AH00898: Error reading from remote server (502 Proxy Error) Nginx / Apache Origin: Edge & web server OSI layer 7 · Application Last updated 5 Nov 2026

Apache: [proxy_http:error] AH01102: error reading status line from remote server 127.0.0.1:3000 / AH00898: Error reading from remote server returned by /api

mod_proxy couldn't read a valid response from the backend, so Apache returned 502/503.

Exact message you may see AH00898: Error reading from remote server returned by /apiAH01102: error reading status line from remote server 127.0.0.1:3000[proxy_http:error] AH01102: error reading status line from remote server502 Proxy Error Reason: Error reading from remote serverThe proxy server received an invalid response from an upstream server
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Seen on: Apache Linux

Meaning

The backend crashed, closed the connection, speaks a different protocol, or responded too slowly. Check the backend log, ProxyTimeout, and that ProxyPass points to the right scheme/port. Set SetEnv proxy-initial-not-pooled 1 or ProxyPass ... disablereuse=On for keepalive races.

Common causes

  • Backend crashed/restarted
  • HTTP vs HTTPS mismatch to the backend
  • Timeout (ProxyTimeout) too low
  • Keepalive connection reuse race
  • Backend not running (AH00957 / AH01114 variants)

⚡ Quick fix

  1. Check the backend service and its log
  2. Match the protocol/port in ProxyPass
  3. Tune ProxyTimeout and disablereuse=On

Detailed fix by platform

Linux

  1. sudo tail -30 /var/log/apache2/error.log; curl -I http://127.0.0.1:3000/

How to diagnose

  1. Backend — Alive?
  2. Scheme — http vs https?
  3. Timeout — ProxyTimeout?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Edge & web server. Errors that are often confused with or caused by this one (click to open):

407 — HTTP 407 Proxy Authentication Required (HTTP)407417 — HTTP 417 Expectation Failed (HTTP)417502 — HTTP 502 Bad Gateway (HTTP)502511 — HTTP 511 Network Authentication Required (HTTP)511AH00015: Unable to open logs — Apache: AH00091: apache2: could not open error log file /var/log/apache2/error.log. AH00015: Unable to open logs (Permission denied) (Nginx / Apache)AH00015: Unable to op…AH00037: Symbolic link not allowed or link target not accessible — Apache: [core:error] AH00037: Symbolic link not allowed or link target not accessible: /var/www/html/current (Nginx / Apache)AH00037: Symbolic lin…AH00526: Syntax error on line of apache config — Apache: AH00526: Syntax error on line 12 of /etc/apache2/sites-enabled/site.conf: Invalid command 'Foo', perhaps misspelled or defined by a module not included in the server configuration (Nginx / Apache)AH00526: Syntax error…AH00558 — Apache: AH00558: apache2: Could not reliably determine the server's fully qualified domain name (Nginx / Apache)AH00558AH00898: …

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