Using a9s Messaging

This topic describes how developers use a9s Messaging.

Use a9s Messaging With an App

To use a9s Messaging with an application, create a service instance and bind the service instance to your application. For more information on managing service instances, see Managing Service Instances with the cf CLI.

View the a9s Messaging Service

After the service is installed, you can see the a9s-messaging and its service plans appear in your CF marketplace. Run cf marketplace to see the service listing:

$ cf marketplace
Getting services from marketplace in org test / space test as admin...
OK
service          plans                                               description
a9s-messaging313 messaging-single-small, messaging-cluster-small,    This is a service creating and managing dedicated Messaging service instances, powered by the
                 messaging-single-big, messaging-cluster-big         anynines Service Framework

Create a Service Instance

To provision a RabbitMQ database, run cf create-service. For example:

cf create-service a9s-messaging313 messaging-single-small my-messaging-service

Depending on your infrastructure and service broker utilization, it might take several minutes to create the service instance.

Run the cf services command to view the creation status. This command displays a list of all your service instances. To view the status of a specific service instance, run cf service NAME-OF-YOUR-SERVICE.

Bind an Application to a Service Instance

After your database is created, run cf bind-service to bind the service to your application:

cf bind-service a9s-rabbitmq-app my-messaging-service

Restage or Restart Your Application

To enable your appliation to access the service instance, run cf restage or cf restart to restage or restart your app.

Obtain Service Instance Access Credentials

After a service instance is bound to an application, the credentials of your RabbitMQ database are stored in the environment variables of the application. Run cf env APP-NAME to display the environment variables.

You can find the credentials in the VCAP_SERVICES key.

$ cf env a9s-rabbitmq-app
Getting env variables for app a9s-rabbitmq-app in org test / space test as admin...
OK

System-Provided:
{
  "VCAP_SERVICES": {
    "a9s-messaging313": [
      {
        "credentials": {
          "host": "hostname.node.dcx.consul",
          "hosts": [
            "hostname.node.dcx.consul"
          ],
          "password": "password",
          "port": 5672,
          "http_api_uri": "http://username:password@hostname.node.dcx.consul/api/",
          "http_api_uris": ["http://username:password@hostname.node.dcx.consul/api/"],
          "protocols": {
            "amqp": {
              "host": "hostname.node.dcx.consul",
              "hosts": [
                "hostname.node.dcx.consul"
              ],
              "password": "password",
              "port": 5672,
              "ssl": false,
              "uri": "amqp://username:password@hostname.node.dcx.consul:5672",
              "username": "username"
            },
            "management": {
              "username": "username",
              "password": "password",
              "path": "/api",
              "ssl": false,
              "host": "hostname.node.dcx.consul",
              "hosts": [
                "hostname.node.dcx.consul"
              ],
              "uri": "http://username:password@hostname.node.dcx.consul",
              "uris": ["http://username:password@hostname.node.dcx.consul"]
            }
          },
          "ssl": false,
          "uri": "username:password@hostname.node.dcx.consul:5672",
          "username": "username"
        },
        "label": "a9s-messaging313",
        "name": "rabbitmq-app",
        "plan": "messaging-single-small",
        "provider": null,
        "syslog_drain_url": null,
        "tags": [
         "messaging",
         "queue"
        ],
        "volume_mounts": []
      }
    ]
  }
}
...

You can use the host, username and password values to connect to your database with a RabbitMQ client.

Protocols Hash

The credentials hash contains a protocols hash that lists credentials by protocol. The credentials at the root level of the credentials are either for AMQP with non SSL service plans or AMQPS with SSL service plans.

Protocol key	Enabled when
amqp	always
amqp+ssl	SSL plan
mqtt	MQTT plugin enabled
mqtt+ssl	SSL plan and MQTT plugin enabled
stomp	STOMP plugin enabled
stomp+ssl	SSL plan and STOMP plugin enabled
management	always

Best Practices

There are some best practices for using service binding information in apps in a separate document.

Delete an a9s Messaging Service Instance

WARNING: Before deleting a service instance, you must backup data stored in your database. This operation cannot be undone and all the data is lost when the service instance is deleted.

Before you can delete a service instance, you must unbind it from all apps.

List Available Services

Run cf services to list your available services.

$ cf services

Getting services in org test / space test as admin...
OK

name                   service           plan                     bound apps         last operation
my-messaging-service   a9s-messaging313   messaging-single-small   a9s-rabbitmq-app   create succeeded

This example shows that my-messaging-service is bound to the a9s-rabbitmq-app application.

Unbind a Service Instance

Run cf unbind-service to unbind the service instance from your app.

cf unbind-service a9s-rabbitmq-app my-messaging-service

Delete a Service Instance

After unbinding the service, it is no longer bound to an application. Run cf delete-service to delete the service:

cf delete-service my-messaging-service

It may take several minutes to delete the service. Deleting a service deprovisions the corresponding infrastructure resources.

Run the cf services command to view the deletion status.

Upgrade the Service Instance to Another Service Plan

Once created, you can upgrade your service instance to another, larger service plan. A larger service plan provides more CPU, RAM and storage. For more information, see the Update a Service Instance of the Managing Service Instances with the cf CLI topic.

cf update-service my-messaging-service -p a-bigger-plan

Add a Graphite Endpoint

caution

Important: Streaming of logs and metrics might not be available for your plan! If unsure, please check your plan description.

If you want to monitor your service with Graphite, you can set the custom parameter graphite. It expects the host and port where the Graphite metrics should be sent to.

For example, in order to send Graphite metrics to an endpoint yourspace.your-graphite-endpoint.com:12345, you can use the following command:

cf update-service my-instance -c '{ "graphite": "yourspace.your-graphite-endpoint.com:12345" }'

The endpoint would then receive metrics in the format:

<service_guid>.<service_type>.<host>.<metric> <metric value> <metric timestamp>

Metrics Frequency

By default, metrics will be emitted every 10 seconds. You can change the interval via the custom parameter metrics_frequency.

For example, in order to send Graphite metrics to an endpoint every minute, you would set the custom parameter metrics_frequency to 60 using the following command:

cf update-service my-instance -c '{  "metrics_frequency": 60 }'

Metrics Prefix

Depending on your graphite provider, you might need to prefix the metrics with a certain value, like an API key for example. In this case you can leverage the custom parameter metrics_prefix.

cf update-service my-instance -c '{  "metrics_prefix": "my-api-key-for-a-certain-provider" }'

The resulting metric path would have the format:

<metrics_prefix>.<service_guid>.<service_type>.<host>.<metric>

Cloud Foundry Org and Space Guid

The platform operators can enable support on a global level to prefix the Graphite metrics with the CloudFoundry organization and space. This means that all metrics of all service instances (not only yours!) contain that information.

In this case the Graphite metric paths have the following format:

<organization_guid>.<space_guid>.<service_guid>.<service_type>.<host>.<metric>

When you enable in addition the metrics_prefix for your instance, you will end up with the metric path format:

<metrics_prefix>.<organization_guid>.<space_guid>.<service_guid>.<service_type>.<host>.<metric>

Metrics

Following a list of the RabbitMQ metric patterns which will be streamed to a colocated Prometheus endpoint. The metrics can be divided into the groups:

• Node Metrics
• Queue Metrics
  • Ghost Queues
• Port Checks
• General

Messaging 4.0 Metrics Changes

Starting with a9s Messaging 4.0, metrics have been changed to include all available RabbitMQ metrics for the three endpoints. Node, Queue and General (Cluster-wide metrics).

For more information about all available metrics for a9s Messaging 4.0 see the RabbitMQ Monitoring documentation and the RabbitMQ HTTP API documentation.

Node Metrics

These metrics provide insight into detailed information about the state of nodes. Most of the metrics represent point-in-time absolute values. The latter metrics are most useful when compared to their previous values and historical mean/percentile values.

Documentation source:

• RabbitMQ Monitoring Node Documentation
• RabbitMQ HTTP API Documentation
  • The metrics description on this documentation might change between version.

Group Id	Type	Description
disk_free	Integer	Disk free space in bytes.
disk_free_details.rate	Float	Rate of the disk_free metric.
disk_free_limit	Integer	Point at which the disk alarm will go off.
fd_total	Integer	File descriptors available.
fd_used	Integer	Used file descriptors.
io_read_avg_time	Integer	Average wall time (milliseconds) for each disk read operation in the last statistics interval.
io_read_avg_time_details.rate	Float	Rate of the io_read_avg_time metric.
io_read_bytes	Integer	Total number of bytes read from disk by the persister.
io_read_bytes_details.rate	Float	Rate of the io_read_bytes metric.
io_read_count	Integer	Total number of read operations by the persister.
io_read_count_details.rate	Float	Rate of the io_read_count metric.
io_sync_avg_time	Integer	Average wall time (milliseconds) for each fsync() operation in the last statistics interval.
io_sync_avg_time_details.rate	Float	Rate of the io_sync_avg_time metric.
io_write_avg_time	Integer	Average wall time (milliseconds) for each disk write operation in the last statistics interval.
io_write_avg_time_details.rate	Float	Rate of the io_write_avg_time metric.
mem_limit	Integer	Point at which the memory alarm will go off.
mem_used	Integer	Memory used in bytes.
mem_used_details.rate	Float	Rate of the mem_used metric.
partitioned	Integer	Displays the partitions visible to this node. The value is 1 when partitions amount is greater than 0, otherwise it is 0.
proc_total	Integer	Maximum number of Erlang processes.
proc_used	Integer	Number of Erlang processes in use.
sockets_total	Integer	File descriptors available for use as sockets.
sockets_used	Integer	File descriptors used as sockets.
uptime	Integer	Time since the Erlang VM started, in milliseconds.

*.rabbitmq.*.*.*.*.node.disk_free
*.rabbitmq.*.*.*.*.node.disk_free_details.rate
*.rabbitmq.*.*.*.*.node.disk_free_limit
*.rabbitmq.*.*.*.*.node.fd_total
*.rabbitmq.*.*.*.*.node.fd_used
*.rabbitmq.*.*.*.*.node.io_read_avg_time
*.rabbitmq.*.*.*.*.node.io_read_avg_time_details.rate
*.rabbitmq.*.*.*.*.node.io_read_bytes
*.rabbitmq.*.*.*.*.node.io_read_bytes_details.rate
*.rabbitmq.*.*.*.*.node.io_read_count
*.rabbitmq.*.*.*.*.node.io_read_count_details.rate
*.rabbitmq.*.*.*.*.node.io_sync_avg_time
*.rabbitmq.*.*.*.*.node.io_sync_avg_time_details.rate
*.rabbitmq.*.*.*.*.node.io_write_avg_time
*.rabbitmq.*.*.*.*.node.io_write_avg_time_details.rate
*.rabbitmq.*.*.*.*.node.mem_limit
*.rabbitmq.*.*.*.*.node.mem_used
*.rabbitmq.*.*.*.*.node.mem_used_details.rate
*.rabbitmq.*.*.*.*.node.partitioned
*.rabbitmq.*.*.*.*.node.proc_total
*.rabbitmq.*.*.*.*.node.proc_used
*.rabbitmq.*.*.*.*.node.sockets_total
*.rabbitmq.*.*.*.*.node.sockets_used
*.rabbitmq.*.*.*.*.node.uptime

Queue Metrics

These metrics provide insight into information about queue metrics. They expose the information of each individual queue available on the system.

Documentation source:

• RabbitMQ List Queues Documentation
• RabbitMQ Monitoring Node Documentation
• RabbitMQ HTTP API Documentation
  • The metrics description on this documentation might change between version.

Group Id	Type	Description
consumers	Integer	Consumers on a queue.
memory	Integer	Queue's memory.
messages	Integer	Sum of ready and unacknowledged messages - total queue depth.
messages_details.rate	Float	Rate of the messages metric.
messages_ram	Integer	Ready and unacknowledged messages stored in memory.
messages_ready	Integer	Messages ready to be delivered to consumers.
messages_ready_details.rate	Float	Rate of the messages_ready metric.
messages_ready_ram	Integer	Ready messages stored in memory.
messages_unacknowledged	Integer	Messages delivered to consumers but not yet acknowledged.
messages_unacknowledged_details	Float	Rate of the messages_unacknowledged metric.
messages_unacknowledged_ram	Integer	Unacknowledged messages stored in memory.
message_bytes	Integer	Size in bytes of ready and unacknowledged messages.
message_bytes_persistent	Integer	Size in bytes of persistent messages.
message_bytes_ram	Integer	Size of ready and unacknowledged messages stored in memory.
message_bytes_ready	Integer	Size in bytes of ready messages.
message_bytes_unacknowledged	Integer	Size in bytes of all unacknowledged messages.
backing_queue_status.avg_ack_egress_rate	Integer	Average rate of leaving unacknowledged messages.
backing_queue_status.avg_ack_ingress_rate	Integer	Average rate of arriving unacknowledged messages.
backing_queue_status.avg_egress_rate	Integer	Average engress rate.
backing_queue_status.avg_ingress_rate	Integer	Average ingress rate.
backing_queue_status.len	Integer	Total queue length.
backing_queue_status.next_seq_id	Integer	Next sequence ID.
backing_queue_status.q1	Integer	Amount of queues type Q1.
backing_queue_status.q2	Integer	Amount of queues type Q2.
backing_queue_status.q3	Integer	Amount of queues type Q3.
backing_queue_status.q4	Integer	Amount of queues type Q4.

*.rabbitmq.*.*.*.*.queue.<queue-name>.consumers
*.rabbitmq.*.*.*.*.queue.<queue-name>.memory
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_details.rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_persistent
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_ram
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_ready
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_ready_details.rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_ready_ram
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_unacknowledged
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_unacknowledged_details.rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.messages_unacknowledged_ram
*.rabbitmq.*.*.*.*.queue.<queue-name>.message_bytes
*.rabbitmq.*.*.*.*.queue.<queue-name>.message_bytes_persistent
*.rabbitmq.*.*.*.*.queue.<queue-name>.message_bytes_ram
*.rabbitmq.*.*.*.*.queue.<queue-name>.message_bytes_ready
*.rabbitmq.*.*.*.*.queue.<queue-name>.message_bytes_unacknowledged
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.avg_ack_egress_rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.avg_ack_ingress_rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.avg_egress_rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.avg_ingress_rate
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.len
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.next_seq_id
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.q1
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.q2
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.q3
*.rabbitmq.*.*.*.*.queue.<queue-name>.backing_queue_status.q4

The backing_queue_status provides information about the state of a queue in RabbitMQ, using various metrics related to the queue’s internal state. These metrics are only present if announced by the RabbitMQ queue information.

Queue Names

Please be aware that the periods (.) of the queue's name are replaced with underscores (_) in the queue metrics. This is necessary since a periods is reserved as path separator for Graphite metric names.

backing_queue_status Deprecation

As of RabbitMQ 3.13, the backing_queue_status metric has been deprecated and is removed with a9s Messaging 4. Therefore, as of a9s Messaging 4.X and above, the backing_queue_status are not available anymore.

Ghost Queues

The idea behind this metric is to support the detection of ghost queues. Ghost queues are a known rabbitmq bug/artefact, so ideally this metric shouldn't appear.

*.rabbitmq.*.*.*.*.<ghost_queue>.<ghost-queue-name>

Queue Names

Please be aware that the periods (.) of the queue's name are replaced with underscores (_) in the queue metrics. This is necessary since a periods is reserved as path separator for Graphite metric names.

Port Checks

These metrics provide insight into information about a9s RabbitMQ services ports.

Group Id	Type	Description
amqp_port_open	Integer (0 - Closed / 1 - Open)	Show the amqp open port.
amqp_tls_port_open	Integer (0 - Closed / 1 - Open)	Show the amqp tls open ports.
epmd_port_open	Integer (0 - Closed / 1 - Open)	Show the epmd open port.
http_api_port_open	Integer (0 - Closed / 1 - Open)	Show the http api open port.
mqtt_client_port_open	Integer (0 - Closed / 1 - Open)	Show the mqtt client open port.
mqtt_client_tls_port_open	Integer (0 - Closed / 1 - Open)	Show the mqtt client tls open port.
stomp_port_open	Integer (0 - Closed / 1 - Open)	Show the stomp open port.
stomp_tls_port_open	Integer (0 - Closed / 1 - Open)	Show the stomp tls open port.
web_mqtt_port_open	Integer (0 - Closed / 1 - Open)	Show the web mqtt tls open port.
web_stomp_port_open	Integer (0 - Closed / 1 - Open)	Show the web stomp open port.

*.rabbitmq.*.*.*.*.port_checks.amqp_port_open
*.rabbitmq.*.*.*.*.port_checks.amqp_tls_port_open
*.rabbitmq.*.*.*.*.port_checks.epmd_port_open
*.rabbitmq.*.*.*.*.port_checks.http_api_port_open
*.rabbitmq.*.*.*.*.port_checks.mqtt_client_port_open
*.rabbitmq.*.*.*.*.port_checks.mqtt_client_tls_port_open
*.rabbitmq.*.*.*.*.port_checks.stomp_port_open
*.rabbitmq.*.*.*.*.port_checks.stomp_tls_port_open
*.rabbitmq.*.*.*.*.port_checks.web_mqtt_port_open
*.rabbitmq.*.*.*.*.port_checks.web_stomp_port_open

General

These metrics provide insight into general information about a9s Messaging.

Documentation source:

• RabbitMQ Monitoring Cluster-Wide-Metrics Documentation
• RabbitMQ HTTP API Documentation
  • The metrics description on this documentation might change between versions.

Group Id	Type	Description
connections	Integer	Total amount of connections.
collect_time	Integer (ms)	The time it took to collect the server status information.
metric_fetch_status	Integer (0 - success / 1 - fail)	Status of the last server status collection operation.

*.rabbitmq.*.*.*.*.connections
*.rabbitmq.*.*.*.*.collect_time
*.rabbitmq.*.*.*.*.metric_fetch_status

System Metrics

Aside from the metrics shown above, this Data Service also provides system metrics, common to all a9s Data Services. They can be seen in the Graphite metrics documentation.

Add a Syslog Endpoint

The cf update-service command used with the -c flag can let you stream your syslog to a third-party service. In this case, the command expects a JSON string containing the syslog key. A single endpoint item for syslog can be provided, as well as an array of endpoints. host and port are mandatory parameters.

The protocol parameter is optional. The accepted values are:

• udp sets rfc by default to rfc3164.
• tcp sets rfc by default to rfc3164.
• ssl-tcp sets rfc by default to rfc6587.
  • For ssl-tcp; ssl_cert and ssl_key are required parameters.
  • If ssl_verify is set to true, then ssl_cacert must also be provided.

To remove all endpoints, simply set syslog to [].

rfc values

Optionally, the rfc parameter can be explicitly overwritten. Valid values: rfc3164, rfc5424 and rfc6587.

cf update-service my-service \
 -c '{
  "syslog": [
    {
      "host": "logs4.your-syslog-endpoint.com",
      "port": "6514",
      "protocol": "ssl-tcp",
      "rfc": "rfc6587",
      "ssl_cert": "-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE-----",
      "ssl_key": "-----BEGIN CERTIFICATE----- ... -----END CERTIFICATE-----",
      "ssl_cacert": "-----BEGIN PRIVATE KEY----- ... -----END PRIVATE KEY-----",
      "ssl_verify": "false"
    }
  ]
}'

Syslog Endpoints' Legacy Format

The legacy format to specify syslog endpoints (["hostname1:port1", "hostname2:port2"]) is still supported.

Cloud Foundry Application Security Groups

This topic describes how to check whether a security group was created.

Each a9s Data Service will automatically create and update Cloud Foundry security groups in order to protected Service Instances to be accessed by applications not running in the same Cloud Foundry applications space.

To get a better understanding about Security Groups you can have a look on the Understanding Application Security Groups topic.

Get Service Instance GUID

Run cf service INSTANCE_NAME --guid to get the guid of the service instance.

$ cf service my-rabbitmq --guid
ca16f111-5073-40b7-973a-156c75dd3028

Check available Security Groups

To see all available security groups use cf security-groups.

$ cf security-groups
Getting security groups as demo@anynines.com
OK

     Name                                         Organization     Space
#0   public_networks
#1   dns
#2   tcp_open
#3   guard_432fb752-876d-443b-a311-a075f4df2237   demonstrations   demo
#4   guard_ca16f111-5073-40b7-973a-156c75dd3028   demonstrations   demo

There we can see a security group with the name guard_ca16f111-5073-40b7-973a-156c75dd3028 was successfully created.

NOTE: in some circumstances the connection between the application and the service instance is not possible, in this case check if a security group was created.

Backup and Restore Service Instances

a9s Messaging provides an easy way to create backups and restore if needed. For a more detailed description, please see the a9s Service Dashboard documentation.

caution

When creating a backup for a9s Messaging, please note that only the queue definitions are stored. The actual messages within the queues are not saved, as this service is designed for non-persistent queues.

When restoring a backup, any missing queues will be added to the service. Meanwhile, the existing queues and their corresponding data, that existed before the backup was created, will be preserved.

RabbitMQ Custom Parameters

As an end user you have the opportunity to customize your service instance by using custom parameters. Custom parameters are passed on to a service instance by using the -c switch of the cf CLI commands cf create-service and cf update-service. For example

cf update-service my-instance -c '{"my_custom_parameter": "value"}'

would set the custom parameter named my_custom_parameter to the value value for the service instance my-instance.

You don't have to utilize those settings. There are sane defaults in place that fit your service plan well.

Every parameter corresponds to a property in the configuration file for the respective RabbitMQ version.

consumer_timeout

RabbitMQ's consumer_timeout parameter, see Delivery Acknowledgement Timeout, can be specified via the custom parameter consumer_timeout.

An integer value greater than or equal to 1800000 is expected. The default value is 1800000. The unit is milliseconds.

tls-protocols

You can specify the TLS protocol version via the custom parameter tls-protocols. The custom parameter tls-protocols correlates with RabbitMQ's configuration parameter ssl_options.versions, see Limiting TLS Versions Used by the Server.

An array with protocol versions is expected. The allowed protocol version values are tlsv1.3 and tlsv1.2.

tls-ciphers

You can limit the TLS ciphers via the custom parameter tls-ciphers. The custom parameter tls-ciphers correlates with RabbitMQ's configuration parameter ssl_options.ciphers, see Configuring Cipher Suites.

An array with cipher names is expected.

WARNING: There is no validation enabled for the user provided value and therefore existing instances can break when applying this parameter.

Use RabbitMQ Plugins

a9s Messaging allows to enable the following RabbitMQ plugins:

• rabbitmq_consistent_hash_exchange
• rabbitmq_federation
• rabbitmq_federation_management
• rabbitmq_mqtt
• rabbitmq_sharding
• rabbitmq_shovel
• rabbitmq_shovel_management
• rabbitmq_stomp
• rabbitmq_tracing

Plugin Activation

You can activate RabbitMQ plugins with the cf create-service and cf update-service commands using additional configuration parameters.

cf create-service a9s-messaging313 rabbitmq-single-small my-messaging-service \
  -c '{ "plugins": ["rabbitmq_shovel", "rabbitmq_shovel_management"] }'

cf update-service my-messaging-service \
  -c '{ "plugins": ["rabbitmq_shovel", "rabbitmq_shovel_management"] }'

Plugins for Protocols

Some plugins that can be enabled with a9s Messaging provide additional protocols for use with RabbitMQ. The usernames and passwords for these protocols are the same as with the default ACMQ protocol. Protocols enabled via plugin will be set to the default \ RabbitMQ vhost.

Protocal	TCP Port	SSL Port	Further information
MQTT	1883	8883	RabbitMQ MQTT Docs
STOMP	61613	61614	RabbitMQ STOMP Docs

Create Messaging Users

a9s Messaging allows to create new users with different roles (permissions) by creating service keys.

The possible roles are:

• management
• policymaker
• monitoring
• administrator

You can read more about RabbitMQ roles and permissions here.

Create a New Role

You can create a new user with specific permissions (roles) giving the role following custom parameter. This parameter receives an array of roles:

cf create-service-key my-messaging-service my-key -c '{"roles": ["administrator", "management"]}'

Use RabbitMQ Management Dashboard

a9s Messaging has management dashboard support enabled. The dashboard is running on the service instance VM so it is not possible to open the dashboard in your browser directly.

Option: via (Go) router

When the platform operator has configured the (Go)router to route the RabbitMQ Management Dashboard the dashboard will be exposed under a URL formatted as https://service-instance-guid.a9s-rabbitmq-dashboard.system.domain.

Obtaining the Dashboard URL

The dashboard URL that provides access to the a9s dashboard contains all the information required, to create a URL that will access the RabbitMQ Dashboard. This command will create the URL you need:

cf service a9s-messaging-serive-instance | grep dashboard | sed  's/^.*https:\/\/\(.*\)\/service-instances\/\(.*\)/https:\/\/\2.\1/'

You can use this URL to navigate to the dashboard login page in your web browser.

Obtaining Credentials

To log into the RabbitMQ dashboard you will need a username and a password. If you want to see the dashboard from the perspective of your app, you could use the apps credentials. Accessing the credential used by your app is simple:

cf env your-app-name

If you would prefer to have a separate RabbitMQ user for accessing the dashboard you can create and use a service key:

cf create-service-key a9s-messaging-service-instance dashboard
cf service-key a9s-messaging-service-instance dashboard

Option: with CF SSH

CF provides a smart way to create SSH forward tunnels via a pushed application.

Make sure that SSH access to the app is enabled. You can enable SSH access with cf enable-ssh MY-AWESOME-APP. If you do not have permission, contact your administrator.

For more information about this feature see the Accessing Apps with SSH section of the CF documentation.

First of all you must have an application bound to the service. How to do this see Bind an Application to a Service Instance.

NOTE: cf ssh support must be enabled in the platform. Ask your administrator if you are not sure.

Get Dashboard Url and Credentials

When you follow this instructions Obtain Service Instance Access Credentials you will get the hostname of the service and the user credentials.

$ cf env rabbitmq-app
Getting env variables for app rabbitmq-app in org phartz / space develop as admin...
OK

System-Provided:
{
 "VCAP_SERVICES": {
  "a9s-messaging313": [
   {
    "credentials": {
     "host": "d67901c.service.dc1.a9svs",
     "username": "a9s-brk-usr",
     "password": "a9s-password",
     "port": 5672,
     "uri": "amqp://a9s-brk-usr:a9s-password@d67901c.service.dc1.a9svs:5672"
    },
    "label": "a9s-messaging313",
    "name": "mymessaging",
    "plan": "messaging-single-small",
    "provider": null,
    "syslog_drain_url": null,
    "tags": [
     "message broker"
    ],
    "volume_mounts": []
  }
  ]
 }
}

Notice the host d67901c.service.dc1.a9svs, the username a9s-brk-usr and the password a9s-password. You will need this in the next step.

Create Tunnel to The Management Dashboard

With the cf ssh as mentioned before you can create a ssh forward tunnel to the management dashboard.

$ cf ssh rabbitmq-app -L 15672:d67901c.service.dc1.a9svs:15672
vcap@956aaf4e-6da9-4f69-4b1d-8e631a403312:~$

NOTE: Don't forget to close the session with exit.

Login to The Management Dashboard

When the ssh tunnel is open, you can access the Dashboard with your Browser. Depending on the service plan used for your service instance, you have to visit one of the following URLs:

• http://localhost:15672 for NON-SSL service instances (any version)
• https://localhost:15672 for SSL service instances (any version)

To login to the management dashboard you need the user credentials.

If the login was successful, you should see the dashboard as followed.

Using High Availability Queues in Cluster Setup

If clusters are enrolled, this does not mean that all created queues are HA queues!

High Availability in a9s Messaging 4.X and above

For a9s Messaging 4.X and above, HA is available by default for all quorum queues. The mirrored classic queues from the previous RabbitMQ versions were removed and the still existing classic queues are not able to be replicated anymore.

High Availability in a9s Messaging 3.13 and below

For a9s Messaging 3.13 and below, there are two policies defined to allow HA queues and no HA queues. These policies are depending on the queue name.

If the queue name starts with ha. the queue is a HA queue and consists of clusternodecount/2 + 1 queues (one master queue and the rest mirror queues).

This guarantees that in the case of a network partition, the queue is still available in the bigger partition. Additionally, it allows to use most of performance of the clusternodes, by reducing replication and queues.

Additionally there is another policy for not important queues, this policy is for all queues starting with noha., in this case the queue is not mirrored and if the node which hold this queue goes down, the queue is also not available anymore.

Using custom policies in RabbitMQ

caution

Important: The a9s Messaging 3.13 and below services configure by default two policies named ha and noha. These policies will always be reconfigured on a restart of a RabbitMQ service instance. Therefore they shouldn't be changed manually.

To create and use custom policies, please see Parameters and Policies — RabbitMQ

Make a Service Instance Locally Available

It is possible to access any of the a9s Data Services locally. That means you can connect with a local client to the service for any purpose such as debbuging. CF provides a smart way to create SSH forward tunnels via a pushed application. For more information about this feature see the Accessing Apps with SSH section of the CF documentation.

First of all you must have an application bound to the service. How to do this see Bind an Application to a Service Instance.

NOTE: cf ssh support must be enabled in the platform. Ask your administrator if you are not sure.

Get The Service Url and Credentials

To get the hostname and user credentials of a Service Instance you can follow the steps provided in Obtain Service Instance Access Credentials.

$ cf env a9s-rabbitmq-app
Getting env variables for app a9s-rabbitmq-app in org test / space test as admin...
OK

System-Provided:
{
  "VCAP_SERVICES": {
   "a9s-messaging": [
    {
      "credentials": {
       "host": [
        "d67901c.service.dc1.a9svs"
       ],
       "username": "a9s-brk-usr",
       "password": "a9s-password"
     },
     "label": "a9s-messaging",
     "name": "my-messaging-service",
     "plan": "messaging-cluster-small"
    }
   ]
  }
}
...

Notice the host d67901c.service.dc1.a9svs, the username a9s-brk-usr and the password a9s-password. You will need them in the next step.

Create a Tunnel to The Service

With the cf ssh as mentioned before you can create a ssh forward tunnel to the management dashboard. Use port 9200 to connect to the a9s Messaging Instance.

$ cf ssh a9s-rabbitmq-app -L 9200:d67901c.service.dc1.a9svs:9200
vcap@956aaf4e-6da9-4f69-4b1d-8e631a403312:~$

When the ssh tunnel is open you can access the instance over the address localhost:9200.

NOTE: Don't forget to close the session with exit.

Create a Fork of a Service Instance

The procedure of forking a service instance involves creating a backup of a service instance and restoring it to a different service instance.

Having two service instances is a prerequisite for the process:

$ cf s
Getting services in org system / space test as admin...

name         service           plan                      bound apps   last operation
messaging1   a9s-messaging313   messaging-cluster-small   bindingo     create succeeded
messaging2   a9s-messaging313   messaging-cluster-small                create succeeded

Fork an a9s Messaging Service Instance Using the Disaster Recovery Feature

Follow the steps described in Disaster Recovery to create a fork of an existing a9s Messaging Service Instance.

Fork an a9s Messaging Service Instance Manually

This approach has additional prerequisites regarding command line tools:

• BASH (some shell)
• cat
• openssl
• python (see below for the verion required)
• node (tested with v6.11.0)

Open the service dashboard of the service instance you want to fork. We use messaging1 for this example. You can find the dashboard URL like this:

$ cf service messaging1
Showing info of service messaging1 in org system / space test as admin...

name:            messaging1
service:         a9s-messaging313
bound apps:      bindingo
tags:
plan:            messaging-cluster-small
description:     This is a service creating and managing dedicated Messaging service instances, powered by the anynines Service Framework
documentation:
dashboard:       https://a9s-messaging-dashboard.de.a9s.eu/service-instances/950cb675-3ed9-4613-8bb6-b2d618391d2f

[...]

Make sure you set a encryption password for the backups using the service instance dashboard. Create a backup using the dashboard. Download the backup to your local machine. The filename will be something like racsd92baee-1522222422893. Decrypt the backup and write its contents to a file:

cat racsd92baee-1522222422893 | openssl enc -aes256 -md md5 -d -pass 'pass:mytopsecretpassword' | gunzip -c > backup_settings.json

Create a tunnel to the admin interface (like explained in a previous chapter) of the RabbitMQ instance that will be the fork of the original instance. I used messaging1 as the original instance and messaging2 as the fork instance. The tunnel is needed to get the matching version of the rabbitmqadmin script as well as to restore the backed up data. I assume you're using something like this to set up the tunnel:

cf ssh someapp -L 127.0.0.1:15672:racsd92baee.service.dc1.a9ssvc:15672

racsd92baee.service.dc1.a9ssvc is the host of the messaging2 service instance.

Go to http://127.0.0.1:15672/cli/ to download the rabbitmqadmin tool. rabbitmqadmin is a python script. On that page you'll find information about the python version required.

Download a copy of the backup script restore_queues.js. Make sure to chmod u+x the script.

Restore the backed up queues using the restore script, e.g.:

./restore_queues.js $(which python) ~/Downloads/rabbitmqadmin 127.0.0.1 15672 a9s-brk-usr-xxxxxxxx xxxxxxxyyyyyyyyyzzzzzzzzz ./backup_settings.json

If you are restoring an SSL instance, you will need to do a small change to the restore script:

 args.push("-p")
 args.push(process.argv[7])

+args.push("-s")
+
 args.push("declare")

After this change to the script, you can restore your SSL instance exactly as a non-SSL one:

./restore_queues.js $(which python) ~/Downloads/rabbitmqadmin 127.0.0.1 15672 a9s-brk-usr-xxxxxxxx xxxxxxxyyyyyyyyyzzzzzzzzz ./backup_settings.json

Setup Disk Usage Alerts

Each service comes with the a9s Parachute. This component monitors ephemeral and persistent disk usage. See the a9s Parachute documentation how to configure the component.