Load test — eviction under memory pressure

Standalone binary that validates v1.7.0's chunked eviction + admission control + client retry against a real smartbotic-database instance.

Not a unit test — runs a real server on a configurable port, hammers it with concurrent inserts, and reports success/failure counts + a pressure-level timeline.

Prerequisites

smartbotic-database package installed (for the server binary)
libsmartbotic-db-client-dev installed (for headers + shared lib)
GCC with C++20 support

Build

cd tests/load_test
g++ -std=c++20 -O2 -I/usr/include load_test.cpp \
    -lsmartbotic-db-client \
    $(pkg-config --libs grpc++) \
    -lspdlog -lfmt -pthread \
    -o load_test

Run

Uses port 9005 and data dir /tmp/smartbotic-loadtest/ to avoid conflicting with any existing instance on the default port 9004.

# 1. Start the test server with its own config (memory capped at 32 MB)
mkdir -p /tmp/smartbotic-loadtest/data /tmp/smartbotic-loadtest/files
smartbotic-database --config ./config.json > /tmp/smartbotic-loadtest/server.log 2>&1 &
SERVER_PID=$!
sleep 2

# 2. Run the load test — default: 20s, 4 writers, 2 KB docs
./load_test [duration_seconds] [writer_threads] [doc_bytes]

# Example — 30s with 8 writers:
./load_test 30 8 2048

# 3. Stop the server
kill $SERVER_PID

# 4. Inspect eviction events
grep -E "Eviction|MEMORY_" /tmp/smartbotic-loadtest/server.log

What to look for

Sample output from a successful run (32 MB cap, 20s, 4 writers, 2 KB docs):

[t=18504ms] pressure=     hard  84% mem=27584KB live=  5276 evicted= 41580 inserts=  46856 fails=    0

=== Summary ===
Duration:                 20162ms
Successful inserts:       51444 (2551 ops/s)
Failed (after retries):   0
Pressure timeline:
  normal:  1.5s
  soft:    5.0s
  hard:    9.0s
  emergency: 2.0s
  Transitions: 19

Verdict: PASS — client-side retry absorbed all transient errors

Key signals

Signal	What it means
`Eviction chunk: N docs evicted, X bytes freed`	T4 chunked eviction is working
`Eviction: nothing evictable this pass, backing off`	T4 hot-write floor is protecting in-flight upserts
`Emitted MEMORY_PRESSURE_HIGH`	T10 edge-triggered event fired
`Insert rejected: memory pressure emergency`	T7 admission control engaged
`Client::insert ...; retrying in Nms (attempt K/5)`	T11 client retry kicked in
`Successful inserts: N == attempts, Failed: 0`	No writes lost under pressure

Tuning for different scenarios

Edit config.json:

Burst write stress: lower hot_write_floor_ms to 500 ms so eviction can actually drop recent writes
Slow drain: raise eviction_chunk_pause_ms to 200 ms
Admission control disabled: raise memory_emergency_percent to 99
Bigger budget: raise max_memory_mb to 256 to see if the chunked approach still works at scale

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