Is there a way I can cause errno 23 (ENFILE File table overflow) on purpose?
I am doing socket programming and I want to check if creating too many sockets can cause this error. As I understand - created socked is treated as a file descriptor, so it should count towards system limit of opened files.
Here is a part of my python script, which creates the sockets
def enfile():
nofile_soft_limit = 10000
nofile_hard_limit = 20000
resource.setrlimit(resource.RLIMIT_NOFILE, (nofile_soft_limit,nofile_hard_limit))
sock_table = []
for i in range(0, 10000):
print "Creating socket number {0}".format(i)
try:
temp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.SOL_UDP)
except socket.error as msg:
print 'Failed to create socket. Error code: ' + str(msg[0]) + ' , Error message : ' + msg[1]
print msg[0]
sock_table.append(temp)
With setrlimit() I change the processes limit of open files to a high value, so that I don't get Errno24 (EMFILE).
I have tried two approaches:
1) Per-user limit
by changing /etc/security/limits.conf
root hard nofile 5000
root soft nofile 5000
(logged in with a new session after that)
2) System-wide limit
by changing /etc/sysctl.conf
fs.file-max = 5000
and then run sysctl -p to apply the changes.
My script easily creates 10k sockets despite per-user and system-wide limits, and it ends with errno 24 (EMFILE).
Is it possible to achieve my goal? I am using two OS'es - CentOS 6.7 and Fedora 20. Maybe there are some other settings to make in these system?
Thanks!
ENFILE will only happen if the system-wide limit is reached, whereas the settings you've tried so far are per-process, so only related to EMFILE. For more details including which system-wide settings to change to trigger ENFILE, see this answer: https://stackoverflow.com/a/24862823/4323 as well as https://serverfault.com/questions/122679/how-do-ulimit-n-and-proc-sys-fs-file-max-differ
You should look for an answer in kernel sources.
Socket call returns ENFILE in __sock_create() when sock_alloc() returns NULL. This can happen only if it can't allocate a new inode.
You can use:
df -i
to check for your inodes usage.
Unfortunately the inode limit can't be changed dynamically.
Generally the total number of inodes and the space reserved for these inodes is set when the filesystem is first created.
Solution?
Modern filesystems like Brtfs and XFS use dynamic inodes to avoid inode limits - if you have one of them it could be impossible to do that.
If you have LVM disk, decreasing the size of the volume could help.
But if you want to be sure of simulating a situation from your post you should create googol of files, 1 byte each and you will run out of inodes long before you run out of disk. Then you can try to create socket.
If I am wrong, please correct me.
Related
I'd like to setup a "timeout" for the ldap library (python-ldap-2.4.15-2.el7.x86_64) and python 2.7
I'm forcing my /etc/hosts to resolve an non existing IP address in
order to raise the timeout.
I've followed several examples and took a look at the documentation or questions like this one without luck.
By now I've tried forcing global timeouts before the initialize:
ldap.set_option(ldap.OPT_NETWORK_TIMEOUT, 1)
ldap.set_option(ldap.OPT_TIMEOUT, 1)
ldap.protocol_version=ldap.VERSION3
Forced the same values at object level:
ldap_obj = ldap.initialize("ldap://%s:389" % LDAPSERVER ,trace_level=9)
ldap_obj.set_option(ldap.OPT_NETWORK_TIMEOUT, 1)
ldap_obj.set_option(ldap.OPT_TIMEOUT, 1)
I've also tried with:
ldap.network_timeout = 1
ldap.timelimit = 1
And used both methods, search and search_st (The synchronous form with timeout)
Finally this is the code:
def testLDAPConex( LDAPSERVER ) :
"""
Check ldap
"""
ldap.set_option(ldap.OPT_NETWORK_TIMEOUT, 1)
ldap.set_option(ldap.OPT_TIMEOUT, 1)
ldap.protocol_version=ldap.VERSION3
ldap.network_timeout = 1
ldap.timelimit = 1
try:
ldap_obj = ldap.initialize("ldap://%s:389" % LDAPSERVER ,trace_level=9)
ldap_result_id = ldap_obj.search("ou=people,c=this,o=place", ldap.SCOPE_SUBTREE, "cn=user")
I've printed the constants of the object OPT_NETWORK_TIMEOUT and OPT_TIMEOUT, the values were assigned correctly.
The execution time is 56s everytime and I'm not able to control the amount of seconds for the timeout.
Btw, the same code in python3 does work as intended:
real 0m10,094s
user 0m0,072s
sys 0m0,013s
After some testing I've decided to rollback the VM to a previous state.
The Networking Team were doing changes across the network configuration, that might have changed the behaviour over the interface and some kind of bug when the packages were being sent over the wire in:
ldap_result_id = ldap_obj.search("ou=people,c=this,o=place", ldap.SCOPE_SUBTREE, "cn=user")
After restoring the VM, which included a restart, the error of not being able to reach LDAP raises as expected.
I'm trying to use pyspeedtest to get the upload/download speed of my connecting but I keep getting the following error which I couldn't resolve:
import pyspeedtest
st = pyspeedtest.SpeedTest()
st.download()
Exception: Cannot find a test server
Any suggestions/insights would be welcome!
It actually does work if you change the url in the pyspeedtest.py file from www.speedtest.net to c.speedtest.net on line 186 in v1.2.7 of the script.
Edit: added an example of how to get it to work
You can edit the pyspeedtest.py script (located at /usr/local/lib/python2.7/dist-packages/pyspeedtest.py on my raspberry pi 3) by using vi, e.g.:
sudo vi /usr/local/lib/python2.7/dist-packages/pyspeedtest.py
Go to line 186 and change the following line:
connection = self.connect('www.speedtest.net')
to:
connection = self.connect('c.speedtest.net')
Then run pyspeedtest using the wrapper in /usr/local/bin:
/usr/local/bin/pyspeedtest
Using server: speedtest.wilkes.net
Ping: 41 ms
Download speed: 46.06 Mbps
Upload speed: 11.58 Mbps
Or use the python interpreter:
>>> import pyspeedtest
>>> st = pyspeedtest.SpeedTest()
>>> st.ping()
41.70024394989014
>>> st.download()
44821310.72337018
>>> st.upload()
14433296.732646577
The project hasn't been updated since mid-2016. And the last update was updated user-agent to prevent SpeedTest block... And if you skim the code, there are [comments like this]:(https://github.com/fopina/pyspeedtest/blob/master/pyspeedtest.py#L188)
# really contribute to speedtest.net OS statistics
# maybe they won't block us again...
And there have been bugs posted to GitHub about the project not working, with no response.
So, my guess is: This project probably violates SpeedTest.net's terms of service, so they blocked it. The author tried to get around the block, they blocked it again, and the author gave up. In the intervening two years, any other servers it used as backups either blocked it, or shut down (e.g., speedtest.serv.pt, mentioned in the docs, no longer exists).
There is a pull request from another user that might fix it, although it appears to be failing the CI test. If you want to try it yourself, you can.
But otherwise, you can't use this library, and there's no way anyone can help you use it; it just doesn't work. You'll have to find another way to do the same thing.
I'm using a NanoPi M1 (Allwinner H3 board) & running a Yocto-based OS. On my first encounter with ZeroConf-python,
>>> from zeroconf import Zeroconf, ServiceBrowser
>>> zero = Zeroconf()
I'm getting the error:
File "/usr/lib/python3.5/site-packages/zeroconf.py", line 1523, in __init__
socket.inet_aton(_MDNS_ADDR) + socket.inet_aton(i))
OSError: [Errno 105] No buffer space available
This error doesn't arise when I run it in Raspbian(on RPI).
I've tried to search for fixes to such errors in homeassistant, but none provide a good overview to the real problem, rest-aside the solution.
Update the net/ipv4/igmp_max_memberships value of sysctl to greater than zero.
Execute the following commands on the terminal:
$ sysctl -w net.ipv4.igmp_max_memberships=20 (or any other value greater than zero)
&
$ sysctl -w net.ipv4.igmp_max_msf=10
Then, restart the avahi-daemon
systemctl restart avahi-daemon
You can verify the existing values of the above keys using
'sysctl net.ipv4.igmp_max_memberships'.
An addition to the answer of Neelotpal:
This post includes a nice solution proposal with all options to check for this problem:
# Bigger buffers (to make 40Gb more practical). These are maximums, but the default is unaffected.
net.core.wmem_max=268435456
net.core.rmem_max=268435456
net.core.netdev_max_backlog=10000
# Avoids problems with multicast traffic arriving on non-default interfaces
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.all.rp_filter=0
# Force IGMP v2 (required by CBF switch)
net.ipv4.conf.all.force_igmp_version=2
net.ipv4.conf.default.force_igmp_version=2
# Increase the ARP cache table
net.ipv4.neigh.default.gc_thresh3=4096
net.ipv4.neigh.default.gc_thresh2=2048
net.ipv4.neigh.default.gc_thresh1=1024
# Increase number of multicast groups permitted
net.ipv4.igmp_max_memberships=1024
I don't suggest to just blindly copy these values but to systematically test which one it is that is limiting your resources:
use sysctl <property> to get the currently set value
verify if the property is currently running at the limit by checking system stats
change the configuration as described by Neelotpal with sysctl -w or by changing /etc/sysctl.conf directly and realoading it via sysctl -p
In my case increasing the net.ipv4.igmp_max_memberships did the trick:
I checked the current value with sysctl net.ipv4.igmp_max_memberships which was 20
I checked how many memberships there are with netstat -gn, realizing that my numerous docker containers take up most of that
finally I increased value in syctl.conf, and it worked
And of course it is also good to read up on those properties to understand what they actually do, for example on sysctl-explorer.net.
I am using the shutil.disk_usage() function to find the current disk usage of a particular path (amount available, used, etc.). As far as I can find, this is a wrapper around os.statvfs() calls. I'm finding that it is not giving the answers I'd expect, as comparing to the output of "du" in Linux.
I have obscured some of the paths below for company privacy reasons, but the output and code are otherwise undoctored. I am using Python 3.3.2 64-bit version.
#!/apps/python/3.3.2_64bit/bin/python3
# test of shutils.diskusage module
import shutil
BytesPerGB = 1024 * 1024 * 1024
(total, used, free) = shutil.disk_usage("/data/foo/")
print ("Total: %.2fGB" % (float(total)/BytesPerGB))
print ("Used: %.2fGB" % (float(used)/BytesPerGB))
(total1, used1, free1) = shutil.disk_usage("/data/foo/utils/")
print ("Total: %.2fGB" % (float(total1)/BytesPerGB))
print ("Used: %.2fGB" % (float(used1)/BytesPerGB))
Which outputs:
/data/foo/drivecode/me % disk_usage_test.py
Total: 609.60GB
Used: 291.58GB
Total: 609.60GB
Used: 291.58GB
As you can see, the main problem is I would expect the second amount for "Used" to be much smaller, as it is a subset of the first directory.
/data/foo/drivecode/me % du -sh /data/foo/utils
2.0G /data/foo/utils
As much as I trust "du," I find it hard to believe the Python module would be incorrect either. So perhaps it is just my understanding of Linux filesystems that could be the issue. :)
I wrote a module (based heavily on someone's code here at SO) which recursively gets the disk_usage, which I was using until now. It appears to match the "du" output but is MUCH, much slower than the shutil.disk_usage() function, so I'm hoping I can make that one work.
Thanks much in advance.
The problem is that shutil uses the statvfs system call underneath to determine the space used. This system call has no file-path granularity as far as I'm aware, only file-system granularity. What this means is that the path you provide it with only helps to identify the file system you want to query, not the path's.
In other words, you gave it the path /data/foo/utils and then it determined which file system backs this file path. Then it queried the file system. This becomes apparent when you consider how the used parameter is defined in shutil:
used = (st.f_blocks - st.f_bfree) * st.f_frsize
Where:
fsblkcnt_t f_blocks; /* size of fs in f_frsize units */
fsblkcnt_t f_bfree; /* # free blocks */
unsigned long f_frsize; /* fragment size */
This is why it's giving you the total space used on the entire file system.
Indeed, it seems to me like the du command itself also traverses the file structure and adds up the file sizes. Here is GNU coreutils du command's source code.
The shutil.disk_usage returns the disk usage (i.e. the mount point which backs the path) and not actual file usage under that path. It is equivalent of running df /path/to/mount and not du /path/to/files. Notice that for both directories you got the exact same usage.
From the docs: "Return disk usage statistics about the given path as a named tuple with the attributes total, used and free, which are the amount of total, used and free space, in bytes."
Update for anyone stumbling upon this after 2013:
Depending on your Python version and OS, shutil.disk_usage might support files and directories for the path variable. Here's the breakdown:
Windows:
3.3 - 3.5: only suports mountpoint/filesystem
3.6 - 3.7: directory support
3.8+: file & directory support
Unix:
3.3 - 3.5: only suports mountpoint/filesystem
3.6+: file & directory support
I am trying to set the cachesize in giga bytes for a bdb file. I am using the python interface for bdb. I see the underlying 'C' api for bdb has this option.
int DB->set_cachesize(DB *db, u_int32_t gbytes, u_int32_t bytes, int ncache);
But I am able to pass only one cachesize argument to the btopen function which is being interpreted as cache_size in bytes. This is restricting the max cache_size to 2GB. I would like to be able to set cache size to atleast 4gb.
Any help to be able to set/increase the cache size would be greatly appreciated, thanks in advance!
Below is the python function i am using to set the cache_size.
cache_size = (2*1024*1024*1024) - 1
db = bsddb.btopen(self._bdbFileName, cachesize=cache_size, flag='n')
i am not familiar with python interface of BDB. When i use c api, i really appreciate opening the bdb with an environment and set a lot configurations in the environment.
For example, open a bdb file with environment and the env dir is set to ~/env/. Then put a file named DB_CONFIG in ~/env/ with content:
set_cachesize 4 0 1
The cachesize will be set to 4GB. No code needed.
You can check this for all the available configurations in DB_CONFIG.