Notification of Changes
Applications that need change notification can use a persistent search or read the external change log:
Defined in the Internet-Draft, Persistent Search: A Simple LDAP Change Notification Mechanism, a persistent search is like a regular search that never returns. Every time a change happens in the scope of the search, the server returns an additional response:
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 rightsThe following command grants access under
dc=example,dc=comtoMy App:$
ldapmodify \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePasswordFile /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");) EOFStart 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 \ --trustStorePasswordFile /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, see the--persistentSearchoption in "Options".Make changes that impact the persistent search results.
To prepare to modify an entry, download the LDIF changes
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 \ --trustStorePasswordFile /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$ldapdelete \ --hostname localhost \ --port 1636 \ --useSsl \ --usePkcs12TrustStore /path/to/opendj/config/keystore \ --trustStorePasswordFile /path/to/opendj/config/keystore.pin \ --bindDN uid=kvaughan,ou=People,dc=example,dc=com \ --bindPassword bribery \ uid=tpierce,ou=People,dc=example,dc=comThe result is the following responses to the persistent search:
dn: uid=bjensen,ou=People,dc=example,dc=com objectClass: posixAccount objectClass: top objectClass: organizationalPerson objectClass: person objectClass: inetOrgPerson mail: bjensen@example.com roomNumber: 0209 preferredLanguage: en, ko;q=0.8 manager: uid=trigden, ou=People, dc=example,dc=com ou: Product Development ou: People givenName: Barbara telephoneNumber: +1 408 555 1862 sn: Jensen cn: Barbara Jensen cn: Babs Jensen homeDirectory: /home/bjensen facsimileTelephoneNumber: +1 408 555 1992 gidNumber: 1000 userPassword: {PBKDF2-HMAC-SHA256}10000:<hash> uidNumber: 1076 description: Hello, persistent search uid: bjensen l: San Francisco dn: uid=tpierce,ou=People,dc=example,dc=com objectClass: top objectClass: inetOrgPerson objectClass: posixAccount objectClass: organizationalPerson objectClass: person mail: tpierce@example.com roomNumber: 1383 manager: uid=scarter, ou=People, dc=example,dc=com ou: Accounting ou: People givenName: Tobias telephoneNumber: +1 408 555 1531 sn: Pierce cn: Tobias Pierce homeDirectory: /home/tpierce facsimileTelephoneNumber: +1 408 555 9332 gidNumber: 1000 userPassword: {PBKDF2-HMAC-SHA256}10000:<hash> uidNumber: 1042 uid: tpierce l: Bristol departmentNumber: 1000 preferredLanguage: en-gb street: Broad Quay House, Prince StreetIf the data is replicated, the results include the entry
dc=example,dc=com. Replication updates theds-sync-*operational attributes ondc=example,dc=com, and those changes appear in the results because the entry is in the scope of the persistent search.Terminate the persistent search.
Interrupt the command with CTRL+C (
SIGINT) orSIGTERM:$
kill -s SIGTERM $PSEARCH_PID
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 seen. 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 uid=admin to read the change log. Other accounts require sufficient access and privileges to read the change log. For instructions, see "Let a User Read the Changelog":
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 \ --trustStorePasswordFile /path/to/opendj/config/keystore.pin \ --bindDN uid=admin \ --bindPassword password \ --baseDN cn=changelog \ --control "ecl:false" \ "(&)" \ changes changeLogCookie targetDN# Public changelog exchange control(1.3.6.1.4.1.26027.1.5.4): <COOKIE1> dn: replicationCSN=<CSN1>,dc=example,dc=com,cn=changelog changes:: cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldyBkZXNjcmlwdGlvbgotCnJlcGxhY2U6IG1vZGlmaWVyc05hbWUKbW9kaWZpZXJzTmFtZTogdWlkPWJqZW5zZW4sb3U9UGVvcGxlLGRjPWV4YW1wbGUsZGM9Y29tCi0KcmVwbGFjZTogbW9kaWZ5VGltZXN0YW1wCm1vZGlmeVRpbWVzdGFtcDogMjAxNjEwMTQxNTA5MTJaCi0K targetDN: uid=bjensen,ou=People,dc=example,dc=com changeLogCookie: <COOKIE1> # Public changelog exchange control(1.3.6.1.4.1.26027.1.5.4): <COOKIE2> dn: replicationCSN=<CSN2>,dc=example,dc=com,cn=changelog changes:: cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldywgaW1wcm92ZWQgZGVzY3JpcHRpb24KLQpyZXBsYWNlOiBtb2RpZmllcnNOYW1lCm1vZGlmaWVyc05hbWU6IHVpZD1iamVuc2VuLG91PVBlb3BsZSxkYz1leGFtcGxlLGRjPWNvbQotCnJlcGxhY2U6IG1vZGlmeVRpbWVzdGFtcAptb2RpZnlUaW1lc3RhbXA6IDIwMTYxMDE0MTUwOTE5WgotCg== 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 the first change:
$
base64 decode --encodedData cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldyBkZXNjcmlwdGlvbgotCnJlcGxhY2U6IG1vZGlmaWVyc05hbWUKbW9kaWZpZXJzTmFtZTogdWlkPWJqZW5zZW4sb3U9UGVvcGxlLGRjPWV4YW1wbGUsZGM9Y29tCi0KcmVwbGFjZTogbW9kaWZ5VGltZXN0YW1wCm1vZGlmeVRpbWVzdGFtcDogMjAxNjEwMTQxNTA5MTJaCi0Kreplace: description description: New description - replace: modifiersName modifiersName: uid=bjensen,ou=People,dc=example,dc=com - replace: modifyTimestamp modifyTimestamp: <timestamp> -Notice the
changeLogCookievalue, which has the formbase-dn:CSN. Here, CSN is a change sequence number.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 \ --trustStorePasswordFile /path/to/opendj/config/keystore.pin \ --bindDN uid=admin \ --bindPassword password \ --baseDN cn=changelog \ --control "ecl:false:$COOKIE1" \ "(&)" \ changes changeLogCookie targetDN# Public changelog exchange control(1.3.6.1.4.1.26027.1.5.4): <COOKIE2> dn: replicationCSN=<CSN2>,dc=example,dc=com,cn=changelog changes:: cmVwbGFjZTogZGVzY3JpcHRpb24KZGVzY3JpcHRpb246IE5ldywgaW1wcm92ZWQgZGVzY3JpcHRpb24KLQpyZXBsYWNlOiBtb2RpZmllcnNOYW1lCm1vZGlmaWVyc05hbWU6IHVpZD1iamVuc2VuLG91PVBlb3BsZSxkYz1leGFtcGxlLGRjPWNvbQotCnJlcGxhY2U6IG1vZGlmeVRpbWVzdGFtcAptb2RpZnlUaW1lc3RhbXA6IDIwMTYxMDE0MTUwOTE5WgotCg== targetDN: uid=bjensen,ou=People,dc=example,dc=com changeLogCookie: <COOKIE2>The following command decodes the changes:
$
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> -If you lose the cookie, start over from the earliest available change by sending a request with no cookie.