The purpose of this document is to show This document shows how to configure a ClearBlade system so that IF if an MQTT client disconnected disconnects ungracefully (e.g., because of a catastrophic power - cycle) THEN , the system would store stores messages being sent to the disconnected device and deliver delivers them when the device reconnects.PREREQUISITES:
Prerequisites
1. The environment is running ClearBlade Platform Version >= 9.33.4.
2. The ClearBlade console is available for viewing/editing systems (
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for ClearBlade
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IoT Core users: behind a registry, there is a system):
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3. Devices have connected with persistent sessions, which are typically enforced by setting a clean or clean_session flag to FALSE when connecting with the MQTT library of your choice (e.g., paho.mqtt.python).
4. Devices have subscribed to the topics for which they
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want messages stored in case of a catastrophic disconnect with QoS (Quality of Service) 1 or 2.STEPS:
Steps
1. Go to the Messages page on the console and then choose the History Storage tab:
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Note to ClearBlade
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IoT Core users:
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There will be an existing item in History Storage for topic /devices/+/state.
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Do not edit or delete that item.
2. Click Add Topic and configure the History Storage item:
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3. Enter the topic for which message history should be stored. Use wildcards + and # as appropriate for MQTT topics. e.g. /devices/+/commands/#.
4. Check
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the Platform (
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e.
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g., cloud)
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and Edge checkboxes as appropriate.
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Both can be checked if only one is used. For most customers
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, messages only need to be stored on
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the Platform.
5. Set a value for Max Rows. We highly recommend
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not setting this to Infinite. Set this to a maximum number of messages to store, beyond which the benefit of storing messages
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diminishes.
6. Set a value for Max Time. We highly
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recommend not setting this to Forever. Set this to a maximum time beyond which a reconnecting device
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should be treated as a newly connecting device.ing.
NOTE: Messages containing binary payloads will be Hex-hex encoded when saved to Message History.