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Optimizing for Doze and App Standby | Android Developers
Test and optimize your app for the power-saving features in Android 6.0.
app  android  doze  standby 
december 2017 by jberkel
Scaling Postgres with Read Replicas & Using WAL to Counter Stale Reads — Brandur Leach
- Modern databases operating over low latency connections can keep replicas trailing their primary very closely, and probably spend most of their time less than a second out of date. Even systems using read replicas without any techniques for mitigating stale reads will produce correct results most of the time.

- Let’s take a look at a technique to make sure that stale reads never occur. We’ll use Postgres’s own understanding of its replication state and some in-application intelligence around connection management to accomplish it.

1. Postgres commits all changes to a WAL (write-ahead log) for durability reasons.
2. Changes are written to the WAL one entry at a time and each one is assigned a LSN (log sequence number).
3. Changes are batched in 16 MB WAL segments.
4. A Postgres database can dump a representation of its current state to a base backup which can be used to initialize replica.
5. From there, the replica stays in lockstep with its primary by consuming changes in its emitted WAL.
6. A base backup comes with a pointer to the current LSN so that when a replica starts to consume the WAL, it knows where to start.

- There are a few ways for a replica to consume WAL.

1. The first is “log shipping”: completed WAL segments (16 MB chunks of the WAL) are copied from primary to replicas and consumed as a single batch. => secondaries will be at least as behind as the current segment that’s still being written.

2. Another common configuration for consuming WAL is “streaming”, where WAL is emitted by the primary to replicas over an open connection. This has the advantage of secondaries being very current at the cost of some extra resource consumption.


- replicas consuming WAL with log shipping are also known as “warm standbys”
- while those using streaming are called “hot standbys”.

- By routing read operations only to replicas that are caught up enough to run them accurately, we can eliminate stale reads. This necessitates an easy way of measuring how far behind a replica is, and the WAL’s LSN is perfect for this use.

- For any action that will later affect reads, we touch the user’s min_lsn by setting it to the value of the primary’s pg_current_wal_lsn().
postgres  postgresql  scaling  high-availability  architecture  standby 
november 2017 by hellsten
Download Amazing Pointillism Art With Q Tips Is One Of Our Standby, Super Easy Yet Interesting Ac… HD Pictures | Best Images Collections HD For Gadget windows Mac Android
Pointillism art with Q-tips is one of our standby, super-easy-yet-interesting ac… Pointillism art with Q-tips is one of our standby, super-easy-yet-interesting activities and watercolors work great for it! Pointillism art with Q-tips is one of our standby, super-easy-yet-interesting ac…
IFTTT  WordPress  Art  Ac  amazing  download  hd  pictures  Pointillism  Qtips  standby  supereasyyetinteresting 
september 2017 by wotek
Testing App Standby – Google Developers – Medium
App Standby is an idle mode that the system can place your app in if it hasn’t been active in a while. And while this may sound scary, don’t panic. Because other than testing your app, I’ll bet you a…
android  test  standby  idle  mode 
june 2017 by lgtout
How Doze and App Standby finally fixed Android battery life in Marshmallow | Greenbot
apps won’t be able to clutter up your running processes and wakelock cycle.
app  standby  mode  android 
may 2017 by lgtout
Optimizing for Doze and App Standby | Android Developers
Test and optimize your app for the power-saving features in Android 6.0.
android  doze  standby  app 
may 2017 by lgtout

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