[sonic_installer] Add swap setup support

[lolyu]

What I did

• Let's add swap memory setup support for sonic_installer command so it could run on devices with limited memory resources.

How I did it

• Add the following new options to sonic_installer:
  1. --skip-setup-swap: if present, will skip setup swap memory.
  2. --swap-mem-size: this will change the swap memory size(the default swap size is 1024 MiB)
  3. --total-mem-threshold: if the system total memory is less than the value passed to --total-mem-threshold(default 2048 MiB), sonic_installer will setup swap memory.
  4. --available-mem-threshold: if the system available memory is less than the value passed to --available-mem-threshold(default 1200 MiB), sonic_installer will setup swap memory.
• Add class MutuallyExclusiveOption to check the mutually-exclusive relationship between options.
• Add class SWAPAllocator to support swap memory setup/remove functionalities.
• Also, when sonic_installer tries to setup swap, if the system disk free space is less than 4096 MiB, sonic_installer will not setup swap memory.

How to verify it

Run sonic_installer over devices with limited memory

• sonic_installer install --help output:

# sonic_installer install --help
Warning: 'sonic_installer' command is deprecated and will be removed in the future
Please use 'sonic-installer' instead
Usage: sonic_installer install [OPTIONS] URL

  Install image from local binary or URL

Options:
  -y, --yes
  -f, --force                     Force installation of an image of a type
                                  which differs from that of the current
                                  running image
  --skip_migration                Do not migrate current configuration to the
                                  newly installed image
  --skip-package-migration        Do not migrate current packages to the newly
                                  installed image
  --skip-setup-swap               Skip setup temporary SWAP memory used for
                                  installation
  --swap-mem-size INTEGER         SWAP memory space size  [default: (1024
                                  MiB)] NOTE: this argument is mutually
                                  exclusive with arguments: skip_setup_swap
  --total-mem-threshold INTEGER   If system total memory is lower than
                                  threshold, setup SWAP memory  [default:
                                  (2048 MiB)] NOTE: this argument is mutually
                                  exclusive with arguments: skip_setup_swap
  --available-mem-threshold INTEGER
                                  If system available memory is lower than
                                  threhold, setup SWAP memory  [default: (1200
                                  MiB)] NOTE: this argument is mutually
                                  exclusive with arguments: skip_setup_swap
  --help                          Show this message and exit.

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[lgtm-com]

This pull request introduces 1 alert when merging d3cb7bf into 83309c6 - view on LGTM.com

new alerts:

• 1 for Unused import

[lolyu]

• unit tests result

tests/swap_allocator_test.py::TestSWAPAllocator::test_read_from_meminfo PASSED                                                                                                                 [  7%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_setup_swapmem PASSED                                                                                                                     [ 15%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_remove_swapmem PASSED                                                                                                                    [ 23%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_initialization_default_args PASSED                                                                                        [ 30%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_initialization_custom_args PASSED                                                                                         [ 38%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_allocate_true_insufficient_total_memory PASSED                                                              [ 46%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_allocate_true_insufficient_available_memory PASSED                                                          [ 53%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_allocate_true_insufficient_disk_space PASSED                                                                [ 61%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_allocate_true_swapfile_present PASSED                                                                       [ 69%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_setup_error PASSED                                                                                          [ 76%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_enter_allocate_false PASSED                                                                                       [ 84%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_exit_is_allocated_true PASSED                                                                                     [ 92%]
tests/swap_allocator_test.py::TestSWAPAllocator::test_swap_allocator_context_exit_is_allocated_false PASSED                                                                                    [100%]

[lolyu]

@yxieca, could you please take a review for my updates? Thanks!

[lolyu]

Looks like this PR could not be cherry-picked to 202012, will create a separate PR for 202012 branch.

[qiluo-msft]

This commit could not be cleanly cherry-pick to 202012. Please submit another PR.

[judyjoseph]

This commit could not be cleanly cherry-pick to 202106. Please submit another PR.