dohertj2/ScadaBridge
1
0
Fork 0
Code Issues 2 Pull Requests 1 Actions Packages Projects Releases Wiki Activity

chore(docker): size the site-a oplog caps from the phase 2 soak

Browse Source 
MaxBatchSize 500 -> 16. The default is a ROW count, not a byte budget, so the
batch size in bytes is set by the widest replicated column — config_json, which
Task 1 measured at up to ~60-70 KB in production. 70 KB x 500 is ~35 MB against
gRPC's 4 MB default receive limit; 16 keeps a worst-case batch near 1.1 MB.

MaxOplogRows 1,000,000 -> 250,000 and MaxOplogAge 7d -> 2d, sized from the
soak's 0.80 sf_messages rows/sec (~69k rows/day). Tighter than default is
correct here because exceeding a cap is not data loss: the oplog prunes to the
ceiling and sets needs_snapshot, so the peer catches up by snapshot resync
instead of incrementally. That trades a rare full resync for a bounded file.

site-b and site-c stay unreplicated, so the default-OFF posture is still proven
side by side on one rig.

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts
This commit is contained in:
Joseph Doherty
2026-07-20 04:41:47 -04:00
parent 15013156bf
commit 921edab454
2 changed files with 36 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docker/site-a-node-a/appsettings.Site.json
+18 -1
View File
@@ -87,7 +87,24 @@
// pre-host secret expander.
"Replication": {
"PeerAddress": "http://scadabridge-site-a-b:8083",
"ApiKey": "dev-site-a-localdb-sync-key"
"ApiKey": "dev-site-a-localdb-sync-key",
// ---- Phase 2 sizing, from the Task 1 rig soak (not from the defaults) ----
//
// MaxBatchSize (default 500) is a ROW count, not a byte budget, so the batch
// size in bytes is set by the widest replicated column. That is
// deployed_configurations.config_json: ~721 B on this rig, but up to ~60-70 KB
// in production (measured, Task 1) - and 70 KB x 500 is ~35 MB against gRPC's
// 4 MB default receive limit. 16 keeps a worst-case batch near 1.1 MB.
"MaxBatchSize": 16,
// Backlog caps bound the oplog while the peer is offline. Exceeding them is
// NOT data loss: the oplog is pruned to the ceiling and needs_snapshot is set,
// so the peer catches up by snapshot resync instead of incrementally. That
// makes tighter-than-default correct here - it trades a rare full resync for a
// bounded file. Sized from the soak's 0.80 sf_messages rows/sec (the only
// non-zero writer measured): ~69k rows/day, so 2 days is ~138k. 250,000 leaves
// room for burst without approaching the 1,000,000 default.
"MaxOplogRows": 250000,
"MaxOplogAge": "2.00:00:00"
}
}
}
docker/site-a-node-b/appsettings.Site.json
+18 -1
View File
@@ -80,7 +80,24 @@
// fail-closed, so a typo here does not degrade to unauthenticated replication;
// it rejects every stream and the pair silently stops converging.
"Replication": {
"ApiKey": "dev-site-a-localdb-sync-key"
"ApiKey": "dev-site-a-localdb-sync-key",
// ---- Phase 2 sizing, from the Task 1 rig soak (not from the defaults) ----
//
// MaxBatchSize (default 500) is a ROW count, not a byte budget, so the batch
// size in bytes is set by the widest replicated column. That is
// deployed_configurations.config_json: ~721 B on this rig, but up to ~60-70 KB
// in production (measured, Task 1) - and 70 KB x 500 is ~35 MB against gRPC's
// 4 MB default receive limit. 16 keeps a worst-case batch near 1.1 MB.
"MaxBatchSize": 16,
// Backlog caps bound the oplog while the peer is offline. Exceeding them is
// NOT data loss: the oplog is pruned to the ceiling and needs_snapshot is set,
// so the peer catches up by snapshot resync instead of incrementally. That
// makes tighter-than-default correct here - it trades a rare full resync for a
// bounded file. Sized from the soak's 0.80 sf_messages rows/sec (the only
// non-zero writer measured): ~69k rows/day, so 2 days is ~138k. 250,000 leaves
// room for burst without approaching the 1,000,000 default.
"MaxOplogRows": 250000,
"MaxOplogAge": "2.00:00:00"
}
}
}