Notification of changes
Applications that need change notification can use a persistent search or read the external change log.
Use persistent search
Defined in the Internet-Draft, Persistent Search: A Simple LDAP Change Notification Mechanism, a persistent search is like a regular search that never stops returning results. Every time a change happens in the scope of the search, the server returns an additional response:
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Grant access to perform a persistent search, by adding an ACI to use the persistent search control.
Persistent searches consume server resources, so servers do not allow them by default. If an application does not have access, the request fails with an unavailable critical extension error:
The LDAP search request failed: 12 (Unavailable Critical Extension) Additional Information: The request control with Object Identifier (OID) "2.16.840.1.113730.3.4.3" cannot be used due to insufficient access rights
The following command grants access under
dc=example,dc=com
toMy App
:$ ldapmodify \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN uid=admin \ --bindPassword password << EOF dn: dc=example,dc=com changetype: modify add: aci aci: (targetcontrol = "PSearch") (version 3.0;acl "Allow Persistent Search for My App"; allow (read)(userdn = "ldap:///cn=My App,ou=Apps,dc=example,dc=com");) EOF
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Start the persistent search.
The following example initiates a persistent search, where notifications are sent for all update operations, only notifications about changed entries are returned, and no additional information are returned:
$ ldapsearch \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN 'cn=My App,ou=Apps,dc=example,dc=com' \ --bindPassword password \ --baseDN dc=example,dc=com \ --persistentSearch ps:all:true:false \ '(&)' >> /tmp/psearch.txt & $ export PSEARCH_PID=$!
Notice the search filter,
(&)
, which is always true, meaning that it matches all entries. For details on settings for a persistent search, refer to the--persistentSearch
option in ldapsearch Options. -
Make changes that impact the persistent search results.
Show commands
To prepare to modify an entry, save the following LDIF in a file named
description.ldif
:dn: uid=bjensen,ou=People,dc=example,dc=com changetype: modify replace: description description: Hello, persistent search
The following commands perform a modify operation, and a delete operation:
$ ldapmodify \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN uid=kvaughan,ou=People,dc=example,dc=com \ --bindPassword bribery << EOF dn: uid=bjensen,ou=People,dc=example,dc=com changetype: modify replace: description description: Hello, persistent search EOF $ ldapdelete \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN uid=kvaughan,ou=People,dc=example,dc=com \ --bindPassword bribery \ uid=tpierce,ou=People,dc=example,dc=com
Show persistent search results
The result is the following responses to the persistent search:
dn: uid=bjensen,ou=People,dc=example,dc=com objectClass: person objectClass: cos objectClass: oauth2TokenObject objectClass: inetOrgPerson objectClass: organizationalPerson objectClass: posixAccount objectClass: top classOfService: bronze cn: Barbara Jensen cn: Babs Jensen description: Hello, persistent search facsimileTelephoneNumber: +1 408 555 1992 gidNumber: 1000 givenName: Barbara homeDirectory: /home/bjensen l: San Francisco mail: bjensen@example.com manager: uid=trigden, ou=People, dc=example,dc=com oauth2Token: {"access_token":"123","expires_in":59,"token_type":"Bearer","refresh_token":"456"} ou: Product Development ou: People preferredLanguage: en, ko;q=0.8 roomNumber: 0209 sn: Jensen telephoneNumber: +1 408 555 1862 uid: bjensen uidNumber: 1076 userPassword: {PBKDF2-HMAC-SHA256}10:<hash> dn: uid=tpierce,ou=People,dc=example,dc=com objectClass: person objectClass: cos objectClass: inetOrgPerson objectClass: organizationalPerson objectClass: posixAccount objectClass: top classOfService: gold cn: Tobias Pierce departmentNumber: 1000 description: Description on ou=People diskQuota: 100 GB facsimileTelephoneNumber: +1 408 555 9332 gidNumber: 1000 givenName: Tobias homeDirectory: /home/tpierce l: Bristol mail: tpierce@example.com mailQuota: 10 GB manager: uid=scarter, ou=People, dc=example,dc=com ou: Accounting ou: People preferredLanguage: en-gb roomNumber: 1383 sn: Pierce street: Broad Quay House, Prince Street telephoneNumber: +1 408 555 1531 uid: tpierce uidNumber: 1042 userPassword: {PBKDF2-HMAC-SHA256}10:<hash>
If the data is replicated, the results include the entry
dc=example,dc=com
. Replication updates theds-sync-*
operational attributes ondc=example,dc=com
, and those changes appear in the results because the entry is in the scope of the persistent search. -
Terminate the persistent search.
Interrupt the command with CTRL+C (
SIGINT
) orSIGTERM
:$ kill -s SIGTERM $PSEARCH_PID
Use the external change log
You read the external change log over LDAP. When you poll the change log, you can get the list of updates that happened since your last request.
The external change log mechanism uses an LDAP control with OID 1.3.6.1.4.1.26027.1.5.4
.
This control allows the client application to bookmark the last changes observed.
The control returns a cookie that the application sends to the server to read the next batch of changes.
These steps show the client binding as directory superuser (uid=admin
) to read the change log.
Other accounts require sufficient access and privileges to read the change log.
For instructions, refer to Let a user read the changelog:
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Send an initial search request using the LDAP control with no cookie value.
In this example, two changes appear in the changelog:
$ ldapsearch \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN uid=admin \ --bindPassword password \ --baseDN cn=changelog \ --control "ecl:false" \ "(&)" \ changes changeLogCookie targetDN dn: cn=changelog dn: replicationCSN=<CSN1>,dc=example,dc=com,cn=changelog changes:: <base64Changes1> targetDN: uid=bjensen,ou=People,dc=example,dc=com changeLogCookie: <COOKIE1> dn: replicationCSN=<CSN2>,dc=example,dc=com,cn=changelog changes:: <base64Changes2> targetDN: uid=bjensen,ou=People,dc=example,dc=com changeLogCookie: <COOKIE2>
The changes are base64-encoded. You can decode them using the
base64
command. The following example decodes a change:$ base64 decode --encodedData cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldyBkZXNjcmlwdGlvbgotCnJlcGxhY2U6IG1vZGlmaWVyc05hbWUKbW9kaWZpZXJzTmFtZTogdWlkPWJqZW5zZW4sb3U9UGVvcGxlLGRjPWV4YW1wbGUsZGM9Y29tCi0KcmVwbGFjZTogbW9kaWZ5VGltZXN0YW1wCm1vZGlmeVRpbWVzdGFtcDogMjAxNjEwMTQxNTA5MTJaCi0K replace: description description: New description - replace: modifiersName modifiersName: uid=bjensen,ou=People,dc=example,dc=com - replace: modifyTimestamp modifyTimestamp: <timestamp> -
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To start reading a particular change in the changelog, provide the cookie with the control:
$ ldapsearch \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePassword:file /path/to/opendj/config/keystore.pin \ --bindDN uid=admin \ --bindPassword password \ --baseDN cn=changelog \ --control "ecl:false:$COOKIE1" \ "(&)" \ changes changeLogCookie targetDN dn: replicationCSN=<CSN2>,dc=example,dc=com,cn=changelog changes:: <base64Changes2> targetDN: uid=bjensen,ou=People,dc=example,dc=com changeLogCookie: <COOKIE2>
The following command decodes the change returned:
$ base64 decode --encodedData cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldywgaW1wcm92ZWQgZGVzY3JpcHRpb24KLQpyZXBsYWNlOiBtb2RpZmllcnNOYW1lCm1vZGlmaWVyc05hbWU6IHVpZD1iamVuc2VuLG91PVBlb3BsZSxkYz1leGFtcGxlLGRjPWNvbQotCnJlcGxhY2U6IG1vZGlmeVRpbWVzdGFtcAptb2RpZnlUaW1lc3RhbXA6IDIwMTYxMDE0MTUwOTE5WgotCg== replace: description description: New, improved description - replace: modifiersName modifiersName: uid=bjensen,ou=People,dc=example,dc=com - replace: modifyTimestamp modifyTimestamp: <timestamp> -
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If you lose the cookie, start over from the earliest available change by sending a request with no cookie.