[ClusterLabs] DLM connection channel switch take too long time (> 5mins)

[FeldHost™ Admin]

Hello Gang He,

which type of corosync rrp_mode you use? Passive or Active? Did you try test both? Also, what kernel version you use? I see some SCTP fixes in latest kernels.

> On 8 Mar 2018, at 08:52, Gang He <ghe at suse.com> wrote:
> 
> Hello list and David Teigland,
> 
> I got a problem under a two rings cluster, the problem can be reproduced with the below steps.
> 1) setup a two rings cluster with two nodes.
> e.g. 
> clvm1(nodeid 172204569)  addr_list eth0 10.67.162.25 eth1 192.168.152.240
> clvm2(nodeid 172204570)  addr_list eth0 10.67.162.26 eth1 192.168.152.103
> 
> 2) the whole cluster works well, then I put eth0 down on node clvm2, and restart pacemaker service on that node.
> ifconfig eth0 down
> rcpacemaker restart
> 
> 3) the whole cluster still work well (that means corosync is very smooth to switch to the other ring).
> Then, I can mount ocfs2 file system on node clvm2 quickly with the command 
> mount /dev/sda /mnt/ocfs2 
> 
> 4) Next, I do the same mount on node clvm1, the mount command will be hanged for about 5 mins, and finally the mount command is done.
> But, if we setup a ocfs2 file system resource in pacemaker,
> the pacemaker resource agent will consider ocfs2 file system resource startup failure before this command returns,
> the pacemaker will fence node clvm1. 
> This problem is impacting our customer's estimate, since they think the two rings can be switched smoothly.
> 
> According to this problem, I can see the mount command is hanged with the below back trace,
> clvm1:/ # cat /proc/6688/stack
> [<ffffffffa04b8f2d>] new_lockspace+0x92d/0xa70 [dlm]
> [<ffffffffa04b92d9>] dlm_new_lockspace+0x69/0x160 [dlm]
> [<ffffffffa04db758>] user_cluster_connect+0xc8/0x350 [ocfs2_stack_user]
> [<ffffffffa0483872>] ocfs2_cluster_connect+0x192/0x240 [ocfs2_stackglue]
> [<ffffffffa0577efc>] ocfs2_dlm_init+0x31c/0x570 [ocfs2]
> [<ffffffffa05c2983>] ocfs2_fill_super+0xb33/0x1200 [ocfs2]
> [<ffffffff8120e130>] mount_bdev+0x1a0/0x1e0
> [<ffffffff8120ea1a>] mount_fs+0x3a/0x170
> [<ffffffff81228bf2>] vfs_kern_mount+0x62/0x110
> [<ffffffff8122b123>] do_mount+0x213/0xcd0
> [<ffffffff8122bed5>] SyS_mount+0x85/0xd0
> [<ffffffff81614b0a>] entry_SYSCALL_64_fastpath+0x1e/0xb6
> [<ffffffffffffffff>] 0xffffffffffffffff
> 
> The root cause is in sctp_connect_to_sock() function in lowcomms.c,
> 1075
> 1076         log_print("connecting to %d", con->nodeid);
> 1077
> 1078         /* Turn off Nagle's algorithm */
> 1079         kernel_setsockopt(sock, SOL_TCP, TCP_NODELAY, (char *)&one,
> 1080                           sizeof(one));
> 1081
> 1082         result = sock->ops->connect(sock, (struct sockaddr *)&daddr, addr_len,
> 1083                                    O_NONBLOCK);  <<= here, this invoking will cost > 5 mins before return ETIMEDOUT(-110).
> 1084         printk(KERN_ERR "sctp_connect_to_sock connect: %d\n", result);
> 1085
> 1086         if (result == -EINPROGRESS)
> 1087                 result = 0;
> 1088         if (result == 0)
> 1089                 goto out;
> 
> Then, I want to know if this problem was found/fixed before? 
> it looks DLM can not switch the second ring very quickly, this will impact the above application (e.g. CLVM, ocfs2) to create a new lock space before it's startup.
> 
> Thanks
> Gang
> 
> 
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