4.1

Plugins

Lenses is extendable, and the following implementations can be specified:

  1. Serializers/Deserializers Plug you own serializer and deserializer to enable observability over any data format (i.e. protobuf / thrift)

  2. Custom authentication Authenticate users on your own proxy and inject permissions HTTP headers. See Authentication

  3. LDAP lookup Use multiple LDAP servers, or your own group mapping logic. See LDAP

  4. SQL UDFs User Defined Functions (UDF) that extend SQL and streaming SQL capabilities. See UDF

Once built, the jar files and any dependencies of the plugin should be added to Lenses and, in the case of Serializers and UDFs, to the SQL Processors if required.

Adding plugins 

Lenses 

On startup, Lenses loads plugins from the $LENSES_HOME/plugins/ directory and any location set in the environment variable LENSES_PLUGINS_CLASSPATH_OPTS. These locations are watched, and dropping a new plugin will hot-reload it. For the Lenses docker (and Helm chart) you may also use /data/plugins which is defined as a volume.

Any first level directories under the aforementioned paths which are detected on startup will also be monitored for new files. During startup the list of monitored locations will be shown in the logs to help confirm the setup.

...
Initializing (pre-run) Lenses
Installation directory autodetected: /opt/lenses
Current directory: /data
Logback configuration file autodetected: logback.xml
These directories will be monitored for new jar files:
 - /opt/lenses/plugins
 - /data/plugins
 - /opt/lenses/serde
Starting application
...

Whilst all jar files may be added to the same directory (e.g /data/plugins), it is suggested to use a directory hierarchy to make management and maintenance easier.

An example hierarchy for set of plugins:

├── security
│   └── sso_header_decoder.jar
├── serde
│   ├── protobuf_actions.jar
│   └── protobuf_clients.jar
└── udf
    ├── eu_vat.jar
    ├── reverse_geocode.jar
    └── summer_sale_discount.jar

SQL Processors in Kubernetes 

There are two ways to add custom plugins (UDFs and Serializers) to the SQL Processors; (1) via making available a tar.gz archive at an http(s) address, or (2) via creating a custom docker image.

Archive served via HTTP 

With this method, a tar archive, compressed with gzip, can be created that contains all plugin jars and their dependencies. Then this archive should be uploaded to a web server that the SQL Processors containers are able to access, and its address set with the option lenses.kubernetes.processor.extra.jars.url.

Step by step:

  1. Create a tar.gz file that includes all required jars at its root:
    tar -czf [FILENAME.tar.gz] -C /path/to/jars/ *
    
  2. Upload to a web server, ie. https://example.net/myfiles/FILENAME.tar.gz
  3. Set
    lenses.kubernetes.processor.extra.jars.url=https://example.net/myfiles/FILENAME.tar.gz
    

    For the docker image set the corresponding environment variable

    LENSES_KUBERNETES_PROCESSOR_EXTRA_JARS_URL=https://example.net/myfiles/FILENAME.tar.gz`
    

Custom Docker image 

The SQL Processors that run inside Kubernetes use the docker image lensesio-extra/sql-processor. It is possible to build a custom image and add all the required jar files under the /plugins directory, then set lenses.kubernetes.processor.image.name and lenses.kubernetes.processor.image.tag options to point to the custom image.

Step by step:

  1. Create a Docker image using lensesio-extra/sql-processor:VERSION as base and add all required jar files under /plugins:
    FROM lensesio-extra/sql-processor:4.1
    ADD jars/* /plugins
    
    docker build -t example/sql-processor:4.1 .
    
  2. Upload the docker image to a registry:
    docker push example/sql-processor:4.1
    
  3. Set
    lenses.kubernetes.processor.image.name=example/sql-processor
    lenses.kubernetes.processor.image.tag=4.1
    

    For the docker image set the corresponding environment variables

    LENSES_KUBERNETES_PROCESSOR_IMAGE_NAME=example/sql-processor
    LENSES_KUBERNETES_PROCESSOR_IMAGE_TAG=4.1
    

SQL Processors in Kafka Connect 

To add custom plugins (UDFs and Serializers) to the SQL Processor for Kafka Connect (connector), all the required jars should be added together with the connector jars.

Step by step

  1. Extract the SQL Processor connector under the plugin.path of Kafka Connect to all Connect worker nodes. E.g for plugin.path=/usr/share/java/kafka/plugins/:
    mkdir -p /usr/share/java/kafka/plugins/sql-processor
    tar -xzf lenses-sql-connect.tar.gz \
        -C /usr/share/java/kafka/plugins/sql-processor \
        --wildcards */connector/* --strip-components=2
    
  2. Copy the custom plugins and rest of required jars to all Connect worker nodes:
    cp /path/to/plugins/jars/* /usr/share/java/kafka/plugins/sql-processor