Hi guys, I'm working on a pre migration checks implementation. The patch files attached provide a framework to execute pre-migration-checks before the domain migration. ================================================================ 1 - FRAMEWORK OVERVIEW ================================================================ Pre-Migration-Checks are enabled by adding a "--pmc" option in "virsh migrate" command $ virsh migrate --pmc ... In this way, before the execution of function virDomainMigrate(), an array of "checks" are performed. Return value of every check set if the migration will continue or not. ================================================================ 2 - FRAMEWORK STRUCTURE ================================================================ Every check is defined in the file libvirt/src/util/pmc.c Check list is defined by object "chklist". This is a struct defined as static virPMCCheckList chklist = { .count = 2, .check = {&chk1,&chk2,NULL} }; where "count" define the current array size, and "check" is an array of pointer to virPMCCheck object. virPMCCheck is a stuct defined as struct _virPMCCheck { const char *name; virPMCCheckRun run; }; where "name" is the name of the check needed for debugging messages, and "run" is a pointer to check function. ================================================================ 3 - HOW TO ADD NEW CHECK ================================================================ Adding new check is very simple! You have to define a check funcion as static int pmcCheckFooCheck(virDomainPtr domain, virConnectPtr dconn) { /* do something */ return CHECK_SUCCESS } then you have to define a "check-hook" as static virPMCCheck chk3 = { .name = "this is fooCheck", .run = pmcCheckFooCheck }; and update the object "chklist" static virPMCCheckList chklist = { .count = 3, /* previous value was 2 */ .check = {&chk1,&chk2,&chk3,NULL} /* previous content not * include a pointer to * chk3 object */ }; ================================================================ 4 - POSSIBLE ENHANCHEMENT ================================================================ 1. Adding infos in _virPMCCheck struct about check security level. Example: if a check with level CRITICAL return CHECK_FAIL, migration process is stopped, 2. Implementing framework not as util, but as driver. For example this can permit to define new checks by xml file. 3. Define external checks loadable by shared library. ================================================================ 5 - PATCH FILE DESCRIPTION ================================================================ file: datatypes.h.patch desc: define new type virPMCCheckRun define struct _virPMCCheck define struct _virPMCCheckList file: libvirt.c.patch desc: impement public API virDomainMigratePMC() file: libvirt.h.in.patch desc: impement public API virDomainMigratePMC() prototype define type virPMCCheck define type virPMCCheckPtr define type virPMCCheckList define type virPMCCheckListPtr define macro PMC_LIST_SIZE file: libvirt_public.syms desc: export public API virDomainMigratePMC() file: pmc.c.patch, pmc.h.patch desc: define and implements pre migration checks and some auxiliary functions. file: virsh.c.patch desc: add option "pmc" to virsh migrate command ================================================================ 6 - NOTES ================================================================ I start to implement this framework on git sources, but the latest sources produce a regress on my code. For this reason I applied my code on latest stable release of libvirt (0.8.1). What do you think about that? Is this a good approach to implement pre migration checks? Have you a suggestions? There is a possibility to include this patch in future libvirt distributions? Waiting for feedback... Paolo Smiraglia -- PAOLO SMIRAGLIA http://portale.isf.polito.it/paolo-smiraglia