SLAPD-ASYNCMETA(5) File Formats Manual SLAPD-ASYNCMETA(5)
NAME
slapd-asyncmeta - asynchronous metadirectory backend to slapd
SYNOPSIS
/etc/ldap/slapd.conf
DESCRIPTION
The asyncmeta backend to slapd(8) performs basic LDAP proxying with re-
spect to a set of remote LDAP servers, called "targets". The informa-
tion contained in these servers can be presented as belonging to a sin-
gle Directory Information Tree (DIT).
A good knowledge of the functionality of the slapd-meta(5) backend is
recommended. This backend has been designed as an asynchronous ver-
sion of the meta backend. Unlike meta , the operation handling threads
are no longer pending on the response from the remote server, thus de-
creasing the number of threads necessary to handle the same load. While
asyncmeta maintains the functionality of meta and has a largely similar
codebase, some changes in operation and some new configuration direc-
tives have been added. Some configuration options, such as
conn-pool-max , conn-ttl , single-conn , and use-temporary-conn have
been removed, as they are no longer relevant.
New connection handling:
Unlike meta, which caches bound connections, the asyncmeta works with a
configured maximum number of connections per target. For each request
redirected to a target, a different connection is selected. Each con-
nection has a queue, to which the request is added before it is sent to
the remote server, and is removed after the last response for that re-
quest is received.
For each new request, the connection with the smallest number of pend-
ing requests is selected, or using round-robin if the numbers are
equal.
Overlays:
Due to implementation specifics, there is no guarantee that any of the
existing OpenLDAP overlays will work with asyncmeta backend.
EXAMPLES
Refer to slapd-meta(5) for configuration examples.
CONFIGURATION
These slapd.conf options apply to the ASYNCMETA backend database. That
is, they must follow a "database asyncmeta" line and come before any
subsequent "backend" or "database" lines. Other database options are
described in the slapd.conf(5) manual page.
SPECIAL CONFIGURATION DIRECTIVES
Target configuration starts with the "uri" directive. All the configu-
ration directives that are not specific to targets should be defined
first for clarity, including those that are common to all backends.
They are:
default-target none
This directive forces the backend to reject all those operations
that must resolve to a single target in case none or multiple
targets are selected. They include: add, delete, modify, mod-
rdn; compare is not included, as well as bind since, as they
don't alter entries, in case of multiple matches an attempt is
made to perform the operation on any candidate target, with the
constraint that at most one must succeed. This directive can
also be used when processing targets to mark a specific target
as default.
dncache-ttl {DISABLED|forever|<ttl>}
This directive sets the time-to-live of the DN cache. This
caches the target that holds a given DN to speed up target se-
lection in case multiple targets would result from an uncached
search; forever means cache never expires; disabled means no DN
caching; otherwise a valid ( > 0 ) ttl is required, in the for-
mat illustrated for the idle-timeout directive.
onerr {CONTINUE|report|stop}
This directive allows one to select the behavior in case an er-
ror is returned by one target during a search. The default,
continue, consists in continuing the operation, trying to return
as much data as possible. If the value is set to stop, the
search is terminated as soon as an error is returned by one tar-
get, and the error is immediately propagated to the client. If
the value is set to report, the search is continued to the end
but, in case at least one target returned an error code, the
first non-success error code is returned.
max-timeout-ops <number>
Specify the number of consecutive timed out requests, after
which the connection will be considered faulty and dropped.
max-pending-ops <number>
The maximum number of pending requests stored in a connection's
queue. The default is 128. When this number is exceeded,
LDAP_BUSY will be returned to the client.
max-target-conns <number>
The maximum number of connections per target. Unlike
slapd-meta(5), no new connections will be created once this num-
ber is reached. The default value is 255.
norefs <NO|yes>
If yes, do not return search reference responses. By default,
they are returned unless request is LDAPv2. If set before any
target specification, it affects all targets, unless overridden
by any per-target directive.
noundeffilter <NO|yes>
If yes, return success instead of searching if a filter is unde-
fined or contains undefined portions. By default, the search is
propagated after replacing undefined portions with (!(object-
Class=*)), which corresponds to the empty result set. If set
before any target specification, it affects all targets, unless
overridden by any per-target directive.
protocol-version {0,2,3}
This directive indicates what protocol version must be used to
contact the remote server. If set to 0 (the default), the proxy
uses the same protocol version used by the client, otherwise the
requested protocol is used. The proxy returns unwillingToPer-
form if an operation that is incompatible with the requested
protocol is attempted. If set before any target specification,
it affects all targets, unless overridden by any per-target di-
rective.
pseudoroot-bind-defer {YES|no}
This directive, when set to yes, causes the authentication to
the remote servers with the pseudo-root identity (the identity
defined in each idassert-bind directive) to be deferred until
actually needed by subsequent operations. Otherwise, all binds
as the rootdn are propagated to the targets.
quarantine <interval>,<num>[;<interval>,<num>[...]]
Turns on quarantine of URIs that returned LDAP_UNAVAILABLE, so
that an attempt to reconnect only occurs at given intervals in-
stead of any time a client requests an operation. The pattern
is: retry only after at least interval seconds elapsed since
last attempt, for exactly num times; then use the next pattern.
If num for the last pattern is "+", it retries forever; other-
wise, no more retries occur. This directive must appear before
any target specification; it affects all targets with the same
pattern.
rebind-as-user {NO|yes}
If this option is given, the client's bind credentials are re-
membered for rebinds, when trying to re-establish a broken con-
nection, or when chasing a referral, if chase-referrals is set
to yes.
session-tracking-request {NO|yes}
Adds session tracking control for all requests. The client's IP
and hostname, and the identity associated to each request, if
known, are sent to the remote server for informational purposes.
This directive is incompatible with setting protocol-version to
2. If set before any target specification, it affects all tar-
gets, unless overridden by any per-target directive.
TARGET SPECIFICATION
Target specification starts with a "uri" directive:
uri <protocol>://[<host>]/<naming context> [...]
Identical to meta. See slapd-meta(5) for details.
acl-authcDN <administrative DN for access control purposes>
DN which is used to query the target server for acl checking, as
in the LDAP backend; it is supposed to have read access on the
target server to attributes used on the proxy for acl checking.
There is no risk of giving away such values; they are only used
to check permissions. The acl-authcDN identity is by no means
implicitly used by the proxy when the client connects anony-
mously.
acl-passwd <password>
Password used with the acl-authcDN above.
bind-timeout <microseconds>
This directive defines the timeout, in microseconds, used when
polling for response after an asynchronous bind connection. See
slapd-meta(5) for details.
chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated to
the underlying libldap, with rebinding eventually performed if
the rebind-as-user directive is used. The default is to chase
referrals. If set before any target specification, it affects
all targets, unless overridden by any per-target directive.
client-pr {accept-unsolicited|DISABLE|<size>}
This feature allows one to use RFC 2696 Paged Results control
when performing search operations with a specific target, irre-
spective of the client's request. See slapd-meta(5) for details.
default-target [<target>]
The "default-target" directive can also be used during target
specification. With no arguments it marks the current target as
the default. The optional number marks target <target> as the
default one, starting from 1. Target <target> must be defined.
filter <pattern>
This directive allows specifying a regex(5) pattern to indicate
what search filter terms are actually served by a target.
In a search request, if the search filter matches the pattern
the target is considered while fulfilling the request; otherwise
the target is ignored. There may be multiple occurrences of the
filter directive for each target.
idassert-authzFrom <authz-regexp>
if defined, selects what local identities are authorized to ex-
ploit the identity assertion feature. The string <authz-regexp>
follows the rules defined for the authzFrom attribute. See
slapd.conf(5), section related to authz-policy, for details on
the syntax of this field.
idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
[credentials=<simple password>] [saslmech=<SASL mech>]
[secprops=<properties>] [realm=<realm>] [authcId=<authentication
ID>] [authzId=<authorization ID>] [authz={native|proxyauthz}]
[mode=<mode>] [flags=<flags>] [starttls=no|yes|critical]
[tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>]
[tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand]
[tls_reqsan=never|allow|try|demand] [tls_cipher_suite=<ciphers>]
[tls_ecname=<names>] [tls_protocol_min=<major>[.<minor>]]
[tls_crlcheck=none|peer|all] Allows one to define the parameters
of the authentication method that is internally used by the
proxy to authorize connections that are authenticated by other
databases. See slapd-meta(5) for details.
idle-timeout <time>
This directive causes a a persistent connection to be dropped
after it has been idle for the specified time. The connection
will be re-created the next time it is selected for use. A
connection is considered idle if no attempts have been made by
the backend to use it to send a request to the backend server.
If there are still pending requests in its queue, the connection
will be dropped after the last request one has either received a
result or has timed out.
[<d>d][<h>h][<m>m][<s>[s]]
where <d>, <h>, <m> and <s> are respectively treated as days,
hours, minutes and seconds. If set before any target
specification, it affects all targets, unless overridden by any
per-target directive.
keepalive <idle>:<probes>:<interval>
The keepalive parameter sets the values of idle, probes, and
interval used to check whether a socket is alive; idle is the
number of seconds a connection needs to remain idle before TCP
starts sending keepalive probes; probes is the maximum number of
keepalive probes TCP should send before dropping the connection;
interval is interval in seconds between individual keepalive
probes. Only some systems support the customization of these
values; the keepalive parameter is ignored otherwise, and
system-wide settings are used.
tcp-user-timeout <milliseconds>
If non-zero, corresponds to the TCP_USER_TIMEOUT set on the
target connections, overriding the operating system setting.
Only some systems support the customization of this parameter,
it is ignored otherwise and system-wide settings are used.
map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
This maps object classes and attributes as in the LDAP backend.
See slapd-ldap(5).
network-timeout <time>
Sets the network timeout value after which poll(2)/select(2)
following a connect(2) returns in case of no activity while
sending an operation to the remote target. The value is in
milliseconds, and it can be specified as for idle-timeout. If
set before any target specification, it affects all targets,
unless overridden by any per-target directive.
nretries {forever|never|<nretries>}
This directive defines how many times forwarding an operation
should be retried in case of temporary failure in contacting a
target. The number of retries is per operation, so if a bind to
the target is necessary first, the remaining number is
decremented. If defined before any target specification, it
applies to all targets (by default, 3 times); the global value
can be overridden by redefinitions inside each target
specification.
rewrite* ...
The rewrite options are identical to the meta backend. See the
REWRITING section of slapd-meta(5).
subtree-{exclude|include} <rule>
This directive allows one to indicate what subtrees are actually
served by a target. See slapd-meta(5) for details.
suffixmassage <local suffix> <remote suffix>
slapd-asyncmeta does not support the rewrite engine used by the
LDAP and META backends. suffixmassage can be used to perform DN
suffix rewriting, the same way as the obsoleted suffixmassage
directive previously used by the LDAP backend.
t-f-support {NO|yes|discover}
enable if the remote server supports absolute filters (see RFC
4526 for details). If set to discover, support is detected by
reading the remote server's root DSE. If set before any target
specification, it affects all targets, unless overridden by any
per-target directive.
timeout [<op>=]<val> [...]
This directive allows one to set per-operation timeouts.
Operations can be
<op> ::= bind, add, delete, modrdn, modify, compare, search
By default, the timeout for all operations is 2 seconds.
See slapd-meta(5) for details.
tls {none|[try-]start|[try-]propagate|ldaps}
B [starttls=no] [tls_cert=<file>] [tls_key=<file>]
[tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand]
[tls_reqsan=never|allow|try|demand] [tls_cipher_suite=<ciphers>]
[tls_ecname=<names>] [tls_crlcheck=none|peer|all]
Specify TLS settings regular connections.
If the first parameter is not "none" then this configures the
TLS settings to be used for regular connections. The StartTLS
extended operation will be used when establishing the connection
unless the URI directive protocol scheme is ldaps://. In that
case this keyword may only be set to "ldaps" and the StartTLS
operation will not be used.
With propagate, the proxy issues the StartTLS operation only if
the original connection has a TLS layer set up. The try- prefix
instructs the proxy to continue operations if the StartTLS
operation failed; its use is not recommended.
The TLS settings default to the same as the main slapd TLS
settings, except for tls_reqcert which defaults to "demand",
tls_reqsan which defaults to "allow", and starttls which is
overshadowed by the first keyword and thus ignored.
If set before any target specification, it affects all targets,
unless overridden by any per-target directive.
SCENARIOS
See slapd-meta(5) for configuration scenarios.
ACLs
ACL behavior is identical to meta. See slapd-meta(5).
ACCESS CONTROL
The asyncmeta backend does not honor all ACL semantics as described in
slapd.access(5). In general, access checking is delegated to the
remote server(s). Only read (=r) access to the entry pseudo-attribute
and to the other attribute values of the entries returned by the search
operation is honored, which is performed by the frontend.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd.conf(5), slapd-ldap(5), slapd-meta(5), slapo-pcache(5), slapd(8),
regex(7), re_format(7).
AUTHOR
Nadezhda Ivanova, based on back-meta by Pierangelo Masarati.
OpenLDAP 2.5.13+dfsg-5 2022/07/14 SLAPD-ASYNCMETA(5)
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