问题
Google Analytics (using iOS SDK version 3.14 and it's built in sessions tracking) is reporting a significant percentage of app sessions as 1 second.
Maybe users are launching an app to view a page and (effectively) then instantly leaving the app, but that seems unlikely (that it should continue as the top use case. You think such users would stop using or uninstall.)
Initially I suspected this was related to "background fetch" but when I look at a prior incarnation of the application (that did not have background fetch enabled or used) I still see these (seemingly) bogus sessions also. That application (pre iOS9) had no universal links.
The (obvious) reason I don't want to see these sessions (especially if from automated action not user action) is it removes all value of "user behavior"; i.e. loyalty, recency and skews "average session length". These are the main reasons I want to use GA, i.e. to see if folks are using it more/valuing it more.
My questions:
- What might these sessions be caused by? Are they bogus?
- If bogus, how can I stop them?
- Can I ensure new "background fetch" code doesn't somehow trigger them?
Some things I've considered / looked into:
- I am seeing a similarly large set of "short sessions" on an Android application (this application's peer) and again with extremely high numbers. I've been wondering if this was a result of a web searches & site links, with those site links automatically loading the app, and the a (very) quick user "move on". (Universal linking is something the new iOS application is working towards, but doesn't see much of yet.) Given it is not that on iOS I am starting to doubt that it is that on Android.
- There is a "optOut" option on GA. That feels like a sledgehammer solution to this walnut problem. It is also a persistent setting, which feels risky to use for a transient situation. I could attempt to toggle it at applicationDidEnterBackground / applicationDidBecomeActive (and will if it is deemed the solution) but worry it could have negative side-effects.
- One can have multiple trackers. I am planning to attempt one for human foreground activity and one for background operations (which might allow time /event tracking when in background, w/o impacting human user tracking numbers. That said, I don't know / believe this is the cause of the bogus sessions. )
- One can manage sessions manually and also customize the sessions interval timeout, but I don't see why this application should need any custom behavior. It is a normal application.
- The application isn't reporting crash totals to match these numbers; it is a generally well liked 4/5 star app w/ few crashes.
回答1:
Google Analytics measures duration as the time between interactions.
This means that in order to be able to measure duration, Google Analytics needs a minimum of two interactions to measure between. But they still need to collect data on one-interaction Sessions, and from the reporting perspective, every session starts the same - with an interaction. It's just that some don't go any further. To account for this, Google Analytics keeps a running total of Session duration.
- When a user first interacts, that total is set to 0.
- 31 seconds later, they interact again. That total is updated to 31 seconds.
- 10 seconds later, they interact a third time. Total is now 41 seconds.
- 35 seconds later, they quit. This is not measurable, and hence not an interaction. Google Analytics waits faithfully for 30 minutes, before deciding that they aren't coming back.
Your total Session Duration is recorded as 41 seconds, as that was the last point at which you checked in. There's no way of knowing that you stuck around an extra 35 seconds.
This isn't an issue if you looked at 4 or 5 pages, but if you had only looked at 1 page, we would have been left with a Session Duration of 0. This is what happens with every 'Bounce'; every Session with only one interaction is measured '0' seconds long.
Throw into that a handful of people who interacted 8 or 9 seconds later, and you have an average of 1 second for the '0 - 10' category.
回答2:
Turns out the problem was inside the Google Analytics SDK. A new version has been posted:
[Google Analytics SDK issue with short sessions][1]
来源：https://stackoverflow.com/questions/37774306/google-analytics-ios-sdk-1-second-sessions-possibly-background-sessions