Hi Guys I start Mongo remotely on Putty SSH and after mongod, it says "listening for ports" but I can't then leave without shutting down the server. how do I do that?
On linux, look up the Screen module. There are other alternatives that do the same thing as well. It basically makes a saved session that you can reattach to later -- I use it extensively to run long tests/services that I can reattach to quickly.
The Starting and Stopping Mongo documentation article explains several options, one of which is using the --fork command line parameter to start mongod as a background process. Additionally, you can look into using service controls provided by your operating system (e.g. Windows services, init.d, upstart).
You can make a quick Mongo service script in either Windows or Linux.
You can also press CTRL+Z which will basically switch it to a background process. This basically gives you back temrinal (or at least does for me).
I also like "Screen". It is quite powerful and easy to navigate so I would personally give that a try.
Related
MySQL, for example, does not require this. Why MongoDB does?
The problem:
I'm writing an app (for PC) in Java that uses MongoDB. I downloaded a driver (3rd version, the newest) and everything is fine...
...except for the need to launch mongod.exe to actually use a database.
In terms of app, it is extremely user-unfriendly. So in order to use my app, he will need to launch mongod.exe first, and even if it's done automatically by my app (via using runtime), user will still have 2 windows.
Moreover, instead of seeing just my app icon on taskbar.
How it should be:
User will see my app icon and mongod icon:
How it is:
Is there any solution to that? If not, can somebody explain why do we need to start mongod at all? It's very poor design from MongoDB devs, for example when using MySQL your Java app can connect to databases directly, without running any other software that is displayed on taskbar.
If apps that use MongoDB will require from user to launch mongod beforehand, or even if they do it themselves but there are 2 icons on the taskbar and that large black window of mongod running, it would be totally unfriendly to user so there would be no sense to use Mongo.
Mongod is mongoDB server application! without running it there's nothing back there listening to your requests!
Regarding to MySQL, you probably set it as a windows service and windows automatically runs mysqld.exe at windows start up! otherwise you would need to run mysqld.exe too!
I'm trying to start Libreoffice impress automatically once my raspberry pi has started up.
I created:
.config/lxsession/LXDE/autostart
and added my presentation:
sudo libreoffice -show /home/pi/test.odp
When i execute the command in a terminal, all works fine.
However the autostart doesn't seem to work at boot. Libreoffice starts, but then says it can't find the file...
The file .config/lxsession/LXDE/autostart is used to start applications without root privileges. Therefore, you should remove "sudo" from your code:
libreoffice -show /home/pi/test.odp
That should work as intended. If your presentation need root privileges (I don't see why it would, but anyway), you could use gksudo on your code, then at boot you would see a window asking for your password to proceed. The new code would look like this:
gksudo libreoffice -show /home/pi/test.odp
Important: please note you should not try to open a GUI enabled application with sudo or root privileges, as this can have bad consequences, such as modifying permissions and ownership on program files, which could lead to malfunctioning. If you really need to open a GUI application as root, always use gksudo or gksu.
On the other hand, if you really need to open a program at boot with root privileges, you should look into using the file /etc/rc.local or the cron service for that.
I have a collection with about 3,000,000 entries that I need to reindex. This whole thing began when I tried to add a 2d index. To do this, I created an ssh tunnel, opened the mongo shell and tried to use ensureIndex. I'm in a place with a somewhat unreliable internet connection, and an hour in it ended up breaking the pipe. I then tunneled back in, opened the mongo shell and tried to look at the number of indexes using getIndexes; the new index I created showed up, but I wasn't confident it had finished, so I decided to use reIndex. In retrospect, this was stupid. The pipe broke again. Now when I open the shell and try to issue getIndexes, the shell doesn't respond.
So what should I do? Do I need to repair my database? Can I issue reIndex when I have a more reliable internet connection? Is there a way to issue reIndex without keeping the shell open, but without doing it in the background and having it take eons? (I'll check the mongod shell options to see if I can find anything, then check the node.js mongo api so I can try running something as a service on server)
And also, if I end up running reIndex as a service on the server, is there any way to check if it's working? The most frustrating part of this right now is I have no idea if my database is ok, if reIndex is still running, etc. Any help would be much appreciated. Thanks.
You don't have a problem. Mongo runs commands and only stops them if you explicitly kill the operation (db.killOp()).
You do not need to wait for the index operation to finish!
Regarding the connection problems, try using the screen command.
It enables you to create a "persistent" screen - not in the way of disk persistence, but in the means of connection-loss.
I am using helios Eclipse for debugging my code in postgresql.
My aim is to know how postgresql uses join algorithms during the join query, so I started to debug nodenestloop.c which is in the Executor folder.
I gave break points in that file, But whenever I try to debug that file, the control goes to main.c and never comes back,How do I constraint the control only to that particular file(nodenestloop.c)
Below are the following fields which I gave in Debug configurations of Helios Eclipse.
C/C++ Application - src/backend/postgres and
project - pgsql
I followed the steps given in the following link for running the program.
https://wiki.postgresql.org/wiki/Working_with_Eclipse#
I even uncheked the field "Start on Start up=main" , but When I do that, The step in and Step over buttons are not activated and the following problem has popped up.
Could not save master table to file '/home/ravi/workspace/.metadata/.plugins/org.eclipse.core.resources/.safetable/org.eclipse.core.resources'.
/home/ravi/workspace/.metadata/.plugins/org.eclipse.core.resources/.safetable/org.eclipse.core.resources (Permission denied)
So I started eclipse using sudo, but this time the following error has come in the console of eclipse.
"root" execution of the PostgreSQL server is not permitted.
The server must be started under an unprivileged user ID to prevent
possible system security compromise. See the documentation for
more information on how to properly start the server.
Could any one help me with this.
Thank you
Problem 1: User ID mismatch
Reading between the lines, it sounds like you're trying to debug a PostgreSQL instance that's running as the postgres user, or a different user ID to your own anyway. Hence your attempt to use sudo.
That's painful, especially when using an IDE like Eclipse. With plain gdb you can just sudo the gdb command to the desired uid, e.g. sudo -u postgres -p 12345 to attach to pid 12345 running as user postgres. This will not work with Eclipse. In fact, running it with sudo has probably left your workspace with some messed up file permissions; run:
sudo chown -R ravi /home/ravi/workspace/
to fix file ownership.
If you want to debug processes under other user IDs with Eclipse, you'll need to figure out how to make Eclipse run gdb with sudo. Do not just run all of Eclipse with sudo.
Problem 2: Trying to run PostgreSQL under the control of Eclipse
This:
"root" execution of the PostgreSQL server is not permitted. The server must be started under an unprivileged user ID to prevent possible system security compromise. See the documentation for more information on how to properly start the server.
suggests that you're also attempting to let Eclipse start postgres directly. That's very useful if you're trying to debug the postmaster, but since you're talking about the query planner it's clear you want to debug a particular backend. Launching the postmaster under Eclipse is useless for that, you'll be attached to the wrong process.
I think you probably need to read the documentation on PostgreSQL's internals:
Tour of PostgreSQL Internals
PostgreSQL internals through pictures
Documentation chapter - internals
Doing it right
Here's what you need to do - rough outline, since I've only used Eclipse for Java development and do my C development with vim and gdb:
Compile a debug build of PostgreSQL (compiled with ./configure --enable-debug and preferably also CFLAGS="-ggdb -Og -fno-omit-frame-pointer"). Specify a --prefix within your homedir, like --prefix=$HOME/postgres-debug
Put your debug build's bin directory first on your PATH, e.g. export PATH=$HOME/postgres-debug/bin:$PATH
initdb -U postgres -D $HOME/postgres-debug-data a new instance of PostgreSQL from your debug build
Start the new instance with PGPORT=5599 pg_ctl -D $HOME/postgres-debug-data -l $HOME/postgres-debug-data.log -w start
Connect with PGPORT=5599 psql postgres
Do whatever setup you need to do
Get the backend process ID with SELECT pg_backend_pid() in a psql session. Leave that session open; it's the one you'll be debugging.
Attach Eclipse's debugger to that process ID, using the Eclipse project that contains the PostgreSQL extension source code you're debugging. Make sure Eclipse is configured so it can find the PostgreSQL source code you compiled with too (no idea how to do that, see the manual).
Set any desired breakpoints and resume execution
In the psql session, do whatever you need to do to make your extension run and hit the breakpoint
When execution pauses at the breakpoint in Eclipse, debug as desired.
Basic misunderstandings?
Also, in case you're really confused about how all this works: PostgreSQL is a client/server application. If you are attempting to debug a client program that uses libpq or odbc, and expecting a breakpoint to trigger in some PostgreSQL backend extension code, that is not going to happen. The client application communicates with PostgreSQL over a TCP/IP socket. It's a separate program. gdb cannot set breakpoints in the PostgreSQL server when it's connected to the client, because they are separate programs. If you want to debug the server, you have to attach gdb to the server. PostgreSQL uses one process per connection, so you have to attach gdb to the correct server process. Which is why I said to use SELECT pg_backend_pid() above, and attach to the process ID.
See the internals documentation linked above, and:
PostgreSQL site - coding
PostgreSQL wiki - developer resources
Developer FAQ
Attaching gdb to a backend on linux/bsd/unix
I also faced similar issue and resolved it after some struggle
I misunderstood the following point under Debugging with child processes in the wiki (https://wiki.postgresql.org/wiki/Working_with_Eclipse).
5."Start postmaster & one instant of postgresql client (for creating one new postgres)"
The above step should be performed from terminal by starting postgres server and one client.
Hope this helps
Once this is done then debugger in eclipse needs to be started for C/C++ Attach to Application
I'm trying to install PostgreSQL on Cygwin as a user and i'm getting stuck on the part where I have to create a database server, after i execute the pg_ctl command, it just prints "server starting" and runs in the foregorund indefinitely, here's a picture of what I'm talking about:
http://postimg.org/image/oh7ucgt9h/
Im generally a beginner to databases so any pointers would be great.
Chances you are hanging allocating shared memory. Please go with the native Windows build instead. It is far easier to manage.
However if you insist, make sure the ipc-daemon is running before you run PostgreSQL. This will probably solve your problem.
You could run:
ipc-daemon --install-as-service
net start ipc-daemon
And this should do it.