #current24 $ jinfo (pgrep -f SqlClient) $ […] VM Arguments: java_command: org.apache.flink.table.client.SqlClient —jar /Users/ rmoff/flink/flink-1.18.1/opt/flink-sql-client-1.18.1.jar java_class_path (initial): /Users/rmoff/flink/flink-1.18.1/lib/delta/ aws-java-sdk-bundle-1.12.648.jar:/Users/rmoff/flink/flink-1.18.1/lib/ delta/delta-flink-3.2.0.jar:/Users/rmoff/flink/flink-1.18.1/lib/ delta/delta-standalone_2.12-3.2.0.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/delta-storage-3.2.0.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/flink-sql-parquet-1.18.1.jar:/Users/rmoff/ flink/flink-1.18.1/lib/delta/hadoop-aws-3.3.4.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/shapeless_2.12-2.3.4.jar:/Users/rmoff/flink/

@decodableco @rmoff / #current24 $ jinfo (pgrep -f SqlClient) \ | grep java_class_path $ java_class_path (initial): /Users/rmoff/flink/flink-1.18.1/lib/delta/ aws-java-sdk-bundle-1.12.648.jar:/Users/rmoff/flink/flink-1.18.1/lib/ delta/delta-flink-3.2.0.jar:/Users/rmoff/flink/flink-1.18.1/lib/ delta/delta-standalone_2.12-3.2.0.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/delta-storage-3.2.0.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/flink-sql-parquet-1.18.1.jar:/Users/rmoff/ flink/flink-1.18.1/lib/delta/hadoop-aws-3.3.4.jar:/Users/rmoff/flink/ flink-1.18.1/lib/delta/shapeless_2.12-2.3.4.jar:/Users/rmoff/flink/ flink-1.18.1/lib/flink-cep-1.18.1.jar:/Users/rmoff/flink/ flink-1.18.1/lib/flink-connector-files-1.18.1.jar:/Users/rmoff/flink/ flink-1.18.1/lib/flink-csv-1.18.1.jar:/Users/rmoff/flink/

@decodableco i W 🕵 @rmoff / #current24 reshark 🦈

@rmoff / #current24 tshark Flink SQL> SHOW TABLES; pty set ───────────────────────────────────────── $ tshark -i lo -Y “http and (http.request. ethod==PO or http.response)” Capturing on ‘Loopback: lo0’ 127.0.0.1 → 127.0.0.1 (application/json) HTTP/JSON 2263 HTTP/1.1 200 OK , JSON 127.0.0.1 → 127.0.0.1 HTTP/JSON 292 PO /v2/sessions/ 8827d93e-0deb-43b5-90ab-8d1c5bce8bd1/statements HTTP/1.1 , JSON (application/json) T S m T HTTP/JSON 232 HTTP/1.1 200 OK , JSON S 127.0.0.1 → 127.0.0.1 (application/json) m E @decodableco

@decodableco @rmoff / #current24 Finding JARs Usually the docs ll tell you which JAR you need. i w JARs are very specific to the versions of the tools that you’re using.

@decodableco @rmoff / #current24 Put JARs in the ./lib folder flink-1.20.0 ├── lib │ ├── ext │ │ │ ├── flink-cep-1.20.0.jar │ ├── flink-connector-files-1.20.0.jar │ ├── flink-csv-1.20.0.jar │ ├── flink-dist-1.20.0.jar │ ├── flink-json-1.20.0.jar │ ├── flink-scala_2.12-1.20.0.jar └── flink-sql-parquet-1.20.0.jar

@decodableco @rmoff / #current24 Where does Flink look for JARs? • Flink is invoked th a classpath argument that’s built from constructFlinkClassPath in config.sh, which scans the ./lib folder m i i w m i java_class_path (initial): /Users/rmoff/flink/flink-1.20.0/lib/ext/flink-sql-parquet-1.20.0.jar:/ Users/rmoff/flink/flink-1.20.0/lib/flink-cep-1.20.0.jar:/Users/rm off/flink/flink-1.20.0/lib/flink-connector-files-1.20.0.jar:/Users/rmoff/flink/flink-1.20.0/lib/ flink-csv-1.20.0.jar:/Users/rmoff/flink/flink-1.20.0/lib/flink-jso n-1.20.0.jar:/Users/rmoff/flink/flink-1.20.0/lib/flink-scala_2.12-1.20.0.jar:/Users/rmoff/flink/ flink-1.20.0/lib/flink-table-api-java-uber-1.20.0.jar:/Users/rmoff /flink/flink-1.20.0/lib/flink-table-planner-loader-1.20.0.jar:/Users/rmoff/flink/flink-1.20.0/ lib/flink-table-runt e-1.20.0.jar:/Users/rmoff/flink/flink-1.20.0/l ib/log4j-1.2-api-2.17.1.jar:/Users/rmoff/flink/flink-1.20.0/lib/log4j-api-2.17.1.jar:/Users/ rmoff/flink/flink-1.20.0/lib/log4j-core-2.17.1.jar:/Users/rmoff/flink/ flink-1.20.0/lib/log4j-slf4j- pl-2.17.1.jar:/Users/rmoff/flink/flink-1.20.0/lib/flinkdist-1.20.0.jar::::

@decodableco @rmoff / #current24 Hadoop classpath $ export HADOOP_CLASSPATH= (/opt/hadoop/bin/hadoop classpath) to n i l ecessary JARs d rect y i $ n h i l f i h l n i l (or just c erry-p ck t e F k’s ./ b o der)

@decodableco @rmoff / #current24 Don’t forget to restart!

@decodableco @rmoff / #current24 What’s inside a JAR? $ jar tf flink-sql-parquet-1.20.0.jar 1 $ l 1 $ $ 1 t t $ $ $ t t t 1 $ I I w w W t $ l org/apache/flink/formats/parquet/ParquetColumnarRo nputForma ColumnarRowReaderBatch.class org/apache/flink/formats/parquet/ParquetColumnarRo nputForma .class org/apache/flink/formats/parquet/Parque riterFactory.class org/apache/flink/formats/parquet/ParquetVectorizedInputForma .class org/apache/flink/formats/parquet/ParquetFileFormatFactory$ParquetBulkDecodingFormat.class org/apache/flink/formats/parquet/ParquetVectorizedInputForma ParquetReaderBatch.class org/apache/flink/formats/parquet/ParquetBuilder.class org/apache/flink/formats/parquet/ParquetFileFormatFactory.class org/apache/flink/formats/parquet/ParquetVectorizedInputForma ParquetReader.class org/apache/flink/formats/parquet/ParquetFileFormatFactory .class org/apache/flink/formats/parquet/utils/SerializableConfiguration.class org/apache/flink/formats/parquet/utils/ ParquetFormatStatisticsReportUti ParquetFileRowCountCalculator.class org/apache/flink/formats/parquet/utils/ParquetFormatStatisticsReportUtil.class org/apache/flink/formats/parquet/utils/ParquetSchemaConverter.class org/apache/flink/formats/parquet/utils/ParquetFormatStatisticsReportUti .class

@rmoff / #current24 What got loaded from where? $ FLINK_ENV_JAVA_OP =”-verbose:class” ./bin/sql-client.sh $ l S T [20.264s][info][class,load] org.apache.flink.table.connector.format.ProjectableDecodingFormat source: file:/ Users/rmoff/flink/flink-1.20.0/lib/flink-table-api-java-uber-1.20.0.jar [20.264s][info][class,load] org.apache.flink.table.connector.format.FileBasedStatisticsReportableInputFormat source: file:/Users/rmoff/flink/flink-1.20.0/lib/flink-table-api-javauber-1.20.0.jar [20.264s][info][class,load] org.apache.flink.formats.parquet.ParquetFileFormatFactory$ParquetBulkDecodingForm at source: file:/Users/rmoff/flink/flink-1.20.0/lib/ext/flink-sqlparquet-1.20.0.jar [20.264s][info][class,load] org.apache.flink.table.factories.FactoryUti TableFactoryHelper$ ambda$971/0x0000000800779c40 source: L $ @decodableco

@decodableco y l l a e r @rmoff / #current24 What Runs Where?

@decodableco i c w / / Ref: https: ki.apache.org/confluence/display/FLINK/FLIP-24:+SQL+Client @rmoff / #current24

@decodableco @rmoff / #current24 tshark T S m j T $ tshark -i lo \ -Y “http and (http.request. ethod==PO or http.response)” \ - son “json”: { “json.object”: { “json.member”: “statement”, “json.member_tree”: { “json.path_with_value”: “/statement:SHOW TABLES;”, “json.member_with_value”: “statement:SHOW TABLES;”, “json.value.string”: “SHOW TABLES;”, “json.key”: “statement”, “json.path”: “/statement” },

@decodableco what about external stuff? @rmoff / #current24

@decodableco 💩 rises to the top… @rmoff / #current24

@decodableco $ ls -l lib/aws @rmoff / #current24

@decodableco @rmoff / #current24 $ ls -l lib/aws $ jar tf lib/aws/hadoop-aws-3.3.4.jar | grep S3AFileSyste .class m $

@decodableco @rmoff / #current24 $ more log/flink—sql-client-asgard08.log T E T m I M T m T m i m i . . . 2024-09-12 11:20:06,494 ERROR org.apache.flink.table.gateway.service.operation.Operati org.apache.flink.table.api. ableException: Could not execute CREA DATABASE: (catalog at org.apache.flink.table.operations.ddl.CreateDatabaseOperation.execute(Creat at org.apache.flink.table.api.internal. ableEnvironment pl.executeInternal( a […] Caused by: java.lang.Runt eException: Failed to create namespace db01 in Hive Metasto at org.apache.iceberg.hive.HiveCatalog.createNamespace(HiveCatalog.java:299) ~ at org.apache.iceberg.flink.FlinkCatalog.createDatabase(FlinkCatalog.java:223) at org.apache.iceberg.flink.FlinkCatalog.createDatabase(FlinkCatalog.java:214) at org.apache.flink.table.catalog.CatalogManager.createDatabase(CatalogManager at org.apache.flink.table.operations.ddl.CreateDatabaseOperation.execute(Creat 14 more Caused by: org.apache.hadoop.hive. etastore.api. etaException: java.lang.Runt eException: java.lang.ClassNotFoundException: Class org.apache.hadoop.fs.s3a.S3AFileSystem not found

@decodableco @rmoff / #current24 $ more log/flink—sql-client-asgard08.log T E T m I S T M T T T T T T m m m m m m m S T T m i m i . . . 2024-09-12 11:20:06,494 ERROR org.apache.flink.table.gateway.service.operation.Operati org.apache.flink.table.api. ableException: Could not execute CREA DATABASE: (catalog at org.apache.flink.table.operations.ddl.CreateDatabaseOperation.execute(Creat at org.apache.flink.table.api.internal. ableEnvironment pl.executeInternal( a […] Caused by: java.lang.Runt eException: Failed to create namespace db01 in Hive Metasto at org.apache.iceberg.hive.HiveCatalog.createNamespace(HiveCatalog.java:299) ~ at org.apache.iceberg.flink.FlinkCatalog.createDatabase(FlinkCatalog.java:223) at org.apache.iceberg.flink.FlinkCatalog.createDatabase(FlinkCatalog.java:214) at org.apache.flink.table.catalog.CatalogManager.createDatabase(CatalogManager at org.apache.flink.table.operations.ddl.CreateDatabaseOperation.execute(Creat 14 more Caused by: org.apache.hadoop.hive. etastore.api. etaException: java.lang.Runt eException: java.lang.ClassNotFoundException: Class org.apache.hadoop.fs.s3a.S3AFileSystem not found at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$create_database_re at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$create_database_re at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$create_database_re at org.apache.thrift. erviceClient.receiveBase( erviceClient.java:86) ~[flin at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$Client.recv_create at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$Client.create_data at org.apache.hadoop.hive. etastore.HiveMetaStoreClient.createDatabase(HiveMet

@decodableco @rmoff / #current24 sql-client→hms create_database db01,s3a: / DATABASE db01 / E T CREA warehouse/db01.db,flink,hive

@decodableco @rmoff / #current24 log hive-metastore $ docker compose S M m I S M m m I i T T 1 1 $ $ S S M M S S M M m m T T I m m T T I I M m m m m m m m m M S M $ m metastore.HiveMetaStore: 1: source:172.17.0.3 create_database: Database(name:db01, des HiveMetaStore.audit: ugi=flink ip=172.17.0.3 cmd=source:172.17.0.3 create_database metastore.ObjectStore: Failed to get database hive.db01, returning NoSuchObjectExcepti metastore.RetryingH Handler: MetaException( essage:java.lang.Runt eException: java.lang.ClassNotFoundException: Class org.apache.hadoop.fs.s3a.S3AFileSystem not found) at org.apache.hadoop.hive. etastore.HiveMetaStore$H Handler.newMetaException(HiveMeta at org.apache.hadoop.hive. etastore.HiveMetaStore$H Handler.create_database(HiveMetaS at sun.reflect.NativeMethodAccessor pl.invoke0(Native Method) at sun.reflect.NativeMethodAccessor pl.invoke(NativeMethodAccessor pl.java:62) at sun.reflect.DelegatingMethodAccessor pl.invoke(DelegatingMethodAccessor pl.java:4 at java.lang.reflect. ethod.invoke( ethod.java:498) at org.apache.hadoop.hive. etastore.RetryingH Handler.invokeInternal(RetryingH Handl at org.apache.hadoop.hive. etastore.RetryingH Handler.invoke(RetryingH Handler.java: at co .sun.proxy. Proxy26.create_database(Unknown Source) at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$Processor$create_database. at org.apache.hadoop.hive. etastore.api. hriftHiveMetastore$Processor$create_database. at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:39) at org.apache.hadoop.hive. etastore. UGIBasedProcessor .run( UGIBasedProcessor.java:1 at org.apache.hadoop.hive. etastore. UGIBasedProcessor .run( UGIBasedProcessor.java:1 at java.security.AccessController.doPrivileged(Native Method)

@decodableco @rmoff / #current24 java.lang.ClassNotFoundException: Class org.apache.hadoop.fs.s3a.S3AFileSystem not found sql-client→hms create_database db01,s3a: / DATABASE db01 / E T CREA warehouse/db01.db,flink,hive

@decodableco TCP packet capture @rmoff / #current24

@decodableco @rmoff / #current24 CREATE CATALOG T / I CATALOG c_iceberg W H ( ‘type’ = ‘iceberg’, ‘catalog-type’=’hive’, ‘warehouse’ = ‘s3a: warehouse’, ‘hive-conf-dir’ = ‘./conf’); / E T CREA

@decodableco @rmoff / #current24 CREATE DATABASE CREA DATABASE c_iceberg.rmoff; 172.17.0.5→172.17.0.2 create_database rmoff,s3a: warehouse/rmoff.db,fli / / E T 172.17.0.2→172.17.0.9 HTTP 152 PUT /warehouse/rmoff.db/ HTTP/1.1 (appli

@decodableco @rmoff / #current24 USE DATABASE USE c_iceberg.rmoff; / @hive#rmoff rmoff,s3a: warehouse/rmoff.db,fli / 172.17.0.5→172.17.0.2 get_database 172.17.0.2→172.17.0.5 get_database

@decodableco @rmoff / #current24 CREATE TABLE CREA TABLE foo (c1 IN , c2 RING); 172.17.0.5 172.17.0.2 create_table th_environment_context foo,rmoff, c1,int,c2,string,s3a: warehouse/rmoff.db/foo, metadata_location,s3a: warehouse/rmoff.db/foo/met current-schema,{“type”:”struct”,”schema-id”:0,”fie / / / / i w _ T S T E T 172.17.0.5 172.17.0.9 HTTP 1229 PUT /warehouse/rmoff.db/foo/metadata/000

@decodableco @rmoff / #current24 CREATE TABLE CREA TABLE foo (c1 IN , c2 RING); 172.17.0.2 172.17.0.9 HTTP 1273 HEAD /warehouse/rmoff.db/foo HTTP/1.1 & F ter=%2 i m /warehouse/?list-type=2&del i T E T S T E T 172.17.0.2 172.17.0.9 HTTP 1380 G

@decodableco @rmoff / #current24 INSERT INTO INSERT INTO foo VALUES (42, ‘never gonna give you up’); 172.17.0.5 172.17.0.2 set_ugi flink,flink 172.17.0.2 172.17.0.5 set_ugi flink 172.17.0.5 172.17.0.2 get_table_req rmoff,foo,hive 172.17.0.2 172.17.0.5 get_table_req foo,rmoff,flink,c1,int,c2,string,s3a previous etadata_location,s3a: warehouse/rmoff.d current-schema,{“type”:”struct”,”schema-id”:0,”fie 172.17.0.5 172.17.0.9 HTTP 1001 HEAD /warehouse/rmoff.db/foo/metadata/00 / / /warehouse/rmoff.db/foo/metadata/000 / T E m _ 172.17.0.5 172.17.0.9 HTTP 1078 G

@decodableco @rmoff / #current24 INSERT INTO INSERT INTO foo VALUES (42, ‘never gonna give you up’); tted to the clust . . i . m i m [INFO] Sub tting SQL update statement to the cluster [INFO] SQL update statement has been successfully sub Job ID: cc43d32a6bb0e2faab5270e542c70499

@decodableco @rmoff / #current24 INSERT INTO INSERT INTO foo VALUES (42, ‘never gonna give you up’); Establish JobManager connection for job cc43d32a6bb0e2faab5270e542c70499 Offer reserved slots to the leader of job cc43d32a6bb0e2faab5270e542c704 Received task Source: Values[3] -> IcebergStreamWriter (1/1) 0 (0b643b78 Downloading cc43d32a6bb0e2faab5270e542c70499/p-c817b883da6db5a2bfd0e5b35 from jobmanager/172.17.0.3:6124 tter -> Sink: IcebergSink c_iceberg.rmoff
i m Received task IcebergFilesCom

@decodableco @rmoff / #current24 INSERT INTO INSERT INTO foo VALUES (42, ‘never gonna give you up’); 172.17.0.10 172.17.0.2 get_table_req rmoff,foo,hive 172.17.0.2 172.17.0.10 get_table_req foo,rmoff,flink,c1,int,c2,string,s3 previous etadata_location,s3a: warehouse/rmoff. current-schema,{“type”:”struct”,”schema-id”:0,”fi / / i m i w _ m _ m 172.17.0.10 172.17.0.2 alter_table th_environment_context @hive#rmoff, current-snapshot-summary,{“flink.operator-id”:”90 “flink. ax-com tted-checkpoint-id”:”922337203685 “added-files-size”:”764”,”changed-partition-count “total-records”:”3”,”total-files-size”:”2292”,”to

@decodableco @rmoff / #current24 INSERT INTO INSERT INTO foo VALUES (42, ‘never gonna give you up’); 172.17.0.10 172.17.0.9 HTTP 1089 G /warehouse/?list-type=2&del ter=% 172.17.0.10 172.17.0.9 HTTP 1004 PUT /warehouse/rmoff.db/foo/data/00000172.17.0.10 172.17.0.9 HTTP 6902 PUT /warehouse/rmoff.db/foo/metadata/ F i m i T E 172.17.0.10 172.17.0.9 HTTP 6914 PUT /warehouse/rmoff.db/foo/metadata/b2

@decodableco What SQL runs where? @rmoff / #current24

@decodableco @rmoff / #current24 In conclusion…

@decodableco @rmoff / #current24 Troubleshoot methodically

@decodableco Understand the architecture @rmoff / #current24

@decodableco Get your JARs right @rmoff / #current24

@decodableco @rmoff / #current24 Get your toolbox ready :)

@decodableco decodable.co/blog @rmoff / #current24

E
@decodableco @rmoff / #current24 OF @rmoff / 18 Sep 2024 / #current24

Robin Moffatt
@rmoff

1 / 118

Apache Flink is a powerful thing to work with but, my, it does test one’s patience sometimes ;-) Particularly if you’re new to using it, understanding how to troubleshoot problems that arise is an important survival skill to acquire. This talk will be a hands-on demonstration packed full of practical tips to solving some of the most common problems that can occur in Flink SQL. We’ll spend time looking at JAR files - what they are, how to find the one you need, and how to check you’ve put it in the right place. After that I’ll show you some of the really funky head-scratching problems that I’ve encountered, including debugging Iceberg, Flink, and Hive Metastore…on Docker containers. Along with all of this I’ll show you some of my favourite bash-based troubleshooting tools. You’ll leave this talk equipped with the knowledge of how to methodically troubleshooting Flink SQL problems, understanding of the primary moving parts of the stack—and some nice additions to your command-line toolkit.

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Robin's squirrels gen AI game is going strong. pic.twitter.com/BQG17OLGyg
— Gunnar Morling 🌍 (@gunnarmorling) September 18, 2024
He is presenting like a Java Engineer 😀 #current24 https://t.co/Zr8qAS0Xrs
— Talat UYARER (@talatuyarer) September 18, 2024
Up next at #Current24: the man, the myth, the legend, the one and only @rmoff, talking about the joys of JARs and Flink SQL troubleshooting. Fun fact: he's having his one year anniversary at @Decodableco this week, and we've halfway turned him into a Java dev proper already 🤓. pic.twitter.com/nkQ7MZYIgY
— Gunnar Morling 🌍 (@gunnarmorling) September 18, 2024

The Joy of JARs (and Other Flink SQL Troubleshooting Tales)

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