What I learned this week⌗

Software⌗

Race Conditions

  • I like this definition of atomic: The capability of performing an uninterrupted update with valid data before and after the update and the data cannot be observed by another observer in any intermediate state it may take on during the update. It may be a single bit or it may be an entire database. S/O ACID!

Semaphore

I was unaware of SAVEPOINT and ROLLBACK TO

The reason for separating raw parsing from semantic analysis is that system catalog lookups can only be done within a transaction, and we do not wish to start a transaction immediately upon receiving a query string.

Greate overview on AWS networking, linking all sub-sections as well

  • Everyone gets their own private network inside AWS.
  • Solves IP address conflicts and security concerns of one big shared network
  • Mapping service connects instances in a single VPC across servers (kind of like a namespace) -The Mapping service can connect servers across AZs but not Regions, VPC span AZs not regions. To connect VPCs in different regions there’s VPC peering or AWS Transit Gateway
  • An internet gateway is like a hole you poke in your VPC so you can talk to the internet.
  • Only a subnet can be connected to the internet gateway.
  • A subnet is a way to group your instances. It’s sort of like tagging them.
  • Private subnets can’t talk to the internet and are the default. Public subnets can talk to the internet.
  • Subnets are availability zone-scoped. To create an instance, we need to specify which availability zone we want to create the instance in.
  • A route is a connection from your subnet to the internet gateway so that your subnet can talk to the internet.
  • Classless Inter-Domain Routing (IP address allocation)
  • Specifies a range of IP addresses by fixing a certain number of bits in a 32 bit IP Address 172.98.0.1/24 (/24 denote the # of bits that are fixed)
  • Each VPC will have a CIDR range, and each subnet within a VPC will have their own ranges within the VPC’s range
  • Route tables are mappings from destination to target, given a destination where to a go next (target)
  • Route tables will always try to match the most specific route.
  • Route tables are created at the VPC level. Every VPC comes with a route table, called the main route table. A VPC can have many route tables
  • all subnets are associated with the main route table by default
  • Security groups operate at the firewall (or EC2 instance) level (They have IB & OB rules), they are ALLOW only
  • IB traffic is allowed if its a response to your request (This is why SG are referred to as stateful)
  • NACLs operate at the network (or subnet) level (They are used to BLOCK an IP(s))

Netmask

Routers can assign private IPs from several private IP address ranges. They are addresses that start with 10.x.x.x, like 10.0.0.1; addresses that start with 192.168.x.x, like 192.168.10.1 and 192.168.12.1; and IPs in the 172.16.0.0 - 172.31.255.255 range.

RFC 6598 defines a Shared Address Space, specifically the 100.64.0.0/10 block, for use by Internet Service Providers (ISPs) in their Carrier-Grade NAT (CGNAT) deployments. This address space is reserved for connecting Customer Premises Equipment (CPE) to the ISP’s core routers.

Business/Finance⌗

Cool blog and public brain concept to explore

Math/Stats⌗

Travel⌗

Suggestion from my Korean Uber Driver: Seoraksan national park go in sept/oct

Spent the week in Seattle for our team Summit

Other⌗