.. _topicschema: Manage Schemas for Topics ========================= Use the |sr| feature in |c3-short| to manage |cp| topic schemas. .. include:: ../../includes/topics-schemas/schemas-intro.rst The |sr| feature in |c3-short| is :ref:`enabled` by default. Disabling the feature disables both viewing and editing of schemas. .. note:: As of |cp| version 5.2, schemas can be created and edited. Versions prior to 5.2 only have view access to schema information in |c3-short|, including comparing version history and downloading schemas. .. _c3_schema_create: Creating a topic schema in |c3-short| ------------------------------------- .. include:: ../../includes/topics-schemas/create-schema-intro.rst **To create a topic value schema:** #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. .. figure:: ../../images/c3-schemas-topics-list.png :width: 600px :alt: Topics list The topic overview page appears. .. figure:: ../../images/c3-schemas-topic-overview.png :width: 600px :alt: Topics list #. Click the **Schema** tab. You are prompted to set a message value schema. .. figure:: ../../images/c3-set-msg-value-schema.png :width: 600px #. Click **Set a schema**. The Schema editor appears pre-populated with the basic structure of an `Avro schema `__ to use as a starting point, if desired. .. figure:: ../../images/c3-schema-value-editor.png :width: 600px #. Select a schema format type: - Avro - JSON - Protobuf .. figure:: ../../images/c3-schema-select-format.png :width: 600px Choose **Avro** if you want to try out the code examples provided in the next steps. .. tip:: To learn more about each of the schema types, see :ref:`sr-serializer`. #. Enter the schema in the editor: .. include:: ../../includes/topics-schemas/schema-basic-structure.rst Copy and paste the following example schema. .. code-block:: JSON { "type": "record", "namespace": "my.examples", "name": "Payment", "fields": [ { "name": "id", "type": "string" }, { "name": "amount", "type": "double" } ] } .. figure:: ../../images/c3-entered-schema.png :width: 600px :alt: Schema for a topic entered into Control Center editor #. Click **Save**. - If the entered schema is valid, the **Schema updated** message is briefly displayed in the banner area. - If the entered schema is not valid, an **Input schema is an invalid Avro schema** error is displayed in the banner area. If applicable, repeat the procedure as appropriate for the topic key schema. **To create a topic key schema:** #. Click the **Key** option. You are prompted to set a message key schema. .. figure:: ../../images/c3-set-msg-key-schema.png :width: 600px #. Click **Set a schema**. #. Enter the schema into the editor and click **Save**. Copy and paste the following example schema, and save it. .. code-block:: JSON { "namespace": "io.confluent.examples.clients.basicavro", "name": "key_my_transactions", "type": "string" } .. figure:: ../../images/c3-key-schema.png :width: 600px .. include:: ../../includes/topics-schemas/message-keys-tip.rst .. _c3_schema_view: Viewing a schema in |c3-short| ------------------------------ .. include:: ../../includes/topics-schemas/view-schema.rst #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. .. figure:: ../../images/c3-schemas-topics-list.png :width: 600px :alt: Topics list The topic overview page appears. #. Click the **Schema** tab. The Value schema is displayed by default. .. figure:: ../../images/c3-view-value-schema.png :width: 600px .. tip:: The |c3-short| schema display may re-order the placement of meta information about the schema. Comparing this view with the example provided in the previous section, note that schema name, namespace, and record type are shown below the field definitions. This is an artifact of the display in |c3-short|; the schema definition is the same. #. Click the **Key** tab to view the key schema if present. .. _c3_schema_edit: Editing a schema in |c3-short| ------------------------------ .. include:: ../../includes/topics-schemas/edit-schema.rst #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. #. Click the **Schema** tab. #. Select the **Value** or **Key** tab for the schema. #. Click **Edit schema** and make the changes in the schema editor. For example, if you are following along with the example: - Select the topic ``my-transactions``, click **Schema**, and select the **Value** tab. - Edit the schema by copy-pasting the following definition for a new ``region`` field, after the ``id`` and ``amount`` fields. Precede your new definition with a comma, per the syntax. .. code-block:: JSON { "name": "region", "type": "string", "default": "" } Note that the new ``region`` field includes a default value, which makes it backward compatible. By plugging in the default value, consumers can use the new schema to read data submitted by producers that use the older schema (without the ``region`` field). #. Click **Save**. - If the schema update is valid and compatible with its prior versions (assuming a backward-compatible mode), the schema is updated and the version count is incremented. You can :ref:`compare the different versions ` of a schema. .. figure:: ../../images/c3-schema-version-updated.png :width: 600px - If the schema update is invalid or incompatible with an earlier schema version, an error is displayed. The example below shows the addition of another new field, ``country``, with no default provided for backward compatibility. .. figure:: ../../images/c3-schema-incompatible.png :width: 600px .. _c3_schema_compare_versions: Comparing schema versions in |c3-short| --------------------------------------- .. include:: ../../includes/topics-schemas/compare-versions.rst #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. #. Click the **Schema** tab. #. Select the **Key** or **Value** tab for the schema. #. Click **Version history**. .. figure:: ../../images/c3-schema-version-history-01.png :width: 600px The current version number of the schema is indicated on the version menu. .. figure:: ../../images/c3-schema-version-history-02.png :width: 600px #. Select the **Turn on version diff** check box. #. Select the versions to compare from each version menu. The differences are highlighted for comparison. .. figure:: ../../images/c3-schema-compare.png :width: 600px .. _c3_schema_compat_mode: Changing the compatibility mode of a schema in |c3-short| --------------------------------------------------------- .. include:: ../../includes/topics-schemas/compat-mode.rst :start-after: compat-intro-start :end-before: compat-intro-end #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. #. Click the **Schema** tab. #. Select the **Key** or **Value** tab for the schema. #. Click **Edit Schema** -> **Compatibility Mode** tab. .. figure:: ../../images/c3-schema-compat-mode.png :width: 600px #. Select a mode option: .. include:: ../../includes/topics-schemas/compat-mode.rst :start-after: mode-details-start :end-before: mode-details-end #. Click **Save**. .. _c3_schema_download: Downloading a schema from |c3-short| ------------------------------------ #. Select a cluster from the navigation bar. #. Click the **Topics** menu. The :ref:`c3_all_topics` appears. #. Select a topic. #. Click the **Schema** tab. #. Select the **Key** or **Value** tab for the schema. #. Click **Download**. A schema JSON file for the topic is downloaded into your Downloads directory. .. include:: ../../includes/topics-schemas/download-schema-example.rst .. _c3_sr_troubleshoot: Troubleshoot error "|sr| is not set up" ---------------------------------------- If you get an error message on |c3-short| when you try to access a topic schema ("|sr| is not set up"), first make sure that |sr| is running. Then verify that the |sr| ``listeners`` configuration matches the |c3-short| ``confluent.controlcenter.schema.registry.url`` configuration. Also check the HTTPS configuration parameters. .. figure:: ../../images/c3-SR-not-set-up.png :width: 600px For more information, see :ref:`c3_schema_registry_not_set_up`, and start-up procedures for :ref:`cos-quickstart`, :ref:`cos-docker-quickstart`, or :ref:`installation`, depending on which one of these you are using to run |cp|. .. _ff_c3_edit_schema: Enabling and disabling |sr| in |c3-short| ----------------------------------------- The feature that allows working with schemas in |c3-short| is enabled by default. The feature can be disabled if an organization does not want any users to access the feature. After disabling the feature, the Topics Schema menu and the Schema tab are no longer visible in the |c3-short| UI. The ability to view and edit schemas is disabled. To disable the edit schema feature in |c3-short|: #. Set the ``confluent.controlcenter.schema.registry.enable`` option in your ``control-center.properties`` file to ``false``. .. sourcecode:: bash confluent.controlcenter.schema.registry.enable=false .. note:: Make the change in the appropriate |c3-short| properties file or files configured for your environments, including ``control-center-dev.properties`` or ``control-center-production.properties``. The properties files are located in ``/path-to-confluent/etc/confluent-control-center/``. #. Restart |c3-short| and pass in the properties file for the configuration to take effect: .. sourcecode:: bash ./bin/control-center-stop ./bin/control-center-start ../etc/confluent-control-center/control-center.properties .. tip:: If you are using a |cp| development environment with a :ref:`confluent_local`, stop and start as follows: .. sourcecode:: bash ./confluent local stop control-center ./confluent local start control-center ../etc/confluent-control-center/control-center-dev.properties To enable the feature again, set the option back to ``true`` and restart |c3-short| with the updated properties file. .. _multi-cluster-sr: Enabling Multi-Cluster |sr| --------------------------- Starting with version 5.4.1, |cp| supports the ability to run multiple schema registries and associate a unique |sr| to each |ak| cluster in multi- cluster environments. The ability to scale up schema registries in conjunction with |ak| clusters is useful for evolving businesses; and particularly supports data governance, organization, and management across departments in large enterprises. When multi-cluster |sr| is configured and running, you can create and manage schemas per topics in |c3-short| as usual. ---------------------------------- Configuration Properties and Files ---------------------------------- Multiple |sr| clusters may be specified with ``confluent.controlcenter.schema.registry.{name}.url`` in the appropriate |c3-short| properties file. To use a |sr| cluster identified in this way, add or verify the following broker and |c3-short| configurations. A new endpoint ``/v1/metadata/schemaRegistryUrls`` has been exposed by |ak| to return the ``confluent.schema.registry.url`` field from the |ak| broker configurations. |c3-short| uses this field to look up the registries from |ak| broker configurations. To use this, you must configure unique listener endpoints for each cluster: - In the broker ``server.properties`` files (unique for each |ak| cluster), specify the REST endpoint with the ``confluent.http.server.listeners`` field, which defaults to ``http://0.0.0.0:8090``. - In the appropriate |c3-short| properties file, use ``confluent.controlcenter.streams.cprest.url`` to define the REST endpoint for ``controlcenter.cluster``. - For additional clusters, define REST endpoints using ``confluent.controlcenter.kafka.{name}.cprest.url``. This should be consistent with the |ak| cluster name used for other |ak| |c3-short| configurations; for example, ``confluent.controlcenter.kafka.{name}.bootstrap.servers``. A minimal viable configuration touches the following files, and includes settings for these properties (example names and ports are given): |c3-short| properties file ^^^^^^^^^^^^^^^^^^^^^^^^^^ The :ref:`c3_properties_files` file includes: - ``confluent.controlcenter.schema.registry.url=http://localhost:8081`` - ``confluent.controlcenter.schema.registry.sr-1.url=http://localhost:8082`` - ``confluent.controlcenter.streams.cprest.url=http://localhost:8090`` - ``confluent.controlcenter.kafka.AK1.cprest.url=http://localhost:8091`` See :ref:`Control Center configuration reference` for a full description of ``confluent.controlcenter.schema.registry.url``. Broker configuration file for the |c3-short| cluster ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The |ak| broker configuration file for ``controlcenter.cluster``, such as ``server0.properties``, includes: - ``confluent.http.server.listeners=http://localhost:8090`` - ``confluent.schema.registry.url=http://localhost:8081`` Broker configuration file for the |ak| cluster ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The |ak| broker configuration file for ``AK1``, ``server1.properties``) includes: - ``confluent.http.server.listeners=http://localhost:8091`` - ``confluent.schema.registry.url=http://localhost:8082`` With these configurations, editing the schema through the |c3-short| UI will connect to ``http://localhost:8081`` for ``controlcenter.cluster`` and ``http://localhost:8082`` for ``AK1``. Defaults and Fallback ^^^^^^^^^^^^^^^^^^^^^ If ``confluent.schema.registry.url`` fields are not specified for any brokers, the ``confluent.controlcenter.schema.registry.url`` |sr| URL is applied. For example, if the |sr| URL was not provided for ``AK1``, ``AK1``'s associated |sr| cluster would also be specified at ``http://localhost:8081``. If ``confluent.controlcenter.schema.registry.url`` is not explicitly specified in the |c3-short| properties file, it defaults to ``http://localhost:8081``. ------- Example ------- Following is a detailed example of a functional multi-cluster |sr| setup with two |ak| clusters connected to |c3-short|, one the ``controlcenter.cluster``, and the other named ``AK1``, each with one broker. The table below shows files and configurations in each for the two cluster example. These are not complete properties files, but rather excerpts from each file that define multi-cluster |sr| specifics, port numbers, and configurations that are important to the example setup or generally not found in default properties files. To run the example, copy default |zk-full|, |ak| (``server.properties``), |sr|, and |c3-short| properties files to new files per the example filenames below, add/modify properties as shown, and run the components as described in :ref:`run-example-multi-cluster-sr`. Key Configurations ^^^^^^^^^^^^^^^^^^ .. raw:: html
File Properties
zookeeper0.properties
  • dataDir=/tmp/zookeeper/zk-0 (fresh logging directory)
  • clientPort=2181 (same as zookeeper.properties)
zookeeper1.properties
  • dataDir=/tmp/zookeeper/zk-1(fresh logging directory)
  • clientPort=2182 (since zookeeper0 is already using 2181)
server0.properties
  • broker.id=0
  • listeners=PLAINTEXT://:9092
  • log.dirs=/tmp/kafka-logs-bk-0 (fresh logging directory)
  • zookeeper.connect=localhost:2181
  • confluent.metrics.reporter.bootstrap.servers=localhost:9092
The following configurations are specific to multi-cluster |sr| setup for this broker:
  • confluent.http.server.listeners=http://0.0.0.0:8090
  • confluent.schema.registry.url=http://localhost:8081
server1.properties
  • broker.id=1
  • listeners=PLAINTEXT://:9093
  • log.dirs=/tmp/kafka-logs-bk-1(fresh logging directory)
  • zookeeper.connect=localhost:2182
  • confluent.metrics.reporter.bootstrap.servers=localhost:9093
The following configurations are specific to multi-cluster Schema Registry setup for this broker:
  • confluent.http.server.listeners=http://0.0.0.0:8091
  • confluent.schema.registry.url=http://localhost:8082
schema-registry0.properties
  • listeners=http://0.0.0.0:8081
  • kafkastore.connection.url=localhost:2181
schema-registry1.properties
  • listeners=http://0.0.0.0:8082
  • kafkastore.connection.url=localhost:2182
control-center-multi-sr.properties
  • bootstrap.servers=localhost:9092
  • zookeeper.connect=localhost:2181
  • confluent.controlcenter.kafka.AK1.bootstrap.servers=localhost:9093
  • confluent.controlcenter.kafka.AK1.zookeeper.connect=localhost:2182
  • confluent.controlcenter.streams.cprest.url=http://0.0.0.0:8090
  • confluent.controlcenter.schema.registry.url=http://localhost:8081
  • confluent.controlcenter.kafka.AK1.cprest.url=http://0.0.0.0:8091
  • confluent.controlcenter.schema.registry.SR-AK1.url=http://localhost:8082
The configurations for cpcrest.url, confluent.controlcenter.kafka.AK1.cprest.url, and confluent.controlcenter.schema.registry.SR-AK1.url are new properties, specific to multi-cluster Schema Registry.
.. _run-example-multi-cluster-sr: Run the Example ^^^^^^^^^^^^^^^ To run the example: #. Start the ZooKeepers. #. Start the |ak| brokers #. Start the |sr| clusters. #. Start |c3|. The following example start commands assume the properties files are in the ``/etc/`` directories shown below, and that you are running the commands from ````. **Start ZooKeepers** :: ./bin/zookeeper-server-start etc/kafka/zookeeper0.properties :: ./bin/zookeeper-server-start etc/kafka/zookeeper1.properties **Start the Kafka brokers** :: ./bin/kafka-server-start etc/kafka/server0.properties :: ./bin/kafka-server-start etc/kafka/server1.properties **Start Schema Registry clusters** :: ./bin/schema-registry-start etc/schema-registry/schema-registry0.properties :: ./bin/schema-registry-start etc/schema-registry/schema-registry1.properties **Start Control Center** :: ./bin/control-center-start etc/confluent-control-center/control-center-multi-sr.properties Manage Schemas for Both Clusters on |c3-short| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ #. When the example clusters are running and |c3-short| finishes initialization, open |c3-short| in your web browser. (|c3-short| runs at ``http://localhost:9021/`` by default, as described in :ref:`controlcenter_userguide`.) #. Select a cluster from the navigation bar, click the **Topics** menu, and explore the schema management options for one or both clusters, starting with :ref:`c3_schema_create`. -------- Security -------- Any other configurations used to set up a |sr| client with |c3-short| can be configured for an additional |sr| cluster by simply appending the |sr| cluster's name to the ``confluent.controlcenter.schema.registry`` prefix. For example, for basic authentication with multi-cluster |sr|, specify the following in the |c3| configuration file: - Use ``confluent.controlcenter.schema.registry.basic.auth.credentials.source`` and ``confluent.controlcenter.schema.registry.basic.auth.user.info`` to define authentication for the ``confluent.controlcenter.schema.registry.url`` cluster. - Use ``confluent.controlcenter.schema.registry.{name}.basic.auth.credentials.source`` and ``confluent.controlcenter.schema.registry.{name}.basic.auth.user.info`` for additional |sr| clusters (associated with the URL fields by ``{name}``). Some |sr| client configurations also include a ``schema.registry`` prefix. For SSL security settings, specify the following in the |c3| configuration file: - Use ``confluent.controlcenter.schema.registry.schema.registry.ssl.truststore.location`` and ``confluent.controlcenter.schema.registry.schema.registry.ssl.truststore.password`` for the ``confluent.controlcenter.schema.registry.url`` cluster. - Use ``confluent.controlcenter.schema.registry.{name}.schema.registry.ssl.truststore.location`` and ``confluent.controlcenter.schema.registry.{name}.schema.registry.ssl.truststore.password`` for additional |sr| clusters (associated with the URL fields by ``{name}``). To learn more, see |sr| authentication properties in the |c3-short| Configuration Reference under :ref:`controlcenter_configuration_encryption` and the section on :ref:`basic-auth-sr` in HTTP Basic Auth. See also, :ref:`How to configure clients to Schema Registry ` in the |sr| Security Overview. -------------------------- Errors and Troubleshooting -------------------------- If the brokers for the cluster have matching |sr| URLs, but these URLs were not defined in the |c3-short| properties file, an error message is displayed on the cluster overview page. .. figure:: ../../images/c3-schema-multi-sr-error.png :align: center :alt: Multi-cluster schema registry error message on Control Center --------------------- Version Compatibility --------------------- The ``confluent.controlcenter.schema.registry.url`` configuration in the |c3-short| properties file acts as a default if a cluster's broker configurations do not contain ``confluent.schema.registry.url fields``. Multiple |sr| clusters may be specified with ``confluent.controlcenter.schema.registry.{name}.url`` fields. Multi-cluster |sr| cannot be used with |ak| versions prior to |ak| 2.4.x, the version current with |cp| 5.4.0. However, using a single cluster |sr| setup will work with earlier |ak| versions. To learn more, see :ref:`cp-ak-compatibility`. ----------------- Suggested Reading ----------------- - See :ref:`schema_registry_tutorial` for hands-on examples of developing schemas, mapping to topics, and sending messages. - See :ref:`schemaregistry_intro` for an overview of |sr| and schema management. - :ref:`controlcenter_configuration` - :ref:`c3_properties_files` - :ref:`c3_schema_registry_not_set_up` in :ref:`controlcenter_troubleshooting` - :ref:`schema_validation` - :ref:`sr-per-topic-subject-name-strategy`