AWS greengrass: Clarify MQTT ping timeout and reconnect delay limits
Summary
Adds notes documenting that the effective maximum ping timeout depends on the MQTT version (mqtt3 caps at 32767 ms; mqtt5 caps at half the negotiated keep-alive) and that the reconnect delay option applies only to mqtt5, with mqtt3 using a fixed 128-second maximum.
Security assessment
The change only documents MQTT connection keep-alive/reconnect timing behavior for the Greengrass nucleus component; it does not alter authentication, encryption, or access control.
Evidence
+The effective maximum of this value depends on the MQTT version that you use. When you use `mqtt3`, the core device limits this value to `32767` (approximately 32.7 seconds) and silently reduces larger values to this limit. When you use `mqtt5`, the core device caps the effective ping timeout at half of the keep-alive interval that the server negotiates. The core device uses the value that you set only if it is less than `keepAliveTimeoutMs` divided by 2.
Diff
diff --git a/greengrass/v2/developerguide/greengrass-nucleus-component.md b/greengrass/v2/developerguide/greengrass-nucleus-component.md index 0975efe..1a82925 100644 --- a//greengrass/v2/developerguide/greengrass-nucleus-component.md +++ b//greengrass/v2/developerguide/greengrass-nucleus-component.md @@ -401,0 +402,4 @@ Default: `30000` (30 seconds) +###### Note + +The effective maximum of this value depends on the MQTT version that you use. When you use `mqtt3`, the core device limits this value to `32767` (approximately 32.7 seconds) and silently reduces larger values to this limit. When you use `mqtt5`, the core device caps the effective ping timeout at half of the keep-alive interval that the server negotiates. The core device uses the value that you set only if it is less than `keepAliveTimeoutMs` divided by 2. + @@ -536,0 +541,4 @@ Default: `120` +###### Note + +The core device applies this option only when you set the MQTT version to `mqtt5`. When you use `mqtt3`, the core device ignores this value and uses a fixed maximum reconnect delay of `128` seconds. +