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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 3 of 3] tools/libxl: xl remus/remus-receive commands
On Mon, 2012-01-23 at 22:46 +0000, rshriram@xxxxxxxxx wrote:
> # HG changeset patch
> # User Shriram Rajagopalan <rshriram@xxxxxxxxx>
> # Date 1327358642 28800
> # Node ID 822536df4aeced5aee00f1f26299086faa622681
> # Parent 0446591bee86eb4e767d75b70c885549c7a3cfef
> tools/libxl: xl remus/remus-receive commands
>
> * xl remus (and its receive counterpart remus-receive) act as frontends
> to enable remus for a given domain.
> * At the moment, only memory checkpointing and blackhole replication are
> supported. Support for disk checkpointing and network buffering will
> be added in future.
> * xl remus borrows some aspects of xl migrate. Replication is currently
> done over a ssh connection. Future versions will use a low-overhead
> plain tcp socket for replication (similar to xend/remus).
Please also patch docs/man/xl.*.pod as required.
Other references to relevant documentation and/or the addition of such
documentation to the tree would also be useful.
>
> Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>
>
> diff -r 0446591bee86 -r 822536df4aec tools/libxl/libxl.c
> --- a/tools/libxl/libxl.c Mon Jan 23 14:44:00 2012 -0800
> +++ b/tools/libxl/libxl.c Mon Jan 23 14:44:02 2012 -0800
> @@ -466,6 +466,40 @@
> return ptr;
> }
>
> +int libxl_domain_remus_start(libxl_ctx *ctx, libxl_domain_remus_info *info,
> + uint32_t domid, int fd)
> +{
> + GC_INIT(ctx);
> + libxl_domain_type type = libxl__domain_type(gc, domid);
> + int rc = 0;
> +
> + if (info == NULL) {
> + LIBXL__LOG(ctx, LIBXL__LOG_ERROR,
> + "No remus_info structure supplied for domain %d", domid);
> + rc = -1;
> + goto remus_fail;
> + }
> +
> + /* TBD: Remus setup - i.e. attach qdisc, enable disk buffering, etc */
> +
> + /* Point of no return */
> + rc = libxl__domain_suspend_common(gc, domid, fd, type, /* live */ 1,
> + /* debug */ 0, info);
> +
> + /*
> + * With Remus, if we reach this point, it means either
> + * backup died or some network error occurred preventing us
> + * from sending checkpoints.
> + */
> +
> + /* TBD: Remus cleanup - i.e. detach qdisc, release other
> + * resources.
> + */
> + remus_fail:
> + GC_FREE;
> + return rc;
> +}
> +
> int libxl_domain_suspend(libxl_ctx *ctx, libxl_domain_suspend_info *info,
> uint32_t domid, int fd)
> {
> diff -r 0446591bee86 -r 822536df4aec tools/libxl/xl_cmdimpl.c
> --- a/tools/libxl/xl_cmdimpl.c Mon Jan 23 14:44:00 2012 -0800
> +++ b/tools/libxl/xl_cmdimpl.c Mon Jan 23 14:44:02 2012 -0800
> @@ -1814,7 +1814,7 @@
> * If we have daemonized then do not return to the caller -- this has
> * already happened in the parent.
> */
> - if ( !need_daemon )
> + if ( daemonize && !need_daemon )
What is this change for?
> exit(ret);
>
> return ret;
> @@ -5853,6 +5853,175 @@
> return ret;
> }
>
> +int main_remus_receive(int argc, char **argv)
Can this not be done as a flag to migrate-receive? Likewise is there
common code between the remus migrate and regular migration?
Is there any reason that remus would not benefit from the xl migration
protocol preamble?
> +{
> + int rc;
> + char *migration_domname;
> + struct domain_create dom_info;
> +
> + signal(SIGPIPE, SIG_IGN);
> + memset(&dom_info, 0, sizeof(dom_info));
> + dom_info.debug = 1;
> + dom_info.no_incr_generationid = 1;
> + dom_info.restore_file = "incoming checkpoint stream";
> + dom_info.migrate_fd = 0; /* stdin - will change in future*/
> + dom_info.migration_domname_r = &migration_domname;
> +
> + rc = create_domain(&dom_info);
I'm totally failing to see where the Remus'ness of this create_domain
comes from.
> + if (rc < 0) {
> + fprintf(stderr, "migration target (Remus): Domain creation failed"
> + " (code %d) domid %u.\n", rc, domid);
> + exit(-rc);
> + }
> +
> + /* If we are here, it means that the sender (primary) has crashed.
> + * If domain renaming fails, lets just continue (as we need the domain
> + * to be up & dom names may not matter much, as long as its reachable
> + * over network).
> + *
> + * If domain unpausing fails, destroy domain ? Or is it better to have
> + * a consistent copy of the domain (memory, cpu state, disk)
> + * on atleast one physical host ? Right now, lets just leave the domain
at least
> + * as is and let the Administrator decide (or troubleshoot).
> + */
> + fprintf(stderr, "migration target: Remus Failover for domain %u\n",
> domid);
> + if (migration_domname) {
> + rc = libxl_domain_rename(ctx, domid, migration_domname,
> + common_domname);
> + if (rc)
> + fprintf(stderr, "migration target (Remus): "
> + "Failed to rename domain from %s to %s:%d\n",
> + migration_domname, common_domname, rc);
> +
> + rc = libxl_domain_unpause(ctx, domid);
> + if (rc)
> + fprintf(stderr, "migration target (Remus): "
> + "Failed to unpause domain %s (id: %u):%d\n",
> + common_domname, domid, rc);
> + }
> +
> + return -rc;
> +}
> +
> +int main_remus(int argc, char **argv)
> +{
> + int opt, rc;
> + const char *ssh_command = "ssh";
> + char *host = NULL, *rune = NULL, *domain = NULL;
> +
> + int sendpipe[2], recvpipe[2];
> + int send_fd = -1, recv_fd = -1;
> + pid_t child = -1;
> +
> + uint8_t *config_data;
> + int config_len;
> +
> + libxl_domain_remus_info r_info;
> +
> + memset(&r_info, 0, sizeof(libxl_domain_remus_info));
> + /* Defaults */
> + r_info.interval = 200;
> + r_info.blackhole = 0;
> + r_info.compression = 1;
> +
> + while ((opt = def_getopt(argc, argv, "bui:s:", "remus", 2)) != -1) {
main_migrate handles a bunch of other options which might also be
interesting in the Remus case? Better would be to add all this as an
option to the std migrate.
> + switch (opt) {
> + case 0: case 2:
> + return opt;
> +
> + case 'i':
> + r_info.interval = atoi(optarg);
> + break;
> + case 'b':
> + r_info.blackhole = 1;
> + break;
> + case 'u':
> + r_info.compression = 0;
> + break;
> + case 's':
> + ssh_command = optarg;
> + break;
> + }
> + }
> +
> + domain = argv[optind];
> + host = argv[optind + 1];
> +
> + if (r_info.blackhole) {
> + find_domain(domain);
> + send_fd = open("/dev/null", O_RDWR, 0644);
> + if (send_fd < 0) {
> + perror("failed to open /dev/null");
> + exit(-1);
> + }
> + } else {
The following duplicates an awful lot of main_migrate which begs for
them to either be the same underlying command or at least for some
refactoring.
> +
> + if (!ssh_command[0]) {
> + rune = host;
> + } else {
> + if (asprintf(&rune, "exec %s %s xl remus-receive",
> + ssh_command, host) < 0)
> + return 1;
> + }
> +
> + save_domain_core_begin(domain, NULL, &config_data, &config_len);
> +
> + if (!config_len) {
> + fprintf(stderr, "No config file stored for running domain and "
> + "none supplied - cannot start remus.\n");
> + exit(1);
> + }
> +
> + MUST( libxl_pipe(ctx, sendpipe) );
> + MUST( libxl_pipe(ctx, recvpipe) );
> +
> + child = libxl_fork(ctx);
> + if (child==-1) exit(1);
> +
> + /* TODO: change this to plain TCP socket based channel
> + * instead of SSH.
There are good reasons for using ssh though. However the user can supply
another command which is not encrypted if they want to.
Whatever happens here the same arguments would apply to non-remus
migration so the changes should be done for both (or better the code
should be made more common.
Ian.
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