Table Of Contents

5. Observability

5.1. Statistics

If you have enabled statistics, QuasarDB will collect runtime statistics per node. QuasarDB uses its direct key/value API to store these statistics.

Key

Type

Description

engine_build_date

blob

The QuasarDB engine build date

engine_version

blob

The QuasarDB engine version

hardware_concurrency

int64

The detected concurrent number of hardware threads supported on the system

startup

int64

The startup timestamp

node_id

blob

A string representing the node id

operating_system

blob

A string representing the operating system

partitions_count

int64

The number of partitions

chord.invalid_requests_count

int64

The number of times a request was incorrectly routed to this node by a client

chord.predecessor_changes_count

int64

The number of times the node’s predecessor changed

chord.successor_changes_count

int64

The number of times the node’s successor changed

chord.unstable_errors_count

int64

The number of times the node returned to a client an “unstable” error

cpu.idle

int64

The cumulated CPU idle time

cpu.system

int64

The cumulated CPU system time

cpu.user

int64

The cumulated CPU user time

disk.path

blob

The persistence path

disk.bytes_free

int64

The bytes free on the persistence path

disk.bytes_total

int64

The bytes total on the persistence path

memory.bytes_resident_size

int64

The computed amount of RAM used for data by QuasarDB

memory.physmem.bytes_total

int64

Physical RAM free bytes count

memory.physmem.bytes_used

int64

Physical RAM used bytes count

memory.resident_count

int64

The number of entries in RAM

memory.vm.bytes_total

int64

Virtual memory free bytes count

memory.vm.bytes_used

int64

Virtual memory used bytes count

network.current_users_count

int64

The current users count

network.sessions.max_count

int64

The configured maximum number of sessions

network.sessions.available_count

int64

The current number of available sessions

network.sessions.unavailable_count

int64

The current number of used sessions

persistence.bytes_capacity

int64

The persistence layer storage capacity, in bytes. May be 0 if the value is unknown.

persistence.bytes_utilized

int64

How many bytes are currently used in the persistence layer.

persistence.bytes_read

int64

The cumulated number of bytes read

persistence.bytes_written

int64

The cumulated number of bytes written

persistence.entries_count

int64

The current number of entries in the persistence layer

requests.total_count

int64

The cumulated number of requests

requests.successes_count

int64

The cumulated number of successful operations

requests.bytes_out

int64

The cumulated number of bytes sent by the server

5.2. Performance Tracing

If you have enabled performance profiling from the server-side, you can run detailed performance traces of the operations that you execute on your cluster. This will provide you with a detailed, step-by-step trace of tje low-level operations, and are usually useful when you are debugging together with your Solution Architect.

If you have enabled statistics in conjunction with performance traces, you will get additional performance trace metrics in your statistics.

To use performance traces from the QuasarDB shell, use the enable_perf_trace command as follows:

$ qdbsh
quasardb shell version 3.5.0master build ce779a9 2019-10-23 00:04:01 +0000
Copyright (c) 2009-2019 quasardb. All rights reserved.
Need some help? Check out our documentation here:  https://doc.quasardb.net

qdbsh > enable_perf_trace
qdbsh > create table testable(col1 int64, col2 double)

*** begin performance trace

total time: 175 us

- function + ts.create_root - 175 us [100.00 %]
           |
           |              data received:         0 us - delta:         0 us [00.00 % - 00.00 %]
           |     deserialization starts:         2 us - delta:         2 us [01.14 % - 01.14 %]
           |       deserialization ends:         7 us - delta:         5 us [02.86 % - 02.86 %]
           |             entering chord:         9 us - delta:         2 us [01.14 % - 01.14 %]
           |                   dispatch:        14 us - delta:         5 us [02.86 % - 02.86 %]
           |     deserialization starts:        24 us - delta:        10 us [05.71 % - 05.71 %]
           |       deserialization ends:        26 us - delta:         2 us [01.14 % - 01.14 %]
           |          processing starts:        28 us - delta:         2 us [01.14 % - 01.14 %]
           |      entry trimming starts:        79 us - delta:        51 us [29.14 % - 29.14 %]
           |        entry trimming ends:        81 us - delta:         2 us [01.14 % - 01.14 %]
           |     content writing starts:        82 us - delta:         1 us [00.57 % - 00.57 %]
           |       content writing ends:       141 us - delta:        59 us [33.71 % - 33.71 %]
           |       entry writing starts:       141 us - delta:         0 us [00.00 % - 00.00 %]
           |         entry writing ends:       172 us - delta:        31 us [17.71 % - 17.71 %]
           |            processing ends:       175 us - delta:         3 us [01.71 % - 01.71 %]

*** end performance trace

In the trace above, for example, we can see the performance trace of the CREATE TABLE statement, and get a detailed idea of where it’s spending most of its time. In this case, the total operation lasted 175 microseconds, and a detailed breakdown of the low level function timings.

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