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qmp: Redo how the client requests out-of-band execution

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Commit cf869d5317 "qmp: support out-of-band (oob) execution" added a
general mechanism for command-independent arguments just for an
out-of-band flag:

    The "control" key is introduced to store this extra flag.  "control"
    field is used to store arguments that are shared by all the commands,
    rather than command specific arguments.  Let "run-oob" be the first.

However, it failed to reject unknown members of "control".  For
instance, in QMP command

    {"execute": "query-name", "id": 42, "control": {"crap": true}}

"crap" gets silently ignored.

Instead of fixing this, revert the general "control" mechanism
(because YAGNI), and do it the way I initially proposed, with key
"exec-oob".  Simpler code, simpler interface.

An out-of-band command

    {"execute": "migrate-pause", "id": 42, "control": {"run-oob": true}}

becomes

    {"exec-oob": "migrate-pause", "id": 42}

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180703085358.13941-13-armbru@redhat.com>
[Commit message typo fixed]
This commit is contained in:
Markus Armbruster 2018-07-03 10:53:38 +02:00
parent 674ed7228f
commit 00ecec151d
6 changed files with 39 additions and 53 deletions
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18
docs/interop/qmp-spec.txt
View file

@ -92,12 +92,16 @@ Currently supported capabilities are:
The format for command execution is:
{ "execute": json-string, "arguments": json-object, "id": json-value,
"control": json-object }
{ "execute": json-string, "arguments": json-object, "id": json-value }
or
{ "exec-oob": json-string, "arguments": json-object, "id": json-value }
Where,
- The "execute" member identifies the command to be executed by the Server
- The "execute" or "exec-oob" member identifies the command to be
executed by the server. The latter requests out-of-band execution.
- The "arguments" member is used to pass any arguments required for the
execution of the command, it is optional when no arguments are
required. Each command documents what contents will be considered
@ -106,9 +110,6 @@ The format for command execution is:
command execution, it is optional and will be part of the response
if provided. The "id" member can be any json-value. A json-number
incremented for each successive command works fine.
- The optional "control" member further specifies how the command is
to be executed. Currently, its only member is optional "run-oob".
See section "2.3.1 Out-of-band execution" for details.
2.3.1 Out-of-band execution
---------------------------
@ -129,9 +130,6 @@ To be able to match responses back to their commands, the client needs
to pass "id" with out-of-band commands. Passing it with all commands
is recommended for clients that accept capability "oob".
To execute a command out-of-band, the client puts "run-oob": true into
execute's member "control".
If the client sends in-band commands faster than the server can
execute them, the server will eventually drop commands to limit the
queue length. The sever sends event COMMAND_DROPPED then.
@ -274,7 +272,7 @@ S: { "timestamp": { "seconds": 1258551470, "microseconds": 802384 },
3.7 Out-of-band execution
-------------------------
C: { "execute": "migrate-pause", "id": 42, "control": { "run-oob": true } }
C: { "exec-oob": "migrate-pause", "id": 42 }
S: { "id": 42,
"error": { "class": "GenericError",
"desc": "migrate-pause is currently only supported during postcopy-active state" } }