Number of channels and billing

Question

I am looking at building an app that monitors the public transport buses for a major city:

I did a quick prototype using pubnub. The buses have a phone transmitting gps signals to a channel and bus users have phones subscribed to channels. I have questions:

1. I am planning for each bus route there is a channel. The city has 50 routes so there will be 50 routes. Does this adhere to the best practice?

   1. Is there an api to list channels ?

2. I am sending a message to a channel every second. Assume, there are 50 routes with 5 buses each running 24 hours. There will be 216000000 daily messages. what will i be charged for a day?

3. Does your Android client open a network connection everytime a publish is call? I want to minimize the bandwith used by the phone that is transmitting the GPS signal.

4. Bus users may want to see location of multiples buses. I know best practice is to subscribe to one public and one private channel. What is the best way to do it?

I would appreciate if you could answer the above questions.

Answer 1

Full disclosure up front - I work for PubNub Customer Success so responses for pricing related questions are informational in nature only and not to be construed as a promotional. Asker specifically mentions PubNub and the information provided below is publicly available from the PubNub website.

Anant, also as an FYI StackOverflow would normally ask that each of these questions gets asked as a separate thread. Moving forward please do your best to adhere to community guidelines.

1 Every implementation will be different as far as the specific architecture and design pattern strategy though your proposed approach seems to be a sensible utilization of channel methodology. PubNub does not limit the total number of channels in use, however as a practical limitation for most mobile development frameworks subscribing to more than 50 channels simultaneously would be around the upper limit. Adding more than that and both iOS and Android will begin exhibiting performance limitations. If new bus lines are added the subscriptions can be managed to only subscribe to nearby routes, etc.

Question 1 the second with the indent. Yes that can be done with the here_now API

2 PubNub charges $1 per million messages (without SSL enabled) so based on your hypothetical your message charges would be $216 per day. That being said, there is significant room here for design pattern optimization so that busses only publish a new location whenever there is a change - repeated publishes while the bus is standing still are unnecessary. This optimization on it's own will bring the message usage figure down significantly, and there are other strategies which can be utilized to further optimize depending on your specific implementation approach. If you anticipate needing more than 1 billion messages per month, a deployment to Global Cloud would make sense so as to avail yourself of volume discount pricing not otherwise available on Go Cloud.

3 Rather than opening a new connection with every publish, PubNub keeps an active socket connection open until unsubscribed or disconnected via loss of network connection/app force close. The bandwidth utilization to keep this connection active over a period of several hours and absent any other publish/subscribe activity typically measures less than 1K depending on your configuration parameters. Android supports background threading so even when the app is not in focus the connection can remain open to facilitate data push alerts which can be used to prompt the user to bring the app back into the foreground to review any updated information.

4 This question is not clear, assuming that the bus locations are published to the public channel what would the purpose of the private channel serve? If you meant a private channel to receive alerts for the arrival of the user's selected bus, then yes that would be an appropriate implementation strategy. Please clarify if you meant something different.