How to implement a state that wait for other minions finishing certain jobs then execute certain state?
For example, I have a cluster of minions called minion-aha1 to minion-aha3, and I install hadoop and hbase on these 3 minions. Now, I would like to convert them to HA mode. Suppose minion-aha1 is the leader. So the logic flow would be:
Start hadoop and hbase on all 3 minions
-> minion-aha1 wait till rest of minions are hadoop and hbase are on and healthy
-> minion-aha1 call join (e.g. stop namenode, hdfs namenode -initializeSharedEdits, start namenode)
-> rest minions call nn2 (e.g. hdfs namenode -bootstrapStandby, start namenode)
I already knew how to convert hbase to HA mode, and I could set the leader in grain, just curious on how to shrink above procedure to single-line, i.e.
salt 'minion-aha*' state.apply hadoop.hbase_to_ha
Or even salt.orch state would be acceptable. The above would fail due to minion-aha1 never know the state of rest of minions. In other words, it might run successfully once if the developer is lucky, but I look for the solution would run successfully every time.
Thank you.
If you want to solve this without making use of an Orchestration SLS, you could look at one of the following approaches:
use the Salt Mine to publish information from a Minion to the Master, which can then be retrieved by another one
use Peer Communication to allow one Minion to generate a job to be executed on another one
Basically I benefit from this answer with some modification:
Trigger event on Master and wait for "response event" on Salt Minion
For custom event sent to the salt master, e.g. mycompany/hbase/status/*/start, I have to send event -> saltutil.sync_all, then the wait_for_event.
This is a Unix/queues/Supervisor question. :)
I'm running PHP command from CLI as one-shot script called in my service. It connects Amazon SQS queue and check if there are jobs to do.
Currently I'm running infinite loop with supervisord using autorestart=true option. Things work great but uptime of this process is always 0:00 (which is understandable) and each time script is called Supervisor creates new process with new PID.
So basically my question is: is this fine to recreate process with new PID all-time-around? It's like: initialize process, run process, end process loop 10x per second. Obviously PID is increasing fast.
Can I leave it as it is or there are other ways to run it as single process and run subprocesses? (Supervisor is running it's jobs already in subprocesses so I guess there cannot be subprocess for subprocess?)
I want to set a cron job in ubuntu with this job
I have a python webscraping program which needs to be scrapped continuously after the program is terminated. In other words the flow is like this
If program is terminated, set the cron job again (until infinity)
Can this be done?
thanks
I was running a process from terminal in an SSH session and started the process in background with nohup and disconnected.
After some time I log back on the server and see that process is still running but cannot bring it back to foreground with current bash terminal since it was not the one which started it. I think the process now belongs to init as the shell which started the process exited when I exited from the first SSH session.
Now, how do I interact the process that I started? I mean it's not that I want to kill it or something, but what if the process takes user input from time to time and now it's waiting for one?
Now, how do I interact the process that I started?
Short answer: you don't. That process' input and output are connected to a terminal that doesn't exist anymore.
What if the process takes user input from time to time and now it's waiting for one?
It won't be waiting for input. If it had tried to get any, it would have received an end-of-file when it tried to read.
Perhaps you would prefer to run such a process under screen so that you can detach the session and reattach it.
In a UNIX-y way, I'm trying to start a process, background it, and tie the lifetime of that process to my shell.
What I'm talking about isn't simply backgrounding the process, I want the process to be sent SIGTERM, or for it to have an open file descriptor that is closed, or something when the shell exits, so that the user of the shell doesn't have to explicitly kill the process or get a "you have running jobs" warning.
Ultimately I want a program that can run, uniquely, for each shell and carry state along with that shell, and close when the shell closes.
IBM's DB2 console commands work this way. When you connect to the database, it spawns a "db2bp" process, that carries the database state and connection and ties it to your shell. You can connect in multiple different terminals or ssh connections, each with its own db2bp process, and when those are closed the appropriate db2bp process dies and that connection is closed.
DB2 queries are then started with the db2 command, which simply hands it off to the appropriate db2bp process. I don't know how it communicates with the correct db2bp process, but maybe it uses the tty device connected to stdin as a unique key? I guess I need to figure that out too.
I've never written anything that does tty manipulation, so I have no clue where to even start. I think I can figure the rest out if I can just spawn a process that is automatically killed on shell exit. Anyone know how DB2 does it?
If your shell isn't a subshell, you can do the following; Put the following into a script called "ttywatch":
#!/usr/bin/perl
my $p=open(PI, "-|") || exec #ARGV; sleep 5 while(-t); kill 15,$p;
Then run your program as:
$ ttywatch commandline... & disown
Disowning the process will prevent the shell from complaining that there are running processes, and when the terminal closes, it will cause SIGTERM (15) to be delivered to the subprocess (your app) within 5 seconds.
If the shell isn't a subshell, you can use a program like ttywrap to at least give it its own tty, and then the above trick will work.
Okay, I think I figured it out. I was making it too complicated :)
I think all db2 is daemon-izing db2bp, then db2bp is calling waitpid on the parent PID (the shell's PID) and exiting after waitpid returns.
The communication between the db2 command and db2bp seems to be done via fifo with a filename based on the parent shell PID.
Waaaay simpler than I was thinking :)
For anyone who is curious, this whole endeavor was to be able to tie a python or groovy interactive session to a shell, so I could test code while easily jumping in and out of a session that would retain database connections and temporary classes / variables.
Thank you all for your help!
Your shell should be sending a SIGHUP signal to any running child processes when it shuts down. Have you tried adding a SIGHUP handler to your application to shut it down cleanly
when the shell exits?
Is it possible that your real problem here is the shell and not your process. My understanding agrees with Jim Lewis' that when the shell dies its children should get SIGHUP. But what you're complaining about is the shell (or perhaps the terminal) trying to prevent you from accidentally killing a running shell with active children.
Consider reading the manual for the shell or the terminal to see if this behavior is configurable.
From the bash manual on my MacBook:
The shell exits by default upon receipt of a SIGHUP. Before exiting, an interactive shell resends the SIGHUP
to all jobs, running or stopped. Stopped jobs are sent SIGCONT to ensure that they receive the SIGHUP. To
prevent the shell from sending the signal to a particular job, it should be removed from the jobs table with
the disown builtin (see SHELL BUILTIN COMMANDS below) or marked to not receive SIGHUP using disown -h.
If the huponexit shell option has been set with shopt, bash sends a SIGHUP to all jobs when an interactive
login shell exits.
which might point you in the right direction.