Prysm: [Mega tracking] - Implement policing service

[shayzluf]

While starting the design process of policing service that will keep an eye at the network for finding slashable events. as well as protect his own subscribers (Validators) from creating a slashable event.

The way to a full blown policing service is comprised of these steps:
Bug fixes:

• [x] grpc proto api #3134
• [x] separate db for slasher #3270
• [x] making slasher grpc server #3271
• [x] Store historical block headers in local db #3270
• [x] Store indexed attestations in db #3322 / #3897
• [x] Store min max span per validator #3941
• [x] Update min max span per validator #3951
• [x] Detect surround attestations using min max span #3967
• [x] Proposer slashing detection (db keys)
• [x] Double Attestation detection (db keys)
• [x] Surround attestation detection (min max span)
• [x] Benchmark surround attestation detection
• [x] Slasher grpc client of beacon node
• [ ] Store active validator state per epoch
• [ ] Store validator index to public key map
• [ ] Validate attestation signature (@rauljordan @0xKiwi they are verified before being put in pull)
• [ ] Purge attestations and historic block headers bucket to max size #3270

• [ ] Beacon server detection of all slashable events of its subscribed validators(bitmap 54000 epoches X number of running validators). By storing all the data concerning them in db and validating against it. Panic in case a rpc call is going to create a slashable event.
• [ ] Slasher server with pruning at weak subjectivity period
• [ ] Beacon node / Slasher communication. to feed slasher with attestations and block proposals.
• [ ] Beacon node / Slasher communication. to listen slashable events
• [ ] Slashing simulator

[prestonvanloon]

Design doc: https://docs.google.com/document/d/12Eg-ysK5aQKQIjTKL6srqu8-ZY44iZ2MNwuqPaymlYk/edit#

[rauljordan]

Suggestion to name the watchtower server Bazel binary that's in charge of policing slashable events across beacon nodes the "Hash Slinging Slasher" after the iconic Spongebob Squarepants villain (credits to @prestonvanloon)

[shayzluf]

Suggestion to name the watchtower server Bazel binary that's in charge of policing slashable events across beacon nodes the "Hash Slinging Slasher" after the iconic Spongebob Squarepants villain (credits to @prestonvanloon)

should i change the folder name?

[rauljordan]

Closing this in favor of #4836