fix(orchestrator): report real V4 header compression ratio

[ValentaTomas]

V4 header serialization LZ4-compresses its inner block, but the upload metric reported equal uncompressed and stored sizes so the ratio was always 1:1. StoreHeader now returns the pre-LZ4 byte count alongside the stored size and the metrics caller uses it. V3 headers stay at 1:1.

[cursor]

PR Summary

Low Risk
Low risk metrics/serialization plumbing change; main risk is any missed StoreHeader caller or incorrect uncompressed-size calculation skewing telemetry.

Overview
StoreHeader now returns both stored bytes and pre-LZ4 uncompressed bytes for V4 headers (plus an effective compression type), and the orchestrator upload metrics use these values so header compression ratio is no longer always reported as 1:1. Watch for any external callers of StoreHeader not updated (signature change) and for telemetry potentially recording compression.level/Enabled defaults while still labeling V4 as LZ4.

^{Reviewed by Cursor Bugbot for commit 112f606. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
2656	2	2654	7

View the full list of 2 ❄️ flaky test(s)

github.com/e2b-dev/infra/tests/integration/internal/tests/orchestrator::TestSandboxMemoryIntegrity

Flake rate in main: 64.48% (Passed 417 times, Failed 757 times)

Stack Traces | 87.4s run time

=== RUN   TestSandboxMemoryIntegrity
=== PAUSE TestSandboxMemoryIntegrity
=== CONT  TestSandboxMemoryIntegrity
    sandbox_memory_integrity_test.go:27: Build completed successfully
--- FAIL: TestSandboxMemoryIntegrity (87.38s)

github.com/e2b-dev/infra/tests/integration/internal/tests/orchestrator::TestSandboxMemoryIntegrity/tmpfs_hash

Flake rate in main: 64.79% (Passed 407 times, Failed 749 times)

Stack Traces | 114s run time

=== RUN   TestSandboxMemoryIntegrity/tmpfs_hash
=== PAUSE TestSandboxMemoryIntegrity/tmpfs_hash
=== CONT  TestSandboxMemoryIntegrity/tmpfs_hash
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{start:{pid:1259}}
Executing command bash in sandbox iy3r2uxwsgxep1rnxldub (user: root)
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{data:{stdout:"Total memory: 985 MB\nUsed memory before tmpfs mount: 188 MB\nFree memory before tmpfs mount: 796 MB\nMemory to use in integrity test (80% of free, min 64MB): 636 MB\n"}}
Executing command bash in sandbox iy3r2uxwsgxep1rnxldub (user: root)
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{data:{stderr:"636+0 records in\n636+0 records out\n666894336 bytes (667 MB, 636 MiB) copied, 3.09547 s, 215 MB/s\n"}}
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{data:{stderr:"\tCommand being timed: \"dd if=/dev/urandom of=/mnt/testfile bs=1M count=636\"\n\tUser time (seconds): 0.00\n\tSystem time (seconds): 3.08\n\tPercent of CPU this job got: 99%\n\tElapsed (wall clock) time (h:mm:ss or m:ss): 0:03.10\n\tAverage shared text size (kbytes): 0\n\tAverage unshared data size (kbytes): 0\n\tAverage stack size (kbytes): 0\n\tAverage total size (kbytes): 0\n\tMaximum resident set size (kbytes): 2704\n\tAverage resident set size (kbytes): 0\n\tMajor (requiring I/O) page faults: 3\n\tMinor (reclaiming a frame) page faults: 343\n\tVoluntary context switches: 4\n\tInvoluntary context switches: 32\n\tSwaps: 0\n\tFile system inputs: 176\n\tFile system outputs: 0\n\tSocket messages sent: 0\n\tSocket messages received: 0\n\tSignals delivered: 0\n\tPage size (bytes): 4096\n\tExit status: 0\n"}}
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{data:{stdout:"Used memory after tmpfs mount and file fill: 829 MB\n"}}
    sandbox_memory_integrity_test.go:70: Command [bash] output: event:{end:{exited:true  status:"exit status 0"}}
    sandbox_memory_integrity_test.go:70: Command [bash] completed successfully in sandbox ic2x8t5yr1zcx5j6yck47
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{start:{pid:1275}}
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{data:{stdout:"6a0d01f2b3580bc3d4b63038f03b7f3cba3a59230e9bb8948b6b1b82dd205b29\n"}}
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{end:{exited:true  status:"exit status 0"}}
    sandbox_memory_integrity_test.go:80: Command [bash] completed successfully in sandbox ic2x8t5yr1zcx5j6yck47
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{start:{pid:1278}}
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{data:{stdout:"6a0d01f2b3580bc3d4b63038f03b7f3cba3a59230e9bb8948b6b1b82dd205b29\n"}}
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{end:{exited:true  status:"exit status 0"}}
    sandbox_memory_integrity_test.go:80: Command [bash] completed successfully in sandbox ic2x8t5yr1zcx5j6yck47
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
    sandbox_memory_integrity_test.go:80: Command [bash] output: event:{start:{pid:1281}}
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
Executing command bash in sandbox ic2x8t5yr1zcx5j6yck47 (user: root)
    sandbox_memory_integrity_test.go:110: 
        	Error Trace:	.../tests/orchestrator/sandbox_memory_integrity_test.go:81
        	            				.../hostedtoolcache/go/1.26.3.../src/runtime/asm_amd64.s:1771
        	Error:      	Received unexpected error:
        	            	failed to execute command bash in sandbox ic2x8t5yr1zcx5j6yck47: unavailable: HTTP status 502 Bad Gateway
    sandbox_memory_integrity_test.go:110: 
        	Error Trace:	.../tests/orchestrator/sandbox_memory_integrity_test.go:78
        	            				.../tests/orchestrator/sandbox_memory_integrity_test.go:110
        	Error:      	Condition never satisfied
        	Test:       	TestSandboxMemoryIntegrity/tmpfs_hash
--- FAIL: TestSandboxMemoryIntegrity/tmpfs_hash (114.27s)

To view more test analytics, go to the Test Analytics Dashboard
_{📋 Got 3 mins? Take this short survey to help us improve Test Analytics.}

[gemini-code-assist]

Code Review

This pull request introduces the HeaderStoreStats struct to track storage metrics and updates the serialization logic to return these statistics. The orchestrator is also updated to record these metrics during artifact uploads. I have no feedback to provide.

[levb]

LGTM