firehose connection loadbalance #4083
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leoyvens
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Oct 20, 2022
docker/docker-compose.yml
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| volumes: | ||
| - ./data/postgres:/var/lib/postgresql/data | ||
| # volumes: | ||
| # - ./data/postgres:/var/lib/postgresql/data |
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Why this change to docker-compose?
graph/src/firehose/endpoints.rs
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| @@ -75,8 +73,7 @@ impl FirehoseEndpoint { | |||
| // Timeout on each request, so the timeout to estabilish each 'Blocks' stream. | |||
| .timeout(Duration::from_secs(120)); | |||
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| // Load balancing on a same endpoint is useful because it creates a connection pool. | |||
| let channel = Channel::balance_list(iter::repeat(endpoint).take(conn_pool_size as usize)); | |||
| let channel = Channel::balance_list(vec![endpoint].into_iter()); | |||
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We can make this let channel = endpoint.connect_lazy(); as it used to be.
graph/src/firehose/endpoints.rs
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| @@ -267,10 +264,12 @@ impl FirehoseEndpoints { | |||
| self.0.len() | |||
| } | |||
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| // selects the FirehoseEndpoint with the lest amount of references, which will help with spliting | |||
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| // selects the FirehoseEndpoint with the lest amount of references, which will help with spliting | |
| // selects the FirehoseEndpoint with the least amount of references, which will help with splitting |
graph/src/firehose/endpoints.rs
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| self.0.iter().choose(&mut rng) | ||
| self.0 | ||
| .iter() | ||
| .min_by(|x, y| Arc::strong_count(x).cmp(&Arc::strong_count(y))) |
graph/src/firehose/endpoints.rs
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| @@ -267,10 +264,12 @@ impl FirehoseEndpoints { | |||
| self.0.len() | |||
| } | |||
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| // selects the FirehoseEndpoint with the lest amount of references, which will help with spliting | |||
| // the load naively across the entire list. | |||
| pub fn random(&self) -> Option<&Arc<FirehoseEndpoint>> { | |||
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One aspect that concerns me is a silent hang if we ever hit the 100 stream limit per connection limit. Perhaps a simple way to make the error explicit would be to add a
const SUBGRAPHS_PER_CONN: usize = 100;
And return an error if the ref count reaches this number. Or even better auto-scale based on this.
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will address this on a separate PR as this could benefit from some metrics in order to detect a stall
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leoyvens
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Oct 21, 2022
| .min_by_key(|x| Arc::strong_count(x)) | ||
| .ok_or(anyhow!("no available firehose endpoints"))?; | ||
| if Arc::strong_count(endpoint) > SUBGRAPHS_PER_CONN { | ||
| return Err(anyhow!("all connections saturated with {} connections, increase the firehose conn_pool_size", SUBGRAPHS_PER_CONN)); |
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Nice work with the actionable error message!
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Oh and lets bump the default to 20. |
leoyvens
approved these changes
Oct 21, 2022
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Fixes #3879