Hi Timo, On 01.03.2016 22:51, Timo Sirainen wrote:
On 29 Feb 2016, at 17:18, Gordon Grubert <gordon.grubert+li...@uni-greifswald.de> wrote:Hi, we are using a round robin dns record for connections to our ldap system. This works fine for almost all cases. In particular, for dovecot does this mean, when an ldap server is stopped, dovecot instantly reconnects to another ldap server. But when the network connection to the active ldap server is broken, dovecot sticks to the failed ldap server. Is there any possibility to define a connection timeout?What should happen is that as long as new requests keep coming, Dovecot realizes after about 60 seconds that the LDAP server is hanging. It then reconnects and the reconnection should work. But... First of all, 60 seconds is likely a much too long timeout. But more importantly it looks like there's something weird now going on with OpenLDAP library. I added this somewhat recently and tested that it works: https://github.com/dovecot/core/commit/fb3178a1924dae52151d88c4d4ded879df43dd3f But now that I'm testing it, the timeout doesn't seem to be triggering. I don't know what happened to it that it suddenly doesn't work.. This also means that OpenLDAP seems to be internally stuck trying to connect to a server that isn't responding. Dovecot doesn't currently make the decisions on which LDAP server to connect to. It just passes through all the hosts to OpenLDAP library and lets it handle it. And it seems like OpenLDAP library can't right now do this failover. So maybe Dovecot should be responsible for that as well.. Anyway, for now you could set up haproxy to localhost and configure Dovecot LDAP to connect to haproxy and haproxy connect to the actual LDAP servers.
today I've upgraded to 2.2.21-1~auto+171 on debian 8 and made a lot of "interruption tests". Your fix not really solved the problem. But I found another interesting fact: The openldap client on debian 8 can handle hard communication interrupts correctly. I've added NETWORK_TIMEOUT 5 TIMEOUT 5 to ldap.conf because man 5 ldap.conf says: NETWORK_TIMEOUT <integer> Specifies the timeout (in seconds) after which the poll(2)/select(2) following a connect(2) returns in case of no activity. TIMEOUT <integer> Specifies a timeout (in seconds) after which calls to synchronous LDAP APIs will abort if no response is received. Also used for any ldap_result(3) calls where a NULL timeout parameter is supplied. We are using the ISC DHCP server with dynamic ldap connections. This daemon uses - like dovecot - the LDAP API of the openldap client for access to the ldap server. The DHCP opens a persistent ldap connection to handle all dhcp requests (same behavior like dovecot). Here, the timeouts for connection loss are working. Therefore, my question: Why does this not work for dovecot, too, when dovecot uses the same API? Dovecot does not get a response from the LDAP server and has to reconnect, only. IMAP server world domination requires a reconnect in case of connection timeouts ;-) Best regards, Gordon -- Technischer Leiter & stellv. Direktor Universitätsrechenzentrum (URZ) E.-M.-Arndt-Universität Greifswald Felix-Hausdorff-Str. 12 17489 Greifswald Germany Tel. +49 3834 86 1456 Fax. +49 3834 86 1401
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