A Technical I.T./DevOps Blog
Problem scenario
You are trying to select a database that is right for your needs. You will not be doing many transactions. The database does not need to support regular ETL or OLTP. You are going to have a large database, and you want it to compress to the smallest size possible. In some cases a column-oriented database better than a row-oriented database. What type of database should you use for this situation?
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Problem scenario
You have read about the Google Datastore and Google Firestore. But you do not know the differences. What are they?
Solution
Go here.
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Continue reading “How Does Google Datastore Compare/Contrast with Google Firestore?”
Problem scenario
You want to install MongoDB on a RHEL server. What do you do?
Solution
1. Create this file: /etc/yum.repos.d/mongodb-org-4.4.repo
[mongodb-org-4.4]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.4/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.4.asc
sudo yum -y update
sudo yum -y install mongodb-org
If you are using Debian or Ubuntu,
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Problem scenario
You have a server in AWS that is in a VPC. You want it to access an S3 bucket. How do you do this?
Solution
Use a VPC endpoint, specifically, use a Gateway Endpoint.
Source: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-endpoints.html
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Continue reading “How Do You Securely Connect an EC-2 Instance in a VPC to a DynamoDB?”
Question
What SQL database underlies Elastic Search?
Answer
There is no relational database for Elastic Search.
Elastic Search will have a cluster that is composed of nodes. Nodes are composed of indexes. Indexes are supported by shards. Shards have primary and replica copies. The replica copies vary. The shards are essentially Lucene indexes (according to this site).
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Problem scenario
You want to use the rdf4j (Resource Description Framework for Java). You want to install the rdf4j server and workbench. You are using Debian 9 Linux. What should you do?
Solution
Prerequisites
i. We recommend having a 30 GB of hard disk free.
ii. We recommend having 5.75 GB of RAM (it can be a combination of RAM and swap space).
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Continue reading “How Do You Install and Configure the rdf4j Server and Workbench GUI?”
Problem scenario
You want to create a database in MongoDB using the CLI. How do you do this from a Linux server and then add a document to the database you just created?
Solution
Prerequisite
Install MongoDB on a Linux server; if you need assistance, see this posting.
Procedures
1.a.
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Continue reading “How Do You Create a Database in MongoDB Not Using using Compass (the GUI)?”
Problem scenario
You start Cassandra with this command: ./bin/cassandra
You see one of the following messages:
INFO [MigrationStage:1] 2018-04-06 19:01:07,144 ColumnFamilyStore.java:391 – Initializing system_auth.resource_role_permissons_index
INFO [MigrationStage:1] 2018-04-06 19:01:07,163 ColumnFamilyStore.java:391 – Initializing system_auth.role_members
No progress is happening. What should you do?
Solution
Possible Solution #1. Try rebooting the server. This could help the problem.
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Problem scenario
When you start Cassandra you see a message such as this:
INFO [main] 2018-02-03 08:45:55,257 ColumnFamilyStore.java:389 – Initializing system.IndexInfo
What should you do?
Possible Solution #1
Try rebooting the server. This could help the problem.
Possible Solution #2
This next one is merely a workaround. It is not a best practice.
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Continue reading “What Do You Do when Cassandra Stalls on “Initializing IndexInfo”?”
Problem scenario
You have two Linux servers in AWS, and each one has the same flavor (i.e., same amount of RAM and same number of processors). One is Ubuntu and another is SUSE. These commands will create working containers in Ubuntu:
docker run –name name1-mongo -d mongo
docker run –name name2-mongo -d mongo:2
This command will not create a working container in SUSE:
docker run –name name2-mongo -d mongo:2
The container that is created will never start.
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Continue reading “Why Would a MongoDB Container Work on an Ubuntu Host but Not a SUSE Host?”