* adds read-only mode for vmstorage
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/269
* changes order a bit
* moves isFreeDiskLimitReached var to storage struct
renames functions to be consistent
change protoparser api - with optional storage limit check for given openned storage
* renames freeSpaceLimit to ReadOnly
* Rename -search.maxMetricsPointSearch to -search.maxSamplesPerQuery, so it is more consistent with the existing -search.maxSamplesPerSeries
* Move the -search.maxSamplesPerQuery from vmstorage to vmselect, so it could effectively limit the number of raw samples obtained from all the vmstorage nodes
* Document the -search.maxSamplesPerQuery in docs/CHANGELOG.md
Previously vmstorage could use only a single CPU core for data processing from a single connection from vminsert.
Now all the CPU cores can be used for data processing from a single connection from vminsert.
This should improve the maximum data ingestion performance for a single vminsert->vmstorage connection.
Previously the time spent on inverted index search could exceed the configured `-search.maxQueryDuration`.
This commit stops searching in inverted index on query timeout.
Previously it was possible that the connection is served after the server is closed if the following
steps are performed:
1) Server accepts new connection.
2) Server.MustClose() is called and successfully finished.
3) Server starts processing the connection accepted at step 1. There could be various crashes
like in https://github.com/VictoriaMetrics/VictoriaMetrics/issues/534 since the storage may be already closed.
Now the server closes the connection at step 3 without processing it.
Previously the duration for graceful shutdown for http server could take more than a minute
because of imporperly set timeouts in setNetworkTimeout.
Now typical duration for graceful shutdown should be reduced to less than 5 seconds.
This should protect from possible data loss when `vmstorage` is stopped while the packet is sent from `vminsert`.
This commit switches to new protocol between vminsert and vmstorage, which is incompatible
with the previous protocol. So it is required that both vminsert and vmstorage nodes are updated.
This eliminates the need for storing block data into temporary files on a single-node VictoriaMetrics
during heavy queries, which touch big number of time series over long time ranges.
This improves single-node VM performance on heavy queries by up to 2x.
Such filters must match all the time series with `label="foo"` plus all the time series without `label`
Previously only time series with `label="foo"` were matched.
The metricID->metricName entry can be missing in the indexdb after unclean shutdown
when only a part of entries for new time series is written into indexdb.
Recover from such a situation by removing the broken metricID. New metricID
will be automatically created for time series with the given metricName
when new data point will arive to it.
