Is there a way to prevent deletion of objects in a mongoDB collection using a constraint or something else?
Maybe you are thinking: Why he doesn't prevent it in his code? Well I'm having an issue with a conflicting package (GroundDB) in my meteor/mongo app which delete records temporarily when syncing after and offline/online period. I need to dig into the issue but so far I want to workaround the issue. Actually it would be good to completely block deletion in that collection, since the user nor the administrator never requires to purgue that data (It's a kind of permanent log).
Thanks in advance.
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I have a MongoDB client in three EC2 instances and I have created a replica set. Last time I had a problem, of space constraint which stopped my mongod process, thereby halting the application and now in an instance couple of days back, some of my tables were gone from database, so I set logging and all to my database just to catch if anything like that happens again. In a fresh incident this morning I was unable to login to my system and that's when I found out that whole database was empty. I checked other SO question like this which suggest setting up a TTL.Which I haven't done at all.
Now how do I debug this situation and do a proper root cause analysis? I can't even find anything in my debug logs as well. The tables just vanished. How do I set up proper logging mechanism and how do I ensure that all my tables are never ever deleted again?
Today I got a mail from Amazon that I was probably running an unsecured version of MongoDB and that may have caused this issue. So who ever is facing this issue please go through the Security Checklist Provided by MongoDB. There are some points that are absolutely necessary in there.
1. Enable Access Control and Enforce Authentication
2. Encrypt Communication
3. Limit Network Exposure
These three are the core and depending upon how many people access your database you can Configure Role-Based Access Control.
These are all the things I have done. Before this incident I had not taken security that seriously but after I was hit by it. I made sure I have all the necessary precautions in place.
Hope this helps someone.
This question has been asked multiple times, here and here, and the answer to get this working is fairly straight forward: add an environmental variable to your bash_profile and all Meteor instances on your localhost will share that MONGO_URL.
What I've noticed however is that while this may be the case, there's quite a bit of latency in the "reactivity" of Meteor. I've tested this with two very lean Meteor apps, with empty collections. Inserting a document to a collection from one Meteor app, where my second app is querying that same collection and printing out a field from the documents does work, but there's a noticeable lag before it updates. I've ruled out the possibility of the collection insertion being the source of the lag (simple console.log callback on the client of the first app, logging the id of the newly inserted document).
My purpose for having multiple apps (two to be precise) sharing the same MongoDB is to separate an admin panel from a mobile app without going crazy regarding name-spacing and bloat. This configuration works, but I'm not sure it's the "proper" way of accomplishing the task, and it certainly seems to be causing a performance hit.
Any insight into this matter would be appreciated. Thank you!
EDIT: To clarify, the db URL I'm using is on my localhost, and isn't something hosted online.
When you use an external database, by default meteor will use periodic polling (every few seconds) in order to observe any changes. The delay you are experiencing is a result of this polling process. You can remove the delay and reduce your app's CPU usage by taking advantage of meteor's oplog tailing feature. In order to use it you will:
Get access to a mongodb instance with the oplog turned on.
Set the environment variable MONGO_OPLOG_URL so your app(s) can read the oplog.
Personally, I'd recommend compose.io for this. They provide exactly this as part of their basic elastic deployment. See this post for detailed instructions.
For users who wish to connect to the oplog created locally for you, you can obtain the URL via:
MongoInternals.defaultRemoteCollectionDriver().mongo._oplogHandle._oplogUrl
It should end up looking something like mongodb://127.0.0.1:3001/local
Is there any way to achieve an atomic transaction using the Rally wsapi. I know a transaction implies state among the consecutive requests, but REST obviously is a stateless protocol. So that might be an issue.
need to be able to pull a portfolioitem/feature and then immediately write it back if I have the most recent version of it. I have a custom field on portfolioitem/feature that WILL be edited by multiple people simultaneously, and I need to make sure that each update happens in the correct order.
Since i don't have access to Rally's server stuff, i must do all this client side, and I can't figure out how to do this. I will be doing this will the Rally SDK also.
I don't think WS API supports atomic transactions. A scenario where updates occur as one atomic transaction so that, for example, if one of the updates fail they are all rolled back is not supported. In the example you mentioned each update will be a distinct transaction and in case of a mid-air collision when the same artifact is updated by different users, one of the users will receive a concurrency error.
I am in the same boat as the OP, the only difference being that hours may pass between the read and subsequent write. Interestingly, I only seem to get concurrency errors when I attempt to update a record while there's another transaction of mine in flight. I don't see any exception raised when I am updating a record using a stale version thereof, i.e. one that someone else has changed from under me.
I will be attempting to fix this soon as it's becoming an issue. The chosen approach is to forcibly chain a GET before every POST, and throw an exception if the VersionID of the record I GET doesn't match the one I have stored in-memory. In case of mismatch, it will refresh the local record (and thus, view) and prompt the user to resubmit their changes. Yes this will be inconvenient for a user but in my app most changes are a single click away so it's reasonable.
I too would like to know if there is a better approach to this problem. One would assume that with every record having a VersionID, it would be handled server-side, with proper support from WsapiProxy on the client end. Maybe I'm missing something obvious, like explicitly fetching VersionID?
I'm using Cloudant and I'm struggling to pull/replicate 600 documents from server to my iPhone. First, it's pretty slow because it has to go one-document-at-a-time, and Second Cloudant was giving me "timeouts" after the 100th-or-so REST request. (I have a ticket with Cloudant for this one, as it's unacceptable!)
I was wondering if anyone has found a way / hack to "bulk" replicate when pulling. I was thinking, perhaps it's possible to "zip up" all of the changes, send them in one file, and fast-forward the iPhone database to the last-change seq.
Any helps is great -- thanks!
Can you not hit _all_docs?include_docs=true to get everything in one shot? http://wiki.apache.org/couchdb/HTTP_Document_API#all_docs
I don't know couchcoccoa but it looks like the API supports this: http://couchbaselabs.github.com/CouchCocoa/docs/interfaceCouchDatabase.html#a49d0904f438587b988860891e8049885
Actually, why not make a view. Make a view that gives you your list and make sure your id is there. With your id, you can then go to the document and get all the rest of the required information that you need in order to update it if you need to.
There really is no reason you would ever need to hit every document individually. They have views and search2.0 for that. Keep in mind you are using a cloud based technology. This stuff is not sitting in your basement, you can't just hit it a million times per device in a few seconds and expect anyone to not notice and/or get upset (an exaggeration, yes I know).
What I do not understand is that you are trying to replicate it to an iPhone? Are you running apache and couchdb in your app? Why not just read the JSON data and throw it into a database. or just throw it into a file if it updates that much and keep overwriting it. There is so many options that are a whole lot less messy.
I have an app with a very large Core Data database. I have versioned it many times over the past year.
The last time I versioned the database I made one simple change to an entity: I added a new optional attribute. For some reason it would not migrate using Light-weight Migration. I found out much later that this was due to a bug in Apple's Light-weight Migration code resulting from the 'renaming identifiers' that I had needed back in another versioning.
Anyway, I digress...
Because of the bug that kept me from using Light-weight migration, I created a mapping file to help with the migration, not understanding that this would was a much heavier process and would force my users to wait while the app loaded the entire database into memory while doing the migration. It turns out that this is not really an option at all with very large databases and many of my users were unable to migrate the database at all due to memory problems, etc.
So now I want to re-release my app and clear up this problem. The trouble is, some of my users have a database that is somehow marked as being 'in the middle of migrating'. Even with my new code, which gets rid of the mapping file and supports Light-weight migration, users that are in this state, 'in the middle of a migration', don't seem to get reset.
What are my options for backing out a migration?
- I can detect that I am in this state because there is a '.myDB.sqlite.migrationdestination_41b5a6b5c6e848c462a8480cd24caef3' file in the Documents directory. Deleting this file does not clear up the migration. My guess is that the database is somehow flagged as being in this state, or is already partially migrated.
- I can detect this state and then delete the database altogether. But this forces my users to re-download their data.
Any Thoughts?
Thanks for you help.
The only thing that occurs to me would be crack open the SQL store of an affected file and look for flags or something else that might signal the db being in a transitory state. You might be able to write directly to the file and alter something.
That's really ugly problem.