Running postgresql 9.x (9.1 - 9.3)
I have a custom web app built using php's PDO library. Every query in our app uses prepared statements (via our internal PDO wrapper library).
Our production system uses AWS EC2 small instances for the web server and RDS for the app server.
For local development, my local machine serves as the web-server, and an office machine running Mac OSX (Mavericks) serves up the DB.
When I'm at work, I can typically ping my local office DB server and get 1-5ms ping times. Everything performs well, page load times are very speedy, my internal timer shows that PHP runs the page from start to end in about 12ms.
Now, the issue comes in when I take my work laptop home-- from home, I get about 50-60ms ping times to the office DB server. If I run my development machine at home, page times now take 5-10 seconds to load-- every time. Granted, there are 4 db queries running per page load, it's very, very little data. I've tried TCP_NOWAIT settings, I've tried loading pgbouncer on my local machine with persistent connections to the remote db-- nothing has helped so far.
When timing the queries, we have a simple query that returns 100 bytes of data that runs in .0006 seconds locally to taking around 1 second to run remotely. Lastly, I'll say it appears to be related to latency only, no matter how much data a query returns, it's like it takes around 1 second longer than it normally would if running locally.. give or take.
I was simply wondering if anyone could help me resolve what this delay might be. It seems that every single query, no matter how much data, imparts a delay of around a second, give or take. The odd thing is that when I run PGAdmin on the my machine connecting to the remote DB, it takes nowhere near that much time to run simple queries.
Does anyone have any idea of other things to try? I'm not runnig an SSL DB connection, or using any compression, I'm willing to try if necessary, however, that's one thing I haven't gotten to work before, and I doubt that'll help with latency anyway.
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I've been idly bashing away at an issue with Postgres for months now. I've a bit of software (custom in-house stuff) that on 24 out of 25 servers does a certain process absolutely fine, no issues what so ever.
On the 25th server though, the process wouldn't quite complete properly, it would fail at the final hurdle which was a simple date change.
It's been a back-burner type issue so I'd not committed much time to working it out until management started to get angsty so I spent most of yesterday bashing away at it.
Obvious checks were done first:
Postgres version (9.6)
Software version
Windows patches (Server 2019)
GPO's
NTFS permissions
etc
All checked out as matches across every server. Went through the Postgres and the in-house software logs at length, had one of the developers build a stand alone executable for the process with a ridiculous amount of logging, still no dice. No indicators. Procmon and Wireshark logs showed the same story, nothing clear at all as to what was going on.
So then we take a backup of the database, load it in with a different name for testing and start running the process to find that it now works fine on the cloned database. This leads us to thinking there's maybe a formatting issue of some kind in the database, conscious of the idea that doing the backup & restore would shake things around. So we go back to the live, back it up again - delete the DB from postgres and restore from the backup.
No dice. Still broken.
Cue some serious confusion. We've done essentially the same thing with cloning live to test and are still getting the same fault at the end of the process.
After some head scratching and more prodding around in the logs I hit upon an idea of doing a fresh backup of the live DB, deleting the database, restoring the backup with a different name and then pointing the live software install to the newly named live DB and testing the process again.
It works!
For clarity, the filenames are basic alpha only. Upper case and lower case. No numbers, no symbols. Less than 15 characters in length.
I'm at a loss as to why it's now working and I'd love to get some input from the community.
It's been almost 3 months I have switched my platform to Google Cloud (Compute Engine + Cloud SQL + Cloud Storage).
I am very happy with it but from time to time I noticed big latency on the Cloud SQL server. My VMs from Compute Engine and my Cloud SQL instance are all on the same location (us-1) datacenter.
Since my Java backend makes a lot of SQL queries to generate a server response, the response times may vary from 250-300ms (normal) up to 2s!
In the console, I notice absolutely nothing: no CPU peaks, no read/write peaks, no backup running, nothing. No alert. Last time it happened, it lasted for a few days and then the response times went suddenly better than ever.
I am pretty sure Google works on the infrastructure behind the scenes... But no way to point that out.
So here's my questions:
Has anybody else ever had noticed the same kind of problem?
It is really annoying for me because my web pages get very slow and I have absolutely no control over it. Plus I loose a lot of time because I generally never first suspect a hardware problem / maintenance but instead something that we introduced in our app. Is it normal or do I have a problem on my SQL instance?
Is there anywhere I can have visibility over what's Google doing on the hardware? I know there are maintenance alerts, but for my zone it seems always empty when it happen.
The only option I have for now is to wait and that is really not acceptable.
I suspect that Google does some sort of IO throttling and their algorithm is not very sophisticated. We have a build server which slows down to a crawl if we do more than two builds within an hour. The build that normally takes 15 minutes will run for more than an hour and we usually terminate it and re-run manually later. This question describes a similar problem and the recommended solution is to use larger volumes as they come with more IO allowance.
I'm a newbie in web server administration. I've read multiple times that flask built-in web server is not designed for "production", and must be used only for tests and debug...
But what if my app touchs only a thousand users who occasionnaly send data to the server ?
If it works, when will I have to bother with the configuration of a more sophisticated web server ? (I am looking for approximative metrics).
In a nutshell, I would love to find what the builtin web server can do (with approx thresholds) and what it cannot.
Thanks a lot !
There isn't one right answer to this question, but here are some things to keep in mind:
With the right amount of horizontal scaling, it is quite possible you could keep scaling out use of the debug server forever. When exactly you would need to start scaling (or switch to using a "real" web server) would also depend on the environment you are hosting in, the expectations of the users, etc.
The main issue you would probably run into is that the server is single-threaded. This means that it will handle each request one at a time, serially. This means that if you are trying to serve more than one request (including favicons, static items like images, CSS and Javascript files, etc.) the requests will take longer. If any given requests happens to take a long time (say, 20 seconds) then your entire application is unresponsive for that time (20 seconds). This is only the default, of course: you could bump the thread counts (or have requests be handled in other processes), which might alleviate some issues. But once again, it can still be slow under a "high" load. What is considered a "high" load will be dependent on your application and the expectations of a maximum acceptable response time.
Another issue is security: if you are concerned at ALL about security (and not just the security of the data in the application itself, but the security of the box that will be running it as well) then you should not use the development server. It is not ready to withstand any sort of attack.
Finally, the development server could just fail outright. It is not designed to be used as a long-running process (days, weeks, months), and so it has not been well tested to work in this capacity.
So, yes, it has limitations. Yes, you could still conceivably use it in production. And yes, I would still recommend using a "real" web server. If you don't like the idea of needing to install something like Apache or Nginx, you can still go with a solution that is still as easy as "run a python script" by using some of the WSGI Standalone servers, which can run a server that is designed to be in production with something just as simple as running python run_app.py in the command line. You typically just need to create a 4-5 line python script to import and create the server object, point it to your Flask app, and run it.
gunicorn could be run with only the following on the command line, no extra script needed:
gunicorn myproject:app
...where "myproject" is the Python package that contains the app Flask object. Keep in mind that one of developers of gunicorn would probably recommend against this approach. See https://serverfault.com/questions/331256/why-do-i-need-nginx-and-something-like-gunicorn.
The OP has long-since moved on, but for those who encounter this question in the future I would just add that setting up an Apache server, even on a laptop, is free and pretty easy. It can be readily configured for as few or as many features as you want just by uncomment in or commenting out lines in the config file. There might be an even easier GUI method for doing that nowdays, but just editing the configs is simple.
I have a application built on Zend Framework I am trying to optimize.
I did some Xdebug profiling and although i cant say i understand every nitty gritty of the results i got, some things were quite obvious from the result.
For instance, the file Bootstrap.php seems to be the one gulping most of the time taking 4,553MS seconds which accounts for 92.49% of the total time.
And if i dig further, I could see that Zend_Application_Bootstrap_Boostrap->run takes the bulk of the time. Checking this out again, I found out that Zend_Controller_Front->Dispatch might actually be the function inside the Boostrap.php that takes time to execute.
Question is, from these indices that i have, how best can I go about Optimizing the application? If it caching, how do i go about applying Caching to this situation?
Thanks
From the look of the callgrinds, on the login page the app is spending most of it's time in curl_exec, which is to be expected if you're doing a remote login. But it is doing 10 separate curl_execs which seems excessive. I'm not familiar with the LinkedIn login auth, but is it possible your app is running the remote login code multiple times?
On the standard page request the app is spending most of its time connecting to MySQL, and it seems to be doing this twice. Are you using a remote DB server, and do you need two separate DB connections?
Assuming you are using a remote DB server and it is on the same network as your web server, there seems to be some networking issue there. I'd check the latency to that server if you can, and try connecting to the IP address instead of a hostname to see if that makes any difference (if doing this is much faster this would suggest an issue with the DNS setup on your web server).
I have a problem with mysql db connection..
My application does a lot of queries to the database.
And loads results of the query in the page.
Before, I used mysql_connect for the connection. I separated
it in a different file the connection and then just
include the file in my subsequent php files.
So it seems like, i open the dbase and query everytime.
The problem came when the server's max connection per hour to the db was set to like 50. then just a couple of tries in my page, it reached the max connection per hour. It turned out
I have not been closing my connections.
So i tried closing the connections every time my php scripts end. I am using AJAX (async calls) to php. The problem was still the same, just a couple of views and then it reaches the max.
So i tried using the mysql_pconnect(). In my wamp, i set the max connections to 2. It kinda worked well, but when transferred to server, in linux, the connection was set to 2 also, it again had the max connection problem.
Apache is used as the webserver. Its really frustrating.
Can somebody give light on this?
Thanks a lot :)