Add server_url to plotly.io.orca to allow for external orca server (#1850)

* Add server_url to plotly.io.orca to allow for external orca server
* Add orca external server test

Author: miriad

Diff for: packages/python/plotly/plotly/io/_orca.py

@@ -380,6 +380,48 @@ def save(self):
                 )
             )
 
+    @property
+    def server_url(self):
+        """
+        The server URL to use for an external orca server, or None if orca
+        should be managed locally
+
+        Overrides executable, port, timeout, mathjax, topojson,
+        and mapbox_access_token
+
+        Returns
+        -------
+        str or None
+        """
+        return self._props.get("server_url", None)
+
+    @server_url.setter
+    def server_url(self, val):
+
+        if val is None:
+            self._props.pop("server_url", None)
+            return
+        if not isinstance(val, str):
+            raise ValueError(
+                """
+The server_url property must be a string, but received value of type {typ}.
+    Received value: {val}""".format(
+                    typ=type(val), val=val
+                )
+            )
+
+        if not val.startswith("http://") and not val.startswith("https://"):
+            val = "http://" + val
+
+        shutdown_server()
+        self.executable = None
+        self.port = None
+        self.timeout = None
+        self.mathjax = None
+        self.topojson = None
+        self.mapbox_access_token = None
+        self._props["server_url"] = val
+
     @property
     def port(self):
         """
@@ -777,6 +819,7 @@ def __repr__(self):
         return """\
 orca configuration
 ------------------
+    server_url: {server_url}
     executable: {executable}
     port: {port}
     timeout: {timeout}
@@ -795,6 +838,7 @@ def __repr__(self):
     config_file: {config_file}
 
 """.format(
+            server_url=self.server_url,
             port=self.port,
             executable=self.executable,
             timeout=self.timeout,
@@ -1344,62 +1388,65 @@ def ensure_server():
     if status.state == "unvalidated":
         validate_executable()
 
-    # Acquire lock to make sure that we keep the properties of orca_state
-    # consistent across threads
-    with orca_lock:
-        # Cancel the current shutdown timer, if any
-        if orca_state["shutdown_timer"] is not None:
-            orca_state["shutdown_timer"].cancel()
+    if not config.server_url:
+        # Acquire lock to make sure that we keep the properties of orca_state
+        # consistent across threads
+        with orca_lock:
+            # Cancel the current shutdown timer, if any
+            if orca_state["shutdown_timer"] is not None:
+                orca_state["shutdown_timer"].cancel()
+
+            # Start a new server process if none is active
+            if orca_state["proc"] is None:
+
+                # Determine server port
+                if config.port is None:
+                    orca_state["port"] = find_open_port()
+                else:
+                    orca_state["port"] = config.port
+
+                # Build orca command list
+                cmd_list = status._props["executable_list"] + [
+                    "serve",
+                    "-p",
+                    str(orca_state["port"]),
+                    "--plotly",
+                    config.plotlyjs,
+                    "--graph-only",
+                ]
 
-        # Start a new server process if none is active
-        if orca_state["proc"] is None:
+                if config.topojson:
+                    cmd_list.extend(["--topojson", config.topojson])
 
-            # Determine server port
-            if config.port is None:
-                orca_state["port"] = find_open_port()
-            else:
-                orca_state["port"] = config.port
-
-            # Build orca command list
-            cmd_list = status._props["executable_list"] + [
-                "serve",
-                "-p",
-                str(orca_state["port"]),
-                "--plotly",
-                config.plotlyjs,
-                "--graph-only",
-            ]
-
-            if config.topojson:
-                cmd_list.extend(["--topojson", config.topojson])
-
-            if config.mathjax:
-                cmd_list.extend(["--mathjax", config.mathjax])
-
-            if config.mapbox_access_token:
-                cmd_list.extend(["--mapbox-access-token", config.mapbox_access_token])
-
-            # Create subprocess that launches the orca server on the
-            # specified port.
-            DEVNULL = open(os.devnull, "wb")
-            with orca_env():
-                orca_state["proc"] = subprocess.Popen(cmd_list, stdout=DEVNULL)
-
-            # Update orca.status so the user has an accurate view
-            # of the state of the orca server
-            status._props["state"] = "running"
-            status._props["pid"] = orca_state["proc"].pid
-            status._props["port"] = orca_state["port"]
-            status._props["command"] = cmd_list
-
-        # Create new shutdown timer if a timeout was specified
-        if config.timeout is not None:
-            t = threading.Timer(config.timeout, shutdown_server)
-            # Make it a daemon thread so that exit won't wait for timer to
-            # complete
-            t.daemon = True
-            t.start()
-            orca_state["shutdown_timer"] = t
+                if config.mathjax:
+                    cmd_list.extend(["--mathjax", config.mathjax])
+
+                if config.mapbox_access_token:
+                    cmd_list.extend(
+                        ["--mapbox-access-token", config.mapbox_access_token]
+                    )
+
+                # Create subprocess that launches the orca server on the
+                # specified port.
+                DEVNULL = open(os.devnull, "wb")
+                with orca_env():
+                    orca_state["proc"] = subprocess.Popen(cmd_list, stdout=DEVNULL)
+
+                # Update orca.status so the user has an accurate view
+                # of the state of the orca server
+                status._props["state"] = "running"
+                status._props["pid"] = orca_state["proc"].pid
+                status._props["port"] = orca_state["port"]
+                status._props["command"] = cmd_list
+
+            # Create new shutdown timer if a timeout was specified
+            if config.timeout is not None:
+                t = threading.Timer(config.timeout, shutdown_server)
+                # Make it a daemon thread so that exit won't wait for timer to
+                # complete
+                t.daemon = True
+                t.start()
+                orca_state["shutdown_timer"] = t
 
 
 @retrying.retry(wait_random_min=5, wait_random_max=10, stop_max_delay=60000)
@@ -1410,9 +1457,12 @@ def request_image_with_retrying(**kwargs):
     """
     from requests import post
 
-    server_url = "http://{hostname}:{port}".format(
-        hostname="localhost", port=orca_state["port"]
-    )
+    if config.server_url:
+        server_url = config.server_url
+    else:
+        server_url = "http://{hostname}:{port}".format(
+            hostname="localhost", port=orca_state["port"]
+        )
 
     request_params = {k: v for k, v, in kwargs.items() if v is not None}
     json_str = json.dumps(request_params, cls=_plotly_utils.utils.PlotlyJSONEncoder)
@@ -1513,29 +1563,41 @@ def to_image(fig, format=None, width=None, height=None, scale=None, validate=Tru
         # Get current status string
         status_str = repr(status)
 
-        # Check if the orca server process exists
-        pid_exists = psutil.pid_exists(status.pid)
-
-        # Raise error message based on whether the server process existed
-        if pid_exists:
+        if config.server_url:
             raise ValueError(
                 """
+Plotly.py was unable to communicate with the orca server at {server_url}
+
+Please check that the server is running and accessible.
+""".format(
+                    server_url=config.server_url
+                )
+            )
+
+        else:
+            # Check if the orca server process exists
+            pid_exists = psutil.pid_exists(status.pid)
+
+            # Raise error message based on whether the server process existed
+            if pid_exists:
+                raise ValueError(
+                    """
 For some reason plotly.py was unable to communicate with the
 local orca server process, even though the server process seems to be running.
 
 Please review the process and connection information below:
 
 {info}
 """.format(
-                    info=status_str
+                        info=status_str
+                    )
                 )
-            )
-        else:
-            # Reset the status so that if the user tries again, we'll try to
-            # start the server again
-            reset_status()
-            raise ValueError(
-                """
+            else:
+                # Reset the status so that if the user tries again, we'll try to
+                # start the server again
+                reset_status()
+                raise ValueError(
+                    """
 For some reason the orca server process is no longer running.
 
 Please review the process and connection information below:
@@ -1544,9 +1606,9 @@ def to_image(fig, format=None, width=None, height=None, scale=None, validate=Tru
 plotly.py will attempt to start the local server process again the next time
 an image export operation is performed.
 """.format(
-                    info=status_str
+                        info=status_str
+                    )
                 )
-            )
 
     # Check response
     # --------------

Diff for: packages/python/plotly/plotly/tests/test_orca/test_orca_server.py

@@ -7,10 +7,14 @@
 import time
 import psutil
 import pytest
+import plotly.graph_objects as go
 
 
 # Fixtures
 # --------
+from plotly.io._orca import find_open_port, which, orca_env
+
+
 @pytest.fixture()
 def setup():
     # Set problematic environment variables
@@ -150,3 +154,45 @@ def test_server_timeout_shutdown():
 
     # Check that ping is no longer answered
     assert not ping_pongs(server_url)
+
+
+def test_external_server_url():
+    # Build server url
+    port = find_open_port()
+    server_url = "http://{hostname}:{port}".format(hostname="localhost", port=port)
+
+    # Build external orca command
+    orca_path = which("orca")
+    cmd_list = [orca_path] + [
+        "serve",
+        "-p",
+        str(port),
+        "--plotly",
+        pio.orca.config.plotlyjs,
+        "--graph-only",
+    ]
+
+    # Run orca as subprocess to simulate external orca server
+    DEVNULL = open(os.devnull, "wb")
+    with orca_env():
+        proc = subprocess.Popen(cmd_list, stdout=DEVNULL)
+
+    # Start plotly managed orca server so we can ensure it gets shut down properly
+    pio.orca.config.port = port
+    pio.orca.ensure_server()
+    assert pio.orca.status.state == "running"
+
+    # Configure orca to use external server
+    pio.orca.config.server_url = server_url
+
+    # Make sure that the locally managed orca server has been shutdown and the local
+    # config options have been cleared
+    assert pio.orca.status.state == "unvalidated"
+    assert pio.orca.config.port is None
+
+    fig = go.Figure()
+    img_bytes = pio.to_image(fig, format="svg")
+    assert img_bytes.startswith(b"<svg class")
+
+    # Kill server orca process
+    proc.terminate()