Krati

Since Camel 2.9

This component allows the use krati datastores and datasets inside Camel. Krati is a simple persistent data store with very low latency and high throughput. It is designed for easy integration with read-write-intensive applications with little effort in tuning configuration, performance and JVM garbage collection.

Camel provides a producer and consumer for krati datastore_(key/value engine)_. It also provides an idempotent repository for filtering out duplicate messages.

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

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

URI format

krati:[the path of the datastore][?options]

The path of the datastore is the relative path of the folder that krati will use for its datastore.

You can append query options to the URI in the following format, ?option=value&option=value&…​

Krati Options

The Krati component has no options.

The Krati endpoint is configured using URI syntax:

krati:path

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

path

Required Path of the datastore is the relative path of the folder that krati will use for its datastore.

String

Query Parameters (29 parameters):

Name Description Default Type

hashFunction (common)

The hash function to use.

HashFunction

initialCapacity (common)

The inital capcity of the store.

100

int

keySerializer (common)

The serializer that will be used to serialize the key.

Serializer

segmentFactory (common)

Sets the segment factory of the target store.

SegmentFactory

segmentFileSize (common)

Data store segments size in MB.

64

int

valueSerializer (common)

The serializer that will be used to serialize the value.

Serializer

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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

maxMessagesPerPoll (consumer)

The maximum number of messages which can be received in one poll. This can be used to avoid reading in too much data and taking up too much memory.

int

sendEmptyMessageWhenIdle (consumer)

If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead.

false

boolean

exceptionHandler (consumer)

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)

Sets the exchange pattern when the consumer creates an exchange.

ExchangePattern

pollStrategy (consumer)

A pluggable org.apache.camel.PollingConsumerPollingStrategy allowing you to provide your custom implementation to control error handling usually occurred during the poll operation before an Exchange have been created and being routed in Camel.

PollingConsumerPoll Strategy

key (producer)

The key.

String

operation (producer)

Specifies the type of operation that will be performed to the datastore.

String

value (producer)

The Value.

String

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

backoffErrorThreshold (scheduler)

The number of subsequent error polls (failed due some error) that should happen before the backoffMultipler should kick-in.

int

backoffIdleThreshold (scheduler)

The number of subsequent idle polls that should happen before the backoffMultipler should kick-in.

int

backoffMultiplier (scheduler)

To let the scheduled polling consumer backoff if there has been a number of subsequent idles/errors in a row. The multiplier is then the number of polls that will be skipped before the next actual attempt is happening again. When this option is in use then backoffIdleThreshold and/or backoffErrorThreshold must also be configured.

int

delay (scheduler)

Milliseconds before the next poll. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour).

500

long

greedy (scheduler)

If greedy is enabled, then the ScheduledPollConsumer will run immediately again, if the previous run polled 1 or more messages.

false

boolean

initialDelay (scheduler)

Milliseconds before the first poll starts. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour).

1000

long

runLoggingLevel (scheduler)

The consumer logs a start/complete log line when it polls. This option allows you to configure the logging level for that.

TRACE

LoggingLevel

scheduledExecutorService (scheduler)

Allows for configuring a custom/shared thread pool to use for the consumer. By default each consumer has its own single threaded thread pool.

ScheduledExecutor Service

scheduler (scheduler)

To use a cron scheduler from either camel-spring or camel-quartz2 component

none

ScheduledPollConsumer Scheduler

schedulerProperties (scheduler)

To configure additional properties when using a custom scheduler or any of the Quartz2, Spring based scheduler.

Map

startScheduler (scheduler)

Whether the scheduler should be auto started.

true

boolean

timeUnit (scheduler)

Time unit for initialDelay and delay options.

MILLISECONDS

TimeUnit

useFixedDelay (scheduler)

Controls if fixed delay or fixed rate is used. See ScheduledExecutorService in JDK for details.

true

boolean

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

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

The component supports 2 options, which are listed below.

Name Description Default Type

camel.component.krati.enabled

Enable krati component

true

Boolean

camel.component.krati.resolve-property-placeholders

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

Boolean

 
krati:/tmp/krati?operation=CamelKratiGet&initialCapacity=10000&keySerializer=#myCustomSerializer

For producer endpoint you can override all of the above URI options by passing the appropriate headers to the message.

Message Headers for datastore

Header Description

CamelKratiOperation

The operation to be performed on the datastore. The valid options are CamelKratiAdd, CamelKratiGet, CamelKratiDelete, CamelKratiDeleteAll

CamelKratiKey

The key.

CamelKratiValue

The value.

Usage Samples

Example 1: Putting to the datastore.

This example will show you how you can store any message inside a datastore.

from("direct:put").to("krati:target/test/producertest");

In the above example you can override any of the URI parameters with headers on the message.

 Here is how the above example would look like using xml to define our
route.
        <route>
            <from uri="direct:put"/>
            <to uri="krati:target/test/producerspringtest"/>
        </route>

Example 2: Getting/Reading from a datastore

This example will show you how you can read the contnet of a datastore.

from("direct:get")
    .setHeader(KratiConstants.KRATI_OPERATION, constant(KratiConstants.KRATI_OPERATION_GET))
    .to("krati:target/test/producertest");

In the above example you can override any of the URI parameters with headers on the message.

 Here is how the above example would look like using xml to define our
route.
<route>
     <from uri="direct:get"/>
     <to uri="krati:target/test/producerspringtest?operation=CamelKratiGet"/>
</route>

Example 3: Consuming from a datastore

This example will consume all items that are under the specified datastore.

    from("krati:target/test/consumertest")
        .to("direct:next");

You can achieve the same goal by using xml, as you can see below.

<route>
    <from uri="krati:target/test/consumerspringtest"/>
    <to uri="mock:results"/>
</route>

Idempotent Repository

As already mentioned this component also offers and idemptonet repository which can be used for filtering out duplicate messages.

from("direct://in").idempotentConsumer(header("messageId"), new KratiIdempotentRepositroy("/tmp/idempotent").to("log://out");
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