AmitPhulera opened a new issue, #5802:
URL: https://github.com/apache/couchdb/issues/5802
[NOTE]: # ( ^^ Provide a general summary of the issue in the title above. ^^
)
## Description
The `couchdb_httpd_clients_requesting_changes` gauge metric is not properly
decremented when clients disconnect from the `_changes` feed. The metric
continues to show the cumulative count of connections rather than the current
active connection count.
Interestingly, the `abandoned_streaming_requests` counter IS being
incremented when disconnections are detected, indicating that the disconnect
detection logic is working, but the main gauge is not being updated.
## Steps to Reproduce
### Setup
1. Start CouchDB 3.5 using Docker:
```bash
docker run -d --name couchdb -p 5984:5984 \
-e COUCHDB_USER=admin -e COUCHDB_PASSWORD=password \
apache/couchdb:3.5
```
2. Create a test database:
```bash
curl -X PUT -u admin:password http://localhost:5984/testdb
```
### Reproduce the issue
3. Check initial stats:
```bash
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/clients_requesting_changes";
# Expected: {"value":0,"type":"counter","desc":"number of clients for
continuous _changes"}
```
4. Start 4 continuous changes feed connections (in separate terminals or
background processes):
```bash
# Terminal 1
curl -u admin:password
"http://localhost:5984/testdb/_changes?feed=continuous&heartbeat=10000";
# Terminal 2
curl -u admin:password
"http://localhost:5984/testdb/_changes?feed=continuous&heartbeat=10000";
# Terminal 3
curl -u admin:password
"http://localhost:5984/testdb/_changes?feed=continuous&heartbeat=10000";
# Terminal 4
curl -u admin:password
"http://localhost:5984/testdb/_changes?feed=continuous&heartbeat=10000";
```
5. Verify connections are counted:
```bash
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/clients_requesting_changes";
# Expected: {"value":4,...}
```
6. Stop all 4 curl processes (Ctrl+C on each terminal)
7. Check stats again:
```bash
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/clients_requesting_changes";
# ACTUAL: {"value":4,...} - still shows 4!
# EXPECTED: {"value":0,...}
```
8. Check abandoned_streaming_requests:
```bash
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/abandoned_streaming_requests";
# Shows: {"value":4,...} - correctly detected 4 abandonments
```
9. Start 4 new connections again and stop them:
```bash
# Start 4 connections, then stop them with Ctrl+C
```
10. Check stats:
```bash
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/clients_requesting_changes";
# ACTUAL: {"value":8,...} - doubled!
# EXPECTED: {"value":0,...}
curl -s -u admin:password
"http://localhost:5984/_node/_local/_stats/couchdb/httpd/abandoned_streaming_requests";
# Shows: {"value":8,...} - correctly shows 8 total abandonments
The Prometheus endpoint correctly types this as a gauge, but the value
doesn't decrease:
```bash
curl -s -u admin:password "http://localhost:5984/_node/_local/_prometheus"; |
grep clients_requesting_changes
# TYPE couchdb_httpd_clients_requesting_changes gauge
# couchdb_httpd_clients_requesting_changes 8
```
## Expected Behaviour
The `clients_requesting_changes` metric should:
1. Increment when a client starts a continuous/longpoll `_changes` feed
2. Decrement when the client disconnects (either normally or via TCP close)
3. Always reflect the **current** number of active changes feed connections
## Actual Behavior
- The metric increments correctly when connections start
- The metric does **NOT** decrement when connections end
- The `abandoned_streaming_requests` counter correctly tracks disconnections
- This causes the gauge to act like a monotonic counter, accumulating over
time
## Your Environment
* CouchDB version used: 3.5.1
* Browser name and version: Brave 1.84.139
* Operating system and version: macOS (Darwin 24.6.0) / Docker
* **Installation method**: Docker (apache/couchdb:3.5 image)
## Additional Context
This issue was discovered while upgrading from CouchDB 3.3.1 to 3.5.1. The
metric worked correctly in 3.3.1.
The issue affects monitoring and alerting systems that rely on this metric
to track the number of active changes feed consumers.
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