REST Proxy Configuration Options

In addition to the settings specified here, the Confluent REST Proxy accepts the settings for the Java admin, consumer and producer. Use these to override the default settings of producers and consumers in the REST Proxy. Use the client. prefix to override the default settings of admins, consumers and producers in Confluent REST Proxy. If you want the configuration to apply only to admins, consumers or producers, then replace the prefix with admin., consumer. or producer., respectively. When configuration options are exposed in the Confluent REST Proxy API, priority is given to settings in the user request, then to overrides provided as configuration options, and finally falls back to the default values provided by the Java Kafka clients.

General

id

Unique ID for the Confluent REST Proxy server instance. This is used in generating unique IDs for consumers that do not specify their ID. The ID is empty by default, which makes a single server setup easier to get up and running, but is not safe for multi-server deployments where automatic consumer IDs are used.

  • Type: string
  • Default: “”
  • Importance: high
bootstrap.servers
A list of Kafka brokers to connect to. For example, PLAINTEXT://hostname:9092,SSL://hostname2:9092. This configuration is particularly important when Kafka security is enabled, because Kafka may expose multiple endpoints that will be stored as metadata, but REST Proxy may need to be configured with just one of those endpoints. The client will make use of all servers irrespective of which servers are specified here for bootstrapping—this list only impacts the initial hosts used to discover the full set of servers. Because these servers are used only for the initial connection to discover the full cluster membership (which may change dynamically), this list need not contain the full set of servers (you may want more than one, though, in case a server is down).
listeners

Comma-separated list of listeners that listen for API requests over either HTTP or HTTPS. If a listener uses HTTPS, the appropriate TLS configuration parameters need to be set as well.

  • Type: list
  • Default: http://0.0.0.0:8082
  • Importance: high
schema.registry.url

The base URL for Schema Registry that should be used by the serializer.

  • Type: string
  • Default: http://localhost:8081
  • Importance: high

Note

The configuration property auto.register.schemas is not supported for Kafka REST Proxy.

consumer.request.max.bytes

Maximum number of bytes in unencoded message keys and values returned by a single request. This can be used by administrators to limit the memory used by a single consumer and to control the memory usage required to decode responses on clients that cannot perform a streaming decode. Note that the actual payload will be larger due to overhead from base64 encoding the response data and from JSON encoding the entire response.

  • Type: long
  • Default: 67108864
  • Importance: medium
consumer.threads

The maximum number of threads to run consumer requests on. Note that this must be greater than the maximum number of consumers in a single consumer group. The sentinel value of -1 allows the number of threads to grow as needed to fulfill active consumer requests. Inactive threads will ultimately be stopped and cleaned up.

  • Type: int
  • Default: 50
  • Importance: medium
consumer.request.timeout.ms

The maximum total time to wait for messages for a request if the maximum number of messages has not yet been reached.

  • Type: int
  • Default: 1000
  • Importance: medium
host.name

The host name used to generate absolute URLs in responses. If empty, the default canonical hostname is used.

  • Type: string
  • Default: “”
  • Importance: medium
access.control.allow.methods

Set value to Jetty Access-Control-Allow-Origin header for specified methods.

  • Type: string
  • Default: “”
  • Importance: low
access.control.allow.origin

Set value for Jetty Access-Control-Allow-Origin header. You may use * for any origin, or you can specify multiple origins separated by commas.

  • Type: string
  • Default: “”
  • Importance: low
response.http.headers.config

Use to select which HTTP headers are returned in the HTTP response for Confluent Platform components. Specify multiple values in a comma-separated string using the format [action][header name]:[header value] where [action] is one of the following: set, add, setDate, or addDate. You must use quotation marks around the header value when the header value contains commas. For example:

response.http.headers.config="add Cache-Control: no-cache, no-store, must-revalidate", add X-XSS-Protection: 1; mode=block, add Strict-Transport-Security: max-age=31536000; includeSubDomains, add X-Content-Type-Options: nosniff
  • Type: string
  • Default: “”
  • Importance: low
reject.options.request

Boolean indicating whether or not to reject the OPTIONS method request to REST services. By default, sending a request with the OPTIONS method to all REST services from Confluent Platform REST Proxy, Confluent Control Center (Legacy) REST endpoint, and so on, returns the list of available methods on the specified endpoint. For example: curl -X OPTIONS http://localhost:8083. When reject.options.request is set to true, requests with -X OPTIONS are rejected and available methods are not returned. Setting reject.options.request to true protects API endpoints that are not specifically used by applications, which reduces the attack surface.

  • Type: boolean
  • Default: false
  • Importance: low
consumer.instance.timeout.ms

Amount of idle time before a consumer instance is automatically destroyed.

  • Type: int
  • Default: 300000
  • Importance: low
consumer.iterator.backoff.ms

Amount of time to backoff when an iterator runs out of data. If a consumer has a dedicated worker thread, this is effectively the maximum error value for the entire request timeout. It should be small enough to closely target the timeout, but large enough to avoid busy waiting.

  • Type: int
  • Default: 50
  • Importance: low
fetch.min.bytes

Minimum number of bytes in message keys and values returned by a single request before the timeout of consumer.request.timeout.ms passes. The special sentinel value of -1 disables this functionality.

  • Type: int
  • Default: -1
  • Importance: medium
consumer.iterator.timeout.ms

Timeout for blocking consumer iterator operations. This should be set to a small enough value that it is possible to effectively peek() on the iterator.

  • Type: int
  • Default: 1
  • Importance: low
debug

Boolean indicating whether extra debugging information is generated in some error response entities.

  • Type: boolean
  • Default: false
  • Importance: low
metric.reporters

A list of classes to use as metrics reporters. Implementing the MetricReporter interface allows plugging in classes that will be notified of new metric creation. The JmxReporter is always included to register JMX statistics.

  • Type: list
  • Default: []
  • Importance: low
metrics.jmx.prefix

Prefix to apply to metric names for the default JMX reporter.

  • Type: string
  • Default: kafka.rest
  • Importance: low
metrics.num.samples

The number of samples maintained to compute metrics.

  • Type: int
  • Default: 2
  • Importance: low
metrics.sample.window.ms

The metrics system maintains a configurable number of samples over a fixed window size. This configuration controls the size of the window. For example, you might maintain two samples each measured over a 30 second period. When a window expires, you erase and overwrite the oldest window.

  • Type: long
  • Default: 30000
  • Importance: low
port

DEPRECATED: port to listen on for new connections. Use listeners instead.

  • Type: int
  • Default: 8082
  • Importance: low
request.logger.name

Name of the SLF4J logger to write the NCSA Common Log Format request log.

  • Type: string
  • Default: io.confluent.rest-utils.request
  • Importance: low
response.mediatype.default

The default response media type that should be used if no specify types are requested in an Accept header.

  • Type: string
  • Default: application/json
  • Importance: low
response.mediatype.preferred

An ordered list of the server’s preferred media types used for responses, from most preferred to least.

  • Type: list
  • Default: [application/json, application/vnd.kafka.v2+json]
  • Importance: low
shutdown.graceful.ms

Amount of time to wait after a shutdown request for outstanding requests to complete.

  • Type: int
  • Default: 1000
  • Importance: low
kafka.rest.resource.extension.class

A list of classes to use as RestResourceExtension. Implementing the interface RestResourceExtension allows you to inject user defined resources like filters to REST Proxy. Typically used to add custom capabilities like logging, security, etc.

  • Type: list
  • Default: “”
  • Importance: low
advertised.listeners

List of advertised listeners. This configuration is used to generate absolute URLs in V3 responses. The HTTP and HTTPS protocols are supported. Each listener must include the protocol, hostname, and port. For example: http://myhost:8080 and https://0.0.0.0:8081.

  • Type: list
  • Default: “”
  • Importance: low
confluent.resource.name.authority

The authority where the governance of the name space is delegated to. This value is defined by the remainder of the CRN. This is used when generating Confluent resource names. Examples: confluent.cloud and mds-01.example.com.

  • Type: string
  • Default: “”
  • Importance: low

Configuration Options for HTTPS

ssl.keystore.location

Used for HTTPS. Location of the keystore file to use for TLS.

Important

Jetty requires that the key’s CN, stored in the keystore, must match the FQDN.

  • Type: string
  • Default: “”
  • Importance: high
ssl.keystore.password

Used for HTTPS. The store password for the keystore file.

  • Type: password
  • Default: “”
  • Importance: high
ssl.key.password

Used for HTTPS. The password of the private key in the keystore file.

  • Type: password
  • Default: “”
  • Importance: high
ssl.keystore.type

Used for HTTPS. The type of keystore file.

  • Type: string
  • Default: JKS
  • Importance: medium
ssl.protocol

Used for HTTPS. The TLS protocol used to generate the SSLContext. The default is TLSv1.3 when running with Java 11 or newer, TLSv1.2 otherwise. This value should be fine for most use cases. Allowed values in recent JVMs are TLSv1.2 and TLSv1.3. TLS, TLSv1.1, SSL, SSLv2 and SSLv3 might be supported in older JVMs, but their usage is discouraged due to known security vulnerabilities. With the default value for this configuration and ssl.enabled.protocols, clients downgrade to TLSv1.2 if the server does not support TLSv1.3. If this configuration is set to TLSv1.2, clients do not use TLSv1.3, even if it is one of the values in ssl.enabled.protocols and the server only supports TLSv1.3.

  • Type: string
  • Default: TLSv1.3
  • Importance: medium
ssl.provider

Used for HTTPS. The TLS security provider name. Leave blank to use Jetty’s default.

  • Type: string
  • Default: “” (Jetty’s default)
  • Importance: medium
ssl.enabled.protocols

Used for HTTPS. A comma-separated list of protocols enabled for TLS connections. Leave blank to use Jetty’s defaults.

  • Type: list
  • Default: “” (Jetty’s default)
  • Importance: medium
ssl.keymanager.algorithm

Used for HTTPS. The algorithm used by the key manager factory for TLS connections. Leave blank to use Jetty’s default.

  • Type: string
  • Default: “” (Jetty’s default)
  • Importance: low
ssl.trustmanager.algorithm

Used for HTTPS. The algorithm used by the trust manager factory for TLS connections. Leave blank to use Jetty’s default.

  • Type: string
  • Default: “” (Jetty’s default)
  • Importance: low
ssl.cipher.suites

Used for HTTPS. A comma-separated list of TLS cipher suites. Leave blank to use Jetty’s defaults.

  • Type: list
  • Default: “” (Jetty’s default)
  • Importance: low
ssl.endpoint.identification.algorithm

Used for HTTPS. The endpoint identification algorithm to validate the server hostname using the server certificate. Leave blank to use Jetty’s default.

  • Type: string
  • Default: https
  • Importance: low

Configuration Options for TLS Encryption between REST Proxy and Apache Kafka Brokers

Note that all the TLS configurations (for REST Proxy to Broker communication) are prefixed with client.. If you want the configuration to apply just to admins, consumers or producers, you can replace the prefix with admin., consumer. or producer. respectively.

In addition to these configurations, make sure bootstrap.servers configuration is set with SSL://host:port end-points, or you’ll accidentally open a TLS connection to a non-TLS port.

Keep in mind that authenticated and encrypted connection to Kafka Brokers will only work when Kafka is running with appropriate security configuration. For details, see Kafka Security.

client.security.protocol

Protocol used to communicate with brokers. Valid values are: PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL.

  • Type: string
  • Default: PLAINTEXT
  • Importance: high
client.ssl.key.password

The password of the private key in the key store file. This is optional for client.

  • Type: password
  • Default: null
  • Importance: high
client.ssl.keystore.location

The location of the key store file. This is optional for client and can be used for two-way client authentication.

  • Type: string
  • Default: null
  • Importance: high
client.ssl.keystore.password

The store password for the key store file. This is optional for client and only needed if ssl.keystore.location is configured.

  • Type: password
  • Default: null
  • Importance: high
client.ssl.truststore.location

The location of the trust store file.

  • Type: string
  • Default: null
  • Importance: high
client.ssl.truststore.password

The password for the trust store file.

  • Type: string
  • Default: null
  • Importance: high
client.ssl.enabled.protocols

The comma-separated list of protocols enabled for TLS connections. The default value is TLSv1.2,TLSv1.3 when running with Java 11 or later, TLSv1.2 otherwise. With the default value for Java 11 (TLSv1.2,TLSv1.3), Kafka clients and brokers prefer TLSv1.3 if both support it, and falls back to TLSv1.2 otherwise (assuming both support at least TLSv1.2).

  • Type: list
  • Default: TLSv1.2,TLSv1.3
  • Importance: medium
client.ssl.keystore.type

The file format of the key store file. This is optional for client.

  • Type: string
  • Default: JKS
  • Importance: medium
client.ssl.protocol

The TLS protocol used to generate the SSLContext. The default is TLSv1.3 when running with Java 11 or newer, TLSv1.2 otherwise. This value should be fine for most use cases. Allowed values in recent JVMs are TLSv1.2 and TLSv1.3. TLS, TLSv1.1, SSL, SSLv2 and SSLv3 might be supported in older JVMs, but their usage is discouraged due to known security vulnerabilities. With the default value for this configuration and ssl.enabled.protocols, clients downgrade to TLSv1.2 if the server does not support TLSv1.3. If this configuration is set to TLSv1.2, clients do not use TLSv1.3, even if it is one of the values in ssl.enabled.protocols and the server only supports TLSv1.3.

  • Type: string
  • Default: TLSv1.3
  • Importance: medium
client.ssl.provider

The name of the security provider used for TLS connections. Default value is the default security provider of the JVM.

  • Type: string
  • Default: null
  • Importance: medium
client.ssl.truststore.type

The file format of the trust store file.

  • Type: string
  • Default: JKS
  • Importance: medium
client.ssl.cipher.suites

A list of cipher suites. This is a named combination of authentication, encryption, MAC, and key exchange algorithms used to negotiate the security settings for a network connection using the TLS network protocol. By default, all the available cipher suites are supported.

  • Type: list
  • Default: null
  • Importance: low
client.ssl.endpoint.identification.algorithm

The endpoint identification algorithm to validate server hostname using server certificate.

  • Type: string
  • Default: null
  • Importance: low
client.ssl.keymanager.algorithm

The algorithm used by key manager factory for TLS connections. Default value is the key manager factory algorithm configured for the Java Virtual Machine.

  • Type: string
  • Default: SunX509
  • Importance: low
client.ssl.secure.random.implementation

The SecureRandom PRNG implementation to use for TLS cryptography operations.

  • Type: string
  • Default: null
  • Importance: low
client.ssl.trustmanager.algorithm

The algorithm used by trust manager factory for TLS connections. Default value is the trust manager factory algorithm configured for the Java Virtual Machine.

  • Type: string
  • Default: PKIX
  • Importance: low

Configuration Options for TLS Encryption between REST Proxy and Schema Registry

Keep in mind that authenticated and encrypted connection to Schema Registry will only work when Schema Registry is running with appropriate security configuration. For details, see Schema Registry.

schema.registry.ssl.key.password

The password of the private key in the key store file. This is optional.

  • Type: password
  • Default: null
  • Importance: high
schema.registry.ssl.keystore.location

The location of the key store file. This is optional and can be used for mutual TLS authentication.

  • Type: string
  • Default: null
  • Importance: high
schema.registry.ssl.keystore.password

The store password for the key store file. This is optional and only needed if ssl.keystore.location is configured.

  • Type: password
  • Default: null
  • Importance: high
schema.registry.ssl.truststore.location

The location of the trust store file.

  • Type: string
  • Default: null
  • Importance: high
schema.registry.ssl.truststore.password

The password for the trust store file.

  • Type: string
  • Default: null
  • Importance: high

Interceptor configuration options

REST Proxy supports interceptor configurations as part of Java new producer and consumer settings.

producer.interceptor.classes

Producer interceptor classes.

  • Type: string
  • Default: “”
  • Importance: low
consumer.interceptor.classes

Consumer interceptor classes.

  • Type: string
  • Default: “”
  • Importance: low

For example, to enable Confluent Control Center (Legacy) monitoring interceptors:

consumer.interceptor.classes=io.confluent.monitoring.clients.interceptor.MonitoringConsumerInterceptor producer.interceptor.classes=io.confluent.monitoring.clients.interceptor.MonitoringProducerInterceptor

For more details about monitoring interceptors, see Monitor Production and Consumption in Control Center (Legacy).

License configuration options

Important

License configurations are only required if you are using principal propagation. For more information, see REST Proxy Authentication.

confluent.license

Confluent will issue a license key to each subscriber. The license key will be a short snippet of text that you can copy and paste. Without the license key, you can use Confluent security plugins for a 30-day trial period. If you are a subscriber and don’t have a license key, contact Confluent Support at support@confluent.io.

  • Type: string
  • Default: “”
  • Importance: high