Snap docs change (#986)

* adds snap docs,
adds release information for snap package,
adds docs notes about configuration management with snap package.

* adds release page mention

* version fix for snap, its awful

* revert version

* Apply suggestions from code review

Co-authored-by: Aliaksandr Valialkin <valyala@gmail.com>

Makefile

@@ -49,6 +49,10 @@ vmutils: \
 	vmbackup \
 	vmrestore
 
+release-snap:
+	snapcraft
+	snapcraft upload "victoriametrics_$(PKG_TAG)_multi.snap" --release beta,edge,candidate
+
 release: \
 	release-victoria-metrics \
 	release-vmutils

README.md

@@ -104,6 +104,7 @@ Alphabetically sorted links to case studies:
 
 * [How to start VictoriaMetrics](#how-to-start-victoriametrics)
   * [Environment variables](#environment-variables)
+  * [Configuration with snap package](#configuration-with-snap-package)
 * [Prometheus setup](#prometheus-setup)
 * [Grafana setup](#grafana-setup)
 * [How to upgrade VictoriaMetrics](#how-to-upgrade-victoriametrics)
@@ -197,6 +198,26 @@ Each flag value can be set via environment variables according to these rules:
 * For repeating flags an alternative syntax can be used by joining the different values into one using `,` char as separator (for example `-storageNode <nodeA> -storageNode <nodeB>` will translate to `storageNode=<nodeA>,<nodeB>`)
 * It is possible setting prefix for environment vars with `-envflag.prefix`. For instance, if `-envflag.prefix=VM_`, then env vars must be prepended with `VM_`
 
+### Configuration with snap package
+
+
+ Command-line flags can be changed with following command:
+
+```text
+echo 'FLAGS="-selfScrapeInterval=10s -search.logSlowQueryDuration=20s"' > $SNAP_DATA/var/snap/victoriametrics/current/extra_flags
+snap restart victoriametrics
+```
+  Or add needed command-line flags to the file `$SNAP_DATA/var/snap/victoriametrics/current/extra_flags`.
+
+ Note you cannot change value for `-storageDataPath` flag, for safety snap package has limited access to host system.
+
+
+ Changing scrape configuration is possible with text editor:
+    ```text
+    vi $SNAP_DATA/var/snap/victoriametrics/current/etc/victoriametrics-scrape-config.yaml
+    ```
+ After changes was made, trigger config re-read with command `curl 127.0.0.1:8248/-/reload`.
+
 
 ## Prometheus setup
 

docs/Release-Guide.md

@@ -10,6 +10,19 @@ Release process guidance
 5. Push release tag to https://github.com/VictoriaMetrics/VictoriaMetrics : `git push origin v1.xx.y`.
 6. Go to https://github.com/VictoriaMetrics/VictoriaMetrics/releases , create new release from the pushed tag on step 5 and upload `*.tar.gz` archive with the corresponding `_checksums.txt` from step 2.
 
+## Building snap package.
+
+ pre-requirements: 
+- snapcraft binary, can be installed with commands:
+   for MacOS `brew install snapcraft` and [install mutipass](https://discourse.ubuntu.com/t/installing-multipass-on-macos/8329),
+   for Ubuntu - `sudo snap install snapcraft --classic`
+- login with `snapcraft login`
+- already created release at github (it operates `git describe` version, so git tag must be annotated).
+
+0. checkout to the latest git tag for single-node version.
+1. execute `make release-snap` - it must build and upload snap package.
+2. promote release to current, if needed manually at release page [snapcraft-releases](https://snapcraft.io/victoriametrics/releases)
+
 ### Public Announcement 
 
 1. Publish message in slack (victoriametrics.slack.com, general channel)

docs/Single-server-VictoriaMetrics.md

@@ -104,6 +104,7 @@ Alphabetically sorted links to case studies:
 
 * [How to start VictoriaMetrics](#how-to-start-victoriametrics)
   * [Environment variables](#environment-variables)
+  * [Configuration with snap package](#configuration-with-snap-package)
 * [Prometheus setup](#prometheus-setup)
 * [Grafana setup](#grafana-setup)
 * [How to upgrade VictoriaMetrics](#how-to-upgrade-victoriametrics)
@@ -197,6 +198,26 @@ Each flag value can be set via environment variables according to these rules:
 * For repeating flags an alternative syntax can be used by joining the different values into one using `,` char as separator (for example `-storageNode <nodeA> -storageNode <nodeB>` will translate to `storageNode=<nodeA>,<nodeB>`)
 * It is possible setting prefix for environment vars with `-envflag.prefix`. For instance, if `-envflag.prefix=VM_`, then env vars must be prepended with `VM_`
 
+### Configuration with snap package
+
+
+ Command-line flags can be changed with following command:
+
+```text
+echo 'FLAGS="-selfScrapeInterval=10s -search.logSlowQueryDuration=20s"' > $SNAP_DATA/var/snap/victoriametrics/current/extra_flags
+snap restart victoriametrics
+```
+  Or add needed command-line flags to the file `$SNAP_DATA/var/snap/victoriametrics/current/extra_flags`.
+
+ Note you cannot change value for `-storageDataPath` flag, for safety snap package has limited access to host system.
+
+
+ Changing scrape configuration is possible with text editor:
+    ```text
+    vi $SNAP_DATA/var/snap/victoriametrics/current/etc/victoriametrics-scrape-config.yaml
+    ```
+ After changes was made, trigger config re-read with command `curl 127.0.0.1:8248/-/reload`.
+
 
 ## Prometheus setup
 

snap/local/README.md

@@ -9,23 +9,13 @@ snap link: https://snapcraft.io/victoriametrics
 
 Install snapcraft and multipass:
  ```text
-snap install snapcraft
-snap install multipass 
+sudo snap install snapcraft --classic
 ```
 
 build victoria-metrics prod binary and run snapcraft ```snapcraft --debug```. 
 It produces snap package with current git version - `victoriametrics_v1.46.0+git1.1bebd021a-dirty_all.snap`.
 You can install it with command: `snap install victoriametrics_v1.46.0+git1.1bebd021a-dirty_all.snap --dangerous`
 
-package and publish:
-
-```text
-make victoria-metrics-package-snap
-snap login
-snap_file=$(ls | grep -e '_multi.snap$')
-snapcraft upload --release=latest/edge "$snap_file"
-rm "$snap_file"
-```
 
 #### usage