fix(signoz): prevent ClickHouse broken-pipe errors in the healthcheck

[julpar]

Problem

The SigNoz ClickHouse healthcheck uses wget --spider. The --spider option closes the connection before it reads the response body. ClickHouse then fails to write the /ping response, and records the failure as an Error with a full C++ stack trace.

The healthcheck runs every 30 seconds, and each failure writes two error lines. That is about 5,700 stack traces a day. The container stays healthy the whole time, because the check still exits 0, so nothing surfaces the problem. The noise hides real ClickHouse errors.

Upstream tracking issue: SigNoz/signoz#5140 (open since June 2024).

Fix

Replace --spider with -O-, so wget reads the response body.

Measurements

On clickhouse-server:25.5.6-alpine — the image this template pins — running each command 25 times and counting new StaticRequestHandler error lines:

command	errors
wget --spider -q 0.0.0.0:8123/ping	22/25
wget -q -O- 0.0.0.0:8123/ping	0/25

Verified on a live Coolify deployment of this template: the error stream went to zero, and the container stays healthy with FailingStreak=0.

Scope

Only the clickhouse healthcheck changes. The signoz healthcheck keeps --spider — it targets a Go server, which closes the connection cleanly and produces no such errors.

Only templates/compose/signoz.yaml is touched. templates/service-templates.json is left alone, matching how previous changes to this template were submitted.

One thing worth flagging

Please do not fix this by changing the host to localhost. In the ClickHouse image, /etc/hosts resolves localhost to ::1 first. On a host with IPv6 disabled the connection is refused:

$ wget -q -O- http://localhost:8123/ping
wget: can't connect to remote host: Connection refused     # rc=1

$ wget -q -O- 0.0.0.0:8123/ping
Ok.                                                        # rc=0

That variant shows no broken-pipe errors only because the request never reaches ClickHouse, and it would make the healthcheck fail.

Related

The same fix for SigNoz's own Coolify casting template: SigNoz/foundry#194

[github-actions]

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