Consul

Since Camel 2.18

Both producer and consumer are supported

The Consul component is a component for integrating your application with Hashicorp Consul.

Maven users will need to add the following dependency to their pom.xml for this component:

    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-consul</artifactId>
        <version>${camel-version}</version>
    </dependency>

URI format

consul://domain?[options]

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The Consul component supports 26 options, which are listed below.

Name Description Default Type

connectTimeout (common)

Connect timeout for OkHttpClient.

Duration

consulClient (common)

Reference to a org.kiwiproject.consul.Consul in the registry.

Consul

key (common)

The default key. Can be overridden by CamelConsulKey.

String

pingInstance (common)

Configure if the AgentClient should attempt a ping before returning the Consul instance.

true

boolean

readTimeout (common)

Read timeout for OkHttpClient.

Duration

tags (common)

Set tags. You can separate multiple tags by comma.

String

url (common)

The Consul agent URL.

String

writeTimeout (common)

Write timeout for OkHttpClient.

Duration

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

action (producer)

The default action. Can be overridden by CamelConsulAction.

String

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

valueAsString (producer)

Default to transform values retrieved from Consul i.e. on KV endpoint to string.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

configuration (advanced)

Consul configuration.

ConsulConfiguration

consistencyMode (advanced)

The consistencyMode used for queries, default ConsistencyMode.DEFAULT.

Enum values:

  • DEFAULT

  • STALE

  • CONSISTENT

DEFAULT

ConsistencyMode

datacenter (advanced)

The data center.

String

nearNode (advanced)

The near node to use for queries.

String

nodeMeta (advanced)

The note meta-data to use for queries.

List

aclToken (security)

Sets the ACL token to be used with Consul.

String

password (security)

Sets the password to be used for basic authentication.

String

sslContextParameters (security)

SSL configuration using an org.apache.camel.support.jsse.SSLContextParameters instance.

SSLContextParameters

useGlobalSslContextParameters (security)

Enable usage of global SSL context parameters.

false

boolean

userName (security)

Sets the username to be used for basic authentication.

String

blockSeconds (watch)

The second to wait for a watch event, default 10 seconds.

10

Integer

firstIndex (watch)

The first index for watch for, default 0.

0

BigInteger

recursive (watch)

Recursively watch, default false.

false

boolean

Endpoint Options

The Consul endpoint is configured using URI syntax:

consul:apiEndpoint

with the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

apiEndpoint (common)

Required The API endpoint.

String

Query Parameters (25 parameters)

Name Description Default Type

connectTimeout (common)

Connect timeout for OkHttpClient.

Duration

consulClient (common)

Reference to a org.kiwiproject.consul.Consul in the registry.

Consul

key (common)

The default key. Can be overridden by CamelConsulKey.

String

pingInstance (common)

Configure if the AgentClient should attempt a ping before returning the Consul instance.

true

boolean

readTimeout (common)

Read timeout for OkHttpClient.

Duration

tags (common)

Set tags. You can separate multiple tags by comma.

String

url (common)

The Consul agent URL.

String

writeTimeout (common)

Write timeout for OkHttpClient.

Duration

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

action (producer)

The default action. Can be overridden by CamelConsulAction.

String

valueAsString (producer)

Default to transform values retrieved from Consul i.e. on KV endpoint to string.

false

boolean

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

consistencyMode (advanced)

The consistencyMode used for queries, default ConsistencyMode.DEFAULT.

Enum values:

  • DEFAULT

  • STALE

  • CONSISTENT

DEFAULT

ConsistencyMode

datacenter (advanced)

The data center.

String

nearNode (advanced)

The near node to use for queries.

String

nodeMeta (advanced)

The note meta-data to use for queries.

List

aclToken (security)

Sets the ACL token to be used with Consul.

String

password (security)

Sets the password to be used for basic authentication.

String

sslContextParameters (security)

SSL configuration using an org.apache.camel.support.jsse.SSLContextParameters instance.

SSLContextParameters

userName (security)

Sets the username to be used for basic authentication.

String

blockSeconds (watch)

The second to wait for a watch event, default 10 seconds.

10

Integer

firstIndex (watch)

The first index for watch for, default 0.

0

BigInteger

recursive (watch)

Recursively watch, default false.

false

boolean

Message Headers

The Consul component supports 31 message header(s), which is/are listed below:

Name Description Default Type

CamelConsulAction (producer)

Constant: CONSUL_ACTION

The Producer action.

String

CamelConsulKey (common)

Constant: CONSUL_KEY

The Key on which the action should applied.

String

CamelConsulEventId (consumer)

Constant: CONSUL_EVENT_ID

The event id.

String

CamelConsulEventName (consumer)

Constant: CONSUL_EVENT_NAME

The event name.

String

CamelConsulEventLTime (consumer)

Constant: CONSUL_EVENT_LTIME

The event LTime.

Long

CamelConsulNodeFilter (consumer)

Constant: CONSUL_NODE_FILTER

The Node filter.

String

CamelConsulTagFilter (consumer)

Constant: CONSUL_TAG_FILTER

The tag filter.

String

CamelConsulSessionFilter (consumer)

Constant: CONSUL_SERVICE_FILTER

The session filter.

String

CamelConsulVersion (consumer)

Constant: CONSUL_VERSION

The data version.

Integer

CamelConsulFlags (common)

Constant: CONSUL_FLAGS

Flags associated with a value.

Long

CamelConsulIndex (producer)

Constant: CONSUL_INDEX

The optional value index.

BigInteger

CamelConsulWait (producer)

Constant: CONSUL_WAIT

The optional value wait.

String

CamelConsulCreateIndex (consumer)

Constant: CONSUL_CREATE_INDEX

The internal index value that represents when the entry was created.

Long

CamelConsulLockIndex (consumer)

Constant: CONSUL_LOCK_INDEX

The number of times this key has successfully been acquired in a lock.

Long

CamelConsulModifyIndex (consumer)

Constant: CONSUL_MODIFY_INDEX

The last index that modified this key.

Long

CamelConsulOptions (common)

Constant: CONSUL_OPTIONS

Options associated to the request.

CamelConsulResult (common)

Constant: CONSUL_RESULT

true if the response has a result.

Boolean

CamelConsulSession (common)

Constant: CONSUL_SESSION

The session id.

String

CamelConsulValueAsString (producer)

Constant: CONSUL_VALUE_AS_STRING

To transform values retrieved from Consul i.e. on KV endpoint to string.

Boolean

CamelConsulNode (producer)

Constant: CONSUL_NODE

The node.

String

CamelConsulService (producer)

Constant: CONSUL_SERVICE

The service.

String

CamelConsulDatacenter (producer)

Constant: CONSUL_DATACENTER

The data center.

String

CamelConsulNearNode (producer)

Constant: CONSUL_NEAR_NODE

The near node to use for queries.

String

CamelConsulNodeMeta (producer)

Constant: CONSUL_NODE_META

The note meta-data to use for queries.

List

CamelConsulLastContact (producer)

Constant: CONSUL_LAST_CONTACT

The last contact.

Long

CamelConsulKnownLeader (producer)

Constant: CONSUL_KNOWN_LEADER

Indicates whether it is the known leader.

Boolean

CamelConsulConsistencyMode (producer)

Constant: CONSUL_CONSISTENCY_MODE

The consistencyMode used for queries.

DEFAULT

ConsistencyMode

CamelConsulHealthyOnly (producer)

Constant: CONSUL_HEALTHY_ONLY

Only on healthy services.

false

Boolean

CamelConsulHealthyState (producer)

Constant: CONSUL_HEALTHY_STATE

The state to query.

Enum values:

  • PASS

  • WARN

  • FAIL

  • ANY

  • UNKNOWN

State

CamelConsulPreparedQueryID (producer)

Constant: CONSUL_PREPARED_QUERY_ID

The id of the prepared query.

String

CamelConsulServiceId (producer)

Constant: CONSUL_SERVICE_ID

The service id for agent deregistration.

String

Api Endpoint

The apiEndpoint denotes the type of consul api which should be addressed.

Domain Producer Consumer

kv

ConsulKeyValueProducer

ConsulKeyValueConsumer

event

ConsulEventProducer

ConsulEventConsumer

agent

ConsulAgentProducer

-

coordinates

ConsulCoordinatesProducer

-

health

ConsulHealthProducer

-

status

ConsulStatusProducer

-

preparedQuery

ConsulPreparedQueryProducer

-

catalog

ConsulCatalogProducer

-

session

ConsulSessionProducer

-

Producer Examples

As an example, we will show how to use the ConsulAgentProducer to register a service by means of the Consul agent api.

Registering and deregistering are examples for possible actions against the Consul agent api.

The desired action can be defined by setting the header ConsulConstants.CONSUL_ACTION to a value from the ConsulXXXActions interface of the respective Consul api. E.g. ConsulAgentActions contains the actions for the agent api.

If you set CONSUL_ACTION to ConsulAgentActions.REGISTER, the agent action REGISTER will be executed.

Which producer action invokes which consul api is defined by the respective producer. E.g. the ConsulAgentProducer maps ConsulAgentActions.REGISTER to an invocation of AgentClient.register. 
from("direct:registerFooService")
    .setBody().constant(ImmutableRegistration.builder()
        .id("foo-1")
        .name("foo")
        .address("localhost")
        .port(80)
        .build())
    .setHeader(ConsulConstants.CONSUL_ACTION, constant(ConsulAgentActions.REGISTER))
    .to("consul:agent");

It is also possible to set a default action on the consul endpoint and do without the header:

consul:agent?action=REGISTER

Registering Camel Routes with Consul

You can employ a ServiceRegistrationRoutePolicy to register Camel routes as services with Consul automatically.

from("jetty:http://0.0.0.0:8080/service/endpoint").routeId("foo-1")
    .routeProperty(ServiceDefinition.SERVICE_META_ID, "foo-1")
    .routeProperty(ServiceDefinition.SERVICE_META_NAME, "foo")
    .routePolicy(new ServiceRegistrationRoutePolicy())
...