memory-buffer

Memory Buffer Demo

This demo proves the memory retention model:

[kept messages][rotating tail]

The demo keeps the first 3 messages forever and rotates only the later tail.

Build First

From the project root:

make demo

That gives you:

• target/debug/ljd
• target/debug/otlp-bofh-emitter
• target/debug/otlp-demo-collector
• target/debug/otlp-wire-forwarder

Run

From this directory:

./run-demo.sh

The script:

1. starts ljd in memory mode with:
   • buffer.keep: 3
   • buffer.messages: 10
2. emits 10 startup messages:
   • this message #1 must be kept
   • ...
   • this message #10 must be kept
3. emits 100 BOFH flood messages with no delay
4. starts the OTLP collector mockup
5. connects a wire forwarder to ljd replay
6. forwards exactly 13 messages to the collector

Expected result:

• the collector shows:
  • the first 3 startup messages
  • the last 10 flood messages
• startup messages #4 through #10 are gone

Why 13 Messages

• kept front jar: 3
• rotating tail: 10
• total retained after the late consumer connects: 13

Notes

• ingest is OTLP/HTTP on 127.0.0.1:4318
• replay listener is the internal wire protocol on 127.0.0.1:7002
• collector mockup listens on 127.0.0.1:4320
• this demo is intentionally deterministic

Memory Show Variant

If you want a smaller visible run where startup messages #4 through #10 are still present together with a few BOFH messages, run:

./run-demo-memshow.sh

This variant uses:

• buffer.keep: 3
• total visible ring of 15 messages
• rotating tail size of 12 messages
• 10 startup messages
• 5 BOFH flood messages

Expected result:

1. you see the first 3 startup messages
2. you see startup messages #4 through #10
3. you see 5 BOFH flood messages

Total retained and forwarded:

• kept front jar: 3
• rotating tail: 12
• total shown: 15

Why the config says buffer.messages: 12:

• in ljd, buffer.messages applies only to the rotating tail
• the first 3 kept messages are outside that limit
• so 3 kept + 12 tail = 15 total visible messages