jm + capacity   13

The problems with DynamoDB Auto Scaling and how it might be improved
'Based on these observations, we hypothesize that you can make two modifications to the system to improve its effectiveness:

trigger scaling up after 1 threshold breach instead of 5, which is in-line with the mantra of “scale up early, scale down slowly”;
trigger scaling activity based on actual request count instead of consumed capacity units, and calculate the new provisioned capacity units using actual request count as well.

As part of this experiment, we also prototyped these changes (by hijacking the CloudWatch alarms) to demonstrate their improvement.'
dynamodb  autoscaling  ops  scalability  aws  scaling  capacity 
4 weeks ago by jm
The Square Root Staffing Law
The square root staffing law is a rule of thumb derived from queueing theory, useful for getting an estimate of the capacity you might need to serve an increased amount of traffic.
ops  capacity  planning  rules-of-thumb  qed-regime  efficiency  architecture 
november 2016 by jm
How to Quantify Scalability
good page on the Universal Scalability Law and how to apply it
usl  performance  scalability  concurrency  capacity  measurement  excel  equations  metrics 
september 2016 by jm
ztellman/dirigiste
'centrally-planned object and thread pools' for java.

'In the default JVM thread pools, once a thread is created it will only be retired when it hasn't performed a task in the last minute. In practice, this means that there are as many threads as the peak historical number of concurrent tasks handled by the pool, forever. These thread pools are also poorly instrumented, making it difficult to tune their latency or throughput. Dirigiste provides a fast, richly instrumented version of a java.util.concurrent.ExecutorService, and provides a means to feed that instrumentation into a control mechanism that can grow or shrink the pool as needed. Default implementations that optimize the pool size for thread utilization are provided. It also provides an object pool mechanism that uses a similar feedback mechanism to resize itself, and is significantly simpler than the Apache Commons object pool implementation.'

Great metric support, too.
async  jvm  dirigiste  java  threadpools  concurrency  utilization  capacity  executors  object-pools  object-pooling  latency 
june 2016 by jm
Should create a separate Hystrix Thread pool for each remote call?
Excellent advice on capacity planning and queueing theory, in the context of Hystrix. Should I use a single thread pool for all dependency callouts, or independent thread pools for each one?
threadpools  pooling  hystrix  capacity  queue-theory  queueing  queues  failure  resilience  soa  microservices 
may 2016 by jm
The Importance of Tuning Your Thread Pools
Excellent blog post on thread pools, backpressure, Little's Law, and other Hystrix-related topics (PS: use Hystrix)
hystrix  threadpools  concurrency  java  jvm  backpressure  littles-law  capacity 
january 2016 by jm
wangle/Codel.h at master · facebook/wangle
Facebook's open-source implementation of the CoDel queue management algorithm applied to server request-handling capacity in their C++ service bootstrap library, Wangle.
wangle  facebook  codel  services  capacity  reliability  queueing 
november 2015 by jm
TCP incast
a catastrophic TCP throughput collapse that occurs as the number of storage servers sending data to a client increases past the ability of an Ethernet switch to buffer packets. In a clustered file system, for example, a client application requests a data block striped across several storage servers, issuing the next data block request only when all servers have responded with their portion (Figure 1). This synchronized request workload can result in packets overfilling the buffers on the client's port on the switch, resulting in many losses. Under severe packet loss, TCP can experience a timeout that lasts a minimum of 200ms, determined by the TCP minimum retransmission timeout (RTOmin).
incast  networking  performance  tcp  bandwidth  buffering  switch  ethernet  capacity 
november 2014 by jm
Eircom have run out of network capacity
This is due in part to huge growth in the data volumes and data traffic that is transported over our network, which has exceeded our forecasted growth. We are making a number of improvements to our international connectivity which will add significant capacity and this work will be completed in the next two or three weeks.


Guess this is what happens when Amazon poach your IP network engineers. doh!

More seriously though, if you're marketing eFibre heavily, shouldn't you be investing in the upstream capacity to go with it?
eircom  fail  internet  capacity  forecasting  networking 
november 2014 by jm
"H" in cron syntax
This is something Jenkins have come up to randomize and distribute load, in order to avoid the "thundering-herd" bug. Good call
jenkins  randomization  load-balancing  load  thundering-herd  ops  capacity  sleep 
april 2014 by jm
Internet Tolls And The Case For Strong Net Neutrality
Netflix CEO Reed Hastings blogs about the need for Net Neutrality:
Interestingly, there is one special case where no-fee interconnection is embraced by the big ISPs -- when they are connecting among themselves. They argue this is because roughly the same amount of data comes and goes between their networks. But when we ask them if we too would qualify for no-fee interconnect if we changed our service to upload as much data as we download** -- thus filling their upstream networks and nearly doubling our total traffic -- there is an uncomfortable silence. That's because the ISP argument isn't sensible. Big ISPs aren't paying money to services like online backup that generate more upstream than downstream traffic. Data direction, in other words, has nothing to do with costs. ISPs around the world are investing in high-speed Internet and most already practice strong net neutrality. With strong net neutrality, new services requiring high-speed Internet can emerge and become popular, spurring even more demand for the lucrative high-speed packages ISPs offer. With strong net neutrality, everyone avoids the kind of brinkmanship over blackouts that plague the cable industry and harms consumers. As the Wall Street Journal chart shows, we're already getting to the brownout stage. Consumers deserve better.
consumer  net-neutrality  comcast  netflix  protectionism  cartels  isps  us  congestion  capacity 
march 2014 by jm
There is NO spare capacity for Dublin's water supply
The problem in a nutshell is that for an uncomfortable amount of the year the demand outstrips what the system can comfortably supply. In the graph below you’ll see the red line (demand for water) matches and regularly exceeds the blue line (what’s produced).
drought  water  dublin  mismanagement  capacity  dcc  dublin-council  graphs 
november 2013 by jm
"What Should I Monitor?"
slides (lots of slides) from Baron Schwartz' talk at Velocity in NYC.
slides  monitoring  metrics  ops  devops  baron-schwartz  pdf  capacity 
october 2013 by jm

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