Logstream

A simple syslog sink: receives logs over UDP/TCP on port 514, stores them in VictoriaLogs, and serves a clean web interface (light/dark theme, live search, live view, color tags, English/French UI).

devices ──514 udp/tcp──▶ logstream (Go) ──HTTP batches──▶ VictoriaLogs
                              ▲    └── SSE (live) ──▶ browser
                              └──── API / UI ◀─────────┘

Getting started

cp .env.example .env      # optional
docker compose up -d --build
./tools/send-test-logs.sh # sends 100 test messages

Then open http://localhost:8080.

Sending logs

• rsyslog (Linux): add *.* @SERVER_IP:514 (UDP) or *.* @@SERVER_IP:514 (TCP) to /etc/rsyslog.d/90-logstream.conf, then run systemctl restart rsyslog.
• Network gear, NAS, firewalls: set the server IP and port 514 in their "remote syslog" settings.
• Manual test: logger -n 127.0.0.1 -P 514 -d "hello error" (util-linux) or echo "<14>test ok" | nc -u -w1 127.0.0.1 514.

Supported formats: RFC 3164 (BSD) and RFC 5424. Over TCP, both "one message per line" and "octet counting" (RFC 6587) framing are accepted.

Search

Simple mode (default): each word is matched as a case-insensitive substring of the message, host and app. Words are combined with AND.

Input	Meaning
error disk	contains "error" and "disk"
"disk full"	contains the exact phrase
error -timeout	contains "error" but not "timeout"

LogsQL mode (Simple / LogsQL button): the full VictoriaLogs query language, e.g. error AND host:web-01, app:~"ssh|nginx", or * | stats by (host) count(). The live view is disabled in this mode.

Each row shows, from left to right: the reception time (server clock), the timestamp found in the message itself (msg_time), severity, host, app and message. Click a host or an app to filter on it.

Logs are indexed, searched and sorted by reception time: devices with a wrong clock (e.g. access points whose NTP fails) still show up in the right time range. Logs stored by versions before this change are indexed by their message timestamp; purge them from Settings to start clean.

Severity badges err/crit and warning use the colors of the error and warning tags.

Shortcuts: / focuses the search box, Esc clears it. Clicking a row shows all its fields.

CSV export

The Export button (next to the log count) downloads every stored log matching the current filters (search, time range, severity, host, app), newest first, up to EXPORT_MAX rows (100,000 by default), not only the rows on screen. Two variants:

• CSV: comma separated, UTF-8.
• CSV for Excel: semicolon separated with a UTF-8 BOM, so French Excel opens it directly with accents. Cells starting with =, +, - or @ are prefixed with ' so that a crafted log message cannot run as a formula.

Columns: received, message_time (both as YYYY-MM-DD HH:MM:SS.mmm in the time zone chosen in Settings), severity, facility, host, host_ip, app, pid, source_ip, proto, message. In LogsQL mode, only the filter part is supported (no | pipes).

From the command line: curl -o logs.csv 'localhost:8080/api/export.csv?q=error&range=24h&tz=Europe/Paris'.

Settings

The gear icon opens the settings, organized in tabs. Everything except color tags is remembered per browser.

• Localization
  • Language: English or French.
  • Date & time: time zone (browser zone, UTC, or about 80 common zones) and the display format of the reception time: DD/MM/YYYY HH:MM:SS (default, the usual French display), with milliseconds, YYYY-MM-DD, 12-hour clock, ISO 8601 or Unix epoch. The time zone applies to every date shown.
• Filters: color tags. Each tag has a keyword, a background color (the text automatically switches to black or white to stay readable) and options: whole word, match case, regular expression, active. Tags are stored on the server in /data/tags.json (logstream-data volume), so they are shared by every browser. Default tags (pastel): warning (orange), error (red), ok (green). Default tags still using the colors of earlier versions are switched to the pastel ones automatically.
• Interface
  • Theme: System (follows the computer/phone preference), Light or Dark. The sun/moon button in the header switches between light and dark.
  • Log display: font size (tiny, small, medium, large) and font: the system monospace font, or one of 12 free fonts made for dense text (JetBrains Mono, Fira Code, Source Code Pro, IBM Plex Mono, Cascadia Code, Roboto Mono, Ubuntu Mono, Inconsolata, Red Hat Mono, Noto Sans Mono, Victor Mono, DM Mono). They are loaded by the browser from Bunny Fonts, a privacy-friendly European font service; without internet access, the system font is used. Ligatures are disabled so -> or != show as typed.
• Data: "Delete all logs" permanently erases every stored log (you must type PURGE to confirm). Tags and settings are kept. VictoriaLogs needs -delete.enable (already set in docker-compose.yml); set ALLOW_PURGE=false to disable the feature. Anyone who can open the UI can purge: set AUTH_USER / AUTH_PASS if the UI is reachable by others.

Host names (reverse DNS)

When a device sends its IP address as host name (or no host name at all), Logstream looks up its DNS name (PTR record) and stores the name in host and the IP in host_ip. Results are cached (1 hour, 10 minutes when there is no name). Logs stored earlier with an IP are resolved on display, and the host filter shows name (IP).

The container uses Docker's DNS, which forwards to the host's resolvers. If your local names are only known by your router or a local DNS (Pi-hole, AdGuard, Unbound…), set DNS_SERVER=192.168.1.1 (its address). Set RDNS=off to disable lookups.

• Color tags: each tag has a keyword, a background color (the text automatically switches to black or white to stay readable) and options: whole word, match case, regular expression, active. Tags are stored in /data/tags.json (logstream-data volume). Default tags (pastel): warning (orange), error (red), ok (green). Default tags still using the colors of earlier versions are switched to the pastel ones automatically.

Configuration

Variable	Default	Purpose
SYSLOG_PORT	514	syslog port published on the host
HTTP_PORT	8080	web UI port
RETENTION	30d	how long VictoriaLogs keeps logs
AUTH_USER / AUTH_PASS	empty	HTTP Basic authentication for the UI
RDNS	on	resolve IP hosts to DNS names
DNS_SERVER	empty	DNS server for reverse lookups (ip or ip:port)
ALLOW_PURGE	true	allow "Delete all logs" in Settings
EXPORT_MAX	100000	maximum number of rows in a CSV export
TZ	Europe/Paris	time zone for RFC 3164 timestamps (which carry none)
BATCH_SIZE, FLUSH_MS, QUEUE_SIZE	1000, 1000, 100000	ingestion tuning

Debugging

• docker compose logs -f logstream: receive errors and errors sending to VictoriaLogs.
• The bottom bar shows received / stored / dropped counters and the last storage error.
• http://localhost:9428/select/vmui: VictoriaLogs' own UI to try LogsQL queries.
• API:

  curl 'localhost:8080/api/logs?q=error&range=1h&limit=5'   # the response includes the generated LogsQL query
  curl localhost:8080/api/stats
  curl localhost:8080/api/tags
  

• Running outside Docker (Go 1.22+): VLOGS_URL=http://localhost:9428 DATA_DIR=./data SYSLOG_ADDR=:5514 go run .

Code layout

File	Contents
main.go	configuration, startup, authentication
syslog.go	UDP/TCP listeners and RFC 3164 / 5424 parsing
store.go	batched inserts into VictoriaLogs and LogsQL queries
query.go	turns UI filters into LogsQL; live-view filter
hub.go	pushes new messages to browsers (SSE)
rdns.go	cached reverse DNS lookups
export.go	streamed CSV export
tags.go	color tag storage
api.go	/api/* HTTP routes
web/	UI (HTML, CSS, plain JavaScript, no build step), embedded in the binary; translations live in web/app.js (I18N)

Note

With Docker Desktop (macOS/Windows), the source IP seen by the container for UDP packets is the Docker gateway. The host field still comes from the syslog header, which normally carries the sender's real name.