Initial flamegraph implementation

[aboudreault]

Here's the PR so we can begin to review.

Setup

1. Install system dependencies

   sudo apt-get install cmake dtach linux-tools-`uname -r`

2. Ensure your kernel has performance profling support:

   $ sudo perf record -F 99 -g -p <a_running_process_pid> -- sleep 10
   [ perf record: Woken up 1 times to write data ]
   [ perf record: Captured and wrote 0.098 MB perf.data (~4278 samples) ]

3. Add NOPASSWD sudo configuration for the cstar user:

   echo "cstar ALL = (root) NOPASSWD: ALL" | sudo tee /etc/sudoers.d/perf

4. Enable flamegraph feature in your cluster configuration:

   "flamegraph": true,
   "flamegraph_directory": "/mnt/data/cstar_perf/flamegraph"

   The flamegraph working directory default to /tmp/flamegraph if not specified.

5. Migrate the cstar_perf DB using the following script. (ENSURE you have a backup before)

   # Execute with CQL, DONT FORGET TO SET '[csv] field_size_limit=1000000000' in ~/.cassandra/cqlshrc
   frontend/cstar_perf/frontend/migrations/0002.cql

When enabled, you should see a new flamegraph artifact available in the ViewTest page.

[aboudreault]

[aboudreault]

[aboudreault]

UI Integration is done