Re: [Qemu-devel] [PATCH v4 0/4] scripts: qmp-shell: add transaction support

[Kashyap Chamarthy <kchamart@redhat.com>]

On Wed, Apr 29, 2015 at 03:14:00PM -0400, John Snow wrote:
> The qmp-shell is a little rudimentary, but it can be hacked
> to give us some transactional support without too much difficulty.
> 
> (1) Prep.
> (2) Add support for serializing json arrays and
>     improve the robustness of QMP parsing
> (3) Add a special transaction( ... ) syntax that lets users
>     build up transactional commands using the existing qmp shell
>     syntax to define each action.
> (4) Add a verbose flag to display generated QMP commands.
> 
> The parsing is not as robust as one would like, but this suffices
> without adding a proper parser.
> 
> Design considerations:
> 
> (1) Try not to disrupt the existing design of the qmp-shell. The existing
>     API is not disturbed.
> (2) Pick a "magic token" such that it could not be confused for legitimate
>     QMP/JSON syntax. Parentheses are used for this purpose.
> 
> For convenience, this branch is available at:
> https://github.com/jnsnow/qemu.git branch qmp-shell++
> This version is tagged qmp-shell++-v4.
> 
> ===
> v++
> ===
> 
>  - Use the AST to allow 'true', 'false' and 'null' within QMP expressions
>  - Fix a bunch of stupid junk I broke in v2, apparently.
> 
> ===
> v3:
> ===
> 
>  - Folding in hotfix from list (import ast)
> 
> ===
> v2:
> ===
> 
>  - Squash patches 2 & 3:
>  - Remove wholesale replacement of single quotes, in favor of try blocks
>    that attempt to parse as pure JSON, then as Python.
>  - Factored out the value parser block to accomplish the above.
>  - Allow both true/True and false/False for values.
>  - Fix typo in patch 3 cover letter. (was patch 4.)
> 
> John Snow (4):
>   scripts: qmp-shell: refactor helpers
>   scripts: qmp-shell: Expand support for QMP expressions
>   scripts: qmp-shell: add transaction subshell
>   scripts: qmp-shell: Add verbose flag
> 
>  scripts/qmp/qmp-shell | 147 +++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 116 insertions(+), 31 deletions(-)


Quick test, works as advertized. This time, I ran this series on top of
your incremental backup branch:

A positive test (sorry for the un-wrapped long lines). I already had the
target image pre-created:

$ ./qmp-shell -v ./qmp-sock
Welcome to the QMP low-level shell!
Connected to QEMU 2.2.94
(QEMU)
(QEMU) transaction(
TRANS> blockdev-snapshot-internal-sync device=drive-ide0-0-0 name=snapshot5
TRANS> block-dirty-bitmap-add node=drive-ide0-0-0 name=bitmap1
TRANS> block-dirty-bitmap-clear node=drive-ide0-0-0 name=bitmap0                                                                                                                           
TRANS> drive-backup device=drive-ide0-0-0 bitmap=bitmap1 sync=dirty-bitmap target=./incremental.0.img mode=existing format=qcow2
TRANS> )
{"execute": "transaction", "arguments": {"actions": [{"data": {"device": "drive-ide0-0-0", "name": "snapshot5"}, "type": "blockdev-snapshot-internal-sync"}, {"data": {"node": "drive-ide0-0-0", "name": "bitmap1"}, "type": "block-dirty-bitmap-add"}, {"data": {"node": "drive-ide0-0-0", "name": "bitmap0"}, "type": "block-dirty-bitmap-clear"}, {"data": {"target": "./incremental.0.img", "format": "qcow2", "sync": "dirty-bitmap", "bitmap": "bitmap1", "mode": "existing", "device": "drive-ide0-0-0"}, "type": "drive-backup"}]}}
{"return": {}}
(QEMU)

And a quick negative test: don't pre-create the target image when
running the `drive-backup` command, appropriate error is thrown.


So, FWIW:

  Tested-by: Kashyap Chamarthy <kchamart@redhat.com>

-- 
/kashyap