Merge ~xavpaice/charm-graylog:bug/1818615 into ~graylog-charmers/charm-graylog:master

[Xav Paice]

Determine default network interface

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Xav Paice (xavpaice)]

couple of diff comments, plus Haw's review

review: Needs Fixing

[Haw Loeung (hloeung)]

LGTM

review: Approve (+1)

[Haw Loeung (hloeung)]

Feel free to toggle the 'Status' to 'Approved' and have the mergebot land it.

diff --git a/config.yaml b/config.yaml
index d0d2649..4ac707e 100644
--- a/config.yaml
+++ b/config.yaml
@@ -35,16 +35,19 @@ options:
       Example: http://10.0.0.1:9000/
   rest_transport_uri:
     type: string
-    default: ""
+    default: "http://0.0.0.0:9001/api/"
     description: |
       If set, this will be promoted in the cluster discovery APIs. You will need
       to define this if your Graylog server is running behind a HTTP proxy that
-      is rewriting the scheme, host name, or URI. This must not contain a
-      wildcard address (0.0.0.0).
+      is rewriting the scheme, host name, or URI.
 
       For Graylog 2, this usually takes the form http://10.0.0.1:9001/api/.
       For Graylog 3 and higher, this is known as the 'http_publish_uri' and looks
       like http://10.0.0.1:9000/.
+      
+      If the ip address 0.0.0.0 is specified, the charm will attempt to deduct
+      the network interface that is used for connections to the default gateway and
+      use the associated ip address.
   index_replicas:
     type: int
     default: 0
diff --git a/lib/charms/layer/graylog/utils.py b/lib/charms/layer/graylog/utils.py
index cf89b61..2d383dd 100644
--- a/lib/charms/layer/graylog/utils.py
+++ b/lib/charms/layer/graylog/utils.py
@@ -1,23 +1,26 @@
+import socket
+from urllib.parse import urlparse
+
 from charmhelpers.core import hookenv
 from charms.layer import snap
 
-SNAP_NAME = 'graylog'
+SNAP_NAME = "graylog"
 
 
 def get_api_port():
-    return '9001' if is_v2() else '9000'
+    return "9001" if is_v2() else "9000"
 
 
 def get_api_url():
-    return 'http://127.0.0.1:{}/api/'.format(get_api_port())
+    return "http://127.0.0.1:{}/api/".format(get_api_port())
 
 
 def is_v2():
     version = snap.get_installed_version(SNAP_NAME)
     # If the snap isn't installed yet, base our version off the charm config
     if not version:
-        version = hookenv.config('channel')
-    return True if version.startswith('2') else False
+        version = hookenv.config("channel")
+    return True if version.startswith("2") else False
 
 
 def validate_api_uri(uri):
@@ -27,16 +30,45 @@ def validate_api_uri(uri):
     server hard codes '/api/' to the end of these options and should therefore
     be removed if included in the charm config.
     """
-    if not uri.endswith('/'):
-        uri += '/'
+    if not uri.endswith("/"):
+        uri += "/"
 
     if is_v2():
-        if not uri.endswith('/api/'):
+        if not uri.endswith("/api/"):
             hookenv.log("Appending 'api/' to the configured REST API options")
-            uri += 'api/'
+            uri += "api/"
     else:
-        if uri.endswith('/api/'):
+        if uri.endswith("/api/"):
             hookenv.log("Removing 'api/' from the configurted REST API options")
             uri = uri[:-4]
 
+    parsed_url = urlparse(uri)
+    if parsed_url.hostname == "0.0.0.0":
+        uri = parsed_url._replace(
+            netloc="{}:{}".format(get_ip_address(), parsed_url.port)
+        ).geturl()
+
     return uri
+
+
+def get_ip_address():
+    """Determine the ip address that would be used for outgoing connection.
+
+    This function tries to determine the network ip address, that would be used
+    when access servers in the internet. It uses a dummy UDP connection todo
+    so.
+    As the connection itself is not made, it is safe to use any address.
+    """
+
+    # Start a socket via ipv4, using UDP
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+    # Make dummy attempt to ntp servers from the pool.ntp.org, we hard code one
+    # of them
+
+    sock.connect(("ntp.ubuntu.com", 123))
+
+    ip = sock.getsockname()[0]
+    sock.close()
+    hookenv.log("Found ip {} to use".format(ip))
+    return ip
diff --git a/reactive/graylog.py b/reactive/graylog.py
index b3a6538..89a4843 100644
--- a/reactive/graylog.py
+++ b/reactive/graylog.py
@@ -155,8 +155,8 @@ def configure_graylog():
                 db.set('web_listen_port', url.port)
                 hookenv.open_port(url.port)
 
-        if conf['rest_transport_uri']:
-            set_conf('rest_transport_uri', validate_api_uri(conf['rest_transport_uri']))
+        # We always call set this, so it gets a sensible default
+        set_conf('rest_transport_uri', validate_api_uri(conf['rest_transport_uri']))
 
         if conf['web_endpoint_uri']:
             set_conf('web_endpoint_uri', validate_api_uri(conf['web_endpoint_uri']))
@@ -164,8 +164,8 @@ def configure_graylog():
         if conf['web_listen_uri']:
             url = urlparse(conf['web_listen_uri'])
             set_conf('http_bind_address', url.netloc)
-        if conf['rest_transport_uri']:
-            set_conf('http_publish_uri', validate_api_uri(conf['rest_transport_uri']))
+        # We always call set this, so it gets a sensible default
+        set_conf('http_publish_uri', validate_api_uri(conf['rest_transport_uri']))
         if conf['web_endpoint_uri']:
             set_conf('http_external_uri', validate_api_uri(conf['web_endpoint_uri']))