collectd is described as 'daemon which collects system performance statistics periodically and provides mechanisms to store the values in a variety of ways, for example in RRD files' and is an app in the OS & Utilities category. There are five alternatives to collectd for a variety of platforms, including Linux, Online / Web-based, BSD, Self-Hosted solutions and Mac. The best alternative is Telegraf, which is both free and Open Source. Other great apps like collectd are Observium (Freemium), WhatsUp Gold (Freemium), StatsD (Free, Open Source) and Fluent Bit (Free, Open Source).
Telegraf is a metric collection daemon that can collect metrics from a wide array of inputs and write them into a wide array of outputs. It is plugin-driven for both collection and output of data so it is easily extendable.
Observium is an autodiscovering PHP/MySQL/SNMP based network monitoring which includes support for a wide range of network hardware and operating systems including Cisco, Linux, FreeBSD, Juniper, Brocade, Foundry, HP and many more.
A network daemon that runs on the Node.js platform and listens for statistics, like counters and timers, sent over UDP or TCP and sends aggregates to one or more pluggable backend services (e.g., Graphite).
Fluent Bit is an open source and multi-platform Log Forwarder which allows you to collect data/logs from different sources, unify and send them to multiple destinations. It's fully compatible with Docker and Kubernetes environments.