Eclipse Amlen vs Google Cloud Pub/Sub

Eclipse Amlen is a self-hosted MQTT server for IoT and web messaging. It supports MQTT versions 3 through 5 over TCP/IP and WebSockets, plus JMS, and can convert messages between MQTT and JMS. A protocol plug-in SDK lets users add other protocols, including options for legacy sensors that cannot use MQTT. The Amlen Bridge forwards MQTT messages to another MQTT server or IBM Event Streams for IBM Cloud, with filtering, topic mapping, multiple forwarders, and REST API configuration and monitoring. Security controls include TLS profiles, user ID and password authentication against a configured LDAP server, and policy-based authorization for connections, topics, subscriptions, and queues. Administrators can manage message hubs and endpoints through a WebUI or REST Administration APIs. Supported client platforms include C, Java, Android, iOS, and JavaScript. Server and WebUI downloads are listed for RHEL and AlmaLinux 8, 9, and 10. The free software has configurable delivery guarantees. One limitation is that Amlen supports a single LDAP server connection, so users and groups must be provided through that server.

Google Cloud Pub/Sub is a cloud messaging service for asynchronous communication between services that produce messages and those that process them. It is intended for service-to-service use, including streaming analytics, data integration, middleware, and parallel task queues, rather than direct communication with end users or IoT clients. Communication typically has latency around 100 milliseconds. Synchronous cross-zone replication and per-message receipt tracking provide at-least-once delivery; Dataflow supports exactly-once processing of Pub/Sub streams. There are no shards or partitions, and provisioning scales automatically after quota is set. Message controls include seek and replay, dead letter topics, and attribute-based filtering. Pub/Sub offers fine-grained access controls, end-to-end encryption, and HIPAA compliance. It supports REST and gRPC APIs and client libraries for seven languages; API keys are not supported for authentication. The maximum message size is 10 MB. The free monthly tier is free for the first 10 GB of data per month. Pay-as-you-go is $40 a month beyond 10 GB, with throughput listed at $40 per TB and storage at $0.27 per GiB-month.