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Refactor metrics based on pg_stat_wal:
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- return metric about written WAL based on pg_current_wal_lsn();
- make separate metric based on pg_stat_wal.wal_bytes;
- count WAL fpi as is (not in bytes), due to FPI's might be compressed and its size is unknown;
- remove 'written' word from some metrics names, because it is misleading.
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@lesovsky
lesovsky committed Sep 2, 2021
1 parent 4b472d4 commit d52f099
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Showing 2 changed files with 40 additions and 31 deletions.
52 changes: 30 additions & 22 deletions internal/collector/postgres_wal.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,29 +10,29 @@ import (

const (
postgresWalQuery96 = "SELECT pg_is_in_recovery()::int AS recovery, " +
"(case pg_is_in_recovery() when 't' then pg_last_xlog_receive_location() else pg_current_xlog_location() end) - '0/00000000' AS wal_bytes"
"(case pg_is_in_recovery() when 't' then pg_last_xlog_receive_location() else pg_current_xlog_location() end) - '0/00000000' AS wal_written"

postgresWalQuery13 = "SELECT pg_is_in_recovery()::int AS recovery, " +
"(case pg_is_in_recovery() when 't' then pg_last_wal_receive_lsn() else pg_current_wal_lsn() end) - '0/00000000' AS wal_bytes"
"(case pg_is_in_recovery() when 't' then pg_last_wal_receive_lsn() else pg_current_wal_lsn() end) - '0/00000000' AS wal_written"

postgresWalQueryLatest = "SELECT pg_is_in_recovery()::int AS recovery, wal_records, wal_fpi, " +
"(case pg_is_in_recovery() when 't' then pg_last_wal_receive_lsn() - '0/00000000' else wal_bytes end) AS wal_bytes, " +
"wal_buffers_full, wal_write, wal_sync, wal_write_time, wal_sync_time, " +
"extract('epoch' from stats_reset) as reset_time " +
"(case pg_is_in_recovery() when 't' then pg_last_wal_receive_lsn() - '0/00000000' else pg_current_wal_lsn() - '0/00000000' end) AS wal_written, " +
"wal_bytes, wal_buffers_full, wal_write, wal_sync, wal_write_time, wal_sync_time, extract('epoch' from stats_reset) as reset_time " +
"FROM pg_stat_wal"
)

type postgresWalCollector struct {
recovery typedDesc
records typedDesc
writtenAllBytes typedDesc
writtenBytes typedDesc
buffersFull typedDesc
writes typedDesc
syncs typedDesc
secondsAll typedDesc
seconds typedDesc
resetUnix typedDesc
recovery typedDesc
records typedDesc
fpi typedDesc
bytes typedDesc
writtenBytes typedDesc // based on pg_current_wal_lsn()
buffersFull typedDesc
writes typedDesc
syncs typedDesc
secondsAll typedDesc
seconds typedDesc
resetUnix typedDesc
}

// NewPostgresWalCollector returns a new Collector exposing postgres WAL stats.
Expand All @@ -46,21 +46,27 @@ func NewPostgresWalCollector(constLabels labels, settings model.CollectorSetting
settings.Filters,
),
records: newBuiltinTypedDesc(
descOpts{"postgres", "wal", "written_records_total", "Total amount of WAL records written (zero in case of standby).", 0},
descOpts{"postgres", "wal", "records_total", "Total number of WAL records generated (zero in case of standby).", 0},
prometheus.CounterValue,
nil, constLabels,
settings.Filters,
),
writtenAllBytes: newBuiltinTypedDesc(
descOpts{"postgres", "wal", "written_bytes_all_total", "Total amount of WAL written (or received in case of standby), in bytes.", 0},
fpi: newBuiltinTypedDesc(
descOpts{"postgres", "wal", "fpi_total", "Total number of WAL full page images generated (zero in case of standby).", 0},
prometheus.CounterValue,
nil, constLabels,
settings.Filters,
),
bytes: newBuiltinTypedDesc(
descOpts{"postgres", "wal", "bytes_total", "Total amount of WAL generated (zero in case of standby) since last stats reset, in bytes.", 0},
prometheus.CounterValue,
nil, constLabels,
settings.Filters,
),
writtenBytes: newBuiltinTypedDesc(
descOpts{"postgres", "wal", "written_bytes_total", "Total amount of WAL written by each type of WAL (zero in case of standby), in bytes.", 0},
descOpts{"postgres", "wal", "written_bytes_total", "Total amount of WAL written (or received in case of standby) since cluster init, in bytes.", 0},
prometheus.CounterValue,
[]string{"wal"}, constLabels,
nil, constLabels,
settings.Filters,
),
buffersFull: newBuiltinTypedDesc(
Expand Down Expand Up @@ -125,9 +131,11 @@ func (c *postgresWalCollector) Update(config Config, ch chan<- prometheus.Metric
case "wal_records":
ch <- c.records.newConstMetric(v)
case "wal_fpi":
ch <- c.writtenBytes.newConstMetric(v*float64(config.walBlockSize), "fpi")
ch <- c.fpi.newConstMetric(v)
case "wal_bytes":
ch <- c.writtenAllBytes.newConstMetric(v)
ch <- c.bytes.newConstMetric(v)
case "wal_written":
ch <- c.writtenBytes.newConstMetric(v)
case "wal_buffers_full":
ch <- c.buffersFull.newConstMetric(v)
case "wal_write":
Expand Down
19 changes: 10 additions & 9 deletions internal/collector/postgres_wal_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,13 +12,14 @@ func TestPostgresWalCollector_Update(t *testing.T) {
var input = pipelineInput{
required: []string{
"postgres_recovery_info",
"postgres_wal_written_bytes_all_total",
"postgres_wal_written_bytes_total",
},
// TODO: wait until Postgres 14 has been released, update Postgres version on pgscv-testing docker image
// and move these metrics to 'required' slice.
optional: []string{
"postgres_wal_written_records_total",
"postgres_wal_written_bytes_total",
"postgres_wal_records_total",
"postgres_wal_fpi_total",
"postgres_wal_bytes_total",
"postgres_wal_buffers_full_total",
"postgres_wal_write_total",
"postgres_wal_sync_total",
Expand All @@ -43,25 +44,25 @@ func Test_parsePostgresWalStats(t *testing.T) {
name: "pg14",
res: &model.PGResult{
Nrows: 1,
Ncols: 10,
Ncols: 11,
Colnames: []pgproto3.FieldDescription{
{Name: []byte("recovery")},
{Name: []byte("wal_records")}, {Name: []byte("wal_fpi")}, {Name: []byte("wal_bytes")},
{Name: []byte("wal_records")}, {Name: []byte("wal_fpi")}, {Name: []byte("wal_bytes")}, {Name: []byte("wal_written")},
{Name: []byte("wal_buffers_full")}, {Name: []byte("wal_write")}, {Name: []byte("wal_sync")},
{Name: []byte("wal_write_time")}, {Name: []byte("wal_sync_time")}, {Name: []byte("reset_time")},
},
Rows: [][]sql.NullString{
{
{String: "0", Valid: true},
{String: "58452", Valid: true}, {String: "4712", Valid: true}, {String: "587241", Valid: true},
{String: "58452", Valid: true}, {String: "4712", Valid: true}, {String: "587241", Valid: true}, {String: "8746951", Valid: true},
{String: "1234", Valid: true}, {String: "48541", Valid: true}, {String: "8541", Valid: true},
{String: "874215", Valid: true}, {String: "48736", Valid: true}, {String: "123456789", Valid: true},
},
},
},
want: map[string]float64{
"recovery": 0,
"wal_records": 58452, "wal_fpi": 4712, "wal_bytes": 587241,
"wal_records": 58452, "wal_fpi": 4712, "wal_bytes": 587241, "wal_written": 8746951,
"wal_buffers_full": 1234, "wal_write": 48541, "wal_sync": 8541,
"wal_write_time": 874215, "wal_sync_time": 48736, "wal_all_time": 922951, "reset_time": 123456789,
},
Expand All @@ -72,11 +73,11 @@ func Test_parsePostgresWalStats(t *testing.T) {
Nrows: 1,
Ncols: 2,
Colnames: []pgproto3.FieldDescription{
{Name: []byte("recovery")}, {Name: []byte("wal_bytes")},
{Name: []byte("recovery")}, {Name: []byte("wal_written")},
},
Rows: [][]sql.NullString{{{String: "0", Valid: true}, {String: "123456789", Valid: true}}},
},
want: map[string]float64{"recovery": 0, "wal_bytes": 123456789},
want: map[string]float64{"recovery": 0, "wal_written": 123456789},
},
}

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