This demo demonstrates the behavior of Couchbase Lite C when attempting to connect to a Sync Gateway, while the process has various numbers of file descriptors open. Once a process uses more than 1024 file descriptors, behavior of Couchbase Lite C changes.

Linux

Setup

In the /linux directory, do the following:

1. Unpack the Couchbase Lite package for the host platform into the vendor directory.
2. Run mkdir build && cd build && cmake .. && cmake --build .
3. Make sure no Sync Gateway is running at localhost:5000.
4. Run ./build/main <fd-count> where fdCount is the number of file descriptors to open before attempting to replicate with a Sync Gateway.

Observed behavior on Ubuntu 20.04:

When running the demo with a low number (~100) of file descriptors, the demo will just fail to connect to the sync gateway with POSIX error 111, "Connection refused".

When running the demo with a high number (1000+) of file descriptors, the demo will fail to connect with the wrong error: POSIX error 110, "Connection timed out".

Android

In the /android directory, do the following:

1. Unpack the Couchbase Lite package for android into the vendor directory. The expected name of the package directory is libcblite-3.0.0.
2. Open the project with Android Studio.
3. Run the App until it crashes with the following abort message:

   Abort message: 'FORTIFY: FD_SET: file descriptor 1076 >= FD_SETSIZE 1024'
   

4. Run adb logcat -d > logcat.txt to get the logcat output.
5. Use nkd-stack to symbolicate the stack trace:

   ndk-stack -sym vendor/libcblite-3.0.0/lib/$ANDROID_ABI$/ -i logcat.txt
   

/data contains an example logcat.txt file and the corresponding stack-trace.txt.

Relevant Files

• CmakeLists.txt: to build native-lib library and package CBL C with the app.
• app/src/main/cpp/native-lib.cc: Native shared library which calls CBL C.
• app/src/main/java/com/example/cbl_c_fd_max_demo/NativeLib.java: Java code which calls native-lib
• app/src/main/java/com/example/cbl_c_fd_max_demo/MainActivity.kt: runDemo method launches demo code.