Add views for metrics about pageserver requests #9008

hlinnaka · 2024-09-16T08:51:41Z

The metrics include a histogram of how long we need to wait for a GetPage request, number of reconnects, and number of requests among other things.

The metrics are not yet exported anywhere, but you can query them manually.

This is what the view looks like:

postgres=# select * from neon_perf_counters ;
                   metric                   |  value  
--------------------------------------------+---------
 getpage_wait_seconds_count                 |    6881
 getpage_wait_seconds_sum                   | 0.93566
 getpage_wait_seconds_bucket{le="0.000020"} |       0
 getpage_wait_seconds_bucket{le="0.000030"} |       0
 getpage_wait_seconds_bucket{le="0.000060"} |    1324
 getpage_wait_seconds_bucket{le="0.000100"} |    2886
 getpage_wait_seconds_bucket{le="0.000200"} |    5589
 getpage_wait_seconds_bucket{le="0.000300"} |    6611
 getpage_wait_seconds_bucket{le="0.000600"} |    6875
 getpage_wait_seconds_bucket{le="0.001"}    |    6880
 getpage_wait_seconds_bucket{le="0.002"}    |    6880
 getpage_wait_seconds_bucket{le="0.003"}    |    6880
 getpage_wait_seconds_bucket{le="0.006"}    |    6880
 getpage_wait_seconds_bucket{le="0.010"}    |    6880
 getpage_wait_seconds_bucket{le="0.020"}    |    6881
 getpage_wait_seconds_bucket{le="0.030"}    |    6881
 getpage_wait_seconds_bucket{le="0.060"}    |    6881
 getpage_wait_seconds_bucket{le="0.100"}    |    6881
 getpage_wait_seconds_bucket{le="0.200"}    |    6881
 getpage_wait_seconds_bucket{le="0.300"}    |    6881
 getpage_wait_seconds_bucket{le="0.600"}    |    6881
 getpage_wait_seconds_bucket{le="1"}        |    6881
 getpage_wait_seconds_bucket{le="2"}        |    6881
 getpage_wait_seconds_bucket{le="3"}        |    6881
 getpage_wait_seconds_bucket{le="6"}        |    6881
 getpage_wait_seconds_bucket{le="10"}       |    6881
 getpage_wait_seconds_bucket{le="20"}       |    6881
 getpage_wait_seconds_bucket{le="30"}       |    6881
 getpage_wait_seconds_bucket{le="60"}       |    6881
 getpage_wait_seconds_bucket{le="100"}      |    6881
 getpage_wait_seconds_bucket{le="+Inf"}     |    6881
 prefetch_requests_total                    |      67
 sync_requests_total                        |    6815
 pageserver_requests_sent_total             |    6899
 pageserver_requests_disconnects_total      |       0
 pageserver_send_flushes_total              |    6899
 prefetch_misses_total                      |       0
 prefetch_discards_total                    |       0
 file_cache_hits_total                      |       0
(39 rows)

orca-security-us

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0 0 0 0	View in Orca
Passed	Secrets	0 0 0 0	View in Orca
Passed	Vulnerabilities	0 0 0 0	View in Orca

github-actions · 2024-09-16T09:02:43Z

5038 tests run: 4874 passed, 0 failed, 164 skipped (full report)

Flaky tests (19)

Postgres 17

test_pageserver_compaction_smoke: release-x86-64, release-arm64
test_scrubber_physical_gc[4]: debug-x86-64
test_delete_timeline_client_hangup: debug-x86-64
test_subscriber_restart: release-x86-64
test_restart_endpoint_after_switch_wal: debug-x86-64
test_wal_restore: release-arm64
test_wal_restore_initdb: release-arm64

Postgres 16

test_slots_and_branching: release-x86-64
test_location_conf_churn[1]: release-x86-64
test_tenant_import[None-real_s3]: release-x86-64
test_scrubber_physical_gc[4]: release-x86-64
test_subscriber_restart: release-x86-64

Postgres 15

test_subscriber_restart: release-x86-64
test_restart_endpoint_after_switch_wal: release-x86-64

Postgres 14

test_scrubber_physical_gc[4]: release-arm64, release-x86-64
test_subscriber_restart: release-x86-64
test_restart_endpoint_after_switch_wal: release-x86-64

Code coverage* (full report)

functions: 31.9% (7433 of 23317 functions)
lines: 49.9% (59914 of 120118 lines)

* collected from Rust tests only

_{The comment gets automatically updated with the latest test results
562992a at 2024-09-21T13:49:00.955Z :recycle:}

MMeent · 2024-09-16T09:27:20Z

getpage_wait_seconds_bucket{le="0.000200"}

Can't this use additional columns for dimensions? I'm an unfan of prometheus' format and would appreciate not exposing such opinionated names.

hlinnaka · 2024-09-16T09:55:29Z

getpage_wait_seconds_bucket{le="0.000200"}

Can't this use additional columns for dimensions? I'm an unfan of prometheus' format and would appreciate not exposing such opinionated names.

I actually wrote it that way at first, with an explicit "bucket" column. But to then convert them to the prometheus metrics format in the exporter, you need a pretty complex SQL query. I found it easier to do that in C code directly.

MMeent · 2024-09-16T10:17:51Z

But to then convert them to the prometheus metrics format in the exporter, you need a pretty complex SQL query

Why can't the exporter do the table-to-metrics transformation? Shouldn't it be able to handle that transformation by itself?

hlinnaka · 2024-09-16T10:26:48Z

But to then convert them to the prometheus metrics format in the exporter, you need a pretty complex SQL query

Why can't the exporter do the table-to-metrics transformation? Shouldn't it be able to handle that transformation by itself?

You can give the exporter an arbitrary SQL, and do the transformation in the SQL query.

MMeent · 2024-09-16T10:50:47Z

You can give the exporter an arbitrary SQL, and do the transformation in the SQL query.

I know you can do that, but shouldn't the exporter by itself know how to treat (absense of) labels like le in results?

E.g. if I query select metric as __name__, bucket_range_max as le, count as value from my_metrics_view, shouldn't it automatically translate any non-null values for le as label? AFAIK, that's what happens for every other exported metric with labels.

See e.g. https://github.com/neondatabase/neon/blob/0a8c5e1214fcd3f59767a6ca4adeb68612977e51/vm-image-spec.yaml#L439C1-L449C85 where labels are read from columns.

test_runner/regress/test_compute_metrics.py

hlinnaka · 2024-09-16T21:44:13Z

You can give the exporter an arbitrary SQL, and do the transformation in the SQL query.

I know you can do that, but shouldn't the exporter by itself know how to treat (absense of) labels like le in results?

E.g. if I query select metric as __name__, bucket_range_max as le, count as value from my_metrics_view, shouldn't it automatically translate any non-null values for le as label? AFAIK, that's what happens for every other exported metric with labels.

See e.g. https://github.com/neondatabase/neon/blob/0a8c5e1214fcd3f59767a6ca4adeb68612977e51/vm-image-spec.yaml#L439C1-L449C85 where labels are read from columns.

A-ha, now I understand. I didn't know sql_exporter can do that. Yeah, that makes sense, I'll do that.

ololobus · 2024-09-17T09:14:25Z

There is an Epic from John for that #8926

pgxn/neon/neon.control

pgxn/neon/neon_perf_counters.h

pgxn/neon/neon--1.4--1.5.sql

hlinnaka · 2024-09-17T17:09:08Z

You can give the exporter an arbitrary SQL, and do the transformation in the SQL query.

I know you can do that, but shouldn't the exporter by itself know how to treat (absense of) labels like le in results?
E.g. if I query select metric as __name__, bucket_range_max as le, count as value from my_metrics_view, shouldn't it automatically translate any non-null values for le as label? AFAIK, that's what happens for every other exported metric with labels.
See e.g. https://github.com/neondatabase/neon/blob/0a8c5e1214fcd3f59767a6ca4adeb68612977e51/vm-image-spec.yaml#L439C1-L449C85 where labels are read from columns.

A-ha, now I understand. I didn't know sql_exporter can do that. Yeah, that makes sense, I'll do that.

Done. It now looks like this:

postgres=# select * from neon_perf_counters ;
                metric                 | bucket_le |  value   
---------------------------------------+-----------+----------
 getpage_wait_seconds_count            |           |      300
 getpage_wait_seconds_sum              |           | 0.048506
 getpage_wait_seconds_bucket           |     2e-05 |        0
 getpage_wait_seconds_bucket           |     3e-05 |        0
 getpage_wait_seconds_bucket           |     6e-05 |       71
 getpage_wait_seconds_bucket           |    0.0001 |      124
 getpage_wait_seconds_bucket           |    0.0002 |      248
 getpage_wait_seconds_bucket           |    0.0003 |      279
 getpage_wait_seconds_bucket           |    0.0006 |      297
 getpage_wait_seconds_bucket           |     0.001 |      298
 getpage_wait_seconds_bucket           |     0.002 |      298
 getpage_wait_seconds_bucket           |     0.003 |      298
 getpage_wait_seconds_bucket           |     0.006 |      300
 getpage_wait_seconds_bucket           |      0.01 |      300
 getpage_wait_seconds_bucket           |      0.02 |      300
 getpage_wait_seconds_bucket           |      0.03 |      300
 getpage_wait_seconds_bucket           |      0.06 |      300
 getpage_wait_seconds_bucket           |       0.1 |      300
 getpage_wait_seconds_bucket           |       0.2 |      300
 getpage_wait_seconds_bucket           |       0.3 |      300
 getpage_wait_seconds_bucket           |       0.6 |      300
 getpage_wait_seconds_bucket           |         1 |      300
 getpage_wait_seconds_bucket           |         2 |      300
 getpage_wait_seconds_bucket           |         3 |      300
 getpage_wait_seconds_bucket           |         6 |      300
 getpage_wait_seconds_bucket           |        10 |      300
 getpage_wait_seconds_bucket           |        20 |      300
 getpage_wait_seconds_bucket           |        30 |      300
 getpage_wait_seconds_bucket           |        60 |      300
 getpage_wait_seconds_bucket           |       100 |      300
 getpage_wait_seconds_bucket           |  Infinity |      300
 getpage_prefetch_requests_total       |           |       69
 getpage_sync_requests_total           |           |      231
 getpage_prefetch_misses_total         |           |        0
 getpage_prefetch_discards_total       |           |        0
 pageserver_requests_sent_total        |           |      323
 pageserver_requests_disconnects_total |           |        0
 pageserver_send_flushes_total         |           |      323
 file_cache_hits_total                 |           |        0
(39 rows)

and that can be converted to prometheus style format with a pretty simple query:

postgres=# select case when bucket_le is null then metric when bucket_le = 'Infinity' then format('%s{le="+Inf"}', metric) else format('%s{le="%s"}', metric, bucket_le::numeric) end, value from neon_perf_counters ;
                  format                   |  value   
-------------------------------------------+----------
 getpage_wait_seconds_count                |      312
 getpage_wait_seconds_sum                  | 0.051847
 getpage_wait_seconds_bucket{le="0.00002"} |        0
 getpage_wait_seconds_bucket{le="0.00003"} |        0
 getpage_wait_seconds_bucket{le="0.00006"} |       71
 getpage_wait_seconds_bucket{le="0.0001"}  |      124
 getpage_wait_seconds_bucket{le="0.0002"}  |      250
 getpage_wait_seconds_bucket{le="0.0003"}  |      288
 getpage_wait_seconds_bucket{le="0.0006"}  |      309
 getpage_wait_seconds_bucket{le="0.001"}   |      310
 getpage_wait_seconds_bucket{le="0.002"}   |      310
 getpage_wait_seconds_bucket{le="0.003"}   |      310
 getpage_wait_seconds_bucket{le="0.006"}   |      312
 getpage_wait_seconds_bucket{le="0.01"}    |      312
 getpage_wait_seconds_bucket{le="0.02"}    |      312
 getpage_wait_seconds_bucket{le="0.03"}    |      312
 getpage_wait_seconds_bucket{le="0.06"}    |      312
 getpage_wait_seconds_bucket{le="0.1"}     |      312
 getpage_wait_seconds_bucket{le="0.2"}     |      312
 getpage_wait_seconds_bucket{le="0.3"}     |      312
 getpage_wait_seconds_bucket{le="0.6"}     |      312
 getpage_wait_seconds_bucket{le="1"}       |      312
 getpage_wait_seconds_bucket{le="2"}       |      312
 getpage_wait_seconds_bucket{le="3"}       |      312
 getpage_wait_seconds_bucket{le="6"}       |      312
 getpage_wait_seconds_bucket{le="10"}      |      312
 getpage_wait_seconds_bucket{le="20"}      |      312
 getpage_wait_seconds_bucket{le="30"}      |      312
 getpage_wait_seconds_bucket{le="60"}      |      312
 getpage_wait_seconds_bucket{le="100"}     |      312
 getpage_wait_seconds_bucket{le="+Inf"}    |      312
 getpage_prefetch_requests_total           |       69
 getpage_sync_requests_total               |      243
 getpage_prefetch_misses_total             |        0
 getpage_prefetch_discards_total           |        0
 pageserver_requests_sent_total            |      335
 pageserver_requests_disconnects_total     |        0
 pageserver_send_flushes_total             |      335
 file_cache_hits_total                     |        0
(39 rows)

pgxn/neon/libpagestore.c

pgxn/neon/neon--1.5--1.4.sql

The metrics include a histogram of how long we need to wait for a GetPage request, number of reconnects, and number of requests among other things. The metrics are not yet exported anywhere, but you can query them manually.

ololobus

I had a look on the metrics list and some aux code -- LGTM. Haven't had a look at C code, so someone might want to check it

pgxn/neon/neon_perf_counters.h

arpad-m · 2024-09-24T12:35:48Z

pgxn/neon/neon_perf_counters.c

+	{
+		/* shared memory is initialized to zeros, so nothing to do here */
+	}
+}


this broke the mac OS build (CI link):

2024-09-24T12:26:48.6843180Z /Users/runner/work/neon/neon//pgxn/neon/neon_perf_counters.c:50:1: error: non-void function does not return a value [-Werror,-Wreturn-type] 2024-09-24T12:26:48.6844290Z /Applications/Xcode_15.4.app/Contents/Developer/usr/bin/make -C ../../../../src/backend generated-headers 2024-09-24T12:26:48.6892290Z } 2024-09-24T12:26:48.6892680Z make: Nothing to be done for `distprep'. 2024-09-24T12:26:48.6905160Z ^ 2024-09-24T12:26:48.6905560Z make: Nothing to be done for `generated-header-symlinks'. 2024-09-24T12:26:48.6948200Z 1 error generated.

cc @problame @skyzh

hlinnaka requested review from problame and MMeent September 16, 2024 08:51

hlinnaka requested review from a team as code owners September 16, 2024 08:51

orca-security-us bot reviewed Sep 16, 2024

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hlinnaka force-pushed the add-compute-getpage-metrics branch from 48130d2 to 1993f22 Compare September 16, 2024 08:56

hlinnaka force-pushed the add-compute-getpage-metrics branch from 1993f22 to d2f47a0 Compare September 16, 2024 09:20

jcsp mentioned this pull request Sep 16, 2024

Epic: compute performance observability (as a storage client) #8926

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koivunej reviewed Sep 16, 2024

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test_runner/regress/test_compute_metrics.py Show resolved Hide resolved

ololobus reviewed Sep 17, 2024

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hlinnaka force-pushed the add-compute-getpage-metrics branch from 95dd419 to b80597a Compare September 17, 2024 17:07

hlinnaka force-pushed the add-compute-getpage-metrics branch from b80597a to 367de54 Compare September 17, 2024 18:13

tristan957 reviewed Sep 20, 2024

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hlinnaka added 4 commits September 21, 2024 04:03

Add views for metrics about pageserver requests

1e65b43

The metrics include a histogram of how long we need to wait for a GetPage request, number of reconnects, and number of requests among other things. The metrics are not yet exported anywhere, but you can query them manually.

Add bucket_le as an explicit column to the views

762576f

Add 'getpage_' prefix to some metrics, reorder for clarity

b680d53

Revert default 'neon' extension version to 1.4

175d7dd

hlinnaka force-pushed the add-compute-getpage-metrics branch from 367de54 to 175d7dd Compare September 21, 2024 01:03

whitespace fixes

562992a

hlinnaka enabled auto-merge (squash) September 21, 2024 17:42

hlinnaka requested a review from ololobus September 21, 2024 17:43

hlinnaka requested review from koivunej and tristan957 September 21, 2024 17:43

ololobus approved these changes Sep 23, 2024

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MMeent approved these changes Sep 23, 2024

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hlinnaka mentioned this pull request Sep 23, 2024

Metrics for compute -> pageserver errors #9111

Open

hlinnaka merged commit 263dfba into main Sep 23, 2024
79 checks passed

hlinnaka deleted the add-compute-getpage-metrics branch September 23, 2024 18:28

arpad-m reviewed Sep 24, 2024

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bayandin mentioned this pull request Sep 24, 2024

Fix compiler warnings on macOS #9128

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Add views for metrics about pageserver requests #9008

Add views for metrics about pageserver requests #9008

hlinnaka commented Sep 16, 2024

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Postgres 17

Postgres 16

Postgres 15

Postgres 14

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arpad-m Sep 24, 2024

Add views for metrics about pageserver requests #9008

Add views for metrics about pageserver requests #9008

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Orca Security Scan Summary

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5038 tests run: 4874 passed, 0 failed, 164 skipped (full report)

Postgres 17

Postgres 16

Postgres 15

Postgres 14

Code coverage* (full report)

MMeent commented Sep 16, 2024

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