firestore emulator on wsl2 does not work, results in ERR_CONNECTION_REFUSED

[bartlomiejborzucki]

The main discussion is here: firebase/firebase-tools#2334

REQUIRED] Environment info
firebase-tools:8.6.0

Platform: wsl2 with Ubuntu-18.04

[REQUIRED] Test case
Start emulator firebase emulators:start --only firestore
Navigate to http://127.0.0.1:4000/firestore
Try to write in the database or simply check console

[NOT WORKING SOLUTION]

FYI, the fix for 0.0.0.0 went out with Firebase CLI v8.6.0. Please try that if you see issues with WSL with localhost / 127.0.0.1.

The above solution does not work

Summary:
Firebase emulator is running on wsl2 and we want to open firebase-tools-ui on the host machine.The page is loaded and everything works except the connection to the firestore backend. I use the following configuration:
"emulators": {
"firestore": {
"host": "0.0.0.0", // or host: 'localhost' or host: '127.0.0.1'
"port": "8080"
},
"ui": {
"enabled": true,
"port": 4000
}
}

Workaround:
Change host value to wsl2 ip address.

Screenshots:

[yuchenshi]

Looks like the UI cannot reach Firestore emulator at 127.0.0.1 and thanks for providing the information. Again, this is new to me as I haven't worked with WSL before and this is most likely an WSL issue.

With that being said, I've found microsoft/WSL#4353 seems to describe the issue you're experiencing. Would you mind updating WSL to version 18970 and disable Fast Startup and see if the issue still reproduces? You may have to install Developer Preview (or whatever they call it) to get the latest version. Once you have it and disable Fast Startup, try both localhost and 0.0.0.0 and see which one works for you.

[bartlomiejborzucki]

I had a problem with the localhost and I needed to disable Fast Startup - I'am an angular developer, and without disabling fast startup I was not able to develop my application on wsl2.
Right now my application works (the only problem is a problem with IP address on firebase emulator and connection refused on localhost IP address) -
TEMPORARY WORKAROUND: I need to set wsl IP address in my configuration (I've written about in the first post).
I've checked localhost and 0.0.0.0 after disabled Fast Startup and I got the same result
I've added these two lines to my c:/windows/system32/drivers/etc/hosts andI got the same result too :(

::1 localhost
127.0.0.1 localhost

I cannot update WSL to newest version (fast/slow ring) because of the corporate policy but IMHO I am up to date.
My windows 10 version is :

[yuchenshi]

Yeah I think you're up to date then. Would you mind digging into it a little bit further? Here are some steps to get you started on debugging connectivity:

Try curl http://127.0.0.1:8080/ in WSL bash, and then again in your normal Windows environment (e.g. Command Prompt or PowerShell).
Try nc -z -v 127.0.0.1 8080 as well. telnet can also be helpful in case you don't have netcat.

Also, does replacing 127.0.0.1 with localhost or WSL IP address help?

Just in case, please also attach firestore-debug.log after these steps.

[bartlomiejborzucki]

Ok, no problem :)

Firestore: Host: localhost

WSL

PowerShell curl

telnet

Firestore: Host: 0.0.0.0

WSL:

Power shell curl

Telnet
the same as power shell curl

Firestore: Host: 127.0.0.1

wsl

power shell curl

telnet cmd

Firestore: Host: 172.31.46.235

WSL

powershell curl

telnet
the same as powershell

My firebase-debug.log
firebase-debug.log

[yuchenshi]

Thanks! It looks like we're out of luck here, but it bothers me that Angular and Emulator UI web server somehow work while Firestore does not. Could it be... Node.js v.s. Java? Does Realtime Database work for you then?

I'll see if I can get someone from the Firebase team to help troubleshooting this hands-on. But to be honest, I don't think there is much that we can do -- again, mostly likely changes will need to be made in WSL or Java or the Java framework used in Firestore Emulator.

[bartlomiejborzucki]

Thank you very much for helping the community .
I checked the realtime database and I've got the same result.
I also checked Microsoft Edge - the same result.
I changed port to 23123 (random number) - the same result.
I also tried to add this rule: netsh interface portproxy add v4tov4 listenport=8080 listenaddress=0.0.0.0 connectport=8080 connectaddress=172.18.28.x 
and I got new error: connection reset instead of connection refused.

[bartlomiejborzucki]

The workaround is here: microsoft/WSL#5706 (comment)

[yuchenshi]

According to microsoft/WSL#5706 (comment), it seems like the Firestore emulator is listening on IPv6 only when localhost is specified. Let me also investigate on our side and see what is going on.

[hatboysam]

@yuchenshi I am doing some debugging on my personal Windows machine (WSL2).

Here's what I see from netstat -nl when running the Firestore Emulator and the UI with all standard options:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.1:4000          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4400          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4500          0.0.0.0:*               LISTEN
tcp6       0      0 127.0.0.1:38397         :::*                    LISTEN
tcp6       0      0 127.0.0.1:34697         :::*                    LISTEN
tcp6       0      0 127.0.0.1:8080          :::*                    LISTEN
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     SEQPACKET  LISTENING     13335    /run/WSL/7_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14416    /run/WSL/241_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14485    /run/WSL/460_interop

Now if I set the host to 0.0.0.0 in firebase.json:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.1:4000          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4400          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4500          0.0.0.0:*               LISTEN
tcp6       0      0 :::40621                :::*                    LISTEN
tcp6       0      0 :::46573                :::*                    LISTEN
tcp6       0      0 :::8080                 :::*                    LISTEN
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     SEQPACKET  LISTENING     13335    /run/WSL/7_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14416    /run/WSL/241_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14485    /run/WSL/460_interop

And finally with 127.0.0.1:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.1:4000          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4400          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:4500          0.0.0.0:*               LISTEN
tcp6       0      0 :::40621                :::*                    LISTEN
tcp6       0      0 :::46573                :::*                    LISTEN
tcp6       0      0 :::8080                 :::*                    LISTEN
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   Path
unix  2      [ ACC ]     SEQPACKET  LISTENING     13335    /run/WSL/7_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14416    /run/WSL/241_interop
unix  2      [ ACC ]     SEQPACKET  LISTENING     14485    /run/WSL/460_interop

So localhost and 127.0.0.1 give the same result while 0.0.0.0 is different.

[yuchenshi]

So localhost and 127.0.0.1 give the same result while 0.0.0.0 is different.

I think you meant localhost is different while the others are the same? As seen in your snippets output, the first output has 127.0.0.1:8080 in Local Address while the two outputs has :::8080.

But either way, ALL of these show that Firestore Emulator listening to tcp6 instead of tcp4 (or both). This is problematic, especially in the case of 127.0.0.1 and 0.0.0.0 since those are clearly IPv4. In general, Firestore Emulator should respect the chosen protocol indicated by the host IP address format.

The Emulator UI reads hosts from the config, so it tries to connect via IPv4 when 127.0.0.1 or 0.0.0.0 are used. However as you have seen, the Firestore Emulator is actually listening on IPv6, so connection fails on Windows. It works on Linux since the kernel will automatically routes these requests to the IPv6 counterpart, but WSL doesn't support that yet: microsoft/WSL#4851.

tl;dr We should fix Firestore Emulator to listen on IPv4 when 127.0.0.1 or 0.0.0.0 is specified. If localhost is specified, I think the spec-compliant way is to resolve localhost and listen on ALL IP addresses returned. It usually resolves to BOTH 127.0.0.1 and ::1 from /etc/hosts on most setups.