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  • Simple Observation in Django: How Can I Correctly Modify The `attrs` sent to __new__ of a Django Mod

    - by DGGenuine
    Hello, I'm a strong proponent of the observer pattern, and this is what I'd like to be able to do in my Django models.py: class AModel(Model): __metaclass__ = SomethingMagical @post_save(AnotherModel) @classmethod def observe_another_model_saved(klass, sender, instance, created, **kwargs): pass @pre_init('YetAnotherModel') @classmethod def observe_yet_another_model_initializing(klass, sender, *args, **kwargs): pass @post_delete('DifferentApp.SomeModel') @classmethod def observe_some_model_deleted(klass, sender, **kwargs): pass This would connect a signal with sender = the decorator's argument and receiver = the decorated method. Right now my signal connection code all exists in __init__.py which is okay, but a little unmaintainable. I want this code all in one place, the models.py file. Thanks to helpful feedback from the community I'm very close (I think.) (I'm using a metaclass solution instead of the class decorator solution in the previous question/answer because you can't set attributes on classmethods, which I need.) I am having a strange error I don't understand. At the end of my post are the contents of a models.py that you can pop into a fresh project/application to see the error. Set your database to sqlite and add the application to installed apps. This is the error: Validating models... Unhandled exception in thread started by Traceback (most recent call last): File "/Library/Python/2.6/site-packages//lib/python2.6/site-packages/django/core/management/commands/runserver.py", line 48, in inner_run File "/Library/Python/2.6/site-packages/django/core/management/base.py", line 253, in validate raise CommandError("One or more models did not validate:\n%s" % error_text) django.core.management.base.CommandError: One or more models did not validate: local.myothermodel: 'my_model' has a relation with model MyModel, which has either not been installed or is abstract. I've indicated a few different things you can comment in/out to fix the error. First, if you don't modify the attrs sent to the metaclass's __new__, then the error does not arise. (Note even if you copy the dictionary element by element into a new dictionary, it still fails; only using the exact attrs dictionary works.) Second, if you reference the first model by class rather than by string, the error also doesn't arise regardless of what you do in __new__. I appreciate your help. I'll be githubbing the solution if and when it works. Maybe other people would enjoy a simplified way to use Django signals to observe application happenings. #models.py from django.db import models from django.db.models.base import ModelBase from django.db.models import signals import pdb class UnconnectedMethodWrapper(object): sender = None method = None signal = None def __init__(self, signal, sender, method): self.signal = signal self.sender = sender self.method = method def post_save(sender): return _make_decorator(signals.post_save, sender) def _make_decorator(signal, sender): def decorator(view): return UnconnectedMethodWrapper(signal, sender, view) return decorator class ConnectableModel(ModelBase): """ A meta class for any class that will have static or class methods that need to be connected to signals. """ def __new__(cls, name, bases, attrs): unconnecteds = {} ## NO WORK newattrs = {} for name, attr in attrs.iteritems(): if isinstance(attr, UnconnectedMethodWrapper): unconnecteds[name] = attr newattrs[name] = attr.method #replace the UnconnectedMethodWrapper with the method it wrapped. else: newattrs[name] = attr ## NO WORK # newattrs = {} # for name, attr in attrs.iteritems(): # newattrs[name] = attr ## WORKS # newattrs = attrs new = super(ConnectableModel, cls).__new__(cls, name, bases, newattrs) for name, unconnected in unconnecteds.iteritems(): _connect_signal(unconnected.signal, unconnected.sender, getattr(new, name), new._meta.app_label) return new def _connect_signal(signal, sender, receiver, default_app_label): # full implementation also accepts basestring as sender and will look up model accordingly signal.connect(sender=sender, receiver=receiver) class MyModel(models.Model): __metaclass__ = ConnectableModel @post_save('In my application this string matters') @classmethod def observe_it(klass, sender, instance, created, **kwargs): pass @classmethod def normal_class_method(klass): pass class MyOtherModel(models.Model): ## WORKS # my_model = models.ForeignKey(MyModel) ## NO WORK my_model = models.ForeignKey('MyModel')

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  • Norton Ghost 15 prompts for a recovery CD when restoring a disk image. Why?

    - by Zak
    I used ghost 15 to create a drive image. Now I'm trying to restore that image onto identical hardware to recover. However after the whole image has been placed onto the new disk/hardware, at the end of the copy, ghost is asking me to enter the recovery CD. But the recovery CD is in the danged drive(assuming that the recovery CD is the CD used to recover the image)! So first, if I'm just imaging a drive, why is norton asking me for some recovery CD? Second, what recovery CD is norton talking about, if it's not the ghost CD? Does it want me to give it the windows OS recovery CD that sipped with the original hardware? Damn you norton ghost!!!

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  • Windows Recovery Console - forgot password

    - by Jason
    I upgraded to Windows XP SP3, which immediately "broke" the laptop - it never booted with SP3 on it. I put in the Windows XP install disk I had originally used to set up the laptop, and it ran for a while, then said there's no hard disk present, so it can't continue. BIOS still sees the hard disk. I put the hard disk in an external USB case, and I can read/write to it with the other laptop. I then put the hard disk back in it's laptop, restarted with the Windows CD, and tried to get into the Recovery Console, but I forgot the password and can't "log on" to the drive. I'd also like to know if I can fix the broken files (which ones?) from the other laptop (via USB), and if I can "log on" to an external disk with the Recovery Console. (Also, the data won't fit on my other laptop, and I don't have all the install CDs for software on the disk.) Any help appreciated.

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  • Create mirror software raid with bad blocks hdd. How to check data integrity?

    - by rumburak
    There is error in System event log like this one: "The device, \Device\Harddisk1\DR1, has a bad block." Because of above I created Raid 1 on this disk and other one. I'm using Windows Server 2008 R2 software RAID volumes. Volume in Disk Manager is marked as "Failed Redundancy" and "At Risk". I could command to "Reactivate Disk" and it's starts to re-sync, but after a while it stops and returns to previous state. It stops re-sync on bad block on old disk and creates same error in System event log. Old disk status is Errors, new disk status is Online. How can I check that there is exact copy of the old disk on new one ? It is server machine so I would prefer to keep it running during this check.

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  • SQL - Converting 24-hour ("military") time (2145) to "AM/PM time" (9:45 pm)

    - by CheeseConQueso
    I have 2 fields I'm working with that are stored as smallint military structured times. Edit I'm running on IBM Informix Dynamic Server Version 10.00.FC9 beg_tm and end_tm Sample values beg_tm 545 end_tm 815 beg_tm 1245 end_tm 1330 Sample output beg_tm 5:45 am end_tm 8:15 am beg_tm 12:45 pm end_tm 1:30 pm I had this working in Perl, but I'm looking for a way to do it with SQL and case statements. Is this even possible? EDIT Essentially, this formatting has to be used in an ACE report. I couldn't find a way to format it within the output section using simple blocks of if(beg_tm>=1300) then beg_tm = vbeg_tm - 1200 Where vbeg_tm is a declared char(4) variable EDIT This works for hours =1300 (EXCEPT FOR 2230 !!) select substr((beg_tm-1200),0,1)||":"||substr((beg_tm-1200),2,2) from mtg_rec where beg_tm>=1300; This works for hours < 1200 (sometimes.... 10:40 is failing) select substr((mtg_rec.beg_tm),0,(length(cast(beg_tm as varchar(4)))-2))||":"||(substr((mtg_rec.beg_tm),2,2))||" am" beg_tm from mtg_rec where mtg_no = 1; EDIT Variation of casting syntax used in Jonathan Leffler's expression approach SELECT beg_tm, cast((MOD(beg_tm/100 + 11, 12) + 1) as VARCHAR(2)) || ':' || SUBSTRING(cast((MOD(beg_tm, 100) + 100) as CHAR(3)) FROM 2) || SUBSTRING(' am pm' FROM (MOD(cast((beg_tm/1200) as INT), 2) * 3) + 1 FOR 3), end_tm, cast((MOD(end_tm/100 + 11, 12) + 1) as VARCHAR(2)) || ':' || SUBSTRING(cast((MOD(end_tm, 100) + 100) as CHAR(3)) FROM 2) || SUBSTRING(' am pm' FROM (MOD(cast((end_tm/1200) as INT), 2) * 3) + 1 FOR 3) FROM mtg_rec where mtg_no = 39;

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  • High Load mysql on Debian server stops every day. Why?

    - by Oleg Abrazhaev
    I have Debian server with 32 gb memory. And there is apache2, memcached and nginx on this server. Memory load always on maximum. Only 500m free. Most memory leak do MySql. Apache only 70 clients configured, other services small memory usage. When mysql use all memory it stops. And nothing works, need mysql reboot. Mysql configured use maximum 24 gb memory. I have hight weight InnoDB bases. (400000 rows, 30 gb). And on server multithread daemon, that makes many inserts in this tables, thats why InnoDB. There is my mysql config. [mysqld] # # * Basic Settings # default-time-zone = "+04:00" user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp language = /usr/share/mysql/english skip-external-locking default-time-zone='Europe/Moscow' # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. # # * Fine Tuning # #low_priority_updates = 1 concurrent_insert = ALWAYS wait_timeout = 600 interactive_timeout = 600 #normal key_buffer_size = 2024M #key_buffer_size = 1512M #70% hot cache key_cache_division_limit= 70 #16-32 max_allowed_packet = 32M #1-16M thread_stack = 8M #40-50 thread_cache_size = 50 #orderby groupby sort sort_buffer_size = 64M #same myisam_sort_buffer_size = 400M #temp table creates when group_by tmp_table_size = 3000M #tables in memory max_heap_table_size = 3000M #on disk open_files_limit = 10000 table_cache = 10000 join_buffer_size = 5M # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP #myisam_use_mmap = 1 max_connections = 200 thread_concurrency = 8 # # * Query Cache Configuration # #more ignored query_cache_limit = 50M query_cache_size = 210M #on query cache query_cache_type = 1 # # * Logging and Replication # # Both location gets rotated by the cronjob. # Be aware that this log type is a performance killer. #log = /var/log/mysql/mysql.log # # Error logging goes to syslog. This is a Debian improvement :) # # Here you can see queries with especially long duration log_slow_queries = /var/log/mysql/mysql-slow.log long_query_time = 1 log-queries-not-using-indexes # # The following can be used as easy to replay backup logs or for replication. # note: if you are setting up a replication slave, see README.Debian about # other settings you may need to change. #server-id = 1 #log_bin = /var/log/mysql/mysql-bin.log server-id = 1 log-bin = /var/lib/mysql/mysql-bin #replicate-do-db = gate log-bin-index = /var/lib/mysql/mysql-bin.index log-error = /var/lib/mysql/mysql-bin.err relay-log = /var/lib/mysql/relay-bin relay-log-info-file = /var/lib/mysql/relay-bin.info relay-log-index = /var/lib/mysql/relay-bin.index binlog_do_db = 24avia expire_logs_days = 10 max_binlog_size = 100M read_buffer_size = 4024288 innodb_buffer_pool_size = 5000M innodb_flush_log_at_trx_commit = 2 innodb_thread_concurrency = 8 table_definition_cache = 2000 group_concat_max_len = 16M #binlog_do_db = gate #binlog_ignore_db = include_database_name # # * BerkeleyDB # # Using BerkeleyDB is now discouraged as its support will cease in 5.1.12. #skip-bdb # # * InnoDB # # InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/. # Read the manual for more InnoDB related options. There are many! # You might want to disable InnoDB to shrink the mysqld process by circa 100MB. #skip-innodb # # * Security Features # # Read the manual, too, if you want chroot! # chroot = /var/lib/mysql/ # # For generating SSL certificates I recommend the OpenSSL GUI "tinyca". # # ssl-ca=/etc/mysql/cacert.pem # ssl-cert=/etc/mysql/server-cert.pem # ssl-key=/etc/mysql/server-key.pem [mysqldump] quick quote-names max_allowed_packet = 500M [mysql] #no-auto-rehash # faster start of mysql but no tab completition [isamchk] key_buffer = 32M key_buffer_size = 512M # # * NDB Cluster # # See /usr/share/doc/mysql-server-*/README.Debian for more information. # # The following configuration is read by the NDB Data Nodes (ndbd processes) # not from the NDB Management Nodes (ndb_mgmd processes). # # [MYSQL_CLUSTER] # ndb-connectstring=127.0.0.1 # # * IMPORTANT: Additional settings that can override those from this file! # The files must end with '.cnf', otherwise they'll be ignored. # !includedir /etc/mysql/conf.d/ Please, help me make it stable. Memory used /etc/mysql # free total used free shared buffers cached Mem: 32930800 32766424 164376 0 139208 23829196 -/+ buffers/cache: 8798020 24132780 Swap: 33553328 44660 33508668 Maybe my problem not in memory, but MySQL stops every day. As you can see, cache memory free 24 gb. Thank to Michael Hampton? for correction. Load overage on server 3.5. Maybe hdd or another problem? Maybe my config not optimal for 30gb InnoDB ? I'm already try mysqltuner and tunung-primer.sh , but they marked all green. Mysqltuner output mysqltuner >> MySQLTuner 1.0.1 - Major Hayden <[email protected]> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.5.24-9-log [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: -Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 112G (Tables: 1528) [--] Data in InnoDB tables: 39G (Tables: 340) [--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17) [!!] Total fragmented tables: 344 -------- Performance Metrics ------------------------------------------------- [--] Up for: 8h 18m 33s (14M q [478.333 qps], 259K conn, TX: 9B, RX: 5B) [--] Reads / Writes: 84% / 16% [--] Total buffers: 10.5G global + 81.1M per thread (200 max threads) [OK] Maximum possible memory usage: 26.3G (83% of installed RAM) [OK] Slow queries: 1% (259K/14M) [!!] Highest connection usage: 100% (201/200) [OK] Key buffer size / total MyISAM indexes: 1.5G/5.6G [OK] Key buffer hit rate: 100.0% (6B cached / 1M reads) [OK] Query cache efficiency: 74.3% (8M cached / 11M selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 247K sorts) [!!] Joins performed without indexes: 106025 [!!] Temporary tables created on disk: 49% (351K on disk / 715K total) [OK] Thread cache hit rate: 99% (249 created / 259K connections) [!!] Table cache hit rate: 15% (2K open / 13K opened) [OK] Open file limit used: 15% (3K/20K) [OK] Table locks acquired immediately: 99% (4M immediate / 4M locks) [!!] InnoDB data size / buffer pool: 39.4G/5.9G -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance MySQL started within last 24 hours - recommendations may be inaccurate Reduce or eliminate persistent connections to reduce connection usage Adjust your join queries to always utilize indexes Temporary table size is already large - reduce result set size Reduce your SELECT DISTINCT queries without LIMIT clauses Increase table_cache gradually to avoid file descriptor limits Variables to adjust: max_connections (> 200) wait_timeout (< 600) interactive_timeout (< 600) join_buffer_size (> 5.0M, or always use indexes with joins) table_cache (> 10000) innodb_buffer_pool_size (>= 39G) Mysql primer output -- MYSQL PERFORMANCE TUNING PRIMER -- - By: Matthew Montgomery - MySQL Version 5.5.24-9-log x86_64 Uptime = 0 days 8 hrs 20 min 50 sec Avg. qps = 478 Total Questions = 14369568 Threads Connected = 16 Warning: Server has not been running for at least 48hrs. It may not be safe to use these recommendations To find out more information on how each of these runtime variables effects performance visit: http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html Visit http://www.mysql.com/products/enterprise/advisors.html for info about MySQL's Enterprise Monitoring and Advisory Service SLOW QUERIES The slow query log is enabled. Current long_query_time = 1.000000 sec. You have 260626 out of 14369701 that take longer than 1.000000 sec. to complete Your long_query_time seems to be fine BINARY UPDATE LOG The binary update log is enabled Binlog sync is not enabled, you could loose binlog records during a server crash WORKER THREADS Current thread_cache_size = 50 Current threads_cached = 45 Current threads_per_sec = 0 Historic threads_per_sec = 0 Your thread_cache_size is fine MAX CONNECTIONS Current max_connections = 200 Current threads_connected = 11 Historic max_used_connections = 201 The number of used connections is 100% of the configured maximum. You should raise max_connections INNODB STATUS Current InnoDB index space = 214 M Current InnoDB data space = 39.40 G Current InnoDB buffer pool free = 0 % Current innodb_buffer_pool_size = 5.85 G Depending on how much space your innodb indexes take up it may be safe to increase this value to up to 2 / 3 of total system memory MEMORY USAGE Max Memory Ever Allocated : 23.46 G Configured Max Per-thread Buffers : 15.84 G Configured Max Global Buffers : 7.54 G Configured Max Memory Limit : 23.39 G Physical Memory : 31.40 G Max memory limit seem to be within acceptable norms KEY BUFFER Current MyISAM index space = 5.61 G Current key_buffer_size = 1.47 G Key cache miss rate is 1 : 5578 Key buffer free ratio = 77 % Your key_buffer_size seems to be fine QUERY CACHE Query cache is enabled Current query_cache_size = 200 M Current query_cache_used = 101 M Current query_cache_limit = 50 M Current Query cache Memory fill ratio = 50.59 % Current query_cache_min_res_unit = 4 K MySQL won't cache query results that are larger than query_cache_limit in size SORT OPERATIONS Current sort_buffer_size = 64 M Current read_rnd_buffer_size = 256 K Sort buffer seems to be fine JOINS Current join_buffer_size = 5.00 M You have had 106606 queries where a join could not use an index properly You have had 8 joins without keys that check for key usage after each row join_buffer_size >= 4 M This is not advised You should enable "log-queries-not-using-indexes" Then look for non indexed joins in the slow query log. OPEN FILES LIMIT Current open_files_limit = 20210 files The open_files_limit should typically be set to at least 2x-3x that of table_cache if you have heavy MyISAM usage. Your open_files_limit value seems to be fine TABLE CACHE Current table_open_cache = 10000 tables Current table_definition_cache = 2000 tables You have a total of 1910 tables You have 2151 open tables. The table_cache value seems to be fine TEMP TABLES Current max_heap_table_size = 2.92 G Current tmp_table_size = 2.92 G Of 366426 temp tables, 49% were created on disk Perhaps you should increase your tmp_table_size and/or max_heap_table_size to reduce the number of disk-based temporary tables Note! BLOB and TEXT columns are not allow in memory tables. If you are using these columns raising these values might not impact your ratio of on disk temp tables. TABLE SCANS Current read_buffer_size = 3 M Current table scan ratio = 2846 : 1 read_buffer_size seems to be fine TABLE LOCKING Current Lock Wait ratio = 1 : 185 You may benefit from selective use of InnoDB. If you have long running SELECT's against MyISAM tables and perform frequent updates consider setting 'low_priority_updates=1'

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  • What can I do to give some more love and disk space to my database on Ubuntu?

    - by Yaron Naveh
    I'm new to linux. I've deployed a db to ubuntu server on amazon and found out I'm low on disk space. did df (see below) - and found out that I'm 89% capacity on one file system, but less on others. What does this mean? Do I have a few partitions and can now utilize others besides /dev/xvda1? Also /dev/xvdb seems large, is it safe to put the db in it and only use it? If so do I need to mount it or do something special? $> df -lah Filesystem Size Used Avail Use% Mounted on /dev/xvda1 8.0G 6.7G 914M 89% / proc 0 0 0 - /proc sysfs 0 0 0 - /sys none 0 0 0 - /sys/fs/fuse/connections none 0 0 0 - /sys/kernel/debug none 0 0 0 - /sys/kernel/security udev 3.7G 8.0K 3.7G 1% /dev devpts 0 0 0 - /dev/pts tmpfs 1.5G 164K 1.5G 1% /run none 5.0M 0 5.0M 0% /run/lock none 3.7G 0 3.7G 0% /run/shm /dev/xvdb 414G 199M 393G 1% /mnt

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  • Windows 7 - swap file on a USB disk? [closed]

    - by Sara Cohen
    Possible Duplicate: How to move the page file to another physical disk location Windows 7 I was given temporarily a PC, running Windows 7 Ultimate. The problem is it's hard drive is full, there are like 250 MB free. The swap file is set to none. It has 4 GB RAM. When I load a few tabs in Chrome or IE and start a game it runs out of memory. I already emptied Recycle Bin, %temp%, etc. Deleting/moving user files or adding RAM is not an option. Now I have a USB 3 7200 RPM drive, it's connected to a USB 3 port and is really fast. Is there a way to create a swap file on that drive?

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  • How to setup RAM disk drive using python or WMI?

    - by Ming Xie
    Hi, The background of my question is associated with Tesseract, the free OCR engine (1985-1995 by HP, now hosting in Google). It specifically requires an input file and an output file; the argument only takes filename (not stream / binary string), so in order to use the wrapper API such as pytesser and / or python-tesser.py, the OCR temp files must be created. I, however, have a lot of images need to OCR; frequent disk write and remove is inevitable (and of course the performance hit). The only choice I could think about is changing the wrapper class and point the temp file to RAM disk, which bring this problem up. If you have better solution, please let me know. Thanks a lot. -M

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  • NTFS disk mounted as fuseblk in ubuntu 12.10 is very slow and a lot of errors when rsync. Is that not a rare thing?

    - by Pablo Marin-Garcia
    I am having problems with a NTFS disk mounted as a fuseblk in my ubuntu 12.10 through external usb3. When I did a 1.1TB backup with rsync the speed was 1-2MB/s (wiht a ext4 disk speed was 70 MB/s before and after trying the NTFS disk). Also after one hour errors started to appear: rsync: write failed on "xxx": No such file or directory recv_files: "yyy" is a directory #but this file is a FILE not a dir ??!! .... As this is the first time I have mounted the NTFS in linux for heavy usage (the data would be used in windows afterwards), I would like to know if this kind of thinks are common o was only that something became unstable in my system and a simply restart would probably have solved it. This leads me to the these questions: Can I trust fuse for manage NTFS disks? Or is a problem of the NTFS tools in linux not yet totally stables for writing? Do people is still suffering from low performance with fuse-NTFS vs ext4 (in the past I have read about people complaining about this)?

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  • How to create iso dvd image for use with Mac OS X's "Disk Utility"?

    - by adolf garlic
    This seemed way easier on my pc. I would just pop a blank dvd in the drive, it asked what I wanted to do with it, to which I would respond, "burn dvd with nero" (paraphrasing), then I would pick "new" and just drag and drop the folders in there. Mac appears to have "Disk Utility" which just requires that I 'choose an image' but then doesn't bother to detail: how to do this what the options mean e.g. format "Mac OS Extended (Journaled)" is that ever going to be readable on a non Mac machine? I want to create an ISO standard DVD as per the 'default' you'd get on nero. All the stuff on the web points to doing things with 'Terminal' (the whole point of buying a Mac was to get away from command line jiggery pokery - I'm trying to burn some photos not land a friggin lunar module here!) Please, if you can just provide some simple instructions on what I need to achive this I'd be extremely grateful. Ta muchley in advance.

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  • What causes "All-in-one USB Card Reader" to create 6 drives that always appear in Disk Management?

    - by tim11g
    I installed a "All-in-one USB Card Reader" to read SD cards and other media. It has caused six new drives to appear in Disk Management with six new drive letter assignments. These drives and letters are always present, even when there are no cards in the reader. When unused, they are labeled "No Media". Why does this multifunction reader cause these phantom Disks to appear and consume drive letters? Every USB port can (and does) allow removable media to be mounted and assigned a drive letter, and the drive letter assignment "disappears" when the USB drive is removed. Why are these card reader's drives and letters staying allocated permanently? Is there anything that can be done to make the slots work like a typical USB drive? (The reader is in fact connected to USB).

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  • what webserver / mod / technique should I use to serve everything from memory?

    - by reinier
    I've lots of lookuptables from which I'll generate my webresponse. I think IIS with Asp.net enables me to keep static lookuptables in memory which I can use to serve up my responses very fast. Are there however also non .net solutions which can do the same? I've looked at fastcgi, but I think this starts X processes, of which anyone can handle Y requests. But the processes are by definition shielded from eachother. I could configure fastcgi to use just 1 process, but does this have scalability implications? anything using PHP or any other interpreted language won't fly because it is also cgi or fastcgi bound right? I understand memcache could be an option, though this would require another (local) socket connection which I'd rather avoid since everything in memory would be much faster. The solution can work under WIndows or Unix... it doesn't matter too much. The only thing which matters is that there will be a lot of requests (100/sec now and growing to 500/sec in a year), and I want to reduce the amount of webservers needed to process it. The current solution is done using PHP and memcache (and the occasional hit to the SQL server backend). Although it is fast (for php anyway), Apache has real problems when the 50/sec is passed. I've put a bounty on this question since I've not seen enough responses to make a wise choice. At the moment I'm considering either Asp.net or fastcgi with C(++).

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  • Weighted round robins via TTL - possible?

    - by Joe Hopfgartner
    I currently use DNS round robin for load balancing, which works great. The records look like this (I have a ttl of 120 seconds) ;; ANSWER SECTION: orion.2x.to. 116 IN A 80.237.201.41 orion.2x.to. 116 IN A 87.230.54.12 orion.2x.to. 116 IN A 87.230.100.10 orion.2x.to. 116 IN A 87.230.51.65 I learned that not every ISP / device treats such a response the same way. For example some DNS servers rotate the addresses randomly or always cycle them through. Some just propagate the first entry, others try to determine which is best (regionally near) by looking at the ip address. However if the userbase is big enough (spreads over multiple ISPs etc) it balances pretty well. The discrepancies from highest to lowest loaded server hardly every exceeds 15%. However now I have the problem that I am introducing more servers into the systems, that not all have the same capacities. I currently only have 1gbps servers, but I want to work with 100mbit and also 10gbps servers too. So what I want is I want to introduce a server with 10 GBps with a weight of 100, a 1 gbps server with a weight of 10 and a 100 mbit server with a weight of 1. I used to add servers twice to bring more traffic to them (which worked nice. the bandwidth doubled almost.) But adding a 10gbit server 100 times to DNS is a bit rediculous. So I thought about using the TTL. If I give server A 240 seconds ttl and server B only 120 seconds (which is about about the minimum to use for round robin, as a lot of dns servers set to 120 if a lower ttl is specified.. so i have heard) I think something like this should occour in an ideal scenario: first 120 seconds 50% of requests get server A -> keep it for 240 seconds. 50% of requests get server B -> keep it for 120 seconds second 120 seconds 50% of requests still have server A cached -> keep it for another 120 seconds. 25% of requests get server A -> keep it for 240 seconds 25% of requests get server B -> keep it for 120 seconds third 120 seconds 25% will get server A (from the 50% of Server A that now expired) -> cache 240 sec 25% will get server B (from the 50% of Server A that now expired) -> cache 120 sec 25% will have server A cached for another 120 seconds 12.5% will get server B (from the 25% of server B that now expired) -> cache 120sec 12.5% will get server A (from the 25% of server B that now expired) -> cache 240 sec fourth 120 seconds 25% will have server A cached -> cache for another 120 secs 12.5% will get server A (from the 25% of b that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of b that now expired) -> cache 120 secs 12.5% will get server A (from the 25% of a that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of a that now expired) -> cache 120 secs 6.25% will get server A (from the 12.5% of b that now expired) -> cache 240 secs 6.25% will get server B (from the 12.5% of b that now expired) -> cache 120 secs 12.5% will have server A cached -> cache another 120 secs ... i think i lost something at this point but i think you get the idea.... As you can see this gets pretty complicated to predict and it will for sure not work out like this in practice. But it should definitely have an effect on the distribution! I know that weighted round robin exists and is just controlled by the root server. It just cycles through dns records when responding and returns dns records with a set propability that corresponds to the weighting. My DNS server does not support this, and my requirements are not that precise. If it doesnt weight perfectly its okay, but it should go into the right direction. I think using the TTL field could be a more elegant and easier solution - and it deosnt require a dns server that controls this dynamically, which saves resources - which is in my opinion the whole point of dns load balancing vs hardware load balancers. My question now is... are there any best prectices / methos / rules of thumb to weight round robin distribution using the TTL attribute of DNS records? Edit: The system is a forward proxy server system. The amount of Bandwidth (not requests) exceeds what one single server with ethernet can handle. So I need a balancing solution that distributes the bandwidth to several servers. Are there any alternative methods than using DNS? Of course I can use a load balancer with fibre channel etc, but the costs are rediciulous and it also increases only the width of the bottleneck and does not eliminate it. The only thing i can think of are anycast (is it anycast or multicast?) ip addresses, but I don't have the means to set up such a system.

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  • Why is my HDD not showing up?

    - by Mike
    I'm on Windows 7, got a new 2 TiB NON-external hard disk. When I plug it in it doesn't show up on the Disk Management list in the Computer Management window (that you get by right-clicking My Computer and selecting "Manage"). At first I thought it was broken, but I could see it using a friend's computer. I've run a full disk scan using the official tool from Western Digital, no problems. I've formatted it and partitioned it at another friends place, I've even encrypted the disk fully without any problems, then mounted it and placed a text file on it with the word "hello" inside and saved the file. When I boot my own computer the disk shows up in BIOS. So the disk is not broken. I've tried changing what SATA slot on the motherboard I stick it in. Makes no difference. After all this: Why won't my Windows 7 discover the disk???

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  • how to create iso dvd image for use with mac/osx "Disk Utility"?

    - by adolf garlic
    This seemed way easier on my pc. I would just pop a blank dvd in the drive, it asked what I wanted to do with it, to which I would respond, "burn dvd with nero" (paraphrasing), then I would pick "new" and just drag and drop the folders in there. Mac appears to have "Disk Utility" which just requires that I 'choose an image' but then doesn't bother to detail - how to do this - what the options mean e.g. format "mac OS extended (journaled)" is that ever going to be readable on a non mac machine? I want to create an ISO standard dvd as per the 'default' you'd get on nero. All the stuff on the web points to doing things with 'terminal' (the whole point of buying a mac was to get away from command line jiggery pokery - I'm trying to burn some photos not land a friggin lunar module here!) Please, if you can just provide some simple instructions on what I need to achive this I'd be extremely grateful. Ta muchley in advance.

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  • How do I extract all the files in a VHD to a hard disk including permissions?

    - by Middletone
    I'd like to know wha thte best way is to make an exact copy of a vhd image and pu tit onto my hard disk. I've tried xcopy but there seems to be a number of issues rlated to permissions when doing this. Ideally I'd like to copy the bits so that they match exactly on the new drive. I encountered this when trying to restore a vista backup only to discover the idiots work who decided to not let me restore a 400 gig image to a 1 TB drive size. I've sucessfully mounted the drive in Win 7 which is the environment in which I'm trying ot copy these files.

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  • Linux software raid robustness for raid1 vs other raid levels

    - by Waxhead
    I have a raid5 running and now also a raid1 that I set up yesterday. Since raid5 calculates parity it should be able to catch silent data corruption on one disk. However for raid1 the disks are just mirrors. The more I think about it I figure that raid1 is actually quite risky. Sure it will save me from a disk failure but i might not be as good when it comes to protecting the data on disk (who is actually more important for me). How does Linux software raid actually store raid1 type data on disk? How does it know what spindle is giving corrupt data (if the disk(subsystem) is not reporting any errors) If raid1 really is not giving me data protection but rather disk protection is there some tricks I can do with mdadm to create a two disk "raid5 like" setup? e.g. loose capacity but still keep redundancy also for data!?

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  • Server hard disk read speed and client download speed, is there a connection? [closed]

    - by Mywiki Witwiki
    Ok so a client's download speed is only as fast as a server's upload speed, and vice versa. Based on the answers to this post: Does upload speed depend upon download speed of the server? In other words, the data transfer rate between the two computers is only as fast as the speed of the "bottleneck". Let's pretend the two computers are in two different networks and both have 100Mbps internet connection. Ben wants a copy of a file in Mark's computer hard disk with 30Mbps read speed. Does this mean that Ben can download the file at a speed of around 30Mbps only, despite having an internet connection faster than 30Mbps?

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  • What lasts longer: Data stored on non-volatile flash RAM, optical media, or magnetic disk?

    - by Chris W. Rea
    What lasts longer: Data stored on non-volatile flash RAM (USB stick or SD cards?), optical media (CD, DVD, or Blu-Ray?), or magnetic disk (floppies, hard drives?) My gut tells me optical media, but I'm not sure. Furthermore, which of those digital media would be most suitable for long-term data storage where environmental issues are unknown, such as low/high temperature or humidity? For example, what digital media could be stored in a basement, attic, or time capsule, and be expected to survive a reasonably long time? e.g. a lifetime, and then some. Update: Looks like optical media and magnetic tape each have one vote below. Does anybody else have an opinion or know of a study comparing the two?

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  • Maximum disk size for a Debian 6 VMware installation?

    - by Mohamed Abobakr
    I'm planning to install a variety of Linux distributions on VMware Player to get more experience with Linux (I've only used Fedora back in university). I'm starting with Debian 6.0.5 Squeeze, and have already downloaded the small CD i386 netinst image. In the new virtual machine wizard, it's asking me for the maximum disk size of the image. It says that the recommended size for Debian 6 is 8 GB. However, I'm trying to figure out what is the absolute minimal size that I can get away with, since I'm only testing it out with very few software installations (mainly testing web server applications).

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  • How can I mount .IMG floppy disk images which are not 1.44MB or any other floppy format?

    - by Frank Computer
    I have several .IMG files, but they are different sizes which do not comform to any floppy disk format, i.e. not 1.44MB, 720K, 2.88MB... these .IMG files are like 420K, 832K, etc. Additional info: Winimage, rar, Magic ISO... none of these worked. The files I want to download are located in www.vetusware.com under DBMSOracle6. They are 2 files in rar format, but when I extract the rar's, I get forty-two .IMG files with varied sizes, not 1.44MB, etc. If anyone could please give it a try and succeed in mounting or reading the extractd IMG files, I would appreciate you letting me know how you achieved it, I really need this legacy Oracle 6/DOS version!.. IMPORTANT: I have DOS 6.22 running under Microsoft Virtual PC 2007. VPC07 can only mount IMG's which are only 1.44MB ot 720K. Screenshot of IMG file sizes Screenshot of the first IMZ file

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  • Why might a System.String object not cache its hash code?

    - by Dan Tao
    A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is implementation-dependent, so the question "is GetHashCode implemented in the form of X or Y?" is not really answerable. I'm just curious about a few things: If Reflector has disassembled the DLL correctly and this is the implementation of GetHashCode (in my environment), am I correct in interpreting this code to indicate that a string object, based on this particular implementation, would not cache its hash code? Assuming the answer is yes, why would this be? It seems to me that the memory cost would be minimal (one more 32-bit integer, a drop in the pond compared to the size of the string itself) whereas the savings would be significant, especially in cases where, e.g., strings are used as keys in a hashtable-based collection like a Dictionary<string, [...]>. And since the string class is immutable, it isn't like the value returned by GetHashCode will ever even change. What could I be missing? UPDATE: In response to Andras Zoltan's closing remark: There's also the point made in Tim's answer(+1 there). If he's right, and I think he is, then there's no guarantee that a string is actually immutable after construction, therefore to cache the result would be wrong. Whoa, whoa there! This is an interesting point to make (and yes it's very true), but I really doubt that this was taken into consideration in the implementation of GetHashCode. The statement "therefore to cache the result would be wrong" implies to me that the framework's attitude regarding strings is "Well, they're supposed to be immutable, but really if developers want to get sneaky they're mutable so we'll treat them as such." This is definitely not how the framework views strings. It fully relies on their immutability in so many ways (interning of string literals, assignment of all zero-length strings to string.Empty, etc.) that, basically, if you mutate a string, you're writing code whose behavior is entirely undefined and unpredictable. I guess my point is that for the author(s) of this implementation to worry, "What if this string instance is modified between calls, even though the class as it is publicly exposed is immutable?" would be like for someone planning a casual outdoor BBQ to think to him-/herself, "What if someone brings an atomic bomb to the party?" Look, if someone brings an atom bomb, party's over.

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  • Passing Derived Class Instances as void* to Generic Callbacks in C++

    - by Matthew Iselin
    This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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