Android/frameworks_base
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add extra documentation to DiscreteRegistry.

Browse Source 
Fix: 176965672
Test: documentation only
Change-Id: Ia915bab26c4ef66ce8c0b14a2d12f33252912b3e
This commit is contained in:
Stanislav Zholnin
2021-05-04 14:41:13 +01:00
parent 0f314d689f
commit 21d81d0a83
1 changed files with 34 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
services/core/java/com/android/server/appop/DiscreteRegistry.java
View File

@@ -69,18 +69,47 @@ import java.util.Date;
import java.util.List;
/**
* This class manages information about recent accesses to ops for
* permission usage timeline.
* This class manages information about recent accesses to ops for permission usage timeline.
*
* The timeline history is kept for limited time (initial default is 24 hours) and
* discarded after that.
* The discrete history is kept for limited time (initial default is 24 hours, set in
* {@link DiscreteRegistry#sDiscreteHistoryCutoff) and discarded after that.
*
* Discrete history is quantized to reduce resources footprint. By default quantization is set to
* one minute in {@link DiscreteRegistry#sDiscreteHistoryQuantization}. All access times are aligned
* to the closest quantized time. All durations (except -1, meaning no duration) are rounded up to
* the closest quantized interval.
*
* When data is queried through API, events are deduplicated and for every time quant there can
* be only one {@link AppOpsManager.AttributedOpEntry}. Each entry contains information about
* different accesses which happened in specified time quant - across dimensions of
* {@link AppOpsManager.UidState} and {@link AppOpsManager.OpFlags}. For each dimension
* it is only possible to know if at least one access happened in the time quant.
*
* Every time state is saved (default is 30 minutes), memory state is dumped to a
* new file and memory state is cleared. Files older than time limit are deleted
* during the process.
*
* When request comes in, files are read and requested information is collected
* and delivered.
* and delivered. Information is cached in memory until the next state save (up to 30 minutes), to
* avoid reading disk if more API calls come in a quick succession.
*
* THREADING AND LOCKING:
* For in-memory transactions this class relies on {@link DiscreteRegistry#mInMemoryLock}. It is
* assumed that the same lock is used for in-memory transactions in {@link AppOpsService},
* {@link HistoricalRegistry}, and {@link DiscreteRegistry}.
* {@link DiscreteRegistry#recordDiscreteAccess(int, String, int, String, int, int, long, long)}
* must only be called while holding this lock.
* {@link DiscreteRegistry#mOnDiskLock} is used when disk transactions are performed.
* It is very important to release {@link DiscreteRegistry#mInMemoryLock} as soon as possible, as
* no AppOps related transactions across the system can be performed while it is held.
*
* INITIALIZATION: We can initialize persistence only after the system is ready
* as we need to check the optional configuration override from the settings
* database which is not initialized at the time the app ops service is created. This class
* relies on {@link HistoricalRegistry} for controlling that no calls are allowed until then. All
* outside calls are going through {@link HistoricalRegistry}, where
* {@link HistoricalRegistry#isPersistenceInitializedMLocked()} check is done.
*
*/
final class DiscreteRegistry {