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Cherrypick recent changes to gossip RFC 

Delete the RFC since this is all implemented.

See: 02bfcd23a9
This commit is contained in:
Greg Fitzgerald 2018-12-12 11:01:54 -07:00
parent c83538a60c
commit 90a0237457
2 changed files with 18 additions and 88 deletions
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28
book/src/gossip.md
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@ -37,14 +37,12 @@ Upon receiving a push message, a node examines the message for:
1. Duplication: if the message has been seen before, the node responds with 1. Duplication: if the message has been seen before, the node responds with
`PushMessagePrune` and drops the message `PushMessagePrune` and drops the message
2. New information: if the message is new the node 2. New data: if the message is new to the node
* Stores the new information with an updated version in its cluster info and
a. Stores the new information and updates its version purges any previous older value
* Stores the message in `pushed_once` (used for detecting duplicates,
b. Stores the message in `pushed_once` (used for detecting duplicates, purged after `PUSH_MSG_TIMEOUT * 5` ms)
purged after `PUSH_MSG_TIMEOUT * 5` ms) * Retransmits the messages to its own push peers
c. Retransmits the messages to its own push peers
3. Expiration: nodes drop push messages that are older than `PUSH_MSG_TIMEOUT` 3. Expiration: nodes drop push messages that are older than `PUSH_MSG_TIMEOUT`
@ -66,6 +64,16 @@ that represents things it already has. A node receiving a pull message
iterates over its values and constructs a pull response of things that miss the iterates over its values and constructs a pull response of things that miss the
filter and would fit in a message. filter and would fit in a message.
A node constructs the pull Bloom filter by iterating over the values it A node constructs the pull Bloom filter by iterating over current values and
currently has. recently purged values.
A node handles items in a pull response the same way it handles new data in a
push message.
## Purging
Nodes retain prior versions of values (those updated by a pull or push) and
expired values (those older than `GOSSIP_PULL_CRDS_TIMEOUT_MS`) in
`purged_values` (things I recently had). Nodes purge `purged_values` that are
older than `5 * GOSSIP_PULL_CRDS_TIMEOUT_MS`.

78
rfcs/0012-gossip.md
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@ -1,78 +0,0 @@
# Gossip, A.K.A. Cluster Info
This RFC describes the Solana's gossip protocol, also known as the network
control plane.
Nodes continuously share signed data objects among themselves in order to find
each other, structure the network data plane, prevent censoring, etc.
The basic mechanism is a 10Hz loop wherein every node sends a push message
and/or a pull message. Push and pull messages may elicit responses, and push
messages may be forwarded on to others in the network.
Gossip runs on a well-known UDP/IP port, or a port in a well-known range. Once
a network is bootstrapped, nodes advertise to each other where to find their
gossip endpoint (a socket address).
## Gossip Records
Records shared over gossip are arbitrary, but signed and versioned (with a
timestamp), and need to make sense to the node receiving them. A strategy of
"most recent timestamp wins" is employed to manage what's stored in cluster
info. If 2 values from the same creator have the same timestamp, the value
with the greater hash wins.
## Push
### Push Message
A push message is "hey network, I have something new to share". Nodes send
push messages to `PUSH_FANOUT` push peers.
Upon receiving a push message, a node examines the message for:
1. duplication: if the message has been seen before, the node responds with
`PushMessagePrune` and drops the message
2. new data: if the message is new to the node
* stores the new information with an updated version in its cluster info and
purges any previous older value
* stores the message in `pushed_once` (used for detecting duplicates,
purged after `PUSH_MSG_TIMEOUT * 5` ms)
* retransmits the messages to its own push peers
3. expiration: nodes drop push messages that are older than `PUSH_MSG_TIMEOUT`
### Push Peers, Prune Message
A nodes selects its push peers at random from the active set of known peers.
The node keeps this selection for a relatively long time. When a prune message
is received, the node drops the push peer that sent the prune. Prune is an
indication that there is another, faster path to that node than direct push.
The set of push peers is kept fresh by rotating a new node into the set every
`PUSH_MSG_TIMEOUT/2` milliseconds.
## Pull
### Pull Message
A pull message is "hey dude, got anything new?". A pull message is sent to a
single peer at random and comprises a Bloom filter that represents "things I
have or recently had". A node receiving a pull message iterates over its values
and constructs a pull response of things that miss the filter and would fit in a
message.
A node constructs the pull Bloom filter by iterating over current values and
recently purged values.
A node handles items in a pull response the same way it handles new data in a
push message.
## Purging
Nodes retain prior versions of values (those updated by a pull or push) and
expired values (those older than `GOSSIP_PULL_CRDS_TIMEOUT_MS`) in
`purged_values` (things I recently had). Nodes purge `purged_values` that are
older than `5 * GOSSIP_PULL_CRDS_TIMEOUT_MS`.