Adding upstream version 2.5.13+dfsg.upstream/2.5.13+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+# $OpenLDAP$
+# Copyright 2021-2022 The OpenLDAP Foundation, All Rights Reserved.
+# COPYING RESTRICTIONS APPLY, see COPYRIGHT.
+H1: Load Balancing with lloadd
+
+As covered in the {{SECT:Replication}} chapter, replication is a fundamental
+requirement for delivering a resilient enterprise deployment.  As such
+there's a need for an LDAPv3 capable load balancer to spread the load between the
+various directory instances.
+
+{{lloadd}}(8) provides the capability to distribute LDAP v3 requests between a
+set of running {{slapd}} instances.  It can run as a standalone daemon
+{{lloadd}}, or as an embedded module running inside of {{slapd}}.
+
+H2: Overview
+
+{{lloadd}}(8) was designed to handle LDAP loads.
+It is protocol-aware and can balance LDAP loads on a per-operation basis rather
+than on a per-connection basis.
+
+{{lloadd}}(8) distributes the load across a set of slapd instances. The client
+connects to the load balancer instance which forwards the request to one
+of the servers and returns the response back to the client.
+
+H2: When to use the OpenLDAP load balancer
+
+In general, the OpenLDAP load balancer spreads the load across configured backend servers.  It does not perform
+so-called intelligent routing. It does not understand semantics behind the operations being performed by the clients.
+
+More considerations:
+
+ - Servers are indistinguishable with respect to data contents.  The exact same copy of data resides on every server.
+ - Clients do not require 'sticky' sessions.
+ - The sequence of operations isn't important.  For example, read after update isn't required by the client.
+ - If your client can handle both connection pooling and load distribution then it's preferable to lloadd.
+ - Clients that require a consistent session (e.g. do writes), the best practice is to let them set up a direct session to one of the providers.  The read-only clients are still free to use lloadd.
+ - 2.6 release of lloadd will include sticky sessions (coherency).
+
+H2: Runtime configurations
+
+It deploys in one of two ways:
+
+^ Standalone daemon: {{ lloadd }}
++ Loaded into the slapd daemon as a module: {{ lloadd.la }}
+
+It is recommended to run with the balancer module embedded in slapd because dynamic configuration (cn=config) and the monitor backend are then available.
+
+{{B: Sample load balancer scenario:}}
+
+!import "load-balancer-scenario.png"; align="center"; title="Load Balancer Scenario"
+FT[align="Center"] Figure: Load balancer sample scenario
+
+^ The LDAP client submits an LDAP operation to
+the load balancer daemon.
+
++ The load balancer forwards the request to one of the backend instances in its pool of servers.
+
++ The backend slapd server processes the request and returns the response to
+the load balancer instance.
+
++ The load balancer returns the response to the client.  The client's unaware that it's connecting to a load balancer instead of slapd.
+
+H2: Build Notes
+
+To build the load balancer from source, follow the instructions in the
+{{SECT: A Quick-Start Guide}} substituting the following commands:
+
+^ To configure as standalone daemon:
+
+..{{EX:./configure --enable-balancer=yes}}
+
++ To configure as embedded module to slapd:
+
+..{{EX:./configure --enable-modules --enable-balancer=mod}}
+
+H2: Sample Runtime
+
+^ To run embedded as {{ lloadd }} module:
+
+..{{EX: slapd [-h URLs]  [-f lloadd-config-file] [-u user] [-g group]}}
+
+ - the startup is the same as starting the {{ slapd }} daemon.
+ - URLs is for slapd management. The load balancer's listener URLs set in the configuration file or node. (more later)
+
++ To run as standalone daemon:
+
+..{{EX: lloadd [-h URLs]  [-f lloadd-config-file] [-u user] [-g group]}}
+
+ - Other than a different daemon name, running standalone has the same options as starting {{ slapd }}.
+ - -h URLs specify the lloadd's interface directly, there is no management interface.
+
+For a complete list of options, checkout the man page {{ lloadd.8 }}
+
+H2: Configuring load balancer
+
+H3: Common configuration options
+
+Many of the same configuration options as slapd. For complete list, check
+the {{lloadd}}(5) man page.
+
+.{{S: }}
+{{B:Edit the slapd.conf or cn=config configuration file}}.
+
+To configure your working {{lloadd}}(8) you need to make the following changes to your configuration file:
+  ^ include {{ core.schema }} (embedded only)
+  + {{ TLSShareSlapdCTX { on | off } }}
+  + Other common TLS slapd options
+  + Setup argsfile/pidfile
+  + Setup moduleload path (embedded mode only)
+  + {{ moduleload      lloadd.la }}
+  + loglevel, threads, ACL's
+  + {{ backend lload }} begin lloadd specific backend configurations
+  + {{ listen ldap://:PORT }} Specify listen port for load balancer
+  + {{ feature proxyauthz }} Use the proxy authZ control to forward client's identity
+  + {{ io-threads INT }} specify the number of threads to use for the connection manager.  The default is 1 and this is typically adequate for up to 16 CPU cores
+
+H3: Sample backend config
+
+Sample setup config for load balancer running in front of four slapd instances.
+
+>backend lload
+>
+># The Load Balancer manages its own sockets, so they have to be separate
+># from the ones slapd manages (as specified with the -h "URLS" option at
+># startup).
+>listen ldap://:1389
+>
+># Enable authorization tracking
+>feature proxyauthz
+>
+># Specify the number of threads to use for the connection manager.  The default is 1 and this is typically adequate for up to 16 CPU cores.
+># The value should be set to a power of 2:
+>io-threads  2
+>
+># If TLS is configured above, use the same context for the Load Balancer
+># If using cn=config, this can be set to false and different settings
+># can be used for the Load Balancer
+>TLSShareSlapdCTX true
+>
+># Authentication and other options (timeouts) shared between backends.
+>bindconf bindmethod=simple
+>         binddn=dc=example,dc=com credentials=secret
+>         network-timeout=5
+>         tls_cacert="/usr/local/etc/openldap/ca.crt"
+>         tls_cert="/usr/local/etc/openldap/host.crt"
+>         tls_key="/usr/local/etc/openldap/host.pem"
+>
+>
+># List the backends we should relay operations to, they all have to be
+># practically indistinguishable. Only TLS settings can be specified on
+># a per-backend basis.
+>
+>backend-server uri=ldap://ldaphost01 starttls=critical retry=5000
+>               max-pending-ops=50 conn-max-pending=10
+>               numconns=10 bindconns=5
+>backend-server uri=ldap://ldaphost02 starttls=critical retry=5000
+>               max-pending-ops=50 conn-max-pending=10
+>               numconns=10 bindconns=5
+>backend-server uri=ldap://ldaphost03 starttls=critical retry=5000
+>               max-pending-ops=50 conn-max-pending=10
+>               numconns=10 bindconns=5
+>backend-server uri=ldap://ldaphost04 starttls=critical retry=5000
+>               max-pending-ops=50 conn-max-pending=10
+>               numconns=10 bindconns=5
+>
+>#######################################################################
+># Monitor database
+>#######################################################################
+>database        monitor