README
¶
Prometheus SQL Exporter 
Database agnostic SQL exporter for Prometheus.
Overview
SQL Exporter is a configuration driven exporter that exposes metrics gathered from DBMSs, for use by the Prometheus monitoring system. Out of the box, it provides support for MySQL, PostgreSQL, Microsoft SQL Server and Clickhouse, but any DBMS for which a Go driver is available may be monitored after rebuilding the binary with the DBMS driver included.
The collected metrics and the queries that produce them are entirely configuration defined. SQL queries are grouped into collectors -- logical groups of queries, e.g. query stats or I/O stats, mapped to the metrics they populate. Collectors may be DBMS-specific (e.g. MySQL InnoDB stats) or custom, deployment specific (e.g. pricing data freshness). This means you can quickly and easily set up custom collectors to measure data quality, whatever that might mean in your specific case.
Per the Prometheus philosophy, scrapes are synchronous (metrics are collected on every /metrics poll) but, in order to
keep load at reasonable levels, minimum collection intervals may optionally be set per collector, producing cached
metrics when queried more frequently than the configured interval.
Usage
Get Prometheus SQL Exporter, either as a packaged release, as a Docker image or build it yourself:
$ go install github.com/free/sql_exporter/cmd/sql_exporter
then run it from the command line:
$ sql_exporter
Use the -help flag to get help information.
$ ./sql_exporter -help
Usage of ./sql_exporter:
-config.file string
SQL Exporter configuration file name. (default "sql_exporter.yml")
-web.listen-address string
Address to listen on for web interface and telemetry. (default ":9399")
-web.metrics-path string
Path under which to expose metrics. (default "/metrics")
[...]
Configuration
SQL Exporter is deployed alongside the DB server it collects metrics from. If both the exporter and the DB
server are on the same host, they will share the same failure domain: they will usually be either both up and running
or both down. When the database is unreachable, /metrics responds with HTTP code 500 Internal Server Error, causing
Prometheus to record up=0 for that scrape. Only metrics defined by collectors are exported on the /metrics endpoint.
SQL Exporter process metrics are exported at /sql_exporter_metrics.
The configuration examples listed here only cover the core elements. For a comprehensive and comprehensively documented
configuration file check out
documentation/sql_exporter.yml.
You will find ready to use "standard" DBMS-specific collector definitions in the
examples directory. You may contribute your own collector
definitions and metric additions if you think they could be more widely useful, even if they are merely different takes
on already covered DBMSs.
./sql_exporter.yml
# Global settings and defaults.
global:
# Subtracted from Prometheus' scrape_timeout to give us some headroom and prevent Prometheus from
# timing out first.
scrape_timeout_offset: 500ms
# Minimum interval between collector runs: by default (0s) collectors are executed on every scrape.
min_interval: 0s
# Maximum number of open connections to any one target. Metric queries will run concurrently on
# multiple connections.
max_connections: 3
# Maximum number of idle connections to any one target.
max_idle_connections: 3
# The target to monitor and the list of collectors to execute on it.
target:
# Data source name always has a URI schema that matches the driver name. In some cases (e.g. MySQL)
# the schema gets dropped or replaced to match the driver expected DSN format.
data_source_name: 'sqlserver://prom_user:prom_password@dbserver1.example.com:1433'
# Collectors (referenced by name) to execute on the target.
collectors: [pricing_data_freshness]
# Collector definition files.
collector_files:
- "*.collector.yml"
Collectors
Collectors may be defined inline, in the exporter configuration file, under collectors, or they may be defined in
separate files and referenced in the exporter configuration by name, making them easy to share and reuse.
The collector definition below generates gauge metrics of the form pricing_update_time{market="US"}.
./pricing_data_freshness.collector.yml
# This collector will be referenced in the exporter configuration as `pricing_data_freshness`.
collector_name: pricing_data_freshness
# A Prometheus metric with (optional) additional labels, value and labels populated from one query.
metrics:
- metric_name: pricing_update_time
type: gauge
help: 'Time when prices for a market were last updated.'
key_labels:
# Populated from the `market` column of each row.
- Market
static_labels:
# Arbitrary key/value pair
portfolio: income
values: [LastUpdateTime]
query: |
SELECT Market, max(UpdateTime) AS LastUpdateTime
FROM MarketPrices
GROUP BY Market
Data Source Names
To keep things simple and yet allow fully configurable database connections to be set up, SQL Exporter uses DSNs (like
sqlserver://prom_user:prom_password@dbserver1.example.com:1433) to refer to database instances. However, because the
Go sql library does not allow for automatic driver selection based on the DSN (i.e. an explicit driver name must be
specified) SQL Exporter uses the schema part of the DSN (the part before the ://) to determine which driver to use.
Unfortunately, while this works out of the box with the MS SQL Server and
PostgreSQL drivers, the MySQL driver DSNs format does not include
a schema and the Clickhouse one uses tcp://. So SQL Exporter does a bit of massaging
of DSNs for the latter two drivers in order for this to work:
| DB | SQL Exporter expected DSN | Driver sees |
|---|---|---|
| MySQL | mysql://user:passw@protocol(host:port)/dbname |
user:passw@protocol(host:port)/dbname |
| PostgreSQL | postgres://user:passw@host:port/dbname |
unchanged |
| SQL Server | sqlserver://user:passw@host:port/instance |
unchanged |
| Clickhouse | clickhouse://host:port?username=user&password=passw&database=dbname |
tcp://host:port?username=user&password=passw&database=dbname |
Why It Exists
SQL Exporter started off as an exporter for Microsoft SQL Server, for which no reliable exporters exist. But what is the point of a configuration driven SQL exporter, if you're going to use it along with 2 more exporters with wholly different world views and configurations, because you also have MySQL and PostgreSQL instances to monitor?
A couple of alternative database agnostic exporters are available -- https://github.com/justwatchcom/sql_exporter and https://github.com/chop-dbhi/prometheus-sql -- but they both do the collection at fixed intervals, independent of Prometheus scrapes. This is partly a philosophical issue, but practical issues are not all that difficult to imagine: jitter; duplicate data points; or collected but not scraped data points. The control they provide over which labels get applied is limited, and the base label set spammy. And finally, configurations are not easily reused without copy-pasting and editing across jobs and instances.
Documentation
¶
Index ¶
- func OpenConnection(ctx context.Context, logContext, dsn string, maxConns, maxIdleConns int) (*sql.DB, error)
- func PingDB(ctx context.Context, conn *sql.DB) error
- type Collector
- type Exporter
- type Job
- type Metric
- type MetricDesc
- type MetricFamily
- func (mf MetricFamily) Collect(row map[string]interface{}, ch chan<- Metric)
- func (mf MetricFamily) ConstLabels() []*dto.LabelPair
- func (mf MetricFamily) Help() string
- func (mf MetricFamily) Labels() []string
- func (mf MetricFamily) LogContext() string
- func (mf MetricFamily) Name() string
- func (mf MetricFamily) ValueType() prometheus.ValueType
- type Query
- type Target
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func OpenConnection ¶
func OpenConnection(ctx context.Context, logContext, dsn string, maxConns, maxIdleConns int) (*sql.DB, error)
OpenConnection extracts the driver name from the DSN (expected as the URI scheme), adjusts it where necessary (e.g. some driver supported DSN formats don't include a scheme), opens a DB handle ensuring early termination if the context is closed (this is actually prevented by `database/sql` implementation), sets connection limits and returns the handle.
Below is the list of supported databases (with built in drivers) and their DSN formats. Unfortunately there is no dynamic way of loading a third party driver library (as e.g. with Java classpaths), so any driver additions require a binary rebuild.
MySQL ¶
Using the https://github.com/go-sql-driver/mysql driver, DSN format (passed to the driver stripped of the `mysql://` prefix):
mysql://username:password@protocol(host:port)/dbname?param=value
PostgreSQL ¶
Using the https://godoc.org/github.com/lib/pq driver, DSN format (passed through to the driver unchanged):
postgres://username:password@host:port/dbname?param=value
MS SQL Server ¶
Using the https://github.com/denisenkom/go-mssqldb driver, DSN format (passed through to the driver unchanged):
sqlserver://username:password@host:port/instance?param=value
Clickhouse ¶
Using the https://github.com/kshvakov/clickhouse driver, DSN format (passed to the driver with the`clickhouse://` prefix replaced with `tcp://`):
clickhouse://host:port?username=username&password=password&database=dbname¶m=value
func PingDB ¶
PingDB is a wrapper around sql.DB.PingContext() that terminates as soon as the context is closed.
sql.DB does not actually pass along the context to the driver when opening a connection (which always happens if the database is down) and the driver uses an arbitrary timeout which may well be longer than ours. So we run the ping call in a goroutine and terminate immediately if the context is closed.
Types ¶
type Collector ¶
type Collector interface {
// Collect is the equivalent of prometheus.Collector.Collect() but takes a context to run in and a database to run on.
Collect(context.Context, *sql.DB, chan<- Metric)
}
Collector is a self-contained group of SQL queries and metric families to collect from a specific database. It is conceptually similar to a prometheus.Collector.
func NewCollector ¶
func NewCollector(logContext string, cc *config.CollectorConfig, constLabels []*dto.LabelPair) (Collector, errors.WithContext)
NewCollector returns a new Collector with the given configuration and database. The metrics it creates will all have the provided const labels applied.
type Exporter ¶
type Exporter interface {
prometheus.Gatherer
// WithContext returns a (single use) copy of the Exporter, which will use the provided context for Gather() calls.
WithContext(context.Context) Exporter
// Config returns the Exporter's underlying Config object.
Config() *config.Config
}
Exporter is a prometheus.Gatherer that gathers SQL metrics from targets and merges them with the default registry.
func NewExporter ¶
NewExporter returns a new Exporter with the provided config.
type Job ¶
type Job interface {
Targets() []Target
}
Job is a collection of targets with the same collectors applied.
func NewJob ¶
func NewJob(jc *config.JobConfig, gc *config.GlobalConfig) (Job, errors.WithContext)
NewJob returns a new Job with the given configuration.
type Metric ¶
type Metric interface {
Desc() MetricDesc
Write(out *dto.Metric) errors.WithContext
}
A Metric models a single sample value with its meta data being exported to Prometheus.
func NewInvalidMetric ¶
func NewInvalidMetric(err errors.WithContext) Metric
NewInvalidMetric returns a metric whose Write method always returns the provided error.
type MetricDesc ¶
type MetricDesc interface {
Name() string
Help() string
ValueType() prometheus.ValueType
ConstLabels() []*dto.LabelPair
Labels() []string
LogContext() string
}
MetricDesc is a descriptor for a family of metrics, sharing the same name, help, labes, type.
func NewAutomaticMetricDesc ¶
func NewAutomaticMetricDesc( logContext, name, help string, valueType prometheus.ValueType, constLabels []*dto.LabelPair, labels ...string) MetricDesc
NewAutomaticMetricDesc creates a MetricDesc for automatically generated metrics.
type MetricFamily ¶
type MetricFamily struct {
// contains filtered or unexported fields
}
MetricFamily implements MetricDesc for SQL metrics, with logic for populating its labels and values from sql.Rows.
func NewMetricFamily ¶
func NewMetricFamily(logContext string, mc *config.MetricConfig, constLabels []*dto.LabelPair) (*MetricFamily, errors.WithContext)
NewMetricFamily creates a new MetricFamily with the given metric config and const labels (e.g. job and instance).
func (MetricFamily) Collect ¶
func (mf MetricFamily) Collect(row map[string]interface{}, ch chan<- Metric)
Collect is the equivalent of prometheus.Collector.Collect() but takes a Query output map to populate values from.
func (MetricFamily) ConstLabels ¶
func (mf MetricFamily) ConstLabels() []*dto.LabelPair
ConstLabels implements MetricDesc.
func (MetricFamily) LogContext ¶
func (mf MetricFamily) LogContext() string
LogContext implements MetricDesc.
func (MetricFamily) ValueType ¶
func (mf MetricFamily) ValueType() prometheus.ValueType
ValueType implements MetricDesc.
type Query ¶
type Query struct {
// contains filtered or unexported fields
}
Query wraps a sql.Stmt and all the metrics populated from it. It helps extract keys and values from result rows.
func NewQuery ¶
func NewQuery(logContext string, qc *config.QueryConfig, metricFamilies ...*MetricFamily) (*Query, errors.WithContext)
NewQuery returns a new Query that will populate the given metric families.
type Target ¶
type Target interface {
// Collect is the equivalent of prometheus.Collector.Collect(), but takes a context to run in.
Collect(ctx context.Context, ch chan<- Metric)
}
Target collects SQL metrics from a single sql.DB instance. It aggregates one or more Collectors and it looks much like a prometheus.Collector, except its Collect() method takes a Context to run in.
func NewTarget ¶
func NewTarget( logContext, name, dsn string, ccs []*config.CollectorConfig, constLabels prometheus.Labels, gc *config.GlobalConfig) ( Target, errors.WithContext)
NewTarget returns a new Target with the given instance name, data source name, collectors and constant labels. An empty target name means the exporter is running in single target mode: no synthetic metrics will be exported.
Source Files
Directories