README.md

Summary

This repo (RabbitMQ to EventHub Shovel) is a template that contains a NodeJS app that will consume messages from a RabbitMQ queue and immediately send them to an Azure EventHub. It can be run directly using node, nvm or Docker (recommended).

Dependencies

Install NPM Dependencies

• From the /app directory, run npm i.

Secrets, CA_Certificate

See Secrets Explained.

Environment

See Environment Variables Explained.

RabbitMQ & Azure

• Last, you need an RMQ server and an Azure Event Hub. Messages from a queue in the RMQ server will be sent to the Azure Event Hub. Note the routing key sent to RMQ will be passed into Azure Event Hub via the properties bag. (EventHub sends your program an EventData object that has the properties "body" and "properties". The routing key will be passed into EventData.properties.routingKey).

Environment Variables Explained

The .env file is used to control all the parameters for the app.

• You need environment variables set. See the file corresponding to your run method.
  • If you're running natively, see the template /app/environment.template and use it to create a .env file in /app.
  • If you're running rabbitmq-to-eventhub-dev, see the template /rabbitmq-to-eventhub-dev/environment.template and use it to create a .env file in /rabbitmq-to-eventhub-dev.
  • If you're running rabbitmq-to-eventhub-prod, see the template /rabbitmq-to-eventhub-prod/environment.template and use it to create a .env file in /rabbitmq-to-eventhub-prod.

# Set a log level that suits your needs.
# Supported Log Levels:
# OFF	 - nothing is logged
# FATAL - fatal errors are logged
# ERROR - errors are logged
# WARN	 - warnings are logged
# INFO	 - infos are logged
# DEBUG - debug infos are logged
# TRACE - traces are logged
# ALL   - everything is logged
logLevel=all

# RMQ (AMQP) Properties
amqpHost="some.host.com"
# vhost can be left blank or no vhost.
amqpVhost=""
# leave port blank to let the library automatically choose
amqpPort=
# Which Protocol to use to connect to AMQP (amqp, amqps)
amqpProtocol="amqps"
# Name of the queue to consume from (must exist on the RMQ host)
amqpConsumeQueue=""
# Should messages be ACK after consume? This will tell RMQ to remove them from the Queue once processed. (true, false)
ackAfterConsume=false

# EventHub Properties
eventHubName="mkalx-inputeventhub-test"

# Advanced Shovel Parameters

# ************
# Batch Mode *
# ************
# If working in batch mode, uncomment these parameters and comment the oneEach parameters
consumeMode=batch
# AMQP Prefetch Count (the maximum number of messages sent over the channel that can be awaiting acknowledgement).
# Default is unlimited. Either comment this out for unlimited OR set a sufficiently large number to meet your needs.
#amqpPrefetch=300
# How many bytes in flight before a batch is released for consumption
batchMaxSizeBytes=100000
# How many seconds in light before a batch is release for consumption
batchMaxTimeMs=5000

# **************
# OneEach Mode *
# **************
# If working in oneEach mode, uncomment these parameters and comment the batch parameters
#consumeMode=oneEach
# AMQP Prefetch Count (the maximum number of messages sent over the channel that can be awaiting acknowledgement).
# If using consumeLimit, set this to a number less than or equal your limit.
#amqpPrefetch=10
# How many messages to consume (0=all, otherwise enter a limit)
# Should be a multiple of amqpPrefetch (which should not be set to unlimited for limiting to work).
#consumeLimit=10

Note there are two modes for consumeMode:

• oneEach - consumes one message at a time and is suitable for testing or very low volume queues. Messages will be sent to Eventhub one at a time, not in batches.
• batch - consumes messages in batches controlled by batch size. Suitable for high volume queues. Messages will be sent to Eventhub in batches.

What is Prefetch?

Prefetch is the number of messages "in flight" that a connection into RMQ is allowed. "In flight" means messages that have been sent to a consumer but are not yet ACK by said consumer. The default is unlimited and should be used unless you specifically want to slow down message consumption. Setting a value of 1 would beam that each message must be sent to Eventhub (and then ACK) before RMQ will release a new one.

Secrets Explained

The /app/secrets.json5 file is used to hold secrets for the app and is excluded from the repo via .gitignore.

{
  "amqpUsername": "ENTER USERNAME HERE",
  "amqpPassword": "ENTER PASSWORD HERE",
  "amqpCACertName": "ENTER THE NAME OF YOUR CA CERT FILE AND COPY IT TO THE SAME DIR AS secrets.json5",

  // Event Hub Connection String
  "eventHubConnectionString": "Enter the Event Hub Connection String Here"
}

• If your RMQ host uses AMQPS (AMQP over TLS), you'll need the CA Certfile for the server in /app/conf/ca_certfile.pem.
• Be sure to set the environment variable amqpProtocol="amqps".
• Also, in secrets.json5, make sure amqpCACertName="" contains the name of your cert file (recommended name is ca_certfile.pem).

How to run the app

Note: See the Dependencies section before trying to run!

• Running natively via NVM (Node Version Manager)

  • .env in /app, secrets.json5 in /app/conf, possibly ca_certificate.pem (if needed) in /app/conf
  • Be sure you've done npm i
  • Run with: nvm index.js

• Running natively via NodeJS

  • .env in /app, secrets.json5 in /app/conf, possibly ca_certificate.pem (if needed) in /app/conf
  • Be sure you've done npm i
  • node index.js

• Running locally using the Docker dev config

  • .env in /rabbitmq-to-eventhub-dev, secrets.json5 in /app/conf, possibly ca_certificate.pem (if needed) in /app/conf
  • Be sure you've done npm i
  • docker compose up to run interactively or docker compose up -d to run in the background

Deploying and Running on your PROD remote server

Note: See the Dependencies section before trying to build/deploy!

• When deploying to a remote host, either of the following should work:
  • Copy the whole repo (with the secrets.json5 and ca_certificate.pem if required) and then build the production docker compose in-place.
    • On the target server
      • On servers, Docker Compose needs to be installed. Ensure it's installed. If not, see Docker Compose Install.
      • Change into the rabbitmq-to-eventhub-prod folder
      • Ensure you have the proper values in .env
      • Ensure you've edited /conf/secrets.json5 to suit your needs.
      • • If you need a ca_certificate.pem, make sure it's in /conf.
      • docker-compose build
      • docker-compose up to run the container interactively. It is recommended that you run the first time with "ackAfterConsume=false" so you don't lose any messages if there's a container error.
      • Once satisfied the container is working properly, stop the interactive mode, change "ackAfterConsume=true" and run with docker compose up -d to run in the background
      • Note that if you change values in /conf/secrets.json5, or update your ca_certificate.pem, you must repeat the Docker build step. Changing values in .env does not require a rebuild.
  • The production docker compose build can be done in a remote machine and then the docker container can be exported using Docker's export command.
    • On your build workstation
      • Change into the rabbitmq-to-eventhub-prod folder
      • Ensure you have the proper values in .env
      • Ensure you've edited /conf/secrets.json5 to suit your needs.
      • If you need a ca_certificate.pem, make sure it's in /conf.
      • docker compose build
      • docker export rabbitmq-to-eventhub-prod > rabbitmq-to-eventhub-prod.tar
    • On the host
      • Copy the three files (.env, docker-compose.yml, rabbitmq-to-eventhub-prod.tar to the host)
      • docker import rabbitmq-to-eventhub-prod.tar
      • docker compose up to run the container interactively. It is recommended that you run the first time with "ackAfterConsume=false" so you don't lose any messages if there's a container error.
      • Once satisfied the container is working properly, stop the interactive mode, change "ackAfterConsume=true" and run with docker compose up -d to run in the background
      • Note that if you change values in /conf/secrets.json5, or update your ca_certificate.pem, you must repeat the Docker build step (and export/upload/import to your host).

Environment variable notes for running in-place at an RMQ server (it's assumed said server is using AMQPS / AMQP over TLS):

• The prod container rabbitmq-to-eventhub-prod is suitable to run on the RMQ server itself. Therefore, the RMQ host in this case will be the docker host (using the special "host-gateway" alias).
• To avoid TLS issues, we used docker's extra_hosts to create a docker compose level HOSTS entry to map the TLS hostname to "host-gateway". See the section To run the Docker container on your RMQ host.

Azure EventHub Capture

During testing, it might be useful to capture what you send into EventHub in an Azure Storage Container.

• If capturing files to Azure Storage, those will be in AVRO format.
  • There are AVRO viewers. In fact, JetBrains WebStorm has one as a plugin. Install Avro and Parquet Viewer from the JetBrains IDE Plugins manager.
  • To download the files there are options:
    • Azure Storage Explorer to see the files and download.
      • Use the full connection string from STORAGE ACCOUNT | ACCESS KEYS | key1 or key2 connection string
    • Azure Portal also lets you navigate into the folder/files and download.

Edge Cases

To run the Docker container (prod) on your RMQ host

In this edge case, the RMQ hostname needs to be mapped to the Docker host. To avoid TLS issues, we do this by adding the following to the docker-compose.yml service entry for rmq-to-eventhub:

    extra_hosts:
      # If this container will be run on the RMQ host directly, we need to map the RMQ hostname with the internal special host gateway 
      # in order send the traffic to the docker host! This is like setting the HOSTS file inside the container.
      - "${amqpHost}:host-gateway"

• The ${amqpHost} will come from your .env file and is the hostname for the RMQ server.
• "host-gateway" is a special docker setting that represents the host's IP internally.

RMQ host requires an SSH Tunnel in order to connect

In this edge case, the RMQ host is only accessible via an SSH tunnel running on the workstation executing the app. This is not a problem when running NodeJS or NVM natively, but it is a challenge when running inside Docker since the container needs to connect to the host instead of the remote RMQ server.

To do this we add the following to docker-compose.yml service entry for rmq-to-eventhub:

    extra_hosts:
      # If the RMQ host requires an SSH tunnel, we need to map the RMQ hostname with the internal special host gateway 
      # in order send the traffic to the docker host! This is like setting the HOSTS file inside the container.
      - "${amqpHost}:host-gateway"

• The ${amqpHost} will come from your .env file and is the hostname for the RMQ server.
• "host-gateway" is a special docker setting that represents the host's IP internally.

An example SSH tunnel on the docker host: (on the host, port 15671 will be forwarded to the RMQ's port 5671)

ssh -N -i "/path/to/your/key.pem" -L 127.0.0.1:15671:127.0.0.1:5671 -o ServerAliveInterval=15 -o ExitOnForwardFailure=yes -o ServerAliveCountMax=3 -p YOUR-PORT-NUMBER YOUR-USERNAME@YOU-HOST-IP-OR-NAME

TODO:

• Nothing yet noted.