apollo_config_manager: add sender channel to the config manager runner

[ArniStarkware]

Note

Medium Risk
Touches live config reload/update flow by switching change detection to a tokio::sync::watch channel, which could affect when/if dynamic config updates propagate. Still calls the existing config_manager_client update path, but now only after channel state changes.

Overview
ConfigManagerRunner now owns a tokio::sync::watch sender/receiver pair and uses it as the source of truth for the latest NodeDynamicConfig, replacing the prior internal latest_node_dynamic_config field.

update_config now returns Result<()>, computes diffs against the channel’s current value via send_if_modified, logs per-key changes through a new free log_config_diff helper, and only pushes updates (and calls set_node_dynamic_config) when the config actually changes. Node component wiring and runner tests are updated to create/pass the watch channel and validate updates by reading from it.

^{Reviewed by Cursor Bugbot for commit 0c934fc. Bugbot is set up for automated code reviews on this repo. Configure here.}

[reviewable-StarkWare]

This change is 

[ArniStarkware]

• apollo_infra: create component clients with channel #13565 : 2 dependent PRs (#13568 , #13705 )
• apollo_config_manager: add sender channel to the config manager runner #13477 👈 (View in Graphite)
• apollo_infra: refactor client struct to be an enum #13570
• main

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[nadin-Starkware]

@nadin-Starkware reviewed 3 files and all commit messages, and made 3 comments.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on ArniStarkware).

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crates/apollo_config_manager/src/config_manager_runner.rs line 150 at r1 (raw file):

            // block.
            match self.dynamic_config_tx.send(node_dynamic_config.clone()) {
                Ok(()) => info!("Successfully sent node dynamic config to the channel"),

Please change it to debug

Code quote:

info

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crates/apollo_config_manager/src/config_manager_runner.rs line 158 at r1 (raw file):

            match self
                .config_manager_client
                .set_node_dynamic_config(node_dynamic_config.clone())

Please remove

Code quote:

clone()

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crates/apollo_node/src/components.rs line 164 at r1 (raw file):

                    .expect("Config Manager config should be set");
                // TODO(Arni): remove the config_manager.
                let config_manger =

Please fix the typo

Suggestion:

config_manager

[ArniStarkware]

@ArniStarkware made 3 comments.
Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on nadin-Starkware).

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crates/apollo_config_manager/src/config_manager_runner.rs line 150 at r1 (raw file):

Previously, nadin-Starkware (Nadin Jbara) wrote…

Please change it to debug

Done.

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crates/apollo_config_manager/src/config_manager_runner.rs line 158 at r1 (raw file):

Previously, nadin-Starkware (Nadin Jbara) wrote…

Please remove

Done. Note, this changes the return type of this function. Luckily, the return value of this function was never used.

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crates/apollo_node/src/components.rs line 164 at r1 (raw file):

Previously, nadin-Starkware (Nadin Jbara) wrote…

Please fix the typo

Done.

[nadin-Starkware]

@nadin-Starkware reviewed 3 files and all commit messages, made 1 comment, and resolved 3 discussions.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on ArniStarkware).

[ArniStarkware]

@Itay-Tsabary-Starkware made 2 comments.

send_if_modified — done, switched to send_if_modified.

Test comment — the comment is still relevant at this PR level. set_node_dynamic_config exists here and is called by the runner. It's only removed in the downstream remove_client_from_runner PR. The note warns that we don't validate the correct config is passed — that validation would require .withf() on the mock, which isn't worth adding since the method is removed shortly downstream.

[ArniStarkware]

@ArniStarkware made 3 comments.
Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on Itay-Tsabary-Starkware and nadin-Starkware).

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crates/apollo_config_manager/src/config_manager_runner.rs line 37 at r3 (raw file):

Previously, nadin-Starkware (Nadin Jbara) wrote…

Please rename to _dynamic_config_rx

Done.

---

crates/apollo_config_manager/src/config_manager_runner.rs line 137 at r3 (raw file):

Previously, Itay-Tsabary-Starkware wrote…

This entire logic can be very-much simplified by using https://docs.rs/tokio/latest/tokio/sync/watch/struct.Sender.html#method.send_if_modified

Done.

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crates/apollo_config_manager/src/config_manager_runner_tests.rs line 128 at r3 (raw file):

Previously, Itay-Tsabary-Starkware wrote…

Still relevant? Isn't that method removed?

The method set_node_dynamic_config has been removed upstream. This is why the comment states: "This method is soon to be replaced."

[nadin-Starkware]

@nadin-Starkware made 1 comment and resolved 1 discussion.
Reviewable status: 0 of 3 files reviewed, 2 unresolved discussions (waiting on Itay-Tsabary-Starkware).

[Itay-Tsabary-Starkware]

@Itay-Tsabary-Starkware made 3 comments and resolved 2 discussions.
Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on ArniStarkware and nadin-Starkware).

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crates/apollo_config_manager/src/config_manager_runner.rs line 142 at r7 (raw file):

        let changed = self.dynamic_config_tx.send_if_modified(|current| {
            if *current == node_dynamic_config {

Does it make sense to compare the references here? That is,
current == &node_dynamic_config

Code quote:

if *current == node_dynamic_config

---

crates/apollo_config_manager/src/config_manager_runner.rs line 146 at r7 (raw file):

            }
            Self::log_config_diff(current, &node_dynamic_config);
            *current = node_dynamic_config.clone();

Please add a todo to remove this clone, I suspect it is currently required only due to the about-to-be-removed block at the end.

Code quote:

.clone();

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crates/apollo_config_manager/src/config_manager_runner.rs line 182 at r7 (raw file):

                info!("ConfigManagerRunner: {key} changed from {old_value} to {new_value}");
            }
        }

Is there a reason for this function to be a part of the struct's impl block?

Code quote:

    fn log_config_diff(old_config: &NodeDynamicConfig, new_config: &NodeDynamicConfig) {
        let old_config = get_config_presentation(old_config, false).unwrap();
        let new_config = get_config_presentation(new_config, false).unwrap();
        let all_keys: BTreeSet<_> = old_config
            .as_object()
            .unwrap()
            .keys()
            .chain(new_config.as_object().unwrap().keys())
            .collect();

        for key in all_keys {
            let old_value = old_config.as_object().unwrap().get(key).unwrap_or(&Value::Null);
            let new_value = new_config.as_object().unwrap().get(key).unwrap_or(&Value::Null);

            if old_value != new_value {
                info!("ConfigManagerRunner: {key} changed from {old_value} to {new_value}");
            }
        }

[ArniStarkware]

@ArniStarkware made 3 comments.
Reviewable status: 0 of 3 files reviewed, 3 unresolved discussions (waiting on Itay-Tsabary-Starkware and nadin-Starkware).

---

crates/apollo_config_manager/src/config_manager_runner.rs line 142 at r7 (raw file):

Previously, Itay-Tsabary-Starkware wrote…

Does it make sense to compare the references here? That is,
current == &node_dynamic_config

Done.

---

crates/apollo_config_manager/src/config_manager_runner.rs line 146 at r7 (raw file):

Previously, Itay-Tsabary-Starkware wrote…

Please add a todo to remove this clone, I suspect it is currently required only due to the about-to-be-removed block at the end.

Done.

---

crates/apollo_config_manager/src/config_manager_runner.rs line 182 at r7 (raw file):

Previously, Itay-Tsabary-Starkware wrote…

Is there a reason for this function to be a part of the struct's impl block?

Done.

[Itay-Tsabary-Starkware]

@Itay-Tsabary-Starkware reviewed 3 files and all commit messages, made 1 comment, and resolved 3 discussions.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on nadin-Starkware).

[cursor]

PR Summary

Medium Risk
Config update propagation is refactored to use a tokio::sync::watch channel with change detection, which can affect when/if downstream components observe updates and introduces new concurrency/lifecycle considerations.

Overview
ConfigManagerRunner now publishes NodeDynamicConfig updates through a tokio::sync::watch channel instead of storing latest_node_dynamic_config internally and returning the config from update_config.

update_config sends only when the config actually changes (logging diffs), adds a debug log on successful send, and temporarily keeps the existing config_manager_client.set_node_dynamic_config call behind a TODO for later removal. Node startup wiring (apollo_node components.rs) and runner tests are updated to create/pass the watch Sender/Receiver and to assert updates by reading from the channel; log_config_diff is extracted to a free function.

^{Reviewed by Cursor Bugbot for commit 2d54569. Bugbot is set up for automated code reviews on this repo. Configure here.}