File based naming resolver

[beiwei30]

Description

Provide a file based naming resolver to replace mDNS so that dapr can address each other either on the same host or via shared file system, which would be more stable and friendly for development.

The default directory to keep naming informations is: $HOME/.dapr/naming, and it can be customized in Dapr's config.yaml:

apiVersion: dapr.io/v1alpha1
kind: Configuration
metadata:
  name: appconfig
spec:
  nameResolution:
    component: "file"
    configuration:
      dir: "/var/tmp/dapr-naming"

Pro and con of this solution:

• Pro: Since the name resolving is file based, it means that it can not only work in slim mode, but also in standalone mode, since the directory to keep the naming informations can be anywhere as long as it's accessible to Dapr's instances.
• Con: Since there has no lifecycle mechanism for components, this solution doesn't have chance to remove (unregister) its naming info from the file when Dapr instance goes away. It may not a big deal in development stage, but in the worst case user needs to know where the directory locates and delete the files manually.

Issue reference

This PR will close: dapr/dapr#3256

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]

[yaron2]

There's also this PR: #1340.

Both close the same issue, however I do not see a problem accepting both. Thoughts?

[beiwei30]

will continue to update dapr/dapr and dapr/docs once this solution is accepted.

[codecov]

Codecov Report

Merging #1342 (8c15cd8) into master (09fb60c) will decrease coverage by 0.00%.
The diff coverage is 19.84%.

@@            Coverage Diff             @@
##           master    #1342      +/-   ##
==========================================
- Coverage   35.02%   35.01%   -0.01%     
==========================================
  Files         148      150       +2     
  Lines       12825    13004     +179     
==========================================
+ Hits         4492     4554      +62     
- Misses       7853     7950      +97     
- Partials      480      500      +20     

Impacted Files	Coverage Δ
authentication/azure/auth_amqp.go	0.00% <0.00%> (ø)
bindings/aws/kinesis/kinesis.go	2.61% <0.00%> (ø)
bindings/azure/eventgrid/eventgrid.go	3.84% <0.00%> (ø)
bindings/mqtt/mqtt.go	25.00% <0.00%> (-1.42%)	⬇️
configuration/redis/redis.go	37.22% <0.00%> (-1.12%)	⬇️
pubsub/aws/snssqs/policy.go	0.00% <0.00%> (ø)
pubsub/rocketmq/rocketmq.go	0.00% <0.00%> (ø)
state/azure/cosmosdb/cosmosdb.go	13.91% <0.00%> (-1.35%)	⬇️
state/query/query.go	23.91% <ø> (ø)
authentication/azure/auth.go	40.35% <1.92%> (-15.75%)	⬇️
... and 11 more

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[beiwei30]

pls. use #1380 for further review.