[krishvishal]

In the shard router each shard gets an inbox (flume channel) and a vector of senders to all other shards (including itself). When a message arrives at any shard, the router:

1. Decomposes the generic message to extract the operation and namespace
2. Resolves the target shard - metadata ops go to shard 0, partition ops are looked up in the ShardsTable, unknown ops default to shard 0
3. Enqueues a ShardFrame into the target shard's channel

The message pump (run_message_pump) drains the inbox and processes frames sequentially, ensuring all mutations on a given shard are serialized through a single async task.

The ShardsTable trait abstracts partition ownership lookup with two implementations:

• () : no-op for single-shard setups (simulator for now)
• PapayaShardsTable: lock-free concurrent map for multi-shard deployments

[codecov]

Codecov Report

❌ Patch coverage is 0% with 168 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.77%. Comparing base (50423db) to head (d81c3fd).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
core/shard/src/router.rs	0.00%	86 Missing ⚠️
core/shard/src/lib.rs	0.00%	37 Missing ⚠️
core/shard/src/shards_table.rs	0.00%	33 Missing ⚠️
core/common/src/types/consensus/header.rs	0.00%	8 Missing ⚠️
core/simulator/src/replica.rs	0.00%	2 Missing ⚠️
core/metadata/src/impls/metadata.rs	0.00%	1 Missing ⚠️
core/partitions/src/iggy_partitions.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2853      +/-   ##
============================================
- Coverage     67.91%   67.77%   -0.14%     
  Complexity      739      739              
============================================
  Files          1049     1051       +2     
  Lines         84394    84544     +150     
  Branches      60973    61132     +159     
============================================
- Hits          57313    57300      -13     
- Misses        24720    24874     +154     
- Partials       2361     2370       +9     

Flag	Coverage Δ
csharp	67.43% <ø> (-0.19%)	⬇️
go	6.33% <ø> (ø)
java	54.83% <ø> (ø)
node	92.26% <ø> (-0.04%)	⬇️
python	0.00% <ø> (ø)
rust	70.01% <0.00%> (-0.20%)	⬇️

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Files with missing lines	Coverage Δ
core/metadata/src/impls/metadata.rs	16.53% <0.00%> (+0.25%)	⬆️
core/partitions/src/iggy_partitions.rs	0.00% <0.00%> (ø)
core/simulator/src/replica.rs	0.00% <0.00%> (ø)
core/common/src/types/consensus/header.rs	23.57% <0.00%> (-0.70%)	⬇️
core/shard/src/shards_table.rs	0.00% <0.00%> (ø)
core/shard/src/lib.rs	0.00% <0.00%> (ø)
core/shard/src/router.rs	0.00% <0.00%> (ø)

... and 20 files with indirect coverage changes

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[hubcio]

can you use crossfire instead of flume? its much more battle-tested than flume and seems to have better performance.

[krishvishal]

can you use crossfire instead of flume? its much more battle-tested than flume and seems to have better performance.

Okay, I will look into it.

[krishvishal]

Fixed merge conflicts.