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Track Postgres buffer cache usage (#633)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| package postgres | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "time" | ||
|
|
||
| "github.com/pganalyze/collector/state" | ||
| "github.com/pganalyze/collector/util" | ||
| ) | ||
|
|
||
| const bufferCacheExtensionSQL string = ` | ||
| SELECT COALESCE(( | ||
| SELECT nspname | ||
| FROM pg_catalog.pg_extension | ||
| INNER JOIN pg_catalog.pg_namespace n ON extnamespace = n.oid | ||
| WHERE extname = 'pg_buffercache' | ||
| ), '') | ||
| ` | ||
|
|
||
| const bufferCacheSizeSQL string = ` | ||
| SELECT pg_catalog.pg_size_bytes(unit) * pg_catalog.pg_size_bytes(setting) / 1024 / 1024 / 1024 | ||
| FROM pg_catalog.pg_settings | ||
| WHERE name = 'shared_buffers' | ||
| ` | ||
|
|
||
| // https://www.postgresql.org/docs/current/pgbuffercache.html | ||
| const bufferCacheSQL string = ` | ||
| SELECT reldatabase, relfilenode, count(*) * current_setting('block_size')::int | ||
| FROM %s.pg_buffercache | ||
| GROUP BY 1, 2 | ||
| ` | ||
|
|
||
| func GetBufferCache(ctx context.Context, server *state.Server, globalCollectionOpts state.CollectionOpts, logger *util.Logger, postgresVersion state.PostgresVersion, channel chan state.BufferCache) { | ||
| start := time.Now() | ||
| bufferCache := make(state.BufferCache) | ||
| db, err := EstablishConnection(ctx, server, logger, globalCollectionOpts, "") | ||
| if err != nil { | ||
| logger.PrintError("GetBufferCache: %s", err) | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
|
|
||
| schemaName := "" | ||
| db.QueryRowContext(ctx, QueryMarkerSQL+bufferCacheExtensionSQL).Scan(&schemaName) | ||
| if schemaName == "" { | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
|
|
||
| sizeGB := 0 | ||
| db.QueryRowContext(ctx, QueryMarkerSQL+bufferCacheSizeSQL).Scan(&sizeGB) | ||
| if sizeGB > server.Config.MaxBufferCacheMonitoringGB { | ||
| if globalCollectionOpts.TestRun { | ||
| logger.PrintWarning("GetBufferCache: skipping collection. To enable, set max_buffer_cache_monitoring_gb to a value over %d", sizeGB) | ||
| } | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
|
|
||
| stmt, err := db.PrepareContext(ctx, QueryMarkerSQL+fmt.Sprintf(bufferCacheSQL, schemaName)) | ||
| if err != nil { | ||
| logger.PrintError("GetBufferCache: %s", err) | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
| defer stmt.Close() | ||
| rows, err := stmt.QueryContext(ctx) | ||
| if err != nil { | ||
| logger.PrintError("GetBufferCache: %s", err) | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
| defer rows.Close() | ||
| for rows.Next() { | ||
| var reldatabase state.Oid | ||
| var relfilenode state.Oid | ||
| var bytes int64 | ||
| err = rows.Scan(&reldatabase, &relfilenode, &bytes) | ||
| if err != nil { | ||
| logger.PrintError("GetBufferCache: %s", err) | ||
| channel <- bufferCache | ||
| return | ||
| } | ||
| db, ok := bufferCache[reldatabase] | ||
| if ok { | ||
| db[relfilenode] = bytes | ||
| } else { | ||
| bufferCache[reldatabase] = map[state.Oid]int64{relfilenode: bytes} | ||
| } | ||
| } | ||
|
|
||
| logger.PrintVerbose("GetBufferCache: finished after %s", time.Since(start)) | ||
| channel <- bufferCache | ||
| } |
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