@@ -16,15 +16,15 @@ there's no power (mains outage or battery ran out). As you may imagine,
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umqtt.robust won't help you with your flat battery. Most computing
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systems are now networked, and communication is another weak link.
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This is especially true for wireless communications. If two of your
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- systems can't connect reliably communicate via WiFi, umqtt.robust
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+ systems can't connect or reliably communicate over WiFi, umqtt.robust
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can't magically resolve that (but it may help with intermittent
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WiFi issues).
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What umqtt.robust tries to do is very simple - if while trying to
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- perform some operation, it detects that connection to MQTT breaks,
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- it tries to reconnect to it . That's good direction towards "robustness",
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- but the problem that there is no single definition of what "robust"
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- is. Let's consider following usecase :
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+ perform some operation, it detects that the connection to MQTT breaks,
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+ it tries to reconnect. That's a good direction towards "robustness",
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+ but the problem is that there no single definition of what "robust"
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+ is. Let's consider the following usecases :
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1. A temperature reading gets transmitted once a minute. Then the
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best option in case of a transmission error might be not doing
@@ -35,11 +35,11 @@ battery-powered, any connection retries will just drain battery and
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make device "less robust" (it will run out of juice sooner and more
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unexpectedly, which may be a criteria for "robustness").
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- 2. If there's a button, which communicates its press event, then
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- perhaps it's really worth to retry to deliver this event (a user
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+ 2. If there's a button which communicates it's press event, then
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+ perhaps it's really worth it to retry delivering this event (a user
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expects something to happen when they press the button, right?).
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- But if a button is battery-power, unconstrained retries won't do
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- much good still . Consider mains power outage for several hours,
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+ But if a button is on battery-power, unconstrained retries still won't do
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+ much good. Consider mains power outage for several hours,
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MQTT server down all this time, and battery-powered button trying
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to re-publish event every second. It will likely drain battery
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during this time, which is very non-robust. Perhaps, if a press
@@ -48,10 +48,10 @@ on what press does, the above may be good for a button turning
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on lights, but not for something else!)
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3. Finally, let's consider security sensors, like a window broken
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- sensor. That's the hardest case. Apparently, those events are
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+ sensor. That's the hardest case. Those events are
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important enough to be delivered no matter what. But if done with
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short, dumb retries, it will only lead to quick battery drain. So,
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- a robust device would retry, but in smart manner, to let battery
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+ a robust device would retry, but in a smart manner to let the battery
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run for as long as possible, to maximize the chance of the message
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being delivered.
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@@ -61,19 +61,19 @@ a) There's no single definition of what "robust" is. It depends on
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a particular application.
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b) Robustness is a complex measure, it doesn't depend on one single
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feature, but rather many different features working together.
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- Consider for example that to make button from the case 2 above
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+ Consider for example that to make the button from the case 2 above
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work better, it would help to add a visual feedback, so a user
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- knew what happens .
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+ knows what happened .
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As you may imagine, umqtt.robust doesn't, and can't, cover all possible
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"robustness" scenarios, nor it alone can make your MQTT application
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"robust". Rather, it's a barebones example of how to reconnect to an
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MQTT server in case of a connection error. As such, it's just one
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- of many steps required to make your app robust, and majority of those
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+ of the many steps required to make your app robust, and majority of those
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steps lie on *your application * side. With that in mind, any realistic
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- application would subclass umqtt.robust.MQTTClient class and override
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+ application would inherit umqtt.robust.MQTTClient class and override
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delay() and reconnect() methods to suit particular usage scenario. It
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- may even happen that umqtt.robust won't even suit your needs, and you
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+ may even be possible that umqtt.robust doesn't suit your needs, and you
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will need to implement your "robust" handling from scratch.
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@@ -82,18 +82,18 @@ Persistent and non-persistent MQTT servers
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Consider an example: you subscribed to some MQTT topics, then connection
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went down. If we talk "robust", then once you reconnect, you want any
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- messages which arrived when the connection was down, to be still delivered
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+ messages which arrived when the connection was down, to still be delivered
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to you. That requires retainment and persistency enabled on MQTT server.
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As umqtt.robust tries to achieve as much "robustness" as possible, it
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makes a requirement that the MQTT server it communicates to has persistency
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enabled. This include persistent sessions, meaning that any client
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- subscriptions are retained across disconnect , and if you subscribed once,
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+ subscriptions are retained on disconnectivity , and if you subscribed once,
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you no longer need to resubscribe again on next connection(s). This makes
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it more robust, minimizing amount of traffic to transfer on each connection
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(the more you transfer, the higher probability of error), and also saves
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battery power.
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- However, not all broker offer true, persistent MQTT support:
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+ However, not all brokers offer true, persistent MQTT support:
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* If you use self-hosted broker, you may need to configure it for
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persistency. E.g., a popular open-source broker Mosquitto requires
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