Magnolia 5.4 reached end of life on November 15, 2018. This branch is no longer supported, see End-of-life policy.
The RabbitMQ modules have been moved to the Services incubator.
Refer to RMQ Publication in the incubator documentation for up-to-date information. This page is no longer maintained.
The RabbitMQ module bundle provides an alternative way of publishing content and synchronizing instances in Magnolia.
RabbitMQ is open source message broker software (a.k.a message-oriented middleware) that implements the Advanced Message Queuing Protocol (AMQP).
The Magnolia RabbitMQ modules are suitable for:
The RabbitMQ alternative:
This document guides you through the process of setting up RabbitMQ in your environment and installing and configuring the modules.
The RabbitMQ modules were built for Magnolia 5.5+. Working modules can be made available on request to
Magnolia 5.4+ users, and 5.3+ users.
The RabbitMQ bundle contains three modules:
The modules are interdependent. Please install all three modules.
Maven is the easiest way to install the modules. Add the following dependencies to your bundle:
Follow the instructions at RabbitMQ to download and install the service. Instructions and packages are provided for all operating systems.
Note:
RabbitMQ exchanges and consumers are configured in the connector module. The exchange is configured on the author or producing instance and the consumer on the public or receiving instance.
The module ships with an example client configuration in /modules/rabbitmq-connector/rabbitmq-client/sampleClient
.
Node name | Value |
---|---|
rabbitmq-connector | |
rabbitmq-client | |
sampleClient | |
exchangeConfig | |
consumerDefinitions | |
clientName | sample-client |
enabled | false |
hostName | localhost |
password | guest |
portNumber | 5672 |
userName | guest |
virtualHost | / |
Properties:
rabbitmq-client | required RabbitMQ client folder. |
| required Client configuration node. One for each client. |
| required |
| required |
| required Name of the client. Note, the clientName can be different from the <client name> node name. Important: the clientName specified here must match the clientName property in the activate and deactivate commands for Rabbit MQ, e.g. /modules/activation/commands/withContentSyncingVersioned/activate/rabbitmq-activate@clientName If you change the client name in one, be sure to change it in the other. |
| required Enables and disables the client. Toggling this property restarts the client. |
| required Address of the broker. |
| required Password of the user account to connect with. |
| required Port number to connect the AMQP service. |
| required Username of the user account to connect with. |
| required Virtualhost to connect to. |
The exchange configuration is configured on the author or producing instance.
The exchange is the kind of router that the queues connect to. The producer instance pushes messages to the exchange and the exchange then decides what to do with them.
The example exchange configuration is in /modules/rabbitmq-connector/rabbitmq-client/sampleClient/exchangeConfig
.
Node name | Value |
---|---|
sampleClient | |
exchangeConfig | |
queueConfigList | |
queue | |
autodelete | false |
exclusive | false |
name | fan1 |
routingKey | - |
name | testfanoutAck |
type | fanout |
Properties:
exchangeConfig | required Exchange configuration node. See RabbitMQExchangeConfig . |
| required List of queue definitions to bind with the exchange. |
| required Queue node. See AMQP 0-9-1 Model Explained for more. |
| optional Automatically deletes queue when last consumer unsubscribes. |
| optional, default is Used for only one connection. Queue is deleted when that connection closes. |
| required Name of the queue. |
| optional Key used to route messages. Queue binds to the exchange with the routing key. Applicable when direct mode is enabled in the exchange. See Configuring monitoring. |
| required Name of the exchange. Important: the name specified here must match the exchangeName property in the activate and deactivate commands for Rabbit MQ, e.g. /modules/activation/commands/withContentSyncingVersioned/activate/rabbitmq-activate@exchangeName If you change the exchange name in one, be sure to change it in the other. |
| required Exchange type. Options: |
You can test the connection in the RabbitMQ console.
When the client is enabled, the exchanges and queues should be visible in the RabbitMQ console. You can test this at http://localhost:5672
, for example. Make sure the consumer is disabled on the author instance or it will re-consume what it had just tried to publish.
You should be able to see the queue in Queues.
You should be able to see the exchange in Exchanges.
The RabbitMQ Activation module bootstraps preconfigured activation commands in the standard Activation module.
You can select commands/catalogs to match your purpose for using RabbitMQ and use them in your apps. You can also customize them to suit your needs.
The commands are configured in /modules/rabbitmq-activation(activation)/commands/<catalog name>
.
Node name |
---|
rabbitmq-activation/activation |
commands |
default |
versioned |
withContentSyncing |
withContentSyncingVersioned |
rbmqVersioned |
Catalogs:
withContentSyncing | Allows you to hook into transmission over RabbitMQ once you have done a standard activation. |
withContentSyncingVersioned | Adds versioning to withContentSyncing . |
rbmqVersioned | Replaces standard activation with RabbitMQ versioned activation. |
The activate and deactivate commands defined in the above catalogs depend on your client configuration and exchange configuration. The activate and deactivate commands each contain a sub-command that contain the client name and and exchange name as properties.
For example:
Node name | Value |
---|---|
rabbitmq-activation/activation | |
commands | |
default | |
versioned | |
withContentSyncing | |
withContentSyncingVersioned | |
rbmqVersioned | |
activate | |
version | |
activate | |
rabbitmq-activate | |
clientName | <configured client name> |
exchangeName | <configured exchange name> |
The clientName property must be the name of a configured Rabbit MQ client (for example: /modules/rabbitmq-connector/rabbitmq-client/<configured client>@name).
The exchangeName property must be the exchange name of a configured Rabbit MQ client (for example: /modules/rabbitmq-connector/rabbitmq-client/<configured client>/exchangeConfig@name).
You can use the RabbitMQ commands in your apps, for example, to sync your content with another environment after an activation.
Example: Content syncing in the Pages app in /modules/pages/commands/website
.
Node name | Value |
---|---|
pages | |
commands | |
website | |
activate | |
class | info.magnolia.commands.delegateCommand |
commandName | withContentSyncingVersioned-activate |
activateDeletion | |
class | info.magnolia.commands.delegateCommand |
commandName | withContentSyncingVersioned-activateDeletion |
deactivate | |
class | info.magnolia.commands.delegateCommand |
commandName | withContentSyncingVersioned-deactivate |
To test the new commands activate content and then open the RabbitMQ console. You should see messages in the queue (fan1
) .
Consuming messages on a public instance is called activation or publication. On other instances, for example another author instance in a staging environment, it is called syncing.
When the messages have successfully reached the queue:
queueName
property). Make sure the
sampleClient
configuration is enabled on both instances.
The example consumer definition is in /modules/rabbitmq-connector/rabbitmq-client/sampleClient/consumerDefinitions
.
Node name | Value |
---|---|
sampleClient | |
consumerDefinitions | |
activationConsumer | |
ackExchangeName | - |
clientName | sample-client |
consumerClass | info.magnolia.rabbitmq.activation.jobs.ActivationConsumerJob |
enabled | false |
name | activationConsumer |
queueName | fan1 |
Properties:
consumerDefinitions | required Consumer definitions node. See ConsumerDefinition . |
| required Activation consumer node. |
| optional The name of the ACT exchange to use. An ACT exchange is a queue on which activation confirmation messages are sent. It is used for monitoring. Leave empty if you do not need this. |
| required Name of the client to use. |
| required Consumer class to use. ActivationConsumerJob : Activation consumer job. Custom classes must implement AbstractMQConsumerJob . |
| optional Enables and disables the consumer. Toggling this property shuts down and restarts the consumer. |
| required Name of the consumer. |
| required Name of the queue to consume on. |
| optional, default is When set to
|
When the activation consumer is configured, the receiving instance should start consuming messages.
Open the RabbitMQ console to verify that the specific queue (fan1
) is being emptied and that the nodes appear on the receiving instance.
While transactions are possible with RabbitMQ, they are complicated and slow down publishing. The ultimate would be to have the same activation message received by all instances at the same time, but this is technically very difficult to achieve and does not add much advantage in any event.
What is important however is that a Magnolia instance knows when a node is out of sync with another node, and that the load balancer knows which node is late. This is achieved by recording the time stamp and latest message state.
Whenever a message has been consumed and the content activated on the instance, the instance stores the message id (which is a long
that is incremented) and the date the message was activated.
Example:
Instance | Message Id | Timestamp |
Pubic 1 | 4 | 1441631639 |
Public 2 | 4 | 1441631640 |
Public 3 | 3 | 1441631600 |
This information is either sent to the load balancer or made available over a servlet. The goal is that the load balancer knows which instance is behind and by how much. In the example above the load balancer controlling tool knows that Public 1 and Public 2 are synced. It can decide to wait for Public 3 to sync, and if this does not happen, to alert the systems administrator or trigger the creation of a new instance.
The Magnolia RabbitMQ implementation introduces the concepts of SyncState and SyncStore to achieve content synchronicity between public instances.
The mechanism is basically a counter that is incremented when each activation message is sent. The counter is sent in the message header. When the receiving instance gets the message, the instance increments its own activation counter. This means that two public instances which have different SyncStates are out of sync until the counters once again have the same number.
The load balancer calls the REST service of the public nodes and in this way knows which public node is most up to date and which one is out of sync.
Examples:
State | Reason | Action |
REST service is not responding. | Public node down. | Remove from the pool. |
Rest service's sync state is 0. | Public Node is up but completely out of sync. | |
| Public node is working but under heavy load. | Remove public node temporarily from the pool until <x . |
The loadbalancer also knows when the public instances are getting activated. SyncStates are persisted to the JCR.
The Dynamically Weighted Least Connections Algorithm on your load balancer guarantees synchronicity and ensures that public instances do not get too far out of sync. See Least-Connection Algorithm based on variable weight for multimedia transmission for more.
The load balancer plays a big role in this. During a very big and long activation process, the load balancer can decide to redirect the traffic to the instances which have the highest and most equal ids. This increases traffic on these instances, which in turn slows down the activation process. Instances with initial low and unequal ids now have a higher chance of reaching the same state as the instances under load.
The algorithm creates a kind of "auto-damping" system that slows down instances by giving them more traffic, while speeding up the activation process on the others . Having the load balancer actively take the activation mechanism into consideration stabilizes the whole public node group.
The RabbitMQ Monitoring module includes the Public Monitoring app and the Public monitoring REST service
In the Public Monitoring app can can follow the state of any instance that is consuming on a queue. The app will return information messages containing the status of activations, provided the ACK exchange is configured correctly,
If an activation fails, the message is put back into the queue and an exception is pushed into the ackQueue
. The consumer is then stopped allowing you to fix the problem and to remove the faulty instance from the load balancer. There are techniques to fix the problem which are discussed in ACK queue blocked by unacked node
For monitoring to function correctly the ACK client needs to be configured and enabled and the monitoring module installed.
Monitoring is configured on the instance responsible for monitoring, typically the author or producing instance.
Configuration involves three steps:
The ACK client is configured in the connector module.
The example ACK client configuration is in /modules/rabbitmq-connector/rabbitmq-client/ackClient/consumerDefinitions/ackConsumer
.
Node name | Value |
---|---|
rabbitmq-connector | |
rabbitmq-client | |
ackClient | |
exchangeConfig | |
queueConfigList | |
name | actExchange |
type | direct |
consumerDefinitions | |
ackConsumer | |
ackExchangeName | - |
clientName | ack-client |
consumerClass | info.magnolia.rabbitmq.consumers.ConfirmationConsumerJob |
enabled | false |
name | confirmConsumer |
queueName | ackQueue |
clientName | ack-client |
enabled | false |
hostName | localhost |
password | guest |
portNumber | 5672 |
userName | guest |
virtualHost | / |
Properties:
rabbitmq-client | required RabbitMQ client folder. |
| optional ACK client node. |
| required Exchange configuration node. |
| required Queue configuration list node. |
| required Name of the ACT exchange. |
| required Exchange type. See AMQP 0-9-1 Model Explained for more. |
| required Consumer definitions node. |
| required ACK consumer node. |
| optional The name of the ACK exchange to use. |
| required Name of the client to use. |
| required Consumer class to use. ConfirmationConsumerJob : Confirmation consumer job. |
| optional Enables and disables the ACK consumer. Toggling this property shuts down and restarts the consumer. |
| required Name of the consumer. |
| required Name of the queue to monitor. |
| required/optional See Configuring the RabbitMQ connector for details. |
The next step to configuring monitoring is to link the ACT client in the the activation consumer definition .
To do this add the actExchangeName
to the activation consumer definition in /modules/rabbitmq-connector/rabbitmq-client/sampleClient/consumerDefinitions/activationConsumer/ackExchangeName
, for example.
Node name | Value |
---|---|
sampleClient | |
consumerDefinitions | |
activationConsumer | |
ackExchangeName | ackExchange |
clientName | sample-client |
consumerClass | info.magnolia.rabbitmq.activation.jobs.ActivationConsumerJob |
enabled | true |
name | activationConsumer |
queueName | fan1 |
verifyAuthorSignature | false |
The final step to configuring monitoring is to configure REST endpoints and add the access rights to them. Permissions to issue REST requests are controlled by Magnolia's standard role-based security mechanism.
REST endpoints are used for getting information from, monitoring and controlling the activation status
The SyncState REST service allows you to get the current state of activation immediately (without checking the ACK return queue).
The service is configured in the activation module in /modules/rabbitmq-activation/rest-endpoints/syncstate
.
Node name | Value |
---|---|
rabbitmq-activation | |
syncNode | |
seq_nbr | 2,012 |
stamp | 1,467,280,192,928 |
topo_tag | - |
rest-endpoints | |
syncstate | |
class | info.magnolia.rest.service.command.definition.ConfiguredCommandEndpointDefinition |
implementationClass | info.magnolia.rabbitmq.activation.rest.SyncStateRestService |
Properties:
syncNode | required Sync node node. |
| required Sequence number. |
| required Time stamp. |
| required Topo tag. |
rest-endpoints | optional REST endpoints folder. |
| optional SyncState node. |
| required REST endpoint class. ConfiguredCommandEndpointDefinition : Command endpoint definition that adds a white-list for enabled commands. |
| required REST endpoint implementation class. SyncStateRestService : Provides sync status of activation by REST. |
To enable the service:
rest
role: Access control lists:
Workspace | Permission | Scope | Path |
Config | Read only | Selected and sub nodes | /rabbitmq-activation |
Web access:
Permission | Path |
Get & Post | .rest/syncstate/state
|
rest
role to a user or to anonymous
if you need access without credentials. You can use the REST endpoint as follows:
curl http://publicaddress:publicport/.rest/syncstate/state
You should get the following (example):
{"seqNbr":2011,"stamp":1467280192928,"topoTag":""}
The Public monitoring REST service allows you to get the results of all consuming instances returning messages on the ACK queue. This service is used by the Public Monitoring app.
The service is configured in the monitoring module in /modules/magnolia-rabbitmq-monitoring/rest-endpoints/pubstate
.
Node name | Value |
---|---|
magnolia-rabbitmq-monitoring | |
rest-endpoints | |
pubstate | |
class | info.magnolia.rest.service.command.definition.ConfiguredCommandEndpointDefinition |
implementationClass | info.magnolia.rabbitmq.rest.PublicMonitoringService |
Properties:
rest-endpoints | optional REST endpoints folder. |
| optional Pub state node. |
| required REST endpoint class. ConfiguredCommandEndpointDefinition : Command endpoint definition that adds a white-list for enabled commands. |
| required REST endpoint implementation class. PublicMonitoringService : Provides public monitoring status by REST. |
To enable the service:
rest
role: Access control lists:
Workspace | Permission | Scope | Path |
PblcMntrng | Read only | Selected and sub nodes | / |
Web access:
Permission | Path |
Get & Post | .rest/public-monitoring* |
rest
role to a user or to anonymous
if you need access without credentials.You can use the REST endpoint as follows:
curl http://monitoringinstance:port/.rest/public-monitoring/all
This should return something like:
[{"workspace":"dam","address":"192.168.10.85","name":"administrators-MacBook-Pro.local","syncStamp":"1466422838236","diff":"0","uuid":"2acd7055-7168-4926-b66a-47400ab78d2e","seqNbr":"1977","exceptions":"{}"}]
Properties:
workspace | Workspace of last activated node. |
| IP of consuming instance. |
name | hostName of consuming instance. |
syncStamp | Time stamp of last activated node. |
diff | Difference on seqNbr with other instances who activated a similar node. |
| UUID of last activated node. |
seqNbr | Sequence number of last activated node. |
exceptions | Errors. |
You can access the monitoring screen at http://localhost:8080/.resources/magnolia-rabbitmq-monitoring/webresources/visualisations/public_monitoring.html
or in the Public Monitoring app.
The client control REST service allows you to restart the consumer on the remote instance via a cURL command.
The service is configured in the connector module in /modules/rabbitmq-connector/rest-endpoints/consumer
.
Node name | Value |
---|---|
rabbitmq-connector | |
rest-endpoints | |
consumer | |
class | info.magnolia.rest.service.command.definition.ConfiguredCommandEndpointDefinition |
implementationClass | info.magnolia.rabbitmq.activation.rest.ClientControlRestService |
Properties:
rest-endpoints | optional REST endpoints folder. |
| optional Consumer node. |
| required REST endpoint class. ConfiguredCommandEndpointDefinition : Command endpoint definition that adds a white-list for enabled commands. |
| required REST endpoint implementation class. ClientControlRestService : Provides RabbitMQ client control by REST. |
To enable the service:
rest
role: Web access:
Permission | Path |
Get & Post | .rest/rbmqClients*
|
rest
role to a user or to anonymous
if you need access without credentials.You can use the REST endpoint as follows:
curl http://publicaddress:publicport/.rest/rbmqClients/restartAll
The command will restart all consumers and clients on that instance.
Public instance backups should be done when the SyncState message id is identical for all public nodes. You can then choose one public node and to do a dump. Once the dump is done, create a new historical queue and empty the old queue by consuming all messages. The instance will then be ready to receive new activation messages which post-date the last dump.
Whenever you need to create a new instance, always use the latest dump. The new instance will be registered to the new historical queue. This will mean that the message id is in SyncState
with the latest activation message. New activation messages will be sent to the new historical queue before they register in the old historical queue. The new historical queue will start getting all messages after the last message in old historical queue.
This series of diagrams shows the best setup for scaling up when adding new public instances to the load balancer.
Once the remaining messages are consumed a backup is created. This serves as the new state for new instances. This is also the time to add the new public instance to the load balancer.
When to do a backup?
Each message has a version number or tag in its header. When a new public is added it can tell the author instance or the exchange about its presence by sending its identity before consuming starts. This enables the exchange or author to create the new queue for the public instance.
From this point, all activation messages contain a new version or tag and the consumer starts consuming messages in the queue. When the consumer comes across a message with the newest version number, it does the backup.
Standard backups
Regular backups are needed to prevent the queue becoming too big. Whenever you do a backup on the instances the spare queue can be emptied.
This example shows you how to add a new queue to the example testfanoutAck
exchange:
Add the queue:
curl -i -u guest:guest -H "content-type:application/json" \ -XPUT -d'{"auto_delete":false,"durable":true,"arguments":{},"node":"rabbit@localhost"}' \ http://localhost:55672/api/queues/%2f/fan2
Declare it to be bound to correct exchange:
curl -i -u guest:guest -H "content-type:application/json" \ -d'{"routing_key":"","arguments":[]}' \ http://localhost:55672/api/bindings/%2f/fan2/testfanoutAck
See RabbitMQ Management HTTP API for more.
The node order is respected when a node is created, but it is not respected on update.
To ensure that the node order is respected on update you can add the PUB_POLICY
property to the parent of the nodes that need a specific order.
The PUB_POLICY
property has two valid values that result in the following behaviors:
respect_order | |
remove_orphan_nodes |
When a consumer encounters an issue because of an activation exception, the consumer stops consuming. The message is sent back to the queue with a non-ack, and an exception is sent over the ACK exchange.
To illustrate this we deleted a node on the public instance and then tried to deactivate it on the author instance.
The deletion and attempted deactivation resulted in the following error:
ERROR lia.rabbitmq.activation.jobs.ActivationConsumerJob: /bla
The exception is visible in the Public Monitoring app. You can see from the PathNotFoundException
that the consumer did not find the path that was deleted directly of the public instance.
In the RabbitMQ console the:
When more nodes are published into the queue they become blocked behind the unacked message.
There are two ways to solve this:
Here's a step-by-step solution using option 2 (because it demonstrates how to delete an unacked message):
Restart the consumer on the public instance.
curl http://localhost:8081/.rest/rbmqClients/restartAll