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| = Monitor Protocol = | | = PAGE MOVED!! = |
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| The QEMU Monitor Protocol (QMP) project goal is to implement a [http://www.json.org JSON] based protocol for QEMU.
| | This page has moved to: http://wiki.qemu.org/QMP |
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| == Problem ==
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| QEMU does not provide a way for applications to control it at the "machine level", that is, the current existing interface (called Monitor) was designed for human interaction only.
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| This is very problematic for applications, for the following reasons: | |
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| * It is needed to parse output meant to be read by humans
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| * It is not reliable, because it is not always possible to know whether a command has been successfully executed or not
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| * It lacks support for asynchronous events
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| == Solution ==
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| Improve QEMU's Monitor to support a machine protocol with the following features:
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| * Use a lightweight, text-based, easy to parse data format (JSON has been chosen)
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| * Protocol stability should be guaranteed
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| * Asynchronous events support
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| * Parallel execution of commands
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| * A standard way to query protocol capabilities
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| A draft specification already exists and can be found [http://repo.or.cz/w/qemu/qmp-unstable.git?a=blob;f=QMP/qmp-spec.txt;h=3633b0dddd8205328d33d51f0d35ce1c76c0d593;hb=HEAD here].
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| == Project status (2009-10-20) ==
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| Most of the infrastructure has been merged, a JSON decoder should be merged in the next days. The important missing parts are the error framework and the JSON encoder.
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| Additionally, all command handlers need to be converted to use ''QObjects''. This work is in progress, but several handlers depend on the JSON decoder.
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| === Main building blocks ===
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| * QObject Layer ('''merged''')
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| * QObject Monitor infrastructure ('''merged''')
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| * JSON decoder ('''under review''')
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| * JSON encoder ('''not started''')
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| * Error framework ('''under discussion''')
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| === Command handlers conversion work ===
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| * Input through QDict ('''merged''')
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| * Output in QObject style ('''in progress''')
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| * Error handling ('''not started''')
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| == Libqmp ==
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| Although this is still under discussion, we are also going to provide a C library with a stable ABI.
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| The short-term plan is to have a simple API to send commands and receive responses, this way C clients do not need to have their own JSON implementation.
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| The long-term plan is to provide a full management API for QEMU.
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| == Development ==
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| The development takes place in the QMP unstable tree:
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| http://repo.or.cz/w/qemu/qmp-unstable.git
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| '''NOTE''': all branches in this repository are constantly rebased.
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| The ''master'' branch contains a functional QMP implementation for emission only (includes asynchronous messages). Protocol documentation can be found in the [http://repo.or.cz/w/qemu/qmp-unstable.git?a=tree;f=QMP;h=290262119cc6c9e07a6ef7a078384ef12c491e51;hb=HEAD QMP directory ] of the same branch.
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| == History ==
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| This is the fourth proposal for a machine protocol, past discussions can be found in the following links:
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| * http://www.mail-archive.com/qemu-devel@nongnu.org/msg14593.html
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| * http://lists.gnu.org/archive/html/qemu-devel/2009-01/msg00655.html
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| * http://lists.gnu.org/archive/html/qemu-devel/2009-06/msg01584.html
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