fix(flashblocks): Increase Flashblocks Broadcast Buffer Size

[refcell]

Description

Increases the broadcast channel buffer from 20 to 1000 to prevent RecvError::Lagged errors when flashblock processing falls behind.

Problem

Nodes with flashblocks enabled show "WAL containing too many blocks" warnings every ~6 minutes, with flashblocks-canon lagging ~400 blocks behind (#316). The 20-message buffer overflows when processing can't keep up with incoming flashblocks.

Fix

Increase buffer to 1000 messages (~200s of headroom), preventing subscriber lag during temporary processing delays.

Note

Makes progress on #316.

[cb-heimdall]

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[haardikk21]

How do we know it is related to the buffer size? I don't understand how the math adds up here. Our metrics for processing duration dont have spikes which would delay processing significantly enough for a buffer of even size 20 to be full.

[refcell]

How do we know it is related to the buffer size? I don't understand how the math adds up here. Our metrics for processing duration dont have spikes which would delay processing significantly enough for a buffer of even size 20 to be full.

You're right -- I overlooked where this was being sent. Closing