Hello,
thank you for your advices and sorry to not have detailed infra
ismael> I'm currently benchmarking new hardware aimed to serve around ismael> 70k users For now, our IMAP server have 13k users.
This doesn't help us help you. Is this a new rasperry Pi 4? Is it a Dual CPU AMD Rzyzen with 128gb of memory and fast NVMe disks? What is your system setup?
Sorry, I have two servers to bench :
first one (a model like our current IMAP servers) is 18To HDD, 256Go RAM, 8c/16th
second (new one aimed to serve many more customers) is 24 x 14 TO (HDD SAS), 192GB DDR4 2,6Ghz, 12c/24t - 2.4GHz/3.5GHz
OS is FreeBSD 12.2
ismael> To run imaptest, I've spwan some bench clients.
Are these tests run from remote hosts? What kind of network are you using?
Yes, imaptest is running from kvm remote virtual machines in the same DC. They are some networks hops between them, but few.
ismael> Each bench client can run imaptest with 1000 clients. ismael> More than 1000 clients will load CPU of this bench client
ismael> imaptest command (command are chosen from usage stat on our other IMAP servers):
ismael> imaptest host=xxxxx port=xxx userfile=userfile mbox=/root/dovecot-crlf ismael> pass=sxxxx seed=123 clients=1000 select=194 uidfetch=94 noop=70 ismael> status=82 append=49 fetch=276 list=12 store=19 expunge=22 ismael> msubs=4 search=4 logout=1 delete=81 no_pipelining
ismael> With one bench client, everything runs smoothly.
ismael> # ps aux | grep dovecot | awk '{print $11,$12,$13,$14,$15,$16,$17,$18}' | sort | uniq -c ismael> 1 anvil: [221 connections] (anvil) ismael> 1 auth: [13 wait, 0 passdb, 0 userdb] (auth) ismael> 1 dovecot/config ismael> 1 dovecot/imap ismael> 84 dovecot/imap-login ismael> 1 dovecot/log ismael> 20 dovecot/pop3-login ismael> 1 grep dovecot ismael> 1 stats: [1307 connections] (stats)
ismael> When a second instance bench instance start imaptest, clients ismael> of first and second instance begin to stall :
ismael> 1400 stalled for 20 secs in command: 1 LOGIN"fakeuser644@mailbench...." "password"
So how is your dovecot authentication setup? Are you using a mysql backend? LDAP? Where is the server you're querying against? Are you running mysql on the same server you're running dovecot on?
In production, we use a remote galera cluster. On benchmarking, for now, I use static for passdb and a file for userdb.
Are you running multiple dovecot servers with dovecot director in front of them to help spread the load and to offer resilience if/when a backend server fails?
No. I'm directly benchmarking backend.
ismael> And :
ismael> # ps aux | grep dovecot | awk '{print $11,$12,$13,$14,$15,$16,$17,$18}' | sort | uniq -c ismael> 1 anvil: [221 connections] (anvil) ismael> 1 auth: [1227 wait, 0 passdb, 0 userdb] (auth) ismael> 1 dovecot/config ismael> 1 dovecot/imap ismael> 37 dovecot/imap-login ismael> 1 dovecot/log ismael> 20 dovecot/pop3-login ismael> 1 grep dovecot ismael> 1 stats: [680 connections] (stats)
ismael> Every auth go in wait, number of connection decreases.
ismael> Using mysql or a password file give same results.
Where is mysql located?
Remote one, but I'll go, for now, with a passwd-file to exclude potentials DB problems at the beginning of benchmarking.
ismael> I have used different values for service_count with also no success.
Post your configuration details.
#doveconf -n
auth_cache_negative_ttl = 0 auth_cache_size = 100 M auth_cache_ttl = 2 mins auth_failure_delay = 5 secs auth_master_user_separator = * auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@%+ auth_username_translation = %@ auth_verbose = yes auth_worker_max_count = 500 base_dir = /var/run/dovecot/ default_client_limit = 100000 disable_plaintext_auth = no imap_idle_notify_interval = 30 secs listen = xxxxxxxxxxxx login_greeting = xxxxxxxxxxxxxxxxxx login_trusted_networks = xxxxxxxxxxxxxxxxxxx mail_gid = xxxx mail_uid = xxxx mailbox_list_index = no namespace { inbox = yes location = prefix = INBOX. separator = . type = private } namespace { hidden = yes inbox = no list = no location = prefix = separator = . type = private } passdb { args = password=#hidden_use-P_to_show# driver = static } plugin { acl = vfile quota = maildir:User quota } protocols = imap pop3
service anvil { client_limit = 97000 unix_listener anvil-auth-penalty { mode = 00 } } service auth-worker { client_limit = 1 idle_kill = 0 process_limit = 6000000 process_min_avail = 0 service_count = 1 vsz_limit = 18446744073709551615 B } service auth { client_limit = 0 idle_kill = 0 process_limit = 1 process_min_avail = 1 service_count = 0 vsz_limit = 1000 M } service imap-login { client_limit = 26000 process_min_avail = 16 service_count = 0 vsz_limit = 1 G } service imap { drop_priv_before_exec = yes process_limit = 10000 } service pop3-login { service_count = 0 } service pop3 { drop_priv_before_exec = yes process_limit = 10000 } ssl = no
userdb { driver = passwd-file args = username_format=%Ln /usr/local/etc/dovecot/passwd-file default_fields = uid=xxxx gid=xxxx
} verbose_proctitle = yes version_ignore = yes protocol imap { imap_max_line_length = 64 k mail_max_userip_connections = 100000 mail_plugins = quota imap_quota acl } protocol pop3 { mail_max_userip_connections = 100 mail_plugins = quota pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, size=%s pop3_uidl_format = %f }
ismael> I think my use of imaptest could be false.
It could be. Are you thinking that 2000 users will all be logging into the system at the same time?
No, except when a backend is restarted, so I put delay on imaptest command :
imaptest host=xxx port=143 userfile=userfile mbox=/root/dovecot-crlf pass=password seed=123 clients=1000 delay=5 secs=3600 select=194 uidfetch=94 noop=70 status=82 append=49 fetch=276 list=12 store=19 expunge=22 msubs=4 search=4 logout=10 delete=81 no_pipelining
ismael> My understanding of service auth is limited for now because ismael> I'm quite new to Dovecot (I have previously worked with ismael> Cyrus).
Can't really give you any hints until you tell us more about your setup.
I understand, sorry again, hoping this new details are enough.
Thanks, Ismaël