I want to run a SQL every time that my Postgresql cluster starts.
What is the best approach? Modify the start script? Or the PostgreSQL contains some functionality to run?
I use PostgreSQL default install on Ubuntu.
The scenario is: I run the pg_prewarm() function that do the warm table permanently on memory, speeding up the results but, if my DB stops or restart for some reason, I need to run this script manually.
If you are using Postgres 11 or better, pg_prewarm has a pg_prewarm.autoprewarm feature.
For earlier versions, you could try to re-invent this yourself, but I wouldn't recommend it. Spend the time upgrading rather than working around limitations imposed by not upgrading.
Related
If it's possible, I'm interested in being able to embed a PostgreSQL database, similar to sqllite. I've read that it's not possible. I'm no database expert though, so I want to hear from you.
Essentially I want PostgreSQL without all the configuration and installation. If it's possible, tell me how.
Run postgresql in a background process.
Start a separate thread in your application that would start a postgresql server in local mode either by binding it to localhost with some random free port or by using sockets (does windows support sockets?). That should be fairly easy, something like:
system("C:\Program Files\MyApplication\pgsql\postgres.exe -D C:\Documents and Settings\User\Local Settings\MyApplication\database -h 127.0.0.1 -p 12345");
and then just connect to 127.0.0.1:12345.
When your application quits, you can always send a SIGTERM to your thread and then wait a few seconds for postgresql to quit (ie join the thread).
PS: You can also use pg_ctl to control your "embedded" database, even without threads, just do a "pg_ctl start" (with appropriate options) when starting the application and "pg_ctl stop" when quitting it.
You cannot embed it, nor should you try.
For embedding you should use sqlite as you mentioned or firebird rdbms.
Unless you do a major rewrite of code, it is not possible to run Postgres "embedded". Either run it as a separate process or use something else. SQLite is an excellent choice. But there are others. MySQL has an embedded version. See it at http://mysql.com/oem/. Also several java choices, and Mac has Core Data you can write too. Hell, you can even use FoxPro. What OS you on and what services you need from the database?
You can't embed it as a in process type thing like sqlite etc, but you can easily embed it into your application setup using Inno setup at http://www.innosetup.org. Search their mailing list archive and you will find someone did most of the work for you and all you have to to is grab the zipped distro and you can easily have postgresql installed when the user installs your app. You can then use the pg_hba.conf file to restrict the server to local host only. Not a true embedded DB, but it would work.
PostgreSQL is intended to run as a stand-alone server; it's probably possible to embed it if you hack at it hard and long enough, but it would be much easier to just run it as intended in a separate process.
HSQLDB (http://hsqldb.org/) is another db which is easily embedded. Requires Java, but is an excellent and often-used choice for Java applications.
Anyone tried on Mac OS X:
http://pagesperso-orange.fr/bruno.gaufier/xhtml/prod_postgresql.xhtml
http://www.macosxguru.net/article.php?story=20041119135924825
(Of course sqlite would be my embedded db of choice as well)
Well, I know this is a very very very old post, but if anyone has nowadays this question, I would refer to:
You can use containers running Postgres. Here's a post that could be helpful, doing something along this line using R:
https://rsangole.netlify.app/post/2021/08/07/docker-based-rstudio-postgres/?utm_source=pocket_mylist
Take a look at duckdb https://duckdb.org/docs/installation/ It is relatively new and still needs to mature. But it works pretty much like an embedded database ("In-process, serverless"), with bindings for several languages (Python, R, Java, ...)
when i create a postgresql database and create tables and columns and even insert data into the columns. I cant restart my machine without losing the created databases and all the data.
i have tried changing a coupe things in the configuration file but nothing helped.
I also have to reset the password for postgres everytime I restart my machine. I mainly use mongodb I am just learning postgreSQL just so I can use it if I ever need to in the future. I am runing a Linux machine QubesOS. I have a few problems like this useing QubesOS. every tutorial I watch everybody uses Macs. Which a mac seems good and all kinda a mix between windows and linux The best of both worlds. Easy package installs and terminal control but I dont want to trade my linux machine for a Mac I would much rather just fix these problems I am having with PostgreSQL on my linux machine
You ran into an important security feature of QubesOS: All data modifications are discarded on shutdown of a so called "Qube". They are reset to their original state.
But there is the exception of data kept in some very special directories.
If you convince your data base packages to put their data into these directories, it will be preserved over reboots of your data base Qube:
Read this documentation for more information.
Today I found out that a linux's server clock, hosting a PostgreSql cluster in a production environment, is late and I need take it to the current time.
I've used these lines in my local machine:
sudo date --set="2017-01-19 12:09:59.990"
sudo hwclock --systohc
I've listed the time on PostgreSql
select now()
before and after the changes, and everything worked fine.
Is there any impact that I should look for ?
Am I overthinking this ?
I cannot think of any problems that PostgreSQL itself would have with that, and jumping forward in time should not be a problem anyway – it is much like a time with zero activity.
Jumping back in time may not be a problem for PostgreSQL, but it might confuse an application to find future timestamps in the database.
I am working on a webapp that will be published in production and then updated on regular basis as features and bug fixes are coming.
I run it like node app.js which loads config, connects to database, starts web server.
I wonder, what's the process of updating the app when I have next version?
I suppose, I have to kill the process and start after update and deploy? It means, that there will be some downtime?
Should I collect stats on the least use during the week/month and apply the update during that period? Or should I start the current version on another machine, redirect all requests to it and update the main one, then switch back?
I think the second approach is better.
The first one won't prevent downtime, it will just make sure it impacts the least number of users, while the second one creates no down-time at all.
Moreover, I think you should keep the old version running in the other machine for some time in case you will find out the new version must be reverted due to whatever reason. In that case you will just have to redirect traffic to the old node without any downtime.
Also, if you're setting up production environment I would recommend that instead of just running your process with "node" command, you will use something like forever or pm2 in order to do automatic restarts and some other advanced features.
I need to create a nodejs "server" which wont actually serve any assets or content, but will just run some scheduled job to fetch contents from one database and update another database. The schedule of the job should be configurable and should be able to cancel the job at any time. Basically what I need is to run a node script periodically. In past, I have created node/express projects, but I am having a hard time understanding how to implement such a node instance which will run on a remote machine and how to start or terminate it. I found a npm package called "node-schedule" which runs the job periodically, but how to put this package on a remote machine instance and run it?
One possibility that was considered was to schedule a cron job on remote machine which will execute "node updateDB.js" on set schedule, but it is a requirement to keep everything in node package and not depend on cron.
Sounds like a job for ssh.
Personally I wouldn't use NodeJS for this, this should be pretty trivial to do, with Node or otherwise, not sure why you are stuck, honestly. I have nothing against Node, but I don't see why it would be necessary for this task, but certainly you could use it for such a thing.
EDIT: After reading your comment I'm convinced someone thinks Node is a good tool for this task. I guess I don't understand where you are stuck. What part are you stuck on?
I think you should be able to puzzle this out pretty fast. The link below should be enough to put this together. http://book.mixu.net/node/ch9.html
If you need to execute ad hoc commands on a remote server you could use Node to call an Ansible playbook, in that case you'll need to share the public ssh key on the target instance(s) with the instance issuing the commands. There are other ways to skin this cat, but based on the information given, that's how I'd do it. I'd use Node and Ansible (requires python) + SSH.
Oh neato, maybe if I were forced to use NodeJS I'd use this package. https://www.npmjs.com/package/ssh2-exec
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