June 2007 - Devel - libvirt List Archives

[Libvir] Proposal: New virDomainLookup function to indicate Not found vs Error
by Richard W.M. Jones 29 Jun '07

29 Jun '07

virt-install has some code which waits for a domain to appear just after it has been created. It looks like the loop attached to the end of this email, and is functional but has two problems. Problem (1) is that self.conn.lookupByName doesn't distinguish between a "Not found" domain and an actual error. For example there is no way to tell the difference between being unable to contact xend (an actual error), and being able to contact xend, but xend not being able to find the domain (not found). As shown here: >>> import libvirt >>> conn = libvirt.open ("xen+tls:///") >>> d = conn.lookupByName ("Domain-0") >>> d = conn.lookupByName ("doesnotexist") [...] libvirt.libvirtError: virDomainLookupByName() failed then I deliberately kill the remote daemon: >>> d = conn.lookupByName ("doesnotexist") libvir: Remote error : Error in the push function. [...] The first exception is a Not found condition (not an error) whereas the second is an error. Problem (2) is that virterror is over anxious to print error messages to stderr, even if the caller can handle them and even if (as in the Not found case) they don't indicate errors. In practical terms this means that the virt-install loop attached below may print out 1 or 2 error messages even when it is functioning normally. You'll see an error like this appearing [sic]: libvir: Xen Daemon error : GET operation failed: Since it's difficult to change the LookupBy* functions without changing the ABI, I suspect that the best thing to do is going to be to add a new call with better semantics. Therefore I suggest: virDomainPtr * virDomainLookup (virConnectPtr conn, int flags, int id, char *str, int *error); where flags is one of: VIR_LOOKUP_BY_ID, VIR_LOOKUP_BY_NAME, VIR_LOOKUP_BY_UUID or VIR_LOOKUP_BY_UUID_STRING The return values are: ret = domain, *error = 0 => found it ret = NULL, *error = 0 => not found ret = NULL, *error = 1 => error (check virterror) Addition 1: There would be a similar function virNetworkLookup, but without needing the 'id' parameter because networks don't have IDs. Addition 2: Change the driver internals so that they don't call virterror in the not found case. (This requires quite a bit of rejigging in xend_internal, but is not too hard). Addition 3: Language bindings could be modified to detect this function and if present change their existing LookupBy* functions to use the new interface. Thoughts? Rich. ---------------------------------------------------- This is the troublesome loop: logging.debug("Created guest, looking to see if it is running") # sleep in .25 second increments until either a) we find # our domain or b) it's been 5 seconds. this is so that # we can try to gracefully handle domain creation failures num = 0 d = None while num < (5 / .25): # 5 seconds, .25 second sleeps try: d = self.conn.lookupByName(self.name) break except libvirt.libvirtError, e: logging.debug("No guest running yet " + str(e)) pass num += 1 time.sleep(0.25) -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] PATCH 0/20: Re-factor libvirtd / QEMU driver
by Daniel P. Berrange 28 Jun '07

28 Jun '07

The work to refactor the QEMU driver to use the regular libvirt driver API is now complete. The next 20 (!) patches provide fairly fine-grained steps refactoring the code. Aside from that which adds an event loop, and the very last one, they should all be pretty much straightforward refactoring with no functional change. With this patch series fully applied there is now only a single daemon which can serve both remote & QEMU drivers in one go, with no deadlock issues. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] libvirt 0.1.8 Help
by Omer Khalid 27 Jun '07

27 Jun '07

Hi, I have the following code working on libvirt 0.1.9: ######################################## conn = libvirt.openReadOnly(None) if conn == None: print 'Failed to open connection to the hypervisor' #sys.exit(1) try: domains = conn.listDomainsID() num = conn.numOfDomains() except: print 'Failed to find the list of domains' for i in range(num): try: dom0 = conn.lookupByID(domains[i]) domInfo = dom0.info() except: print "Unexpected error:", sys.exc_info() ############################################## For legacy reason, I have to get it working on libvirt 0.1.8 but I am constantly getting the following error: Unexpected error: (<class libvirt.libvirtError at 0xb7f49f2c>, < libvirt.libvirtError instance at 0xb7f4f2cc>, <traceback object at 0xb7f44c5c>) Any help would be much appreciated! Cheers Omer -- ---------------------------------------------------------- CERN – European Organization for Nuclear Research, IT Department, CH-1211 Geneva 23, Switzerland Phone: +41 (0) 22 767 2224 Fax: +41 (0) 22 766 8683 E-mail : Omer.Khalid(a)cern.ch Homepage: http://cern.ch/Omer.Khalid

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[Libvir] [PATCH] Move common buffer code to lib/ directory
by Richard W.M. Jones 26 Jun '07

26 Jun '07

I haven't quite got to my goal of removing _GNU_SOURCE (yet), but this patch along the way creates a lib/ subdirectory and moves the common buffer code (from qemud/buf.[ch] and in src/xml.[ch]) there. There are many, many places which call the buffer functions without checking the return value. I have manually verified / fixed up the calls which do bother to check return values, but not added any more checks where they don't. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] [PATCH] Add virConnectGetHostname and virConnectGetURI calls, virsh commands, and some related fixes
by Richard W.M. Jones 26 Jun '07

26 Jun '07

This patch adds two calls: /** + * virConnectGetHostname: + * @conn: pointer to a hypervisor connection + * + * This returns the system hostname on which the hypervisor is + * running (the result of the gethostname(2) system call). If + * we are connected to a remote system, then this returns the + * hostname of the remote system. + * + * Returns the hostname which must be freed by the caller, or + * NULL if there was an error. + */ +char * +virConnectGetHostname (virConnectPtr conn) and: +/** + * virConnectGetURI: + * @conn: pointer to a hypervisor connection + * + * This returns the URI (name) of the hypervisor connection. + * Normally this is the same as or similar to the string passed + * to the virConnectOpen/virConnectOpenReadOnly call, but + * the driver may make the URI canonical. If name == NULL + * was passed to virConnectOpen, then the driver will return + * a non-NULL URI which can be used to connect to the same + * hypervisor later. + * + * Returns the URI string which must be freed by the caller, or + * NULL if there was an error. + */ +char * +virConnectGetURI (virConnectPtr conn) It also fixes a kind of accidental memory leak which turns out not to be a memory leak. In the current version of libvirt CVS, when using remote connections, remote's private data is not freed by remote_internal.c. However it turns out that it _is_ freed by qemuNetworkClose. Obviously some confusion there, but this patch fixes that. (Fixing that is a dependency of this patch, which is why the two are done together in one patch). I've added "virsh hostname" and "virsh uri" commands: $ src/virsh -c test:///default uri test:///default $ src/virsh -c test:///default hostname localhost.localdomain (Yeah, I haven't set the hostname on this machine ...) I've updated the Xen, test and remote drivers to support the calls. However I didn't update qemu because of Dan's big changes to qemu. Once we have decided whether to put in Dan's changes, I'll go back and implement this for qemu. (I'm actually not sure I would need to implement them, if remote supports the calls already). I haven't updated the Python bindings, but will do so next. I decided not to implement the proposed virConnectGetTransport call because I think it needs more thought. It would obviously be useful to find out whether the current connection is local or remote, encrypted or unencrypted, authenticated or unauthenticated, because all of these things could be usefully communicated back to the user by icons in virt-manager. Simply returning the transport name doesn't really do this. The user might also want to find out _how_ the session is encrypted (what TLS parameters are in use), and again a simple string can't do that. Before applying this patch you will need to do: rm qemud/remote_dispatch_localvars.h \ qemud/remote_dispatch_proc_switch.h \ qemud/remote_dispatch_prototypes.h \ qemud/remote_protocol.c \ qemud/remote_protocol.h and after applying you will need to do: make -C qemud remote_protocol.c Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] [PATCH] Add virDomainGetConnect and virNetworkGetConnect
by Richard W.M. Jones 25 Jun '07

25 Jun '07

As described in this thread: https://www.redhat.com/archives/libvir-list/2007-June/thread.html#00352 * These functions don't change the reference count for virConnectPtr. It's be a pain in the neck for callers otherwise. * I haven't changed the Python bindings, because I'm not confident enough that I can do that correctly and keep it backwards compatible for all callers (and anyway what would happen if newer Python bindings were used together with an older libvirt?). However I did add a comment to the generator noting that this could be changed in future. * I tested this with the OCaml bindings with no apparent ill-effects. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] [PATCH] Cleanup - remove virDomainKernel structure
by Richard W.M. Jones 25 Jun '07

25 Jun '07

... unless anyone can remember what it was for. It still builds fine without it. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] OCaml bindings for libvirt
by Richard W.M. Jones 25 Jun '07

25 Jun '07

Weekend project: http://et.redhat.com/~rjones/ocaml-libvirt/ Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] Useful additional functions for libvirt
by Richard W.M. Jones 25 Jun '07

25 Jun '07

[I haven't implemented any of these yet, but if people think they're a good idea, or at least not an actively bad idea, then I'll post a patch.] virDomainGetConnection virNetworkGetConnection Purpose: Given a virDomainPtr or virNetworkPtr, obtain the virConnectPtr. Reason: All the language bindings to libvirt need to keep the virConnectPtr separately alongside the virDomain/NetworkPtr, in the main so that they can query if an error has happened from inside some deep call. This is wasteful since the connection pointer is already included in the virDomain or virNetwork structure, so we should just provide a call to get it. virConnectGetHostname virConnectGetTransport virConnectGetURI Purpose: Get the remote hostname, remote transport (tls, ssh, etc.), and URI. Reason: In virt-manager it would be nice to display the remote hostname. However doing this at the moment requires parsing the connection URI, which is duplicated code and also significantly complicated. Instead, allow the remote driver to just give us this information, and in non-remote cases default to something sensible. The case for the other two calls is weaker, but it might still be useful to know something about the security of the actual transport selected, and also to not have to keep the URI around with the connection (we might also canonicalise the transport for the user). virConnectPing Purpose: "Ping" the hypervisor to see if its up. Reason: Since we now support remote connections, there is a much more signficant chance that we will lose contact with the hypervisor, for example if the host goes down. This will do some very minimal operation to cheaply test whether the hypervisor can be contacted. Of course we could do something like 'virConnectNumOfDomains', but it's not clear to me that this operation would always be cheap (eg. if we had to implement it through xend). Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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[Libvir] [PATCH] Allow maxnames to be 0 in List{, Defined}{Domains, Networks}
by Richard W.M. Jones 25 Jun '07

25 Jun '07

It seems a bit pathological to check if maxNames <= 0 and throw an error if it is 0. In particular if you don't have any defined domains or networks (both fairly common scenarios) then this causes an error when you just pass the result of NumOfNetworks straight into ListNetworks. Backend drivers & QEMU seem to have no problem with maxNames being zero, so let's allow it. Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

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