Use PostgreSQL's NOTIFY/LISTEN for event pub/sub #100
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
slashdotdash
force-pushed
the
feature/listen-notify
branch
from
c410a00 to
99b7057
Compare
slashdotdash
added a commit
that referenced
this pull request
Jan 11, 2018
Include #100 in CHANGELOG
slashdotdash
force-pushed
the
feature/listen-notify
branch
2 times, most recently
from
8a7383c to
9df1755
Compare
slashdotdash
added a commit
that referenced
this pull request
Jan 11, 2018
Include #100 in CHANGELOG
slashdotdash
force-pushed
the
feature/listen-notify
branch
from
52378ed to
89169e1
Compare
Using PostgreSQL for pub/sub removes need for EventStore to form a cluster of nodes. It can be used on a single node, or multiple nodes, but they don't need to be directly connected. Instead the database will be used to distribute events. This simplifies running EventStore on a cluster.
Listener module is now a cluster singleton so only one PostgreSQL `LISTEN` connection is used per event store cluster.
Create PostgreSQL connection for notify test. Allow short delay for distributed subscription tests. Increase assert receive and refute timeouts in `distributed` env. Use latest Elixir and Erlang versions in Travis CI config. Use default logger format in test envs. Additional subscription logging to help identify intermittent test failure in `:distributed` env.
Include #100 in CHANGELOG
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Using PostgreSQL for pub/sub removes the requirement for EventStore to form a cluster of nodes.
It can be used on a single node or multiple nodes, but they don't need to be directly connected. The database will be used to distribute events instead. This simplifies running EventStore on a cluster and removes the dependency upon Swarm.
A single listener process subscribes to event notifications using PostgreSQL's
LISTENcommand. Whenever events are appended to storage aNOTIFYcommand is executed by a table trigger. The notification payload contains the first and last event number of the appended events (e.g.1,2). These events are then read from storage and published to interested subscribers. Elixir'sGenStageis used to read and forward events to subscriptions.PG2 groups are now used for event pub/sub when run in distributed mode.