Thursday, March 4, 2021

[389-users] Chain on Update problem

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 -

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)

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.

Is this by design, a bug, or an implementation fault on my behalf? Configuration below;


## 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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