[Gluster-users] GlusterFS cluster stalls if one server from the cluster goes down and then comes back up

[Daniel Kanchev]

Hi, everyone.

We are using GlusterFS configured in the following way:

[root at web1 ~]# gluster volume info

Volume Name: share
Type: Replicate
Volume ID: hidden data on purpose
Status: Started
Number of Bricks: 1 x 3 = 3
Transport-type: tcp
Bricks:
Brick1: c10839:/gluster
Brick2: c10840:/gluster
Brick3: web3:/gluster
Options Reconfigured:
cluster.consistent-metadata: on
performance.readdir-ahead: on
nfs.disable: true
cluster.self-heal-daemon: on
cluster.metadata-self-heal: on
auth.allow: hidden data on purpose
performance.cache-size: 256MB
performance.io-thread-count: 8
performance.cache-refresh-timeout: 3

Here is the output of the status command for the volume and the peers:

[root at web1 ~]# gluster volume status
Status of volume: share
Gluster process                             TCP Port  RDMA Port  Online  Pid
------------------------------------------------------------------------------
Brick c10839:/gluster                       49152     0          Y
540
Brick c10840:/gluster                       49152     0          Y
533
Brick web3:/gluster                         49152     0          Y
782
Self-heal Daemon on localhost               N/A       N/A        Y
602
Self-heal Daemon on web3                    N/A       N/A        Y
790
Self-heal Daemon on web4                    N/A       N/A        Y
636
Self-heal Daemon on web2                    N/A       N/A        Y
523

Task Status of Volume share
------------------------------------------------------------------------------
There are no active volume tasks

[root at web1 ~]# gluster peer status
Number of Peers: 3

Hostname: web3
Uuid: b138b4d5-8623-4224-825e-1dfdc3770743
State: Peer in Cluster (Connected)

Hostname: web2
Uuid: b3926959-3ae8-4826-933a-4bf3b3bd55aa
State: Peer in Cluster (Connected)
Other names:
c10840.sgvps.net

Hostname: web4
Uuid: f7553cba-c105-4d2c-8b89-e5e78a269847
State: Peer in Cluster (Connected)

All in all, we have three servers that are servers and actually store the
data and one server which is just a peer and is connected to one of the
other servers.

*The Problem*: If any of the 4 servers goes down then the cluster continues
to work as expected. However, once this server comes back up then the whole
cluster stalls for a certain period of time (30-120 seconds). During this
period no I/O operations could be executed and the apps that use the data
on the GlusterFS simply go down because they cannot read/write any data.

We suspect that the issue is related to the self-heal daemons but we are
not sure. Could you please advice how to debug this issue and what could be
causing the whole cluster to go down. If it is the self-heal as we suspect
do you think it is ok to disable it. If some of the settings are causing
this problem could you please advice how to configure the cluster to avoid
this problem.

If any info from the logs is requested please let us know what do you need.

Thanks in advance!

Regards,
Daniel
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