Mongo M101P MongoDB for Developers week 3

Handling blobs (4 min)

GRIDFS
documents limited to 16MB in mongodb
breaks up large files into chunks and store them into a collection and meta data into another
By default GridFS limits chunk size to 256k
GridFS uses two collections to store files. One collection stores the file chunks, and the other stores file metadata.
collection
videos.chunks
videos.files
videos_meta?

When to denormalize (2 min)

Trees (2.5 min)

Benefits of embedding (2 min)

PERFORMANCE!

Multikeys (4 min)

Many to many relations (5 min)

One to many relations (5 min)

One to one relations (4 min)

Living without transactions (4 min)

Living without constraints (3 min)

Alternative schema for Blog (3 min)

Mongo design for Blog (4.5 min)

Relational normalization (5 min)

relational strives for 3rd normal form
denormalized

Goals of Normalization:

• frees database of modification anomalies (recall Andrews email example)
• minimize redesign when extending
• avoid any bias toward a particular access pattern (NOT A MONGO CONCERN)

"When you are not biased toward a particular access pattern you are equally bad at all of them"...Andrew Erlichson

Mongodb schema design (3 min)


mongo does not join in journal
joins are hard to scale
think about what data you want to use together
mongo has no constraints
atomic operations on documents

Quiz: MongoDB Schema Design

Whats the single most important factor in designing your application schema within MongoDB?

Making the design extensible.Making it easy to read by a human.Matching the data access patterns of your application.Keeping the data in third normal form.

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Funniest video I’ve seen in a while …

Cornish Rex cat screaming “Im Wet!” while being bathed … hysterical

I stole that from a friend’s timeline on Facebook … videos like this are probably Facebook’s and YouTube’s greatest strength …

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Remember Who Knows When Youve Been Naughty or Nice When You Are Sleeping And When You Are Awake

Its not Santa Claus.  Its NSA.

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As ye sow … so shall ye reap … Apple wins an early battle very big but do they lose the war

There is this somewhat silly concept called karma, which perfectly describes the concept of behaving as you would want others to behave towards you – the “golden rule” if you will. In other words, if you screw someone to get ahead, you are accruing “bad karma” …

So when Apple won that wet dream award of $1B from some wing nut jury over their patent dispute with Samsung, things were looking pretty rosy. (Note: The award has been reduced already by a judge with a capacity for reason.)

Things must have looked pretty rosy for Apple and I’m sure more than a few corks were popped … but as they say, karma is a bitch.

And now Samsung is tightening the supply chain noose for displays and processors and that has Apple predicting a “divot” in their upcoming profits.

http://www.zdnet.com/is-apple-about-to-feel-samsung-squeeze-on-iphone-costs-7000014654/?s_cid=e539&ttag=e539

I laughed out loud when I read this paragraph quoting analyst Peter Misek:

Apple is having to switch from in-cell to on-cell for the iPhone 6 as in-cell is proving unable to ramp to 4.8”. This new technology is unproven and Apple will incur significant costs to ramp production. We also believe that this is a stopgap technology in front of OLED. We believe it will take Apple and partners two years or more to commercialize OLED as the OLED market for smaller displays is effectively controlled by Samsung who will not supply Apple. In the meantime both LG Display and Japan Display will be forced to be on a dual track for screen technologies for Apple.

This transition for Apple will raise screen prices by 10 to 25 percent. Remember that it is Samsung who has completely swung the market towards the larger displays and even “phablets”, a crossover tablet and phone. Think they had something in mind?

But it gets better … I read this next and howled …

Apple is trying to switch processor manufacturing completely to TSMC and away from Samsung. The problem: Apple need Samsung for its older chips and cant cut over production. Misek said Samsung will start raising prices on legacy chips in the summer which will raise Apples bill of materials another 20 percent to 30 percent.

This is a beautiful example of how the opponent’s next move is sometimes subtle. Apple may not yet be defeated, but I think they earned themselves this swift kick in the jewels :-)

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Mongo dba week 7 security backups

Additional Resources (2.5 min)

• Docs - mongodb.org
• Driver docs - 
• Bug database / feature request database [JIRA]
• Support forums (in Google Groups) - mongodb-user
• IRC - channel: freenode.net/#mongodb
• Source code on github
• Blog
• Twitter (@mongodb)
• Mongo Meetup Groups (MMUGs) - look on meetup.com

Hardware Tips (7.5 min)

Additional Features (4.5 min)

Geospatial Indexes (5 min)

location
latitude and longitude things
built on top of b-tree structures
uses variation of geo-hash codes

Data Recovery with MMS (4 min)

Quiz: Data Recovery with MMS Backup

You rack up $3.50 in MMS charges from a small backup restoration. What are your out-of-pocket costs?

-$1.50$0.00$1.50$3.50$5.00

Installing MMS Backup (3.5 min)

Introduction to MMS Backup ( min)

Backup Strategies (3 min)

Quiz: Backup Strategies

Which are true statements?

You can copy Mongo datafiles while a mongod is running.Its always safe to do a true snapshot of the data volume while mongod is running.mongoexport has the ability to directly access MongoDB datafiles in addition to connecting to a MongoDB cluster or server via the network.

Backups (12 min)

Intra-cluster Security (4 min)

Security and Clients (6.5 min)

--auth : runs it in a security mode.
to authenticate:
NOTE: users are added per-database
db.addUser(...) - system.users (which is used to create credentials in mongodb)
db.addUser( { user: "", pwd: "", roles: [] } ) - 2.4+
db.auth(username,password) - to authenticate in the shell
Types of users:
admin users - created in the admin database.  has privileges across all databases
regular users - access a specific database, read/write or read only.

Start by adding an administrative user:

> use admin

switched to db admin

> db.addUser("the_admin", "testpassword" )

{

"user" : "the_admin",

"readOnly" : false,

"pwd" : "8b7c802b3626405fd30fa921fcf41cf9",

"_id" : ObjectId("52851114c2e7840b9b05b49f")

}

> db

admin

> show collections

system.indexes

system.users

> db.system.users.find()

{ "_id" : ObjectId("52851114c2e7840b9b05b49f"), "user" : "the_admin", "readOnly" : false, "pwd" : "8b7c802b3626405fd30fa921fcf41cf9" }

passwords are hashed (not stored in plain text [i.e. a message digest])

Once the admin user has been added to the admin database, the rule that you can connect from the localhost no longer applies.  Meaning that we will have to authenticate or it wont let us in (even if we are on localhost).

> show dbs

Thu Nov 14 11:07:59.449 JavaScript execution failed: listDatabases failed:{ "ok" : 0, "errmsg" : "unauthorized" } at src/mongo/shell/mongo.js:L46

> // now we authenticate to do useful things

> db.auth("the_admin", "testpassword" )

1

> show dbs

admin 0.0625GB

local 0.03125GB

test (empty)

Quiz: Security and Clients

Which are true?

You can give a user read-only access to one database and write access to another database.The users password is sent over the network unencrypted.The users password is stored on disk unencrypted.

Security (5 min)

Introduction ( min)

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How Do I Download or Upload Pictures or Videos from my Camera

This question comes up a lot. A new or used camera owner may run into camera software issues. Theyll plug in their camera, but for some reason their computer fails to see or recognize the camera. Another problem is they may lose or may never have had the USB cable or needed software that came with the camera. Is there any other way to get the photos or videos off the camera and onto their computer?

First of all keep in mind IMO the only reason that the camera companies include a capability for cable download is to get you accustomed to using their bundled software that came with the camera. In most cases this software is rather pitiful, again IMO. If you absolutely must use photo organizing or editing software, there are much better freeware options available than what came with your camera (a future blog post is brewing).

But as a solution to downloading your photos, I highly recommend that you instead consider using a card reader to move the photos or videos to your computer. Card readers do not require software (although Windows 98 and earlier may require drivers), are very inexpensive, are much faster downloading files from the camera, do not use the cameras batteries during the download, and are much less prone to file corruption of the photos during the download. Really, it would be better for the camera user if one of these was included with the camera instead of the cable and bundled software.

Portable SD Card Reader/Writer

"All in One" Multi-Card Reader/Writer

You place the cameras card in the reader, plug the reader into the USB port, and your computer sees it as a hard drive. You simply copy/paste or drag/drop your photos onto your hard drive. For this simplicity, most professional photographers utilize card readers exclusively. Youll save yourself a lot of heartache if you convert to using one of these.

Here are examples from Amazon. Dont be fooled by the cost. Some of the most inexpensive ones work just fine. But make sure that you do read the reviews first before purchasing. Also make sure that you get a reader that is clearly stated capable of reading your card, particularly if you use SDHC, XD, CF, or MS cards.

For international readers of this blog, and even those in the US, heres another source for card readers (free international shipping too :-). I use the $1.95 portable SD/SDHC card model (SKU7230), and it works great. Note that the free shipping can take up to three weeks though as theyre located in Hong Kong.

Now go throw away that cable and go download your photos.

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