Added extra docs about updating Golang version. (thanos-io#1209)

Signed-off-by: Bartek Plotka <[email protected]>

Author: bwplotka

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,6 +3,8 @@
     about what components it touches e.g "query:" or ".*:"
 -->
 
+* [] CHANGELOG entry if change is relevant to the end user.
+
 ## Changes
 
 <!-- Enumerate changes you made -->

CHANGELOG.md

@@ -9,10 +9,16 @@ NOTE: As semantic versioning states all 0.y.z releases can contain breaking chan
 
 We use *breaking* word for marking changes that are not backward compatible (relates only to v0.y.z releases.)
 
-## [v0.5.0-rc.0](https://github.com/improbable-eng/thanos/releases/tag/v0.5.0-rc.0) - 2019.05.30
+## Unreleased.
+
+## [v0.5.0-rc.0](https://github.com/improbable-eng/thanos/releases/tag/v0.5.0-rc.0) - 2019.05.31
 
 TL;DR: Store LRU cache is no longer leaking, Upgraded Thanos UI to Prometheus 2.9, Fixed auto-downsampling, Moved to Go 1.12.5 and more.
 
+This version moved tarballs to Golang 1.12.5 from 1.11 as well, so same warning applies if you use `container_memory_usage_bytes` from cadvisor. Use `container_memory_working_set_bytes` instead.
+
+*breaking* As announced couple of times this release also removes gossip with all configuration flags (`--cluster.*`).
+
 ### Fixed
 
 - [#1142](https://github.com/improbable-eng/thanos/pull/1142) fixed major leak on store LRU cache for index items (postings and series).
@@ -65,7 +71,7 @@ TL;DR: Store LRU cache is no longer leaking, Upgraded Thanos UI to Prometheus 2.
 
 ## Deprecated 
 
-- [#1008](https://github.com/improbable-eng/thanos/pull/1008) Removed Gossip implementation.
+- [#1008](https://github.com/improbable-eng/thanos/pull/1008) *breaking* Removed Gossip implementation. All `--cluster.*` flags removed and Thanos will error out if any is provided.
 
 ## [v0.4.0](https://github.com/improbable-eng/thanos/releases/tag/v0.4.0) - 2019.05.3
 
@@ -74,7 +80,7 @@ TL;DR: Store LRU cache is no longer leaking, Upgraded Thanos UI to Prometheus 2.
 This release also disables gossip mode by default for all components.
 See [this](docs/proposals/approved/201809_gossip-removal.md) for more details.
 
-:warning: This release moves Thanos docker images and artifacts to Golang 1.12. This release includes change in GC's memory release which gives following effect (source: https://golang.org/doc/go1.12):
+:warning: This release moves Thanos docker images (NOT artifacts by accident) to Golang 1.12. This release includes change in GC's memory release which gives following effect (source: https://golang.org/doc/go1.12):
 
 > On Linux, the runtime now uses MADV_FREE to release unused memory. This is more efficient but may result in higher reported RSS. The kernel will reclaim the unused data when it is needed. To revert to the Go 1.11 behavior (MADV_DONTNEED), set the environment variable GODEBUG=madvdontneed=1.
 
@@ -170,7 +176,7 @@ Note that this is required to have SRV resolution working on [Golang 1.11+ with
    * tooling: [FEATURE] New dump command to tsdb tool to dump all samples.
    * compactor: 
       * [ENHANCEMENT] When closing the db any running compaction will be cancelled so it doesn't block.
-      * [CHANGE] Renamed flag `--sync-delay` to `--consistency-delay` [#1053](https://github.com/improbable-eng/thanos/pull/1053)
+      * [CHANGE] *breaking* Renamed flag `--sync-delay` to `--consistency-delay` [#1053](https://github.com/improbable-eng/thanos/pull/1053)
 
   For ruler essentially whole TSDB CHANGELOG applies beween v0.4.0-v0.6.1: https://github.com/prometheus/tsdb/blob/master/CHANGELOG.md
 

VERSION

@@ -1 +1 @@
-0.5.0-rc.0
+0.5.0-rc.0-master

docs/contributing/how-to-change-go-version.md

@@ -0,0 +1,16 @@
+---
+title: Changing Golang version
+type: docs
+menu: contributing
+slug: /how-to-change-go-version.md
+---
+
+Thanos build system is pinned to certain Golang version. This is to ensure that Golang version
+changes is done by us in controlled, traceable way.
+
+To update Thanos build system to newer Golang:
+
+1. Edit [.promu.yaml](/.promu.yml) and edit `go: version: <go version>` in YAML to desired version. This will ensure that all artifacts are 
+  built with desired Golang version. How to verify? Download tarball, unpack and invoke `thanos --version`
+1. Edit [.circleci/config.yaml](/.circleci/config.yml) and edit ` - image: circleci/golang:<go version>` to desired 
+  Golang version. This will ensure that all docker images and go tests are using desired Golang version. How to verify? Invoke `docker pull improbable/thanos:<version> --version`

docs/release-process.md

@@ -1,4 +1,9 @@
-# Releases
+---
+title: Release Process
+type: docs
+menu: thanos
+slug: /release-process.md
+---
 
 This page describes the release cadence and process for Thanos project.