While K-@ Mail 1.56 focuses on reducing the duration and number of wake locks (used to keep the device awake while the app synchronizes mails), K-@ Mail brings a completely redesigned IMAP IDLE implementation (push email). While the "old" IMAP IDLE implementation was performing well enough if the network connection was stable (strong WLAN or mobile network without switching between networks), it didn't do so well when the network connection changed a lot (on the move), the signal was weak and some other "non-ideal" network situations. This could in some cases lead to heavy battery drain. The new implementation should be able to cope with these situations much better.
While we usually don't compare K-@ Mail publicly to other email clients, it's important in this case to show the impact these changes can have on battery use, so we compared K-@ Mail 1.5.7 with K-9 Mail 4.903 which used more or less the same mail synchronization code as K-@ Mail before version 1.5.6. We analyzed the following four situations:
- Strong WLAN - arbitrary mobile network
- No WLAN - weak mobile network
- WLAN not authenticated - arbitrary mobile network
- No connection at all
The tests were performed with an identical setup for K-@ Mail and K-9 Mail: three Gmail accounts, three 1gravity accounts, three IMAP accounts (all nine accounts using IMAP IDLE and no polling), 1 Hotmail + 1 Yahoo! account (no IMAP IDLE but polling every 15 minutes).
Here are the results:
Strong WLAN - arbitrary mobile network
In this scenario the device is connected to a stable WLAN and while it's also connected to a mobile network that network connection doesn't matter because all data transfer goes through the WLAN.
As expected there are no issues with wake locks and battery lifetime in this scenario.
No WLAN - weak mobile network
In this scenario the device is connected to a weak mobile network only. "Weak" means it might lose the connection from time to time or it might switch between 3g and 4g occasionally depending on the signal strength of the network. With each network change the IMAP IDLE connection has to be re-established too and that means waking up the device and using the radio.
As we can see K-@ Mail outperforms K-9 Mail when it comes to the duration of the wake locks by a factor of 3 and used a little over a 3rd of the battery K-9 Mail used.
WLAN not authenticated - arbitrary mobile network
When you're on the move in a city there are a lot of "open" WLANs your device might connect to without you even knowing. Most of them aren't really open but require to pay using a web authentication (and payment) mechanism. Should your device connect to one of these WLANs then it's theoretically connected to the "Internet" but the connection ends with the operator of that network. Email clients will find that the device is connected but they won't be able to connect to the email provider. Since the goal of each email client is to reliably synchronize emails they will retry after they fail the first time. And then try again, and again and again. Depending on how sophisticated that retry implementation is, your battery might get a really hard hit in this scenario. But let's see the numbers:
While K-9 Mail kept the device awake for more than half the time it was on battery (8:31 hours), it took K-@ Mail not even 2 minutes to "realize" there's no point in retrieving any emails. The battery statistics in impressive too. 28% of the used battery was used by K-9 while K-@ Mail is off the chart (in a good sense), it doesn't even appear on the list of apps using battery.
It has to be noted that both apps automatically synchronized all changes for the 11 mail boxes that were missed during the 8:31 hours downtime without issues once the device got a "real" connection.
No connection at all
If not handled gracefully this situation could lead to battery drain too but good news for both tested email clients. None of them woke the device unnecessarily and used "no" battery, at least not that it would show in the statistics.
K-@ Mail 1.56 has been released already while K-@ Mail 1.5.7 will be released shortly. Stay tuned.