On 5 Mar 2021, at 12:03, Grant Byers
<Grant.Byers(a)aarnet.edu.au> wrote:
Hi All,
Version: 1.3.10
In our environment, we'd like to use a chaining backend to push BIND operations up to
masters by way of the consumer (rather than client referral). We'd like to do this to
ensure password lockout attributes are propagated to all consumers equally via our
standard replication agreements. This is described here -
https://directory.fedoraproject.org/docs/389ds/howto/howto-chainonupdate.....
NOTE, we do not have hubs in our topology. Just masters and consumers, so no intermediate
chaining.
We tested this process in our environment and it worked beautifully until we took it to
production. Currently, we have just 2 masters and they are both sitting on some
over-subscribed hardware that suffers from I/O starvation at certain times of the day. The
plan is to scale out our masters eventually, but we're a little hamstrung with other
projects and priorities. It worked extremely well until that time of day when masters
suffered from I/O starvation, and hence, very long I/O wait times. This is generally short
lived and happens at alternate times of the day for each of the masters. However, it seems
that once both nsfarmservers have "failed", there is never any attempt by the
consumer to retry them. This leads to bind errors as follows;
ldapwhoami -x -D "<binddn>" -W
Enter LDAP Password:
ldap_bind: Operations error (1)
additional info: FARM SERVER TEMPORARY UNAVAILABLE
Except it is not temporary. It never recovers, even though all members of nsfarmservers
are now healthy again (and are never unhealthy at the same time). We can confirm this by
performing binds from the consumers directly against the masters. I thought that setting
nsConnectionLife to something larger than 0 (indefinite) would help this, but it has not.
The chain on update appears to use the chaining plugin timeouts, so you could look at
adjusting these parameters which may help.
nsBindTimeout
nsOperationTimeout
nsBindRetryLimit
nsMaxResponseDelay
nsMaxTestResponseDelay
Is this by design, a bug, or an implementation fault on my behalf? Configuration below;
Thanks,
Grant
## On masters, create a dedicated user for chaining backend
dn: cn=proxy,cn=config
objectClass: person
objectClass: top
cn: proxy
sn: admin
## On all consumers, create chaining backend;
dn: cn=chainbe1,cn=chaining database,cn=plugins,cn=config
objectclass: top
objectclass: extensibleObject
objectclass: nsBackendInstance
nsslapd-suffix: <suffix>
nsfarmserverurl: ldaps://<master1>:636 <master2>:636/
nsMultiplexorBindDN: <binddn>>
nsMultiplexorCredentials: <bindpw>
nsCheckLocalACI: on
nsConnectionLife: 30
cn: chainbe1
## On all consumers, add the backend and repl_chain_on_update function
dn: cn="<suffix>",cn=mapping tree,cn=config
changetype: modify
add: nsslapd-backend
nsslapd-backend: chainbe1
-
add: nsslapd-distribution-plugin
nsslapd-distribution-plugin: libreplication-plugin
-
add: nsslapd-distribution-funct
nsslapd-distribution-funct: repl_chain_on_update
## On all servers, enable global pasword policy
dn: cn=config
changetype: modify
replace: passwordIsGlobalPolicy
passwordIsGlobalPolicy: on
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—
Sincerely,
William Brown
Senior Software Engineer, 389 Directory Server
SUSE Labs, Australia