Re: [PATCH v6 COLO 07/15] implement the cmdline for COLO

[Ian Campbell <ian.campbell@citrix.com>]

On Mon, 2015-06-08 at 11:45 +0800, Yang Hongyang wrote:
> From: Wen Congyang <wency@cn.fujitsu.com>
> 
> Add a new option -c to the command 'xl remus'. If you want
> to use COLO HA instead of Remus HA, please use -c option.
> 
> Update man pages to reflect the addition of a new option to
> 'xl remus' command.
> 
> Also add a new option -c to the internal command 'xl migrate-receive'.

I asked about whether COLO was an extension or a peer to Remus in an
earlier patch. the answer may have an impact here too.

> @@ -498,6 +501,11 @@ Disable network output buffering. Requires enabling unsafe mode.
>  
>  Disable disk replication. Requires enabling unsafe mode.
>  
> +=item B<-c>
> +
> +Enable COLO HA. It is conflict with B<-i> and B<-b>, and memory

"It conflicts with" or "This conflicts with".

> +checkpoint compression must be disabled.
> +
>  =back
>  
>  =item B<pause> I<domain-id>
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 1145ae4..7df2466 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -811,6 +811,22 @@ int libxl_domain_remus_start(libxl_ctx *ctx, libxl_domain_remus_info *info,
>          goto out;
>      }
>  
> +    /* The caller must set this defbool */
> +    if (libxl_defbool_is_default(info->colo)) {
> +        LOG(ERROR, "colo mode must be enabled/disabled");

As I wondered earlier -- this suggests it should not be a defbool, or
that the interfaces should split.

> +        rc = ERROR_FAIL;
> +        goto out;
> +    }
> +
> +    if (libxl_defbool_val(info->colo)) {
> +        libxl_defbool_setdefault(&info->compression, false);

Assuming this isn't invalidated by the above comments, you should make
the existing:
 libxl_defbool_setdefault(&info->compression, true);
into 
 libxl_defbool_setdefault(&info->compression, libxl_defbool_val(colo));

and then do an error check later.

> +        if (libxl_defbool_val(info->compression)) {
> +            LOG(ERROR, "cannot use memory checkpoint compression in COLO mode");
> +            rc = ERROR_FAIL;
> +            goto out;
> +        }
> +    }
> +
>      libxl_defbool_setdefault(&info->allow_unsafe, false);
>      libxl_defbool_setdefault(&info->blackhole, false);
>      libxl_defbool_setdefault(&info->compression, true);
> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> index adfadd1..4bbadd3 100644
> --- a/tools/libxl/xl_cmdimpl.c
> +++ b/tools/libxl/xl_cmdimpl.c
> @@ -4273,6 +4273,9 @@ static void migrate_receive(int debug, int daemonize, int monitor,
>      dom_info.send_fd = send_fd;
>      dom_info.migration_domname_r = &migration_domname;
>      dom_info.checkpointed_stream = remus;
> +    if (remus == LIBXL_CHECKPOINTED_STREAM_COLO)
> +        /* COLO uses stdout to send control message to master */
> +        dom_info.quiet = 1;

Please set a const char * to either "COLO" or "Remus" here and use it
everywhere you've currently got an open coded decision on that.

>  
>      rc = create_domain(&dom_info);
>      if (rc < 0) {
> @@ -4287,7 +4290,8 @@ static void migrate_receive(int debug, int daemonize, int monitor,
>          /* If we are here, it means that the sender (primary) has crashed.
>           * TODO: Split-Brain Check.
>           */
> -        fprintf(stderr, "migration target: Remus Failover for domain %u\n",
> +        fprintf(stderr, "migration target: %s Failover for domain %u\n",
> +                remus == LIBXL_CHECKPOINTED_STREAM_COLO ? "COLO" : "Remus",
>                  domid);
>  
>          /*
> @@ -4304,15 +4308,21 @@ static void migrate_receive(int debug, int daemonize, int monitor,
>              rc = libxl_domain_rename(ctx, domid, migration_domname,
>                                       common_domname);
>              if (rc)
> -                fprintf(stderr, "migration target (Remus): "
> +                fprintf(stderr, "migration target (%s): "
>                          "Failed to rename domain from %s to %s:%d\n",
> +                        remus == LIBXL_CHECKPOINTED_STREAM_COLO ? "COLO" : "Remus",
>                          migration_domname, common_domname, rc);
>          }
>  
> +        if (remus == LIBXL_CHECKPOINTED_STREAM_COLO)
> +            /* The guest is running after failover in COLO mode */
> +            exit(rc ? -ERROR_FAIL: 0);
> +
>          rc = libxl_domain_unpause(ctx, domid);
>          if (rc)
> -            fprintf(stderr, "migration target (Remus): "
> +            fprintf(stderr, "migration target (%s): "
>                      "Failed to unpause domain %s (id: %u):%d\n",
> +                    remus == LIBXL_CHECKPOINTED_STREAM_COLO ? "COLO" : "Remus",
>                      common_domname, domid, rc);
>  
>          exit(rc ? -ERROR_FAIL: 0);
> @@ -4458,7 +4468,7 @@ int main_migrate_receive(int argc, char **argv)
>      int debug = 0, daemonize = 1, monitor = 1, remus = 0;
>      int opt;
>  
> -    SWITCH_FOREACH_OPT(opt, "Fedr", NULL, "migrate-receive", 0) {
> +    SWITCH_FOREACH_OPT(opt, "Fedrc", NULL, "migrate-receive", 0) {
>      case 'F':
>          daemonize = 0;
>          break;
> @@ -4470,8 +4480,10 @@ int main_migrate_receive(int argc, char **argv)
>          debug = 1;
>          break;
>      case 'r':
> -        remus = 1;
> +        remus = LIBXL_CHECKPOINTED_STREAM_REMUS;
>          break;
> +    case 'c':
> +        remus = LIBXL_CHECKPOINTED_STREAM_COLO;
>      }
>  
>      if (argc-optind != 0) {
> @@ -7958,15 +7970,18 @@ int main_remus(int argc, char **argv)
>      pid_t child = -1;
>      uint8_t *config_data;
>      int config_len;
> +    int interval = 0;
>  
>      memset(&r_info, 0, sizeof(libxl_domain_remus_info));
>      /* Defaults */
>      r_info.interval = 200;
>      libxl_defbool_setdefault(&r_info.blackhole, false);
> +    libxl_defbool_setdefault(&r_info.colo, false);
>  
> -    SWITCH_FOREACH_OPT(opt, "Fbundi:s:N:e", NULL, "remus", 2) {
> +    SWITCH_FOREACH_OPT(opt, "Fbundi:s:N:ec", NULL, "remus", 2) {
>      case 'i':
>          r_info.interval = atoi(optarg);
> +        interval = 1;

This duplication of r_info.interval and interval seems odd. Perhaps
interval is really "interval_was_set" but even so I'm not sure this
would be better achieved with some more refactoring.

>          break;
>      case 'F':
>          libxl_defbool_set(&r_info.allow_unsafe, true);
> @@ -7992,11 +8007,28 @@ int main_remus(int argc, char **argv)
>      case 'e':
>          daemonize = 0;
>          break;
> +    case 'c':
> +        libxl_defbool_set(&r_info.colo, true);
>      }
>  
>      domid = find_domain(argv[optind]);
>      host = argv[optind + 1];
>  
> +    if (libxl_defbool_val(r_info.colo)) {
> +        if (!interval)
> +            r_info.interval = 0;
> +
> +        if (r_info.interval || libxl_defbool_val(r_info.blackhole)) {
> +            perror("option -c is conflict with -i or -b");

"...-c conflicts with..."

> +            exit(-1);
> +        }
> +
> +        if (libxl_defbool_is_default(r_info.compression)) {
> +            perror("option -u must be specified when using COLO");

Then enforce it using setdefault I think instead of making the user jump
through a pointless hoop.

Ian.