An error that I see coming up frequently in the Kafka Connect community (e.g. mailing list, Slack group, StackOverflow) is: JsonDeserializer with schemas.enable requires "schema" and "payload" fields and may not contain additional fields or No fields found using key and value schemas for table: foo-bar You can see an explanation, and solution, for the issue in my StackOverflow answer here: https://stackoverflow.com/a/45940013/350613 If you’re using schemas.enable in the Connector configuration, you must have schema and payload as the root-level elements of your JSON message ( Which is pretty much verbatim what the error says 😁), like this:

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Grafana API Reference Export all Grafana data sources to data_sources folder mkdir -p data_sources && curl -s "http://localhost:3000/api/datasources" -u admin:admin|jq -c -M '.[]'|split -l 1 - data_sources/ This exports each data source to a separate JSON file in the data_sources folder. Load data sources back in from folder This submits every file that exists in the data_sources folder to Grafana as a new data source definition. for i in data_sources/*; do \ curl -X "POST" "http://localhost:3000/api/datasources" \ -H "Content-Type: application/json" \ --user admin:admin \ --data-binary @$i done

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Usually connecting external disks in Linux is easy. Plug it in, run fdisk -l or lsblk | grep disk to identify the device ID, and then mount it. Unfortunately in this instance, plugging in my Seagate 2TB wasn’t so simple. The server is running Proxmox: # uname -a Linux proxmox01 4.4.6-1-pve #1 SMP Thu Apr 21 11:25:40 CEST 2016 x86_64 GNU/Linux No device showed up on lsblk or fdisk -l. In dmesg I saw:

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Kafka’s Connect API is a wondrous way of easily bringing data in and out of Apache Kafka without having to write a line of code. By choosing a Connector from the many available, it’s possible to set up and end-to-end data pipeline with just a few lines of configuration. You can configure this by hand, or you can use the Confluent Control Center, for both management and monitoring: BUT … there are times when not all goes well - perhaps your source has gone offline, or one of your targets has been misconfigured.

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A very silly PEBCAK problem this one, but Google hits weren’t so helpful so here goes. Running a console producer, specifying keys: kafka-console-producer \ --broker-list localhost:9092 \ --topic test_topic \ --property parse.key=true \ --property key.seperator=, Failed when I entered a key/value: 1,foo kafka.common.KafkaException: No key found on line 1: 1,foo at kafka.tools.ConsoleProducer$LineMessageReader.readMessage(ConsoleProducer.scala:314) at kafka.tools.ConsoleProducer$.main(ConsoleProducer.scala:55) at kafka.tools.ConsoleProducer.main(ConsoleProducer.scala) kafka.common.KafkaException: No key found on line … but I specified the key, didn’t I?

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How do you try and stay current on technical affairs, given only 24 hours in a day and a job to do as well? Here’s my take on it… One of the many things that has changed perceptibly since the beginning of this century when I started working in IT is the amount of information freely available, and being created all the time. Back then, printed books and manuals were still the primary source of definitive information about a piece of software.

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Mucking about with virtual disks, I wanted to install qemu on a AWS EC2 instance in order to use qemu-img. Not finding it in a yum repo, I built it from scratch: $ uname -a Linux ip-10-0-1-238 4.4.41-36.55.amzn1.x86_64 #1 SMP Wed Jan 18 01:03:26 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux Steps: sudo yum install -y ghc-glib-devel ghc-glib autoconf autogen intltool libtool wget http://download.qemu-project.org/qemu-2.8.0.tar.xz tar xvJf qemu-2.8.0.tar.xz cd qemu-2.8.0 ./configure make sudo make install I hit a few errors, recorded here for passing Googlers:

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So you’ve got a Linux VM that you want to access the contents of in EC2 - how do you do it? Let’s see how. First up, convert the VMDK to raw image file. If you’ve got a ova/ovf then just untar it first (tar -xvf my_vm.ova), from which you should get the VMDK. With that, convert it using qemu-img: $ time qemu-img convert -f vmdk -O raw SampleAppv607p-appliance-disk1.vmdk SampleAppv607p-appliance-disk1.raw real 16m36.

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Wireless Headset for VOIP With No 30-Minute Dalek Timebomb A lot of my work is done remotely, with colleagues and customers. Five years ago I bought a Microsoft LifeChat LX-3000 which plugged into the USB port on my Mac. It did the job kinda fine, with two gripes: it wasn’t wireless. I like to wander whilst I chat, and I didn’t like being tethered. But this in itself wasn’t a reason to ditch it After c.

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After 5 years at Rittman Mead, 126 blog posts, 16 conferences, four published OTN articles, an Oracle ACE award - not to mention, of course, a whole heap of interesting and challenging client work - I’ve decided that it’s time to do something different. Later this month I’ll be joining Confluent as a Partner Technology Evangelist, helping spread the good word of Apache Kafka and the Confluent platform. As always you can find me on Twitter @rmoff, for beer tweets, fried breakfast pics - and lots of Apache Kafka!

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I use BigDataLite for a lot of my sandboxing work. This is a OVA provided by Oracle which can be run on VirtualBox, VMWare, etc and has the Cloudera Hadoop platform (CDH) along with all of Oracle’s Big Data goodies including Big Data Discovery and Big Data Spatial and Graph (BDSG). Something that kept tripping me up during my work with BDSG was that HBase would become unavailable. Not being an HBase expert and simply using it as a data store for my property graph data, I wrote it off as mistakes on my part.

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Using the holt function in Timelion to do anomaly detection on Metricbeat data in Kibana: Expression: $thres=0.02, .es(index='metricbeat*',metric='max:system.cpu.user.pct').lines(1).if(eq, 0, null).holt(0.9, 0.1, 0.9, 0.5h).color(#eee).lines(10).label('Prediction'), .es(index='metricbeat*',metric='max:system.cpu.user.pct').color(#666).lines(1).label(Actual), .es(index='metricbeat*',metric='max:system.cpu.user.pct').lines(1).if(eq, 0, null).holt(0.9, 0.1, 0.9, 0.5h).subtract(.es(index='metricbeat*',metric='max:system.cpu.user.pct')).abs().if(lt, $thres, null, .es(index='metricbeat*',metric='max:system.cpu.user.pct')).points(10,3,0).color(#c66).label('Anomaly').title('max:system.cpu.user.pct / @rmoff') References: https://twitter.com/rashidkpc/status/762754396111327232 https://github.com/elastic/timelion/issues/87 https://github.com/elastic/timelion/blob/master/FUNCTIONS.md

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The world beyond batch: Streaming 101 The world beyond batch: Streaming 102 Data architectures for streaming applications SE-Radio Episode 272: Frances Perry on Apache Beam (img credit)

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By default, the kafka-avro-console-producer will assume that the schema registry is on port 8081, and happily connect to it. Unfortunately, this can lead to some weird errors if another process happens to be listening on port 8081 already! [oracle@bigdatalite tmp]$ kafka-avro-console-producer \ > --broker-list localhost:9092 --topic kudu_test \ > --property value.schema='{"type":"record","name":"myrecord","fields":[{"name":"id","type":"int"},{"name":"random_field", "type": "string"}]}' {"id": 999, "random_field": "foo"} org.apache.kafka.common.errors.SerializationException: Error registering Avro schema: {"type":"record","name":"myrecord","fields":[{"name":"id","type":"int"},{"name":"random_field","type":"string"}]} Caused by: io.confluent.kafka.schemaregistry.client.rest.exceptions.RestClientException: Unexpected character ('<' (code 60)): expected a valid value (number, String, array, object, 'true', 'false' or 'null') at [Source: sun.

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tl;dr Make sure that key.converter.schema.registry.url and value.converter.schema.registry.url are specified, and that there are no trailing whitespaces. I’ve been building on previous work I’ve done with Oracle GoldenGate and Kafka Connect, looking at how to have the change records from the Oracle database come through to Kafka in Avro format rather than the default JSON that the sample configuration gives. Simply changing the Kafka Connect OGG configuration file (confluent.properties) from value.converter=org.apache.kafka.connect.json.JsonConverter key.

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I hit this error running Kafka Connect HDFS connector from Confluent Platform v3.1.1 on BigDataLite 4.6: [oracle@bigdatalite ~]$ connect-standalone /etc/schema-registry/connect-avro-standalone.properties /etc/kafka-connect-hdfs/quickstart-hdfs.properties [...] Exception in thread "main" java.lang.IncompatibleClassChangeError: Implementing class at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:763) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) at java.net.URLClassLoader.access$100(URLClassLoader.java:73) at java.net.URLClassLoader$1.run(URLClassLoader.java:368) at java.net.URLClassLoader$1.run(URLClassLoader.java:362) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:361) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:763) The fix was to unset the CLASSPATH first: unset CLASSPATH

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Presented without comment, warranty, or context - other than these might help a wandering code hacker. When using SigV4, you must specify a ‘host’ parameter boto.s3.connection.HostRequiredError: BotoClientError: When using SigV4, you must specify a 'host' parameter. To fix, switch conn_s3 = boto.connect_s3() for conn_s3 = boto.connect_s3(host='s3.amazonaws.com') You can see a list of endpoints here. boto.exception.S3ResponseError: S3ResponseError: 400 Bad Request Make sure you’re specifying the correct hostname (see above) for the bucket’s region.

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Similar to the previous issue, the sample config in the docs causes another snafu: OGG-15051 Java or JNI exception: oracle.goldengate.util.GGException: Class not found: "kafkahandler". kafkahandler Class not found: "kafkahandler". kafkahandler This time it’s in the kafka.props file: gg.handler.kafkahandler.Type = kafka Should be gg.handler.kafkahandler.type = kafka No capital T in Type! (Image credit: https://unsplash.com/@vanschneider)

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In the documentation for the current release of Oracle GoldenGate for Big Data (12.2.0.1.1.011) there’s a helpful sample configuration, which isn’t so helpful … [...] gg.handler.kafkahandler.ProducerRecordClass = com.company.kafka.CustomProducerRecord [...] This value for gg.handler.kafkahandler.ProducerRecordClass will cause a failure when you start the replicat: [...] Class not found: "com.company.kafka.CustomProducerRecord" [...] If you comment this configuration item out, it’ll use the default (oracle.goldengate.handler.kafka.DefaultProducerRecord) and work swimingly! (Image credit: https://unsplash.com/@vanschneider)

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There are various reasons for this error, but the one I hit was that the table name is case sensitive, and returned from Oracle by the JDBC driver in uppercase. If you specify the tablename in your connecter config in lowercase, it won’t be matched, and this error is thrown. You can validate this by setting debug logging (edit etc/kafka/connect-log4j.properties to set log4j.rootLogger=DEBUG, stdout), and observe: (I’ve truncated some of the output for legibility)

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