ARGO Messaging

The ARGO Messaging Service is a Publish/Subscribe Service, which implements the Google PubSub protocol. Instead of focusing on a single Messaging API specification for handling the logic of publishing/subscribing to the broker network the API focuses on creating nodes of Publishers and Subscribers as a Service. It provides an HTTP API that enables Users/Systems to implement message oriented services using the Publish/Subscribe Model over plain HTTP. In the Publish/Subscribe paradigm, Publishers are users/systems that can send messages to named-channels called Topics. Subscribers are users/systems that create Subscriptions to specific topics and receive messages.

Prerequisites

Build Requirements

• Golang 1.19

Datastore Requirements

• The service has been tested with mongodb from version 3.2.22 up to 4.2.3.

Broker requirements

• Kafka 2.2.1
• Zookeeper 3.4.5

Push Server

In order to support push enabled subscriptions AMS relies on an external service that handles the actual pushing of messages, while AMS holds the configuration for the subscriptions.You can create push enabled subscriptions even when the push-server isn't available, they will be picked up automatically when the push-server is up and running.

• Push server

Configuration

Configuration Location

Configuration for the service takes place inside a config.json file, that resides in two possible locations:

1. Same folder as the binary

2. /etc/argo-messaging/config.json

Configuration values

• port - port the service will bind to
• zookeeper_hosts - list of zookeeper hosts, e.g. [zoo1:2181,zoo2:2181,zoo3:2181]
• store_host - store host, e.g. 'mongo1:27017,mongo2:27017,mongo3:27017'
• store_db - mongo db database name
• certificate - /path/to/tls/certificate
• certificate_key - /path/to/cert/ley
• certificate_authorities_dir - dir containing CAs
• log_level - DEBUG,INFO,WARNING, ERROR or FATAL
• push_enabled - (true|false) whether or not the service will support push enabled subscriptions
• push_tls_enabled - (true|false), whether or not the service will communicate over TLS with the push server
• push_server_host - push1.grnet.gr
• push_server_port - 443
• verify_push_server - (true|false) mutual TLS for the push server
• push_worker_token - token for the active push worker user
• log_facilities - ["syslog", "console"]
• auth_option - (key|header|both), where should the service look for the access token.
• proxy_hostname - The FQDN of any proxy or load balancer that might serve request in place of the AMS

Run the tests

Inside the project's root directory issue the command:

go test ./...

For the db store integration test suite, you can issue the command:

go test ./... -tags integration

Build & Run the service

In order to build the service, inside the AMS repo issue the command:

go build

In order to run the service,

./argo-messaging

X509 Authentication

Although AMS doesn't support direct authentication through an x509 certificate, you can use the argo-authentication-service to map an x509 certificate to an AMS key. The service will also validate the certificate. The ams-library will effortlessly hide this complexity if you decide to use it in order to access AMS.

Managing the protocol buffers and gRPC definitions

In order to modify any .proto file you will need the following

• Read on how to install the protoc compiler on your platform here.

• Install the go plugin. go get -u github.com/golang/protobuf/protoc-gen-go

• install the go gRPC package. go get -u google.golang.org/grpc

• Inside push/grpc compile. protoc -I proto/ proto/ams.proto --go_out=plugins=grpc:proto

Helpful utilities

Inside the tools folder you can find various scripts that can help you perform common tasks OR help you get started with interacting with AMS.

There is also a handy python library for interacting with AMS.

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Credits

The ARGO Messaging Service is developed by GRNET

The work represented by this software was partially funded by

• EGI-ENGAGE project through the European Union (EU) Horizon 2020 program under Grant number 654142.
• EOSC-Hub project through the European Union (EU) Horizon 2020 program under Grant number 77753642.
• EOSC-Future project through the European Union (EU) Horizon 2020 program under Grant number 101017536.
• DICE project through the European Union (EU) Horizon 2020 program under Grant number 101017207.