How to transfer DNS records to new DNS provider with very little or no downtime in resolution

I’d like to transfer DNS records from Network Solutions to DNS Made Easy, mainly to take advantage of “DNS Failover” provided by DNS Made Easy to automatically fail a couple of key A records over to new IPs in my data center where I replicate servers to for DR if DNS Made Easy senses that the primary IP on prem is unavailable.

This guide is helpful, but I don’t understand the first step regarding TTLs. My understanding of TTLs has always been that hosts cache records for an amount of time as told by the TTL when querying records. If that understanding is correct, how can I have any control over expiration?

My plan is to:

  1. Create new zone files on new DNS provider at my leisure
  2. Change existing nameservers at the registrar to the new DNS Made Easy nameservers at night, cross my fingers and wait for morning

What can I do in relation to the TTLs to improve my chances of making this seamless?

Zero downtime database revisioning


Case 1

For an application, we have a single backend service layer that reads/writes data to multiple tables in database layer. Database layer has just tables, no indexes, no views and no triggers.

Case 2

For an application, we have two backend services in backend layer that talk to database layer. Database layer has just tables, no indexes, no views and no triggers.

Backend is Java

Front end is Angular


Currently mysql database is running standalone with no cluster setup.

Database revisioning may include adding a new data column, modifying existing data column(like increasing width of data column), adding a new table etc…

There is no chance of adding triggers, views and indexes.

Currently backend service are just functional components and they do not hold any responsibility of database revisioning with zero downtime.

My understanding is that, writing a separate component only for database revisioning does not help go for zero downtime, because the state is maintained by running backend service. Correct me.


If the backend service(functional component) itself take an additional responsibility about managing the database revisioning(one time on start up with java liquibase plugin)

1) What would be the approach(algorithm) for adding a column, renaming a column, with zero downtime? By maintaining extra temporary column amidst database revisioning by backend-service_new_version when backend-service_old_version does not break existing user sessions.

2) Amidst database revisioning by new version backend service, Can new version backend service accept new user connections, when old version backend service is serving existing sessions and then go shutdown? In terms of re-routing all new user requests to new version of backend…

Trace routes to find the downtime reason

Our server was down for serving http requests for some minutes. The web server is nginx and php-fpm handles the php processes. So in the middle of downtime duration I took a look at nginx’s access.log file. Most of requests were getting a 499 response code which is nginx particular status code for when client closes the connection before the server answers.

I restarted nginx sudo nginx -s reload but that didn’t seem to effect the behavior. I then restarted php-fpm service and everything came back normal. Before issuing service restart, htop was showing no high CPU usage.

My question is how can I find the reason in such situations and where should I start from to get to the bottleneck?

Rolling updates without downtime using kubernetes

Scenario:

  • I got 3 replicas of a service running
  • I want to update its version

This is whats happening:

  • The new container will be created
  • As soon the container are switching their status from ContainerCreation to Running kubernetes will start terminating old versions of this container.

Problem: Status Running does not make sure the application is available. How can I prevent kubernetes from terminating services before it is not sure the containers application is available? Maybe adding a necessary health check?

How to award Downtime and Renown in Curse of Strahd?

I’m trying to locate details on awarding downtime and renown in the Curse of Strahd.

The Curse of Strahd DM’s Guide from Adventurers League says this about awarding renown (page 6):

Many adventures offer a renown award in the form of renown points for members of certain factions. Usually, this renown award will range from 0 to 2 points. Award renown points at the conclusion of an episode or adventure.

And about awarding downtime (page 6):

At the conclusion of each episode or adventure, award downtime days to each character. Adventures typically award 10 downtime days at the end of the episode or adventure unless otherwise specified.

The book is divided into 15 Chapters plus the Death House mini-adventure. In my view it would be much clearer to stipulate that each CoS “chapter” should be treated as an “episode or adventure” for the purposes of DT and Renown calulations but, since I can’t find that exact wording, I’m left wondering.

So, what counts as an “episode or adventure” for the purpose of how to award Downtime and Renown in Curse of Strahd?

Which downtime activities cover lifestyle expenses?

I am puzzled by the interaction between Lifestyle and Downtime Activities, particularly as to lifestyle expenses.

One of the downtime options presented in the Player’s Handbook, p. 187, is Researching, which expressly states:

For each day of research, you must spend 1 gp to cover your expenses. This cost is in addition to your normal lifestyle expenses . . . .

More downtime options appear in the Dungeon Master’s Guide and Xanathar’s Guide to Everything, including several that have associated gold-per-day costs. But none of them state that their costs are in addition to a PC’s lifestyle expenses.

At the same time, certain downtime activities go out of their way to say lifestyle expenses are or might be covered during the activity. For example, Work, XGtE p. 134, contemplates an ability check the outcome of which determines what lifestyle one can maintain without cost during the activity. And Crafting, PHB p. 187, simply says:

While crafting, you can maintain a modest lifestyle without having to pay 1 gp per day, or a comfortable lifestyle at half the normal cost . . . .

In other words, the cost of Crafting subsumes one’s lifestyle costs, at least to an extent. Adding to the confusion is the fact that the downtime options in XGtE are wholly optional “alternatives” that differ from options in the PHB and DMG. There is basically no consistency among them.

Even more confusing, the DMG says, at p. 128, that while engaged in Carousing, a PC “spends money as though maintaining a wealthy lifestyle . . . .” (Emphasis mine.) To my eyes, that “as though” is ambiguous. Does the PC spend money on her normal lifestyle and on the wealthy lifestyle necessary for Carousing? Or does the later subsume the former, as with the PHB‘s version of Crafting?

In short: which downtime activities cover a PC’s lifestyle expenses while performing them, and which don’t?

How Do You Move From Hosting to another with No Downtime or DNS Propagation Delay?

How Do You Move From Hosting to another with No Downtime or DNS Propagation Delay?

Usually Name server changes usually take 24 to 48 hours to fully start working, which may take lot of time for DNS Propagation and website usually get down at some point,

So, how it's possible to do it without much of downtime ? any ideas ?