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@@ -20,6 +20,61 @@ Installation and Usage * Check out the [DTail Documentation](doc/index.md) +Interactive Query Reload +======================== + +`dtail`, `dgrep`, `dcat`, and `dmap` accept `--interactive-query` to keep the +current run open and listen for control commands on the controlling TTY. + +Available control commands: + +* `:reload <flags>` apply a new workload without restarting the client +* `:show` print the current interactive state, including capability counts +* `:help` print the interactive command help text +* `:quit` stop the interactive session + +Reload flags are mode-specific: + +* `dtail` and `dgrep`: `--grep`/`--regex`, `--before`, `--after`, `--max`, + `--invert`, plus shared flags such as `--files`, `--plain`, `--quiet`, and + `--timeout` +* `dmap`, and query-driven `dtail`: `--query` plus the shared flags above +* `dcat`: shared flags such as `--files`, `--plain`, `--quiet`, and `--timeout` + +Examples: + +```bash +dtail --servers app01 --files /var/log/app.log --grep ERROR --interactive-query +# then type: +:reload --grep WARN + +dgrep --servers app01 --files /var/log/app.log --grep ERROR --interactive-query +# then type: +:reload --grep WARN --before 2 --after 3 + +dmap --servers app01 --files /var/log/app.log \ + --query 'from STATS select count($line) group by hostname' \ + --interactive-query +# then type: +:reload --query "from STATS select count($line),avg(latency) group by hostname" +``` + +Compatibility and session reuse: + +* On startup, an interactive client first tries `SESSION START` when the remote + side advertises the `query-update-v1` capability +* If a server is older or does not advertise that capability, startup falls + back to the legacy command stream automatically, so mixed-version + client/server combinations still run the original workload normally +* Live `:reload` updates require every active server to advertise + `query-update-v1`; otherwise the reload is rejected and the current workload + keeps running unchanged +* On capable servers, DTail reuses the existing SSH session and sends + `SESSION UPDATE` messages instead of reconnecting +* Every successful reload advances a generation boundary; late output from the + previous workload is dropped so stale matches do not leak into the new result + stream + Auth-Key Fast Reconnect ======================= |