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IndraMQTT

Sizing

Sizing

This page helps you pick CPU and memory for a node. Use it before you order hosts. You get load numbers that a committed report backs.

flowchart LR
    Load["planned msg/s"] -- "find" --> Row["sustained row in benchmark"]
    Row -- "check" --> Limit["behind list + limits"]
    Limit -- "add" --> Head["headroom x2"]

Before you start

  • Read benchmark/README.md for the full method.
  • Note your shape: point-to-point, fan-in, or fan-out.
  • Note your QoS class and payload size.

Measured numbers

The table shows the highest sustained load at 1 CPU and 1 GB, MQTT 5, 256 B payload, 180 s runs. Source: benchmark/README.md sections 5 and 6, raw data in benchmark/results/. Each value is one search plus one 180 s run on a shared server.

ScenarioSustained loadNote
Point-to-point QoS 0100,000 msg/sStrongest shape
Point-to-point QoS 130,000 msg/sSame shape, ack cost
Fan-in QoS 040,000 msg/sBehind the fastest row at 80,000 msg/s
Fan-out QoS 0160,000 deliveries/sStops at 25,000 subscribers of one topic
10,000 idle connections283 MiBAbout 21 KiB per connection

[!IMPORTANT] The broker is behind in two rows: fan-in at 40,000 msg/s against 80,000 msg/s, and idle memory at 76 MiB with no clients against 1.6 MiB. Plan fan-in and tiny hosts with care.

Rules for use

  • Quote a number only with its scenario, QoS class, payload, CPU, memory, and run length.
  • A figure that still rises at cutoff is “still rising at cutoff”, never final.
  • Double the measured need for headroom. One run is not a guarantee.
  • The test uses MQTT without TLS and one payload size. TLS and large payloads need their own runs.

When the numbers do not apply

  • You use TLS, large payloads, durable sessions, rules, connectors, or clustering. The test uses none of them.
  • You need latency bounds at a different load. Latency values sit at each broker’s own highest load, so they do not compare across brokers.
  • You run many subscribers of one topic past 25,000. Subscriptions did not complete in 180 s there.

Check that it works

Start the broker with this file. Validate the directory. The command prints ok.

[node]
id = "docs-sizing"


[listeners.tcp]
bind = "0.0.0.0:1883"


[listeners.api]
bind = "0.0.0.0:18083"


[logging]
level = "warn"
Terminal window
"${INDRAMQTT_BIN:-indramqtt}" --config-dir "${DOCS_CFG_DIR:-./docs-sizing}" --check-config
ok

Next steps