URL: https://github.com/SSSD/sssd/pull/951
Author: thalman
 Title: #951: sdap: Add randomness to ldap connection timeout
Action: opened

PR body:
"""
In case of mass deployment, mass registration of IPA clients roughly on
the same time leads to regular CPU load spikes on IPA servers, the load
spikes are caused by all/most clients refreshing their LDAP connections
(ldap_connection_expire_timeout) every 15 minutes.

This patch introduces new random value (from 0 up to
ldap_connection_expire_offset) that is added to the timeout.

Resolves:
https://pagure.io/SSSD/sssd/issue/3630
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/951/head:pr951
git checkout pr951
From 5ab431382cb15dea315d9d24ccd7369818094b31 Mon Sep 17 00:00:00 2001
From: Tomas Halman <[email protected]>
Date: Mon, 2 Dec 2019 11:11:52 +0100
Subject: [PATCH] sdap: Add randomness to ldap connection timeout

In case of mass deployment, mass registration of IPA clients roughly on
the same time leads to regular CPU load spikes on IPA servers, the load
spikes are caused by all/most clients refreshing their LDAP connections
(ldap_connection_expire_timeout) every 15 minutes.

This patch introduces new random value (from 0 up to
ldap_connection_expire_offset) that is added to the timeout.

Resolves:
https://pagure.io/SSSD/sssd/issue/3630
---
 src/config/cfg_rules.ini                   |  1 +
 src/man/sssd-ldap.5.xml                    | 19 +++++++++++++++++++
 src/providers/ad/ad_opts.c                 |  1 +
 src/providers/ipa/ipa_opts.c               |  1 +
 src/providers/ldap/ldap_opts.c             |  1 +
 src/providers/ldap/sdap.h                  |  1 +
 src/providers/ldap/sdap_async_connection.c |  7 +++++++
 7 files changed, 31 insertions(+)

diff --git a/src/config/cfg_rules.ini b/src/config/cfg_rules.ini
index 8c73c89ac2..c56d5a6682 100644
--- a/src/config/cfg_rules.ini
+++ b/src/config/cfg_rules.ini
@@ -600,6 +600,7 @@ option = ldap_chpass_dns_service_name
 option = ldap_chpass_update_last_change
 option = ldap_chpass_uri
 option = ldap_connection_expire_timeout
+option = ldap_connection_expire_offset
 option = ldap_default_authtok
 option = ldap_default_authtok_type
 option = ldap_default_bind_dn
diff --git a/src/man/sssd-ldap.5.xml b/src/man/sssd-ldap.5.xml
index 6d1ae23ecb..b2349b5b36 100644
--- a/src/man/sssd-ldap.5.xml
+++ b/src/man/sssd-ldap.5.xml
@@ -509,12 +509,31 @@
                             the two values (this value vs. the TGT lifetime)
                             will be used.
                         </para>
+                        <para>
+                            This timeout can be extended of a random
+			    value specified by
+			    <emphasis>ldap_connection_expire_offset</emphasis>
+                        </para>
                         <para>
                             Default: 900 (15 minutes)
                         </para>
                     </listitem>
                 </varlistentry>
 
+                <varlistentry>
+                    <term>ldap_connection_expire_offset (integer)</term>
+                    <listitem>
+                        <para>
+                            Random offset between 0 and configured value
+			    is added to
+			    <emphasis>ldap_connection_expire_timeout</emphasis>.
+                        </para>
+                        <para>
+                            Default: 0
+                        </para>
+                    </listitem>
+                </varlistentry>
+
                 <varlistentry>
                     <term>ldap_page_size (integer)</term>
                     <listitem>
diff --git a/src/providers/ad/ad_opts.c b/src/providers/ad/ad_opts.c
index cd568e4663..1293219ee1 100644
--- a/src/providers/ad/ad_opts.c
+++ b/src/providers/ad/ad_opts.c
@@ -137,6 +137,7 @@ struct dp_option ad_def_ldap_opts[] = {
     { "ldap_deref_threshold", DP_OPT_NUMBER, { .number = 10 }, NULL_NUMBER },
     { "ldap_sasl_canonicalize", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_connection_expire_timeout", DP_OPT_NUMBER, { .number = 900 }, NULL_NUMBER },
+    { "ldap_connection_expire_offset", DP_OPT_NUMBER, { .number = 0 }, NULL_NUMBER },
     { "ldap_disable_paging", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_idmap_range_min", DP_OPT_NUMBER, { .number = 200000 }, NULL_NUMBER },
     { "ldap_idmap_range_max", DP_OPT_NUMBER, { .number = 2000200000LL }, NULL_NUMBER },
diff --git a/src/providers/ipa/ipa_opts.c b/src/providers/ipa/ipa_opts.c
index 7974cb8ea0..4fafa073da 100644
--- a/src/providers/ipa/ipa_opts.c
+++ b/src/providers/ipa/ipa_opts.c
@@ -147,6 +147,7 @@ struct dp_option ipa_def_ldap_opts[] = {
     { "ldap_deref_threshold", DP_OPT_NUMBER, { .number = 10 }, NULL_NUMBER },
     { "ldap_sasl_canonicalize", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_connection_expire_timeout", DP_OPT_NUMBER, { .number = 900 }, NULL_NUMBER },
+    { "ldap_connection_expire_offset", DP_OPT_NUMBER, { .number = 0 }, NULL_NUMBER },
     { "ldap_disable_paging", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_idmap_range_min", DP_OPT_NUMBER, { .number = 200000 }, NULL_NUMBER },
     { "ldap_idmap_range_max", DP_OPT_NUMBER, { .number = 2000200000LL }, NULL_NUMBER },
diff --git a/src/providers/ldap/ldap_opts.c b/src/providers/ldap/ldap_opts.c
index a20ec0d86b..ffd0c6baa2 100644
--- a/src/providers/ldap/ldap_opts.c
+++ b/src/providers/ldap/ldap_opts.c
@@ -107,6 +107,7 @@ struct dp_option default_basic_opts[] = {
     { "ldap_deref_threshold", DP_OPT_NUMBER, { .number = 10 }, NULL_NUMBER },
     { "ldap_sasl_canonicalize", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_connection_expire_timeout", DP_OPT_NUMBER, { .number = 900 }, NULL_NUMBER },
+    { "ldap_connection_expire_offset", DP_OPT_NUMBER, { .number = 0 }, NULL_NUMBER },
     { "ldap_disable_paging", DP_OPT_BOOL, BOOL_FALSE, BOOL_FALSE },
     { "ldap_idmap_range_min", DP_OPT_NUMBER, { .number = 200000 }, NULL_NUMBER },
     { "ldap_idmap_range_max", DP_OPT_NUMBER, { .number = 2000200000LL }, NULL_NUMBER },
diff --git a/src/providers/ldap/sdap.h b/src/providers/ldap/sdap.h
index d0a19a660c..f27b3c4806 100644
--- a/src/providers/ldap/sdap.h
+++ b/src/providers/ldap/sdap.h
@@ -221,6 +221,7 @@ enum sdap_basic_opt {
     SDAP_DEREF_THRESHOLD,
     SDAP_SASL_CANONICALIZE,
     SDAP_EXPIRE_TIMEOUT,
+    SDAP_EXPIRE_OFFSET,
     SDAP_DISABLE_PAGING,
     SDAP_IDMAP_LOWER,
     SDAP_IDMAP_UPPER,
diff --git a/src/providers/ldap/sdap_async_connection.c b/src/providers/ldap/sdap_async_connection.c
index 0260cba6fd..47b4aace63 100644
--- a/src/providers/ldap/sdap_async_connection.c
+++ b/src/providers/ldap/sdap_async_connection.c
@@ -1803,6 +1803,8 @@ static void sdap_cli_auth_step(struct tevent_req *req)
     struct tevent_req *subreq;
     time_t now;
     int expire_timeout;
+    int expire_offset;
+
     const char *sasl_mech = dp_opt_get_string(state->opts->basic,
                                               SDAP_SASL_MECH);
     const char *user_dn = dp_opt_get_string(state->opts->basic,
@@ -1832,6 +1834,11 @@ static void sdap_cli_auth_step(struct tevent_req *req)
      */
     now = time(NULL);
     expire_timeout = dp_opt_get_int(state->opts->basic, SDAP_EXPIRE_TIMEOUT);
+    expire_offset = dp_opt_get_int(state->opts->basic, SDAP_EXPIRE_OFFSET);
+    if (expire_offset > 0) {
+        expire_timeout += sss_rand() % (expire_offset + 1);
+    }
+
     DEBUG(SSSDBG_CONF_SETTINGS, "expire timeout is %d\n", expire_timeout);
     if (!state->sh->expire_time
             || (state->sh->expire_time > (now + expire_timeout))) {
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