Setting Resource Limits

This chapter shows you how to set resource limits that prevent directory clients from using an unfair share of system resources. In this chapter you will learn to:

  • Limit the resources used when a user searches the directory

  • Limit how long connections can remain idle before they are dropped

  • Limit the size of directory server requests

Limiting Search Resources

Well-written directory client applications limit the scope of their searches with filters that narrow the number of results returned. By default, OpenDJ only allows users with appropriate privileges to perform unindexed searches. You can further adjust additional limits on search operations, such as the following:

  • The lookthrough limit defines the maximum number of candidate entries OpenDJ considers when processing a search.

    The default lookthrough limit, which is set by using the global server property lookthrough-limit, is 5000.

    You can override the limit for a particular user by changing the operational attribute, ds-rlim-lookthrough-limit, on the user’s entry.

  • The size limit sets the maximum number of entries returned for a search.

    The default size limit, which is set by using the global server property size-limit, is 1000.

    You can override the limit for a particular user by changing the operational attribute, ds-rlim-size-limit, on the user’s entry.

  • The time limit defines the maximum processing time OpenDJ devotes to a search operation.

    The default time limit, which is set by using the global server property time-limit, is 1 minute.

    You can override the limit for a particular user by changing the operational attribute, ds-rlim-time-limit, on the user’s entry. Times for ds-rlim-time-limit are expressed in seconds.

  • The idle time limit defines how long OpenDJ allows idle connections to remain open.

    No default idle time limit is set. You can set an idle time limit by using the global server property idle-time-limit.

    You can override the limit for a particular user by changing the operational attribute, ds-rlim-idle-time-limit, on the user’s entry. Times for ds-rlim-idle-time-limit are expressed in seconds.

  • The maximum number of persistent searches can be set by using the global server property max-psearches.

To Set Search Limits For a User

  • Change the user entry to set the limits to override:

    $ cat limit.ldif
dn: uid=bjensen,ou=People,dc=example,dc=com
changetype: modify
add: ds-rlim-size-limit
ds-rlim-size-limit: 10

$ ldapmodify \
 --port 1389 \
 --bindDN "cn=Directory Manager" \
 --bindPassword password \
 --filename limit.ldif
Processing MODIFY request for uid=bjensen,ou=People,dc=example,dc=com
MODIFY operation successful for DN uid=bjensen,ou=People,dc=example,dc=com

    Now when Babs Jensen performs a search returning more than 10 entries, she sees the following message:

    Result Code:  4 (Size Limit Exceeded)
Additional Information:  This search operation has sent the maximum of
 10 entries to the client
To Set Search Limits For a Group

  1. Create an LDAP subentry to specify the limits using collective attributes:

    $ cat grouplim.ldif
dn: cn=Remove Administrator Search Limits,dc=example,dc=com
objectClass: collectiveAttributeSubentry
objectClass: extensibleObject
objectClass: subentry
objectClass: top
cn: Remove Administrator Search Limits
ds-rlim-lookthrough-limit;collective: 0
ds-rlim-size-limit;collective: 0
ds-rlim-time-limit;collective: 0
subtreeSpecification: {base "ou=people", specificationFilter "
 (isMemberOf=cn=Directory Administrators,ou=Groups,dc=example,dc=com)" }

$ ldapmodify \
 --port 1389 \
 --bindDN "cn=Directory Manager" \
 --bindPassword password \
 --defaultAdd \
 --filename grouplim.ldif
Processing ADD request for
 cn=Remove Administrator Search Limits,dc=example,dc=com
ADD operation successful for DN
 cn=Remove Administrator Search Limits,dc=example,dc=com

  2. Check the results:

    $ ldapsearch --port 1389 --baseDN dc=example,dc=com uid=kvaughan +|grep ds-rlim
ds-rlim-lookthrough-limit: 0
ds-rlim-time-limit: 0
ds-rlim-size-limit: 0

Limiting Idle Time

If you have applications that leave connections open for long periods, OpenDJ can end up devoting resources to maintaining connections that are no longer used. If your network does not drop such connections eventually, you can configure OpenDJ to drop them by setting the global configuration property, idle-time-limit. By default, no idle time limit is set.

If your network load balancer is configured to drop connections that have been idle for some time, make sure you set the OpenDJ idle time limit to a lower value than the idle time limit for the load balancer. This helps to ensure that idle connections are shut down in orderly fashion. Setting the OpenDJ limit lower than the load balancer limit is particularly useful with load balancers that drop idle connections without cleanly closing the connection and notifying the client and server.

OpenDJ does not enforce idle timeout for persistent searches:

 
$ dsconfig \
 set-global-configuration-prop \
 --port 4444 \
 --hostname opendj.example.com \
 --bindDN "cn=Directory Manager" \
 --bindPassword password \
 --set idle-time-limit:24h \
 --trustAll \
 --no-prompt

The example shown sets the idle time limit to 24 hours.

Limiting Maximum Request Size

The default maximum request size of 5 MB, set using the advanced connection handler property max-request-size, is sufficient to satisfy most client requests. Yet, there are some cases where you might need to raise the request size limit. For example, if clients add groups with large numbers of members, those add requests can go beyond the 5 MB limit:

$ dsconfig \
 set-connection-handler-prop \
 --port 4444 \
 --hostname opendj.example.com \
 --bindDN "cn=Directory Manager" \
 --bindPassword password \
 --handler-name "LDAP Connection Handler" \
 --set max-request-size:20mb \
 --trustAll \
 --no-prompt

The example shown sets the maximum request size on the LDAP connection handler to 20 MB.

Resource Limits and Proxied Authorization

Proxied authorization uses a standard LDAP control to permit an application to bind as one user and then carry out LDAP operations on behalf of other users.

When using proxied authorization as described in "Configuring Proxied Authorization" in the Directory Server Developer’s Guide know that the resource limits do not change when the user proxies as another user. In other words, resource limits depend on the bind DN, not the proxy authorization identity.