MariaDB - Replication. Slave Lagging Behind For an Interval

Question

So I have 1 Master Server and 2 Slave servers running (CentOS-7). I have installed MariaDB-10.1.48 on all the servers. I implemented replication using GTID. All things were working well but an issue arose when I tried to add the 2nd Slave to replication. I am monitoring the servers through Maxscale. Both servers sync the GTID correctly but as soon as Master gets a lot of writes instantly (both users + bots are running), Slave 1 catches up quickly with Master but Slave 2 takes time, when I run show slave status - it says Seconds_behind_master = seconds(up to 50-60) then suddenly it drops to (0). The cnf file of both S1 and S2 are the same and in fact, S2 has a lot more hard disk and CPU power than S1. I have tried looking at things but could not find a solution. I am attaching the cnf file. This file is the same for master and both slaves except the server_id which is of course unique. Any suggestion is greatly appreciated.

slave-skip-errors = 1062
socket=/var/lib/mysql/mysql.sock
datadir=/var/lib/mysql

gtid_strict_mode=1
log_slave_updates=1

sql-mode=""
slow_query_log
slow_query_log_file=/var/log/mysql/mysql-slow.log
long_query_time=2.0
log-error =  /var/log/mysql/mysql-error.log
binlog_format=MIXED
max_connect_errors=2000


server-id = unique_for_every_server
bind-address = 0.0.0.0
log_bin = /var/log/mysql/mysql-bin.log


binlog_do_db = some DBs (main + mysql + informmation_schema)

binlog-ignore-db= (some DBs)


replicate_do_db= some DBs (main + mysql + informmation_schema)

replicate-ignore-db= some DBs

log_bin = /var/log/mysql/mysql-bin.log
log_bin_index =/var/log/mysql/mysql-bin.log.index
relay_log = /var/log/mysql/mysql-relay-bin
relay_log_index = /var/log/mysql/mysql-relay-bin.index

default-time-zone='-04:00'

max_allowed_packet = 1024M

wait_timeout = 60000
interactive_timeout= 60000
connect_timeout= 60000

table_cache = 2048
sort_buffer_size = 100M
thread_concurrency = 500
innodb_thread_concurrency = 0
innodb_read_io_threads = 64
innodb_write_io_threads = 64
query_cache_size = 100M
query_cache_limit = 150M
tmp_table_size = 100M
innodb_buffer_pool_size = 500M
innodb_additional_mem_pool_size = 20M
join_buffer_size=500M
table_open_cache = 7000
key_buffer_size = 50M
thread_cache_size = 50
key_buffer_size  = 150M
read_buffer_size = 100M
read_rnd_buffer_size = 50M
key_buffer = 100M

max_connections = 2000

Answer 1

I just added innodb_flush_log_at_trx_commit = 2 in /my.cnf/ file and the problem was solved.