*: cut 0.20.0

promu: don't build openbsd/arm

Deactivate crossbuilding for openbsd/arm and mips as golang.org/x/sys
does not have the necessary syscalls implemented.

Forward-merge 0.19 fixes into master

Bump version to 0.19.3

This change does just signal a scrape target update to the scraping loop
once an initial target set is fetched.
Before, the scrape pool was directly synced, causing a race against an
uninitialized scrape pool.

Fixes #1703

retrieval: don't sync to uninitialized scrape pool

discovery/marathon: Fix race conditions in test

This change does just signal a scrape target update to the scraping loop
once an initial target set is fetched.
Before, the scrape pool was directly synced, causing a race against an
uninitialized scrape pool.

Fixes #1703

The concurrency applied before is in most cases not even needed. With
a cap=1 channel, most tests are much cleaner.

TestMarathonSDRunAndStop was trickier. It could even have blocked
before.

This also includes a general refactoring of the whole file.

Update scrape config in example prometheus.yml

Forward-merge 0.19 fixes to master

discovery/marathon: #1722 - ignore apps with zero ports

Re-ordering config validation

Do our own date parsing in console template graph controls.

Fixes #1442

web: round last scrape timestamp to milliseconds

config: deprecate `target_groups` for `static_configs`

This change deprecates the `target_groups` option in favor
of `static_configs`. The old configuration is still accepted
but prints a warning.
Configuration loading errors if both options are set.

vendor: update gopkg.in/fsnotify.v1

This updates the fsnotify package, which now uses golang.org/x/sys/unix
package. This fixes #1507.

Relabel: Document whole label set is dropped

From the documentation and current tests, it wasn't immediately clear to
me whether the `target` being dropped as the result of a 'drop' action
was a label key-value pair or the entire labelset.

Add a test that documents this behaviour.

Documentation: https://prometheus.io/docs/operating/configuration/

Kubernetes SD: Add labels for all node addresses and discover node port

Initial local pods before using the pod list to initialize pod targets

notifier: dispatch to multiple Alertmanagers

Make issue reports great again!

This commit extends the notifier to dispatch alert batches
to multiple Alertmanagers concurrently.
It changes the `-alertmanager.url` flag to accept a comma
separated list of URLs and/or to be set multiple times.

fix build with multi-part $GOPATH

Make the number of fingerprint mutexes configurable