Re: [gentoo-user] Cross system dependencies
On Saturday, June 28, 2014 09:23:17 PM thegeezer wrote: On 06/28/2014 07:06 PM, J. Roeleveld wrote: On Saturday, June 28, 2014 01:39:41 PM Neil Bothwick wrote: On Sat, 28 Jun 2014 11:36:11 +0200, J. Roeleveld wrote: I need a way to add dependencies to services which are provided by different servers. For instance, my mail server uses DNS to locate my LDAP server which contains the mail aliases. All these are running on different machines. Currently, I manually ensure these are all started in the correct sequence, I would like to automate this to the point where I can start all 3 servers at the same time and have the different services wait for the dependency services to be available even though they are on different systems. All the dependency systems in the init-systems I could find are all based on dependencies on the same server. Does anyone know of something that can already provide this type of dependencies? Or do I need to write something myself? With systemd you can add ExecStartPre=/some/script to the service's unit file where /some/script waits for the remote services to become available, and possibly return an error if the service does not become available within a set time. That method works for any init-system and writing a script to check and if necessary fail is my temporary fall-back plan. I was actually hoping for a method that can be used to monitor availability and, if necessary, stop services when the dependencies disappear. -- Joost the difficulty is in identifying failed services. local network issue / load issue could mean your services start bouncing. the best way is to have redundancy so it doesn't matter as much I know that. A proper system for this would have a configurable amount of retries with a wait-time in between. having said all of that:: systemd will start servers and buffer network activity - how this works for non local services would be interesting to see. It would, but I am not going to migrate my servers to something like systemd without a clear and proven advantage. For me, that currently does not exist. It also would not work as not all the software I run will happily wait while the rest of the stack starts. I would end up in a bigger mess thanks to timeout issues during startup. with openrc : you could on the DNS server have a service which is just a batch script that uses watches for pid / program path in ps which outputs ACK or NAK to a file in an NFS share say /nfs/monitoring/dns Yes, but in order to access the NFS share, I need DNS to be running. Chicken- egg problem. then on the mail server you could have a service that polls /nfs/monitoring/dns for NAK or ACK you can then choose to have this service directly start your dependent services, or if you adjust /etc/init.d/postfix to have depends = mymonitorDNS which is an empty shell of a service. your watchdog service could stop / start the empty shell of a script mymonitorDNS, and then postfix depends on mymonitorDNS this would save you from i've just stopped the mail server for maintenance and my watchdogservice has just restarted it due to a NAKACK event That is the problem I have with these watchdog services. During boot, I want it to wait. But it needs to understand not to start a service when I stopped it during runtime. Otherwise it could prevent a clean shutdown as well... or... you could have a central master machine which has it's own services, watchdog and monitor... i.e. /etc/init.d/thepostfixserver start / depends on thednsserver which just runs # ssh postfixserver '/etc/init.d/postfix start' or... puppet and it's kin Last time I looked at puppet, it seemed too complex for what I need. I will recheck it again. Thanks, Joost
Re: [gentoo-user] Cross system dependencies
On Sun, 29 Jun 2014 08:55:41 +0200, J. Roeleveld wrote: or... puppet and it's kin Last time I looked at puppet, it seemed too complex for what I need. I will recheck it again. What about something like monit? -- Neil Bothwick Bug: (n.) any program feature not yet described to the marketing department. signature.asc Description: PGP signature
Re: [gentoo-user] Cross system dependencies
On Sunday, June 29, 2014 09:35:33 AM Neil Bothwick wrote: On Sun, 29 Jun 2014 08:55:41 +0200, J. Roeleveld wrote: or... puppet and it's kin Last time I looked at puppet, it seemed too complex for what I need. I will recheck it again. What about something like monit? Hmm... I looked into that before, don't recall why I didn't look into it properly before. Just had a look on the website, it looks usable, will need to check this. Will also replace nagios at the same time, which I find ok, but don't really like it. I might open a new thread at a later stage when I get round to trying it. Thanks, Joost
[gentoo-user] Cross system dependencies
Hi all, This is something I have been looking for for a while now, but not found anything easily usable yet. I need a way to add dependencies to services which are provided by different servers. For instance, my mail server uses DNS to locate my LDAP server which contains the mail aliases. All these are running on different machines. Currently, I manually ensure these are all started in the correct sequence, I would like to automate this to the point where I can start all 3 servers at the same time and have the different services wait for the dependency services to be available even though they are on different systems. All the dependency systems in the init-systems I could find are all based on dependencies on the same server. Does anyone know of something that can already provide this type of dependencies? Or do I need to write something myself? I have been unable to locate anything via Google, but I might be using the wrong search words. Many thanks, Joost
Re: [gentoo-user] Cross system dependencies
On Sat, 28 Jun 2014 11:36:11 +0200, J. Roeleveld wrote: I need a way to add dependencies to services which are provided by different servers. For instance, my mail server uses DNS to locate my LDAP server which contains the mail aliases. All these are running on different machines. Currently, I manually ensure these are all started in the correct sequence, I would like to automate this to the point where I can start all 3 servers at the same time and have the different services wait for the dependency services to be available even though they are on different systems. All the dependency systems in the init-systems I could find are all based on dependencies on the same server. Does anyone know of something that can already provide this type of dependencies? Or do I need to write something myself? With systemd you can add ExecStartPre=/some/script to the service's unit file where /some/script waits for the remote services to become available, and possibly return an error if the service does not become available within a set time. -- Neil Bothwick I have a mind like a steel...uh...thingamajig... signature.asc Description: PGP signature
Re: [gentoo-user] Cross system dependencies
On Saturday, June 28, 2014 01:39:41 PM Neil Bothwick wrote: On Sat, 28 Jun 2014 11:36:11 +0200, J. Roeleveld wrote: I need a way to add dependencies to services which are provided by different servers. For instance, my mail server uses DNS to locate my LDAP server which contains the mail aliases. All these are running on different machines. Currently, I manually ensure these are all started in the correct sequence, I would like to automate this to the point where I can start all 3 servers at the same time and have the different services wait for the dependency services to be available even though they are on different systems. All the dependency systems in the init-systems I could find are all based on dependencies on the same server. Does anyone know of something that can already provide this type of dependencies? Or do I need to write something myself? With systemd you can add ExecStartPre=/some/script to the service's unit file where /some/script waits for the remote services to become available, and possibly return an error if the service does not become available within a set time. That method works for any init-system and writing a script to check and if necessary fail is my temporary fall-back plan. I was actually hoping for a method that can be used to monitor availability and, if necessary, stop services when the dependencies disappear. -- Joost
Re: [gentoo-user] Cross system dependencies
On 06/28/2014 07:06 PM, J. Roeleveld wrote: On Saturday, June 28, 2014 01:39:41 PM Neil Bothwick wrote: On Sat, 28 Jun 2014 11:36:11 +0200, J. Roeleveld wrote: I need a way to add dependencies to services which are provided by different servers. For instance, my mail server uses DNS to locate my LDAP server which contains the mail aliases. All these are running on different machines. Currently, I manually ensure these are all started in the correct sequence, I would like to automate this to the point where I can start all 3 servers at the same time and have the different services wait for the dependency services to be available even though they are on different systems. All the dependency systems in the init-systems I could find are all based on dependencies on the same server. Does anyone know of something that can already provide this type of dependencies? Or do I need to write something myself? With systemd you can add ExecStartPre=/some/script to the service's unit file where /some/script waits for the remote services to become available, and possibly return an error if the service does not become available within a set time. That method works for any init-system and writing a script to check and if necessary fail is my temporary fall-back plan. I was actually hoping for a method that can be used to monitor availability and, if necessary, stop services when the dependencies disappear. -- Joost the difficulty is in identifying failed services. local network issue / load issue could mean your services start bouncing. the best way is to have redundancy so it doesn't matter as much having said all of that:: systemd will start servers and buffer network activity - how this works for non local services would be interesting to see. with openrc : you could on the DNS server have a service which is just a batch script that uses watches for pid / program path in ps which outputs ACK or NAK to a file in an NFS share say /nfs/monitoring/dns then on the mail server you could have a service that polls /nfs/monitoring/dns for NAK or ACK you can then choose to have this service directly start your dependent services, or if you adjust /etc/init.d/postfix to have depends = mymonitorDNS which is an empty shell of a service. your watchdog service could stop / start the empty shell of a script mymonitorDNS, and then postfix depends on mymonitorDNS this would save you from i've just stopped the mail server for maintenance and my watchdogservice has just restarted it due to a NAKACK event or... you could have a central master machine which has it's own services, watchdog and monitor... i.e. /etc/init.d/thepostfixserver start / depends on thednsserver which just runs # ssh postfixserver '/etc/init.d/postfix start' or... puppet and it's kin
