fix(import): crash recovery, stale detection, and InfluxDB v3 timestamps

[Aliaksei-Kharlap]

Fix crash recovery, stale import detection, and InfluxDB v3 timestamp compatibility for the import plugin.

Bug fixes

• Crash recovery: On unhandled errors, the plugin now writes paused state before exiting, so the import can be resumed after fixing the issue. Previously, a crash left the import
  stuck in "running" forever.
• Stale import detection: resume now checks if a "running" import is actually stale (last update >5 min ago) and allows resume instead of returning "already running". If no
  checkpoint exists, restarts from the beginning.
• Missing import_state table on resume: Wrapped query in try/except — if the table doesn't exist yet (crashed before processing any tables), restarts the import.
• InfluxDB v3 timestamps: paused_at_time extraction now handles both int nanoseconds (v1/v2) and ISO 8601 strings (v3).
• Row-level errors: Invalid rows in convert_influxql_to_line_protocol are now skipped with a warning instead of crashing the entire batch.

Improvements

• Added completed state to import_pause_state — pause/cancel/resume now return errors for already-completed imports.
• Extracted _write_import_pause_state() helper — replaced 8 duplicate LineBuilder patterns; fixed a missing time_ns() call in one resume_import path.
• Removed duplicate check_pause_state() function (~48 lines) — replaced with existing get_import_pause_state().

Docs

• Updated README: crash recovery section, stale detection (5-min threshold), troubleshooting for "already running" after crash, completed state handling.

[caterryan]

Closes #45 #46 #47

[caterryan]

This pr does not fix #46

curl -H "Authorization: Bearer $INFLUXDB3_TOKEN" \
         -H "Content-Type: application/json" \
         -X GET "http://localhost:$INFLUXDB3_PORT/api/v3/engine/import?action=status&import_id=e60ff739-fe6c-43c4-9a12-437f1de73364"
{"import_id": "e60ff739-fe6c-43c4-9a12-437f1de73364", "overall_status": "completed", "summary": {"total_tables": 1, "completed_tables": 1, "in_progress_tables": 0, "paused_tables": 0, "cancelled_tables": 0, "pending_tables": 0, "total_rows_imported": 5001, "progress_percentage": 100.0}, "timing": {"started_at": 1773179493947118080, "last_updated_at": 1773179494980521984, "duration_seconds": 1.03}, "config": {"source_url": "http://localhost:8381", "source_database": "demo", "dest_database": "imports", "start_timestamp": "", "end_timestamp": "", "import_direction": "oldest_first", "target_batch_size": 5000, "query_interval_ms": 1, "table_filter": "measurement_xs"}, "pause_state": {"is_paused": false, "is_cancelled": false}, "table_details": [{"table_name": "measurement_xs", "status": "completed", "rows_imported": 5001, "last_update": 1773179494980521984, "paused_at_time": null}]}

curl -H "Authorization: Bearer $INFLUXDB3_TOKEN" \
         -H "Content-Type: application/json" \
         -X POST "http://localhost:$INFLUXDB3_PORT/api/v3/engine/import?action=resume&import_id=e60ff739-fe6c-43c4-9a12-437f1de73364" -d '{"source_username": "demo", "source_password": "demo1234" }'
{"status": "error", "error": "Import e60ff739-fe6c-43c4-9a12-437f1de73364 is already running"}

[caterryan]

This pr does not fix #47

curl -H "Authorization: Bearer $INFLUXDB3_TOKEN" \
         -H "Content-Type: application/json" \
         -X GET "http://localhost:$INFLUXDB3_PORT/api/v3/engine/import?action=status&import_id=230eb551-ffa9-47e7-9b20-dbe4d152dd0c"
{"import_id": "230eb551-ffa9-47e7-9b20-dbe4d152dd0c", "overall_status": "running", "summary": {"total_tables": 1, "completed_tables": 0, "in_progress_tables": 1, "paused_tables": 0, "cancelled_tables": 0, "pending_tables": 0, "total_rows_imported": 30006, "progress_percentage": 0.0}, "timing": {"started_at": 1773179821166896128, "last_updated_at": 1773179827367419904, "duration_seconds": 6.2}, "config": {"source_url": "http://localhost:8381", "source_database": "demo", "dest_database": "imports", "start_timestamp": "", "end_timestamp": "", "import_direction": "oldest_first", "target_batch_size": 5000, "query_interval_ms": 1000, "table_filter": "measurement_l"}, "pause_state": {"is_paused": false, "is_cancelled": false}, "table_details": [{"table_name": "measurement_l", "status": "in_progress", "rows_imported": 30006, "last_update": 1773179827367419904, "paused_at_time": null}]}

curl -H "Authorization: Bearer $INFLUXDB3_TOKEN" \
         -H "Content-Type: application/json" \
         -X POST "http://localhost:$INFLUXDB3_PORT/api/v3/engine/import?action=resume&import_id=230eb551-ffa9-47e7-9b20-dbe4d152dd0c" -d '{"source_username": "demo", "source_password": "demo1234" }'
{"status": "error", "error": "Import 230eb551-ffa9-47e7-9b20-dbe4d152dd0c is already running"}

[Aliaksei-Kharlap]

#47 I added a check for the last entry in the import_state table (written for each time interval for which data is collected (batch)). If the last entry was less than 5 minutes ago, is_running is returned; if it was more than 5 minutes ago, the migration can continue. @caterryan How long did it take you to submit a request to resume migration?

[Aliaksei-Kharlap]

#46 That's strange, I'll double check.

[caterryan]

#47 I added a check for the last entry in the import_state table (written for each time interval for which data is collected (batch)). If the last entry was less than 5 minutes ago, is_running is returned; if it was more than 5 minutes ago, the migration can continue. @caterryan How long did it take you to submit a request to resume migration?

Ah that must be the problem. I didn't wait long enough.