dbpulse 🩺

A lightweight database health monitoring tool that continuously tests database availability for read and write operations. It exposes Prometheus-compatible metrics for monitoring database health, performance, and operational metrics.

Overview

Like a paramedic checking for a pulse, dbpulse performs quick vital sign checks on your database. It goes beyond simple connection tests by performing real database operations (INSERT, SELECT, UPDATE, DELETE, transaction rollback) at regular intervals to verify that your database is truly alive and accepting writes, not just accepting connections.

Quick Pulse Check: Is the database responsive and healthy? ✅ Vital Signs: Latency, errors, read-only status, replication lag 📊 Emergency Indicators: Blocking queries, locked tables, connectivity issues 🚨

This is particularly useful for:

• Galera Clusters - Detecting HALT/LOCK cases where DDL statements stall the cluster or flow-control prevents COMMITS/WRITES
• Read-Only Detection - Identifying when databases enter read-only mode (replicas, maintenance, failover scenarios)
• Replication Monitoring - Tracking replication lag on replica databases
• Lock Detection - Identifying blocking queries that prevent other operations
• Performance Monitoring - Measuring query latency, connection times, and operation throughput

The tool protects itself from hanging on locked tables using configurable timeouts (5s statement timeout, 2s lock timeout), ensuring the health probe remains responsive.

Quick Start

# PostgreSQL
dbpulse --dsn "postgres://user:password@tcp(localhost:5432)/mydb"

# MySQL/MariaDB
dbpulse --dsn "mysql://user:password@tcp(localhost:3306)/mydb"

# With custom interval and range
dbpulse --dsn "postgres://user:pass@tcp(db.example.com:5432)/prod" \
  --interval 60 \
  --range 1000 \
  --port 9300

Access metrics at http://localhost:9300/metrics

Usage

Command-Line Options

dbpulse [OPTIONS] --dsn <DSN>

Required Options

Option	Environment Variable	Description
-d, --dsn <DSN>	DBPULSE_DSN	Database connection string (see DSN Format below)

Optional Settings

Option	Environment Variable	Default	Description
-i, --interval <SECONDS>	DBPULSE_INTERVAL	30	Seconds between health checks
-p, --port <PORT>	DBPULSE_PORT	9300	HTTP port for /metrics endpoint
-l, --listen <IP>	DBPULSE_LISTEN	[::]	IP address to bind to (supports IPv4 and IPv6)
-r, --range <RANGE>	DBPULSE_RANGE	100	Upper limit for random ID generation (prevents conflicts in multi-instance setups)

DSN Format

The Data Source Name (DSN) follows this format:

<driver>://<user>:<password>@tcp(<host>:<port>)/<database>[?param1=value1&param2=value2]

Supported drivers: postgres, mysql

Basic Examples

# PostgreSQL
postgres://dbuser:secret@tcp(localhost:5432)/production

# MySQL/MariaDB
mysql://root:password@tcp(db.example.com:3306)/myapp

# With custom port
postgres://admin:pass@tcp(10.0.1.50:5433)/metrics_db

# Unix socket (PostgreSQL)
postgres://user:pass@unix(/var/run/postgresql)/mydb

TLS/SSL Parameters

Configure TLS directly in the DSN query string:

Parameter	Values	Description
sslmode	disable, require, verify-ca, verify-full	TLS mode (default: disable)
sslrootcert or sslca	/path/to/ca.crt	CA certificate for server verification
sslcert	/path/to/client.crt	Client certificate (mutual TLS)
sslkey	/path/to/client.key	Client private key (mutual TLS)

TLS Mode Details:

• disable - No encryption (plaintext)
• require - Encrypted connection, no certificate verification
• verify-ca - Verify server certificate against CA
• verify-full - Verify certificate and hostname match

TLS Examples

# PostgreSQL with TLS required
dbpulse --dsn "postgres://user:pass@tcp(db.example.com:5432)/prod?sslmode=require"

# PostgreSQL with full certificate verification
dbpulse --dsn "postgres://user:pass@tcp(db.example.com:5432)/prod?sslmode=verify-full&sslrootcert=/etc/ssl/certs/ca.crt"

# MySQL with CA verification
dbpulse --dsn "mysql://user:pass@tcp(db.example.com:3306)/prod?sslmode=verify-ca&sslca=/etc/ssl/ca.crt"

# Mutual TLS (client certificates)
dbpulse --dsn "postgres://user:pass@tcp(db.example.com:5432)/prod?sslmode=verify-full&sslrootcert=/etc/ssl/ca.crt&sslcert=/etc/ssl/client.crt&sslkey=/etc/ssl/client.key"

Environment Variables

All options can be set via environment variables:

export DBPULSE_DSN="postgres://user:pass@tcp(localhost:5432)/mydb"
export DBPULSE_INTERVAL=60
export DBPULSE_PORT=9300
export DBPULSE_RANGE=1000

dbpulse  # Uses environment variables

Complete Examples

Production PostgreSQL with TLS:

dbpulse \
  --dsn "postgres://monitor:secret@tcp(prod-db.example.com:5432)/app?sslmode=verify-full&sslrootcert=/etc/ssl/certs/ca-bundle.crt" \
  --interval 30 \
  --port 9300 \
  --range 1000

MySQL Cluster Monitoring:

dbpulse \
  --dsn "mysql://healthcheck:pass@tcp(galera-lb.internal:3306)/monitoring" \
  --interval 15 \
  --listen "0.0.0.0" \
  --port 8080

Development Setup:

dbpulse --dsn "postgres://postgres:postgres@tcp(localhost:5432)/test" -i 10 -r 50

What It Monitors

Health Check Operations (The Pulse Check 🩺)

Every interval, dbpulse performs a quick vital signs check:

1. Connection Test ⚡ - Establishes database connection with timeouts
2. Version Check 🔍 - Retrieves database version
3. Read-Only Detection 🔒 - Checks if database accepts writes
4. Write Operation ✍️ - INSERT or UPDATE with unique ID and UUID
5. Read Verification ✅ - SELECT to verify written data matches
6. Transaction Test 🔄 - Tests rollback capability
7. Cleanup 🧹 - Deletes old records (keeps table size bounded)

Timeout Protection:

• PostgreSQL: 5s statement timeout, 2s lock timeout
• MySQL/MariaDB: 5s max execution time, 2s lock wait timeout

These timeouts prevent the health probe from hanging on locked tables.

Operational Metrics (Best-effort)

In addition to health checks, dbpulse collects:

• Replication Lag - For replica databases only (PostgreSQL: pg_last_xact_replay_timestamp(), MySQL: SHOW REPLICA STATUS)
• Blocking Queries - Count of queries currently blocking others
• Database Size - Total database size in bytes
• Table Size - Monitoring table size and row count
• Connection Duration - How long connections are held open
• TLS Handshake Time - When TLS is enabled

All operational metrics use if let Ok(...) pattern - they never fail the health check.

Metrics

dbpulse exposes comprehensive Prometheus-compatible metrics on the /metrics endpoint.

Core Health Metrics

Metric	Type	Description
dbpulse_pulse	Gauge	Binary health status (1=healthy, 0=unhealthy)
dbpulse_runtime	Histogram	Total health check duration (seconds)
dbpulse_iterations_total	Counter	Total checks by status (success/error)
dbpulse_last_success_timestamp_seconds	Gauge	Unix timestamp of last successful check
dbpulse_database_readonly	Gauge	Read-only mode indicator (1=read-only, 0=read-write)
dbpulse_database_version_info	Gauge	Value 1 with version label describing DB server build
dbpulse_database_uptime_seconds	Gauge	How long the database has been up (seconds)

Performance Metrics

Metric	Type	Description
dbpulse_operation_duration_seconds	Histogram	Duration by operation (connect, insert, select, etc.)
dbpulse_connection_duration_seconds	Histogram	How long connections are held open
dbpulse_connections_active	Gauge	Currently active database connections

Database Operations

Metric	Type	Description
dbpulse_rows_affected_total	Counter	Total rows affected by operation type (insert, delete)
dbpulse_table_size_bytes	Gauge	Monitoring table size in bytes
dbpulse_table_rows	Gauge	Approximate row count in monitoring table
dbpulse_database_size_bytes	Gauge	Total database size in bytes

Replication & Blocking

Metric	Type	Description
dbpulse_replication_lag_seconds	Histogram	Replication lag for replica databases
dbpulse_blocking_queries	Gauge	Number of queries currently blocking others

Error Tracking

Metric	Type	Description
dbpulse_errors_total	Counter	Total errors by type (authentication, timeout, connection, transaction, query)
dbpulse_panics_recovered_total	Counter	Total panics recovered from

TLS/SSL Metrics

Metric	Type	Description
dbpulse_tls_handshake_duration_seconds	Histogram	TLS handshake duration
dbpulse_tls_connection_errors_total	Counter	TLS-specific connection errors
dbpulse_tls_info	Gauge	TLS version and cipher suite (labels: version, cipher)

For complete documentation, PromQL examples, and alert rules, see grafana/README.md.

Key Metrics Examples

# Database health
dbpulse_pulse

# Success rate
rate(dbpulse_iterations_total{status="success"}[5m]) /
  rate(dbpulse_iterations_total[5m]) * 100

# P99 latency
histogram_quantile(0.99, rate(dbpulse_runtime_bucket[5m]))

# Error rate by type
rate(dbpulse_errors_total[5m])

# Connection time
rate(dbpulse_operation_duration_seconds_sum{operation="connect"}[5m]) /
  rate(dbpulse_operation_duration_seconds_count{operation="connect"}[5m])

Example Alerts

- alert: DatabaseDown
  expr: dbpulse_pulse == 0
  for: 2m
  labels:
    severity: critical

- alert: HighErrorRate
  expr: rate(dbpulse_errors_total[5m]) > 0.1
  for: 5m
  labels:
    severity: warning

- alert: NoRecentSuccess
  expr: time() - dbpulse_last_success_timestamp_seconds > 300
  for: 1m
  labels:
    severity: critical

Database Permissions

The monitoring user needs these permissions:

PostgreSQL:

-- Create monitoring user
CREATE USER dbpulse_monitor WITH PASSWORD 'secret';

-- Grant database access
GRANT CONNECT ON DATABASE mydb TO dbpulse_monitor;
GRANT CREATE ON DATABASE mydb TO dbpulse_monitor;  -- Optional: allows auto-creation

-- Grant schema access
GRANT USAGE ON SCHEMA public TO dbpulse_monitor;
GRANT CREATE ON SCHEMA public TO dbpulse_monitor;

-- Allow table creation and operations
GRANT CREATE ON SCHEMA public TO dbpulse_monitor;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT ALL ON TABLES TO dbpulse_monitor;

MySQL/MariaDB:

-- Create monitoring user
CREATE USER 'dbpulse_monitor'@'%' IDENTIFIED BY 'secret';

-- Grant necessary permissions
GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP ON mydb.* TO 'dbpulse_monitor'@'%';
GRANT REPLICATION CLIENT ON *.* TO 'dbpulse_monitor'@'%';  -- For replication lag monitoring
GRANT PROCESS ON *.* TO 'dbpulse_monitor'@'%';  -- For blocking query detection

FLUSH PRIVILEGES;

Minimal Permissions (read-only monitoring): If the dbpulse_rw table already exists, only these are needed:

-- PostgreSQL
GRANT SELECT, INSERT, UPDATE, DELETE ON TABLE dbpulse_rw TO dbpulse_monitor;

-- MySQL
GRANT SELECT, INSERT, UPDATE, DELETE ON mydb.dbpulse_rw TO 'dbpulse_monitor'@'%';

Note: dbpulse will attempt to create the database if it doesn't exist (requires appropriate permissions).

Monitoring Table

dbpulse creates and manages a table named dbpulse_rw (or custom name if using multiple instances) with this schema:

PostgreSQL:

CREATE TABLE IF NOT EXISTS dbpulse_rw (
    id INT NOT NULL,
    t1 BIGINT NOT NULL,
    t2 TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    uuid UUID,
    PRIMARY KEY(id)
);
CREATE UNIQUE INDEX IF NOT EXISTS idx_uuid ON dbpulse_rw(uuid);
CREATE INDEX IF NOT EXISTS idx_t2 ON dbpulse_rw(t2);

MySQL/MariaDB:

CREATE TABLE IF NOT EXISTS dbpulse_rw (
    id INT NOT NULL,
    t1 BIGINT NOT NULL,
    t2 TIMESTAMP(6) NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    uuid CHAR(36) CHARACTER SET ascii,
    PRIMARY KEY(id),
    UNIQUE KEY(uuid),
    INDEX idx_t2 (t2)
) ENGINE=InnoDB;

Table Cleanup

The table is automatically maintained:

• Hourly cleanup: Records older than 1 hour are deleted (LIMIT 10000 per check)
• Periodic drop: Table is completely dropped and recreated every hour (when row count < 100k and at minute 0)
• Bounded growth: Table size remains small even with frequent checks

Custom Table Names

Use different table names for multiple monitoring instances:

# Instance 1
dbpulse --dsn "postgres://user:pass@tcp(db:5432)/prod" --range 1000

# Instance 2 (different range = different table name)
dbpulse --dsn "postgres://user:pass@tcp(db:5432)/prod" --range 2000

Deployment

Container Image

Container images are automatically published to GitHub Container Registry on each release.

Pull the image:

podman pull ghcr.io/nbari/dbpulse:latest

Run with Docker/Podman:

# PostgreSQL
podman run -d \
  --name dbpulse \
  -p 9300:9300 \
  -e DBPULSE_DSN="postgres://user:password@host.docker.internal:5432/mydb" \
  ghcr.io/nbari/dbpulse:latest

# MySQL/MariaDB with TLS
docker run -d \
  --name dbpulse \
  -p 9300:9300 \
  -v /etc/ssl/certs:/etc/ssl/certs:ro \
  -e DBPULSE_DSN="mysql://user:pass@tcp(db.example.com:3306)/prod?sslmode=verify-ca&sslca=/etc/ssl/certs/ca.crt" \
  -e DBPULSE_INTERVAL=60 \
  ghcr.io/nbari/dbpulse:latest

Multi-architecture support:

• linux/amd64 - x86_64 architecture
• linux/arm64 - ARM64 architecture (AWS Graviton, Apple Silicon, Raspberry Pi)

Systemd Service

[Unit]
Description=Database Pulse Monitor
After=network.target

[Service]
Type=simple
User=dbpulse
Group=dbpulse
Environment="DBPULSE_DSN=postgres://monitor:secret@tcp(localhost:5432)/prod?sslmode=verify-full&sslrootcert=/etc/ssl/certs/ca.crt"
Environment="DBPULSE_INTERVAL=30"
Environment="DBPULSE_PORT=9300"
ExecStart=/usr/local/bin/dbpulse
Restart=always
RestartSec=10

# Security hardening
NoNewPrivileges=true
PrivateTmp=true
ProtectSystem=strict
ProtectHome=true
ReadOnlyPaths=/etc/ssl

[Install]
WantedBy=multi-user.target

Save to /etc/systemd/system/dbpulse.service, then:

sudo systemctl daemon-reload
sudo systemctl enable dbpulse
sudo systemctl start dbpulse
sudo systemctl status dbpulse

Development

Testing

Run all tests (unit, integration, TLS):

just test

Run individual test suites:

just unit-test         # Unit tests only
just test-integration  # Integration tests (non-TLS)
just test-tls          # TLS integration tests

For detailed documentation, see:

• TLS_TESTING.md - TLS testing guide
• scripts/README.md - Script documentation