CouchDB

Since Camel 2.11

Both producer and consumer are supported

The couchdb: component allows you to treat CouchDB instances as a producer or consumer of messages. Using the lightweight LightCouch API, this camel component has the following features:

  • As a consumer, monitors couch changesets for inserts, updates and deletes and publishes these as messages into camel routes.

  • As a producer, can save, update, delete (by using CouchDbMethod with DELETE value) documents and get documents by id (by using CouchDbMethod with GET value) into couch.

  • Can support as many endpoints as required, eg for multiple databases across multiple instances.

  • Ability to have events trigger for only deletes, only inserts/updates or all (default).

  • Headers set for sequenceId, document revision, document id, and HTTP method type.

CouchDB 3.x is not supported.

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

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-couchdb</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

couchdb:http://hostname[:port]/database?[options]

Where hostname is the hostname of the running couchdb instance. Port is optional and if not specified then defaults to 5984.

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 CouchDB component supports 3 options, which are listed below.

Name Description Default Type

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

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

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

Endpoint Options

The CouchDB endpoint is configured using URI syntax:

couchdb:protocol:hostname:port/database

with the following path and query parameters:

Path Parameters (4 parameters)

Name Description Default Type

protocol (common)

Required The protocol to use for communicating with the database.

Enum values:

  • http

  • https

String

hostname (common)

Required Hostname of the running couchdb instance.

String

port (common)

Port number for the running couchdb instance.

5984

int

database (common)

Required Name of the database to use.

String

Query Parameters (11 parameters)

Name Description Default Type

createDatabase (common)

Creates the database if it does not already exist.

false

boolean

deletes (consumer)

Document deletes are published as events.

true

boolean

heartbeat (consumer)

How often to send an empty message to keep socket alive in millis.

30000

long

style (consumer)

Specifies how many revisions are returned in the changes array. The default, main_only, will only return the current winning revision; all_docs will return all leaf revisions (including conflicts and deleted former conflicts.).

Enum values:

  • all_docs

  • main_only

main_only

String

updates (consumer)

Document inserts/updates are published as events.

true

boolean

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

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

password (security)

Password for authenticated databases.

String

username (security)

Username in case of authenticated databases.

String

Message Headers

The CouchDB component supports 6 message header(s), which is/are listed below:

Name Description Default Type

CouchDbDatabase (consumer)

Constant: HEADER_DATABASE

The database the message came from.

String

CouchDbSeq (consumer)

Constant: HEADER_SEQ

The couchdb changeset sequence number of the update / delete message.

String

CouchDbId (common)

Constant: HEADER_DOC_ID

The couchdb document id.

String

CouchDbRev (common)

Constant: HEADER_DOC_REV

The couchdb document revision.

String

CouchDbMethod (common)

Constant: HEADER_METHOD

The method (delete / update).

String

CamelCouchDbResumeAction (consumer)

Constant: COUCHDB_RESUME_ACTION

The resume action to execute when resuming.

String

Headers are set by the consumer once the message is received. The producer will also set the headers for downstream processors once the insert/update has taken place. Any headers set prior to the producer are ignored. That means for example, if you set CouchDbId as a header, it will not be used as the id for insertion, the id of the document will still be used.

Message Body

The component will use the message body as the document to be inserted. If the body is an instance of String, then it will be marshalled into a GSON object before insert. This means that the string must be valid JSON or the insert / update will fail. If the body is an instance of a com.google.gson.JsonElement then it will be inserted as is. Otherwise the producer will throw an exception of unsupported body type.

To update a CouchDB document, it’s _id and _rev field must be part of the json payload routed to CouchDB by Camel.

Samples

For example if you wish to consume all inserts, updates and deletes from a CouchDB instance running locally, on port 9999 then you could use the following:

from("couchdb:http://localhost:9999").process(someProcessor);

If you were only interested in deletes, then you could use the following

from("couchdb:http://localhost:9999?updates=false").process(someProcessor);

If you wanted to insert a message as a document, then the body of the exchange is used

from("someProducingEndpoint").process(someProcessor).to("couchdb:http://localhost:9999")

To start tracking the changes immediately after an update sequence, implement a custom resume strategy. To do so, it is necessary to implement a CouchDbResumeStrategy and use the resumable to set the last (update) offset to start tracking the changes:

public class CustomSequenceResumeStrategy implements CouchDbResumeStrategy {
    @Override
    public void resume(CouchDbResumable resumable) {
        resumable.setLastOffset("custom-last-update");
    }
}