Apply migrations when tink-server boots

[gianarb]

Description

It will be nice to have the tink-server capable of applying migrations
if necessary. The idea to self-apply migrations will may look unusual
but it is an easy way to distribute software capable of migrating
database schema without having to run any external procedures.

$ docker run -d -it -e  POSTGRES_PASSWORD=tinkerbell -e POSTGRES_USER=tinkerbell -p 5432:5432 postgres
# PGPASSWORD=tinkerbell PGUSER=tinkerbell PGSSLMODE=disable PACKET_VERSION=v1 PACKET_ENV=ga ROLLBAR_TOKEN=ignored go run cmd/tink-server/main.go
{"level":"info","ts":1600772721.3009,"caller":"tink-server/main.go:30","msg":"starting version devel","service":"github.com/tinkerbell/tink"}
migrations  1
records  0
{"level":"info","ts":1600772721.309925,"caller":"tink-server/main.go:54","msg":"Your database schema is not up to date. Please apply migrations running tink-server with env var ONLY_MIGRATION set.","service":"github.com/tinkerbell/tink"}
{"level":"info","ts":1600772721.310011,"caller":"metrics/metrics.go:58","msg":"initializing label values","service":"github.com/tinkerbell/tink"}

As suggested you should run tink-server with ONLY_MIGRATION=true

$ ONLY_MIGRATION=true PGPASSWORD=tinkerbell PGUSER=tinkerbell PGSSLMODE=disable PACKET_VERSION=v1 PACKET_ENV=ga ROLLBAR_TOKEN=ignored go run cmd/tink-server/main.go
{"level":"info","ts":1600772853.779405,"caller":"tink-server/main.go:30","msg":"starting version devel","service":"github.com/tinkerbell/tink"}
{"level":"info","ts":1600772853.779805,"caller":"tink-server/main.go:40","msg":"Applying migrations. This process will end when migrations will take place.","service":"github.com/tinkerbell/tink"}
{"level":"info","ts":1600772853.819854,"caller":"tink-server/main.go:45","msg":"Running migrations if necessary","service":"github.com/tinkerbell/tink","num_applied_migrations":1}

This is the logs from docker-compose up, as you can see there is a new service that runs before tink-server and it applies the migrations.

registry_1               | 127.0.0.1 - - [01/Oct/2020:08:58:07 +0000] "GET / HTTP/2.0" 200 0 "" "curl/7.67.0"
db_1                     | 2020-10-01 08:58:04.165 UTC [1] LOG:  database system is ready to accept connections
registry_1               | 127.0.0.1 - - [01/Oct/2020:08:58:12 +0000] "GET / HTTP/2.0" 200 0 "" "curl/7.67.0"
hegel_1                  | 2020/10/01 08:58:05 fetch cert: Get http://127.0.0.1:42114/cert: dial tcp 127.0.0.1:42114: connect: connection refused
tink-server-migration_1  | {"level":"info","ts":1601542686.5914426,"caller":"tink-server/main.go:29","msg":"starting version 81ae632","service":"github.com/tinkerbell/tink"}
tink-server-migration_1  | {"level":"info","ts":1601542686.591473,"caller":"tink-server/main.go:39","msg":"Applying migrations. This process will end when migrations will take place.","service":"github.com/tinkerbell/tink"}
tink-server-migration_1  | {"level":"info","ts":1601542686.6131954,"caller":"tink-server/main.go:45","msg":"Migrations applied successfully","service":"github.com/tinkerbell/tink","num_applied_migrations":0}
deploy_tink-server-migration_1 exited with code 0
tink-server_1            | {"level":"info","ts":1601542687.7541816,"caller":"tink-server/main.go:29","msg":"starting version 81ae632","service":"github.com/tinkerbell/tink"}
tink-server_1            | {"level":"info","ts":1601542687.7602122,"caller":"metrics/metrics.go:58","msg":"initializing label values","service":"github.com/tinkerbell/tink"}
tink-server_1            | {"level":"info","ts":1601542687.7629616,"caller":"grpc-server/grpc_server.go:76","msg":"serving grpc","service":"github.com/tinkerbell/tink"}
tink-server_1            | {"level":"info","ts":1601542687.7635539,"caller":"http-server/http_server.go:90","msg":"serving http","service":"github.com/tinkerbell/tink"}

Why is this needed

Fixes: #295

How Has This Been Tested?

With docker-compose and vagrant.

How are existing users impacted? What migration steps/scripts do we need?

no impact, the workflow is well managed by docker-compose, transparently.

They are not impacted by this change.

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• added unit or e2e tests
• provided instructions on how to upgrade

[codecov]

Codecov Report

Merging #313 into master will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #313      +/-   ##
==========================================
+ Coverage   22.65%   22.67%   +0.01%     
==========================================
  Files          15       15              
  Lines        1271     1270       -1     
==========================================
  Hits          288      288              
+ Misses        964      963       -1     
  Partials       19       19              

Impacted Files	Coverage Δ
grpc-server/grpc_server.go	0.00% <0.00%> (ø)

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