db

Datenbanksysteme

Written by  on Juli 26, 2015

Wenn Du glaubst, Du hast all den Irrsinn rund um verschiedene Datenbank-Systeme wie MySQL, Postgres, CouchDB, MongoDB oder ElasticSearch schon gesehn, dann trifft Dich Oracle…

Zitat des Tages

Written by  on Juli 19, 2015

A lot of your work is done behind the scenes. In fact, people will often wonder what it is you do all day, since much of your work is never actually seen by the end users.

DBA Survivor: Become a Rock Star DBA

Zitat des Tages

Written by  on Juli 18, 2015

Und nochmal über Entwickler und Administratoren:

Unfortunately these two groups rarely interface unless there is a problem (or an opportunity to point fingers at each other).

DBA Survivor: Become a Rock Star DBA

Zitat des Tages

Written by  on Juli 17, 2015

Developers know code, and they know various facets of the business; and because they focus on those items daily, they are not spending time racking servers, installing routers, replacing hard disks, allocating space on the SAN, and so forth. Server administrators do those things, but they do not know how to code or build applications that will drive the business forward at the same speed as a developer.

DBA Survivor: Become a Rock Star DBA

Zitat des Tages

Written by  on Juli 5, 2015

Gilt auch für andere Fachbereiche 🙂

If you come across a developer that believes they know more than anyone else in the room, you can sit back and chuckle because you already know that the DBAs are the smartest, otherwise you wouldn’t always be called to fix their problems all day long.

DBA Survivor: Become a Rock Star DBA

Zitat des Tages

Written by  on Juni 28, 2015

Some might see it as “dumb luck,” but I prefer the term “smart luck.”

DBA Survivor: Become a Rock Star DBA

Zitat des Tages

Written by  on Juni 26, 2015

With that responsibility, you will also find that you start getting more blame than credit for your work. I promise you this: no one will ever stop by your desk in the morning and thank you for the fact that everything ran smoothly last night.

DBA Survivor: Become a Rock Star DBA

Mongodb – Pre-splitting data

Written by  on September 11, 2014

Ein weiterer Teil von Notizen zu M202: MongoDB Advanced Deployment and Operations
Start a config server (would be 3 in production):

mongod --port 27019 --dbpath /data/config --smallfiles --oplogSize 128 --fork --syslog --configsvr

Start the replica sets (okay, these are stand alone servers for testing)

mongod --port 30000 --dbpath /data/shard0 --smallfiles --oplogSize 128 --fork --syslog --shardsvr
mongod --port 30001 --dbpath /data/shard1 --smallfiles --oplogSize 128 --fork --syslog --shardsvr
mongod --port 30002 --dbpath /data/shard2 --smallfiles --oplogSize 128 --fork --syslog --shardsvr

Start a mongo router:

mongos --configdb localhost:27019 --fork --syslog (default uses port 27017)

connect to the mongos with the mongo command and add the single servers to the shard:

mongos> use admin
db.runCommand( { addShard: "localhost:30000", maxSize: 0, name: "shard0" } )
db.runCommand( { addShard: "localhost:30001", maxSize: 0, name: "shard1" } )
db.runCommand( { addShard: "localhost:30002", maxSize: 0, name: "shard2" } )
mongos> sh.status()
--- Sharding Status ---
 sharding version: {
 "_id" : 1,
 "version" : 4,
 "minCompatibleVersion" : 4,
 "currentVersion" : 5,
 "clusterId" : ObjectId("53ebd0db6f0a219ba53abb9e")
}
 shards:
 { "_id" : "shard0", "host" : "localhost:30000" }
 { "_id" : "shard1", "host" : "localhost:30001" }
 { "_id" : "shard2", "host" : "localhost:30002" }
 databases:
 { "_id" : "admin", "partitioned" : false, "primary" : "config" }

Create the Database:

use m202
mongos> db.createCollection("presplit")
{ "ok" : 1 }

Enable sharding for database – and for the collection:

db.runCommand({"enablesharding" : "m202"})
{ "ok" : 1 }
db.runCommand ({ shardCollection: "m202.presplit", key: { a: 1 }, numInitialChunks: 50 })

 

sh.enableSharding("users")
sh.stopBalancer()
sh.shardCollection("m202.presplit", { _id : 1 })
db.adminCommand( { split : "m202.presplit" , middle : { _id : prefix } } );
db.adminCommand( { split : "m202.presplit" , middle : { a : 1 } } );

merge chunks togehter, to build up the required ranges

db.runCommand( { mergeChunks: "m202.presplit",
 bounds: [ { "a": 15 },
 { "a": 20 } ]
 } )

you need to do that multiple times – you can only merge two chunks at a time

just move your chunks around the shards

db.adminCommand({moveChunk : "m202.presplit", find : {a : 23}, to : "shard2"})

It’s sufficient to use find with the starting of the chunk!

Search the changelog for chunk migrations

db.changelog.find().sort({time : -1 }).pretty()

Adding Tags

sh.addShardTag("test-rs01", "USWEST")
sh.addShardTag("test-rs02", "USEAST")

In case something goes wrong, drop the database and start from the beginning:

use <dbname>
db.dropDatabase();