A block commit moves data in the opposite direction of block pull.
Block pull reduces the chain length by dropping backing files after
data has been pulled into the top overlay, and is always safe; block
commit reduces the chain length by dropping overlays after data has
been committed into the backing file, and any files that depended
on base but not on top are invalidated at any point where they have
unallocated data that is now pointing to changed contents in base.
Both directions are useful, however: a qcow2 layer that is more than
50% allocated will typically be faster with a pull operation, while
a qcow2 layer with less than 50% allocation will be faster as a
commit operation. Committing across multiple layers can be more
efficient than repeatedly committing one layer at a time, but
requires extra support from the hypervisor.
This API matches Jeff Cody's proposed qemu command 'block-commit':
https://lists.gnu.org/archive/html/qemu-devel/2012-09/msg02226.html
Jeff's command is still in the works for qemu 1.3, and may gain
further enhancements, such as the ability to control on-error
handling (it will be comparable to the error handling Paolo is
adding to 'drive-mirror', so a similar solution will be needed
when I finally propose virDomainBlockCopy with more functionality
than the basics supported by virDomainBlockRebase). However, even
without qemu support, this API will be useful for _offline_ block
commits, by wrapping qemu-img calls and turning them into a block
job, so this API is worth committing now.
For some examples of how this will be implemented, all starting
with the chain: base <- snap1 <- snap2 <- active
+ These are equivalent:
virDomainBlockCommit(dom, disk, NULL, NULL, 0, 0)
virDomainBlockCommit(dom, disk, NULL, "active", 0, 0)
virDomainBlockCommit(dom, disk, "base", NULL, 0, 0)
virDomainBlockCommit(dom, disk, "base", "active", 0, 0)
but cannot be implemented for online qemu with round 1 of
Jeff's patches; and for offline images, it would require
three back-to-back qemu-img invocations unless qemu-img
is patched to allow more efficient multi-layer commits;
the end result would be 'base' as the active disk with
contents from all three other files, where 'snap1' and
'snap2' are invalid right away, and 'active' is invalid
once any further changes to 'base' are made.
+ These are equivalent:
virDomainBlockCommit(dom, disk, "snap2", NULL, 0, 0)
virDomainBlockCommit(dom, disk, NULL, NULL, 0, _SHALLOW)
they cannot be implemented for online qemu, but for offline,
it is a matter of 'qemu-img commit active', so that 'snap2'
is now the active disk with contents formerly in 'active'.
+ Similarly:
virDomainBlockCommit(dom, disk, "snap2", NULL, 0, _DELETE)
for an offline domain will merge 'active' into 'snap2', then
delete 'active' to avoid leaving a potentially invalid file
around.
+ This version:
virDomainBlockCommit(dom, disk, NULL, "snap2", 0, _SHALLOW)
can be implemented online with 'block-commit' passing a base of
snap1 and a top of snap2; and can be implemented offline by
'qemu-img commit snap2' followed by 'qemu-img rebase -u
-b snap1 active'
* include/libvirt/libvirt.h.in (virDomainBlockCommit): New API.
* src/libvirt.c (virDomainBlockCommit): Implement it.
* src/libvirt_public.syms (LIBVIRT_0.10.2): Export it.
* src/driver.h (virDrvDomainBlockCommit): New driver callback.
* docs/apibuild.py (CParser.parseSignature): Add exception.
The apibuild.py parser needs to be able to parse & ignore
any VIR_ENUM_IMPL/VIR_ENUM_DECL macros in the source. Add
some special case code to deal with this rather than trying
to figure out a generic syntax for parsing macros.
* apibuild.py: Special case VIR_ENUM_IMPL & VIR_ENUM_DECL
Qemu is adding the ability to do a partial rebase. That is, given:
base <- intermediate <- current
virDomainBlockPull will produce:
current
but qemu now has the ability to leave base in the chain, to produce:
base <- current
Note that current qemu can only do a forward merge, and only with
the current image as the destination, which is fully described by
this API without flags. But in the future, it may be possible to
enhance this API for additional scenarios by using flags:
Merging the current image back into a previous image (that is,
undoing a live snapshot), could be done by passing base as the
destination and flags with a bit requesting a backward merge.
Merging any other part of the image chain, whether forwards (the
backing image contents are pulled into the newer file) or backwards
(the deltas recorded in the newer file are merged back into the
backing file), could also be done by passing a new flag that says
that base should be treated as an XML snippet rather than an
absolute path name, where the XML could then supply the additional
instructions of which part of the image chain is being merged into
any other part.
* include/libvirt/libvirt.h.in (virDomainBlockRebase): New
declaration.
* src/libvirt.c (virDomainBlockRebase): Implement it.
* src/libvirt_public.syms (LIBVIRT_0.9.10): Export it.
* src/driver.h (virDrvDomainBlockRebase): New driver callback.
* src/rpc/gendispatch.pl (long_legacy): Add exemption.
* docs/apibuild.py (long_legacy_functions): Likewise.
Set up the types for the block pull functions and insert them into the
virDriver structure definition. Symbols are exported in this patch to
prevent
documentation compile failures.
* include/libvirt/libvirt.h.in: new API
* src/driver.h: add the new entry to the driver structure
* python/generator.py: fix compiler errors, the actual python bindings
* are
implemented later
* src/libvirt_public.syms: export symbols
* docs/apibuild.py: Extend 'unsigned long' parameter exception to this
* API
The current API build scripts will continue and exit with a zero
status even if they find problems. This has been the cause of many
build problems, or hidden build errors, in the past. Change the
scripts so they always exit with a non-zero status for any problems
they do not understand. Also turn off all debug output by default
so they respect $(AM_V_GEN)
* docs/Makefile.am: Use $(AM_V_GEN) for API/HTML scripts
* docs/apibuild.py, python/generator.py: Exit with non-zero status
if problems are found. Also be silent, not outputting any debug
messages.
* src/Makefile.am: Use $(AM_V_GEN) for ESX generator
* python/Makefile.am: Tweak rule
This fixes a number of issues most of them raised by Eric Blake on the
generated documentation output:
- parsing of "long long int" and similar
- add parsing of unions within a struct
- remove spurious " * " fron comments on structure fields and enums
- fix concatenation of base type and name in arrays
- extend XSLT to cope with union in structs
* docs/apibuild.py: fix and extend API extraction tool
* docs/newapi.xsl: extend the stylesheets to cope with union in
public structures
This fixes this three warnings from the parser by allowing the parser
to ignore some macros in the same way as it can ignore functions.
Parsing ./../include/libvirt/libvirt.h
Misformatted macro comment for _virSchedParameter
Expecting '* _virSchedParameter:' got '* virSchedParameter:'
Misformatted macro comment for _virBlkioParameter
Expecting '* _virBlkioParameter:' got '* virBlkioParameter:'
Misformatted macro comment for _virMemoryParameter
Expecting '* _virMemoryParameter:' got '* virMemoryParameter:'
Migration just seems to go from bad to worse. We already had to
introduce a second migration protocol when adding the QEMU driver,
since the one from Xen was insufficiently flexible to cope with
passing the data the QEMU driver required.
It turns out that this protocol still has some flaws that we
need to address. The current sequence is
* Src: DumpXML
- Generate XML to pass to dst
* Dst: Prepare
- Get ready to accept incoming VM
- Generate optional cookie to pass to src
* Src: Perform
- Start migration and wait for send completion
- Kill off VM if successful, resume if failed
* Dst: Finish
- Wait for recv completion and check status
- Kill off VM if unsuccessful
The problems with this are:
- Since the first step is a generic 'DumpXML' call, we can't
add in other migration specific data. eg, we can't include
any VM lease data from lock manager plugins
- Since the first step is a generic 'DumpXML' call, we can't
emit any 'migration begin' event on the source, or have
any hook that runs right at the start of the process
- Since there is no final step on the source, if the Finish
method fails to receive all migration data & has to kill
the VM, then there's no way to resume the original VM
on the source
This patch attempts to introduce a version 3 that uses the
improved 5 step sequence
* Src: Begin
- Generate XML to pass to dst
- Generate optional cookie to pass to dst
* Dst: Prepare
- Get ready to accept incoming VM
- Generate optional cookie to pass to src
* Src: Perform
- Start migration and wait for send completion
- Generate optional cookie to pass to dst
* Dst: Finish
- Wait for recv completion and check status
- Kill off VM if failed, resume if success
- Generate optional cookie to pass to src
* Src: Confirm
- Kill off VM if success, resume if failed
The API is designed to allow both input and output cookies
in all methods where applicable. This lets us pass around
arbitrary extra driver specific data between src & dst during
migration. Combined with the extra 'Begin' method this lets
us pass lease information from source to dst at the start of
migration
Moving the killing of the source VM out of Perform and
into Confirm, means we can now recover if the dst host
can't successfully Finish receiving migration data.
* include/libvirt/libvirt.h.in: some of the function type description
were broken so they could not be automatically documented
* src/util/event.c docs/apibuild.py: event.c exports one public API
so it needs to be scanned too, avoid a few warnings
* docs/Makefile.am (libvirt-api.xml libvirt-refs.xml): Generalize
apibuild.py to work in a non-srcdir build. Pass "srcdir" to it.
* docs/apibuild.py (rebuild): Honor the $srcdir envvar.
* src/internal.h (ATTRIBUTE_SENTINEL): New, it's a ggc feature and
protected as such
* src/util/buf.c (virBufferStrcat): Use it.
* src/util/ebtables.c (ebtablesAddRemoveRule): Use it.
* src/util/iptables.c (iptableAddRemoveRule: Use it.
* src/util/qparams.h (new_qparam_set, append_qparams): Use it.
* docs/apibuild.py: avoid breaking the API generator with that new
internal keyword macro
Implementation of tunnelled migration, using a Unix Domain Socket
on the qemu backend. Note that this requires very new versions of
qemu (0.10.7 at least) in order to get the appropriate bugfixes.
Signed-off-by: Chris Lalancette <clalance@redhat.com>
The python method help docs are copied across from the C
funtion comments, but in the process all line breaks and
indentation was being lost. This made the resulting text
and code examples completely unreadable. Both the API
doc extractor and the python generator were destroying
whitespace & this fixes them to preserve it exactly.
* docs/apibuild.py: Preserve all whitespace when extracting
function comments. Print function comment inside a <![CDATA[
section to fully preserve all whitespace. Look for the
word 'returns' to describe return values, instead of 'return'
to avoid getting confused with code examples including the
C 'return' statement.
* python/generator.py: Preserve all whitespace when printing
function help docs
* src/libvirt.c: Change any return parameter indicated by
'return' to be 'returns', to avoid confusing the API extractor
* docs/libvirt-api.xml: Re-build for fixed descriptions
* configure.in docs/* NEWS: release of 0.5.0
* po/*: updated from the translators and merged
* docs/apibuild.py src/libvirt.c: avoid some warnings at doc
generation time
daniel
* include/libvirt/libvirt.h include/libvirt/libvirt.h.in:
remove Xen centric comments patch from Guido Günther
* docs/apibuild.py: ignore VIR_DEPRECATED
* docs/libvirt-*.xml docs/html/libvirt-*.html: regenerated the
documentation for the API
Daniel
proxy/libvirt_proxy.c qemud/Makefile.am qemud/conf.c qemud/conf.h
qemud/dispatch.c qemud/internal.h qemud/protocol.h
src/driver.h src/internal.h src/libvirt.c src/libvirt_sym.version
src/proxy_internal.c src/proxy_internal.h src/qemu_internal.c
src/test.c src/virsh.c src/virterror.c src/xen_internal.c
src/xen_internal.h src/xend_internal.c src/xm_internal.c
src/xml.h src/xs_internal.c: applied patch from Richard Jones
adding virConnectGetCapabilities(), plus various small little
fixes
* docs/*: fixed the api extractor script and regenerated
Daniel
* include/libvirt/libvirt.h include/libvirt/libvirt.h.in src/driver.h
src/libvirt.c src/proxy_internal.c src/test.c src/virsh.c
src/xen_internal.c src/xend_internal.c src/xm_internal.c
src/xs_internal.c: added support for dumping core of domains
assuming a xend with the latest patch to do so.
Daniel
src/xen_internal.c: fixing the proxy installation, integrate in
the spec file and fix a few bugs in the proxy, seems to behave
correctly now.
* docs/apibuild.py docs/*: fixing the doc and API generator
Daniel
* src/driver.h src/libvirt.c src/test.c src/xen_internal.c
src/xend_internal.c src/xs_internal.c: started to fix some of
the driver related problem raised by Daniel Berrange, added a
ver version field to drivers.
Daniel
* include/libvirt.h include/libvirt.h.in: added intialization function
* include/virterror.h src/virterror.c: one more error code
* src/internal.h: first part of Jim's format checking
* src/libvirt.c src/xen_internal.[ch] src/xend_internal.[ch]
src/xs_internal.[ch]: initialization and registration of drivers
Daniel
src/xen_internal.h docs/apibuild.py: starting the refactoring,
first the direct Xen hypervisor module. New header describing the
entry points of a driver.
Daniel
docs/site.xsl: integates the examples page in the web site
* docs//* : fixed generator and rebuilt the docs
* python/tests/basic.py python/tests/create.py: couple cleanups
Daniel
docs/libvir-refs.xml: fix XML API generation
* include/libvir.h src/libvir.c src/virsh.c: fix the info memory
API again, use KB, not bytes so that an unsigned long is sufficient.
Daniel
