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Hawkeye - ANR Trace

ANR Trace is used to capture the main thread stalling event, and will sampling the main thread stack frame when the jam occurs.

0x00 Usage

After add ANR Trace to MTHawkeyeClient, by default it'll start after MTHawkeyeClient run, you can change it by following steps:

  1. Tap MTHawkeye floating window, enter the main panel.
  2. Tap navigation title view, show the MTHawkeye panel switching view.
  3. Tap Setting in the upper right corner of the switching view, enter the Setting view home.
  4. Find TimeConsuming and go to ANR Trace, turn off Trace ANR, configure ANR Threshold

0x01 Record stalling event

When a method executed on main thread takes longer than the specified threshold (the default is 400ms), ANR Trace will capture a stalling event, and sampling the stack frame of main thread. You can see the recorded stalling events and details within the App while development.

ANR Record list ANR Record detail

If you need a accurate duration time while stalling and the detail calls, consider using UI Time Profiler

0x02 Hard stall event

When the app run into hard stall, it may killed without any logs, you can use MTHANRTracingBuffer to cache and restore the last running context.

0x03 Storage

ANR records is store under Records file. Use a collection name anr, key as the time stalling event generated (The version after 0.12.1 optimizes it, it will split the >16kb or more of the Carton data and store it again. The key will become the timestamp_serial number, which needs to be merged when used externally. Please refer to the merge method in readANRRecords), value is a JSON string with the following fields:

  • duration: stalling duration, in millisecond
  • inBackground: whether it is running in the background
  • stacks: all stack frame during stalling event
    • capturedCount: the number of times recorded, the same record will be deduplicated
    • stackframes: sampling stack frame when the stalling event captured (symbolic needed), hexadecimal address string separated by ,
    • threadCount: current thread count
    • time: the time stalling event generated
    • titleframe: stall event stack title string
  • startFrom: stalling start time, in seconds

examples:

{
    duration = "610.3181838989258";
    inBackground = 0;
    stacks = {
            capturedCount = 1;
            stackframes = "0x10d8fe55e,0x10d896497,0x108455f9a,0x108455c01,0x108455620,0x116a5d3d4,0x116a5d7b1,0x116888611,0x11687945f,0x1168a8865,0x10d8c4856,0x10d8bf2ed,0x10d8bf969,0x10d8bf055,0x10fa8fbaf,0x11687f88c,0x108460821,0x10e0084ac";
            threadCount = 6;
            time = "1565256930.870066";
            titleframe = 0x108455f9a;
        },
        {
            capturedCount = 1;
            stackframes = "0x10d90461b,0x10d8fe6f5";
            threadCount = 6;
            time = "1565256930.975193";
            titleframe = 0x10d90461b;
        }
    startFrom = "1565256930.414564";
}

0x03 Symbolics

ANR Trace records raw stack frame need to symbolized for reading.

If the running App do have DWARF within, you can directly use ANR Trace panel to view the symbolized result generated internal.

In other cases, if you have your own remote symbolization service and did set, switch on the Remote Symbolics, and then you can view the symbolized stack frame directly in the App.

If you wanna get the raw data from the sandbox, manual symbolize yourself as follows:

  1. Get the dyld-images file in the MTHawkeye storage directory.
  2. Get the raw stack frame data from the records.
  3. Get the dSYM files
  4. for each frame
    • find the match dyld-image by frame value, then match a dSYM file.
    • Use atos command to symbolize the frame.