Faster data transfers from MARS.

environment.yml

@@ -23,6 +23,7 @@ dependencies:
   - numpy=1.22.4
   - pandas=1.5.1
   - google-cloud-sdk=410.0.0
+  - aria2=1.36.0
   - pip=22.3
   - pip:
     - earthengine-api==0.1.329

weather_dl/download_pipeline/clients.py

@@ -20,14 +20,17 @@
 import json
 import logging
 import os
+import subprocess
 import typing as t
 import warnings
+from urllib.parse import urljoin
 
 import cdsapi
 import urllib3
-from ecmwfapi import ECMWFService
+from ecmwfapi import ECMWFService, api
 
 from .config import Config, optimize_selection_partition
+from .util import retry_with_exponential_backoff
 
 warnings.simplefilter(
     "ignore", category=urllib3.connectionpool.InsecureRequestWarning)
@@ -55,8 +58,9 @@ def retrieve(self, dataset: str, selection: t.Dict, output: str) -> None:
         """Download from data source."""
         pass
 
+    @classmethod
     @abc.abstractmethod
-    def num_requests_per_key(self, dataset: str) -> int:
+    def num_requests_per_key(cls, dataset: str) -> int:
         """Specifies the number of workers to be used per api key for the dataset."""
         pass
 
@@ -108,7 +112,8 @@ def retrieve(self, dataset: str, selection: t.Dict, target: str) -> None:
     def license_url(self):
         return 'https://cds.climate.copernicus.eu/api/v2/terms/static/licence-to-use-copernicus-products.pdf'
 
-    def num_requests_per_key(self, dataset: str) -> int:
+    @classmethod
+    def num_requests_per_key(cls, dataset: str) -> int:
         """Number of requests per key from the CDS API.
 
         CDS has dynamic, data-specific limits, defined here:
@@ -123,7 +128,7 @@ def num_requests_per_key(self, dataset: str) -> int:
         https://cds.climate.copernicus.eu/cdsapp#!/yourrequests
         """
         # TODO(#15): Parse live CDS limits API to set data-specific limits.
-        for internal_set in self.cds_hosted_datasets:
+        for internal_set in cls.cds_hosted_datasets:
             if dataset.startswith(internal_set):
                 return 5
         return 2
@@ -154,6 +159,80 @@ def __exit__(self, exc_type, exc_value, traceback):
         self._redirector.__exit__(exc_type, exc_value, traceback)
 
 
+class SplitMARSRequest(api.APIRequest):
+    """Extended MARS APIRequest class that separates fetch and download stage."""
+    @retry_with_exponential_backoff
+    def _download(self, url, path: str, size: int) -> None:
+        self.log(
+            "Transferring %s into %s" % (self._bytename(size), path)
+        )
+        self.log("From %s" % (url,))
+
+        dir_path, file_name = os.path.split(path)
+        try:
+            subprocess.run(
+                ['aria2c', '-x', '16', '-s', '16', url, '-d', dir_path, '-o', file_name, '--allow-overwrite'],
+                check=True,
+                capture_output=True)
+        except subprocess.CalledProcessError as e:
+            self.log(f'Failed download from ECMWF server {url!r} to {path!r} due to {e.stderr.decode("utf-8")}')
+
+    def fetch(self, request: t.Dict) -> t.Dict:
+        status = None
+
+        self.connection.submit("%s/%s/requests" % (self.url, self.service), request)
+        self.log("Request submitted")
+        self.log("Request id: " + self.connection.last.get("name"))
+        if self.connection.status != status:
+            status = self.connection.status
+            self.log("Request is %s" % (status,))
+
+        while not self.connection.ready():
+            if self.connection.status != status:
+                status = self.connection.status
+                self.log("Request is %s" % (status,))
+            self.connection.wait()
+
+        if self.connection.status != status:
+            status = self.connection.status
+            self.log("Request is %s" % (status,))
+
+        result = self.connection.result()
+        return result
+
+    def download(self, result: t.Dict, target: t.Optional[str] = None) -> None:
+        if target:
+            if os.path.exists(target):
+                # Empty the target file, if it already exists, otherwise the
+                # transfer below might be fooled into thinking we're resuming
+                # an interrupted download.
+                open(target, "w").close()
+
+            self._download(urljoin(self.url, result["href"]), target, result["size"])
+        self.connection.cleanup()
+
+
+class MARSECMWFServiceExtended(ECMWFService):
+    """Extended MARS ECMFService class that separates fetch and download stage."""
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.c = SplitMARSRequest(
+            self.url,
+            "services/%s" % (self.service,),
+            email=self.email,
+            key=self.key,
+            log=self.log,
+            verbose=self.verbose,
+            quiet=self.quiet,
+        )
+
+    def fetch(self, req: t.Dict) -> t.Dict:
+        return self.c.fetch(req)
+
+    def download(self, res: t.Dict, target: str) -> None:
+        self.c.download(res, target)
+
+
 class MarsClient(Client):
     """A client to access data from the Meteorological Archival and Retrieval System (MARS).
 
@@ -176,25 +255,27 @@ class MarsClient(Client):
 
     def __init__(self, config: Config, level: int = logging.INFO) -> None:
         super().__init__(config, level)
-        self.c = ECMWFService(
+
+    def retrieve(self, dataset: str, selection: t.Dict, output: str) -> None:
+        self.c = MARSECMWFServiceExtended(
             "mars",
-            key=config.kwargs.get('api_key', os.environ.get("MARSAPI_KEY")),
-            url=config.kwargs.get('api_url', os.environ.get("MARSAPI_URL")),
-            email=config.kwargs.get('api_email', os.environ.get("MARSAPI_EMAIL")),
+            key=self.config.kwargs.get('api_key', os.environ.get("MARSAPI_KEY")),
+            url=self.config.kwargs.get('api_url', os.environ.get("MARSAPI_URL")),
+            email=self.config.kwargs.get('api_email', os.environ.get("MARSAPI_EMAIL")),
             log=self.logger.debug,
-            verbose=True
+            verbose=True,
         )
-
-    def retrieve(self, dataset: str, selection: t.Dict, output: str) -> None:
         selection_ = optimize_selection_partition(selection)
         with StdoutLogger(self.logger, level=logging.DEBUG):
-            self.c.execute(req=selection_, target=output)
+            result = self.c.fetch(req=selection_)
+            self.c.download(result, target=output)
 
     @property
     def license_url(self):
         return 'https://apps.ecmwf.int/datasets/licences/general/'
 
-    def num_requests_per_key(self, dataset: str) -> int:
+    @classmethod
+    def num_requests_per_key(cls, dataset: str) -> int:
         """Number of requests per key (or user) for the Mars API.
 
         Mars allows 2 active requests per user and 20 queued requests per user, as of Sept 27, 2021.
@@ -221,7 +302,8 @@ def retrieve(self, dataset: str, selection: t.Dict, output: str) -> None:
     def license_url(self):
         return 'lorem ipsum'
 
-    def num_requests_per_key(self, dataset: str) -> int:
+    @classmethod
+    def num_requests_per_key(cls, dataset: str) -> int:
         return 1
 
 

weather_dl/download_pipeline/clients_test.py

@@ -15,29 +15,20 @@
 import unittest
 
 from .clients import FakeClient, CdsClient, MarsClient
-from .config import Config
 
 
 class MaxWorkersTest(unittest.TestCase):
     def test_cdsclient_internal(self):
-        client = CdsClient(Config.from_dict({'parameters': {'api_url': 'url', 'api_key': 'key'}}))
-        self.assertEqual(
-            client.num_requests_per_key("reanalysis-era5-some-data"), 5)
+        self.assertEqual(CdsClient.num_requests_per_key("reanalysis-era5-some-data"), 5)
 
     def test_cdsclient_mars_hosted(self):
-        client = CdsClient(Config.from_dict({'parameters': {'api_url': 'url', 'api_key': 'key'}}))
-        self.assertEqual(
-            client.num_requests_per_key("reanalysis-carra-height-levels"), 2)
+        self.assertEqual(CdsClient.num_requests_per_key("reanalysis-carra-height-levels"), 2)
 
     def test_marsclient(self):
-        client = MarsClient(Config.from_dict({'parameters': {}}))
-        self.assertEqual(
-            client.num_requests_per_key("reanalysis-era5-some-data"), 2)
+        self.assertEqual(MarsClient.num_requests_per_key("reanalysis-era5-some-data"), 2)
 
     def test_fakeclient(self):
-        client = FakeClient(Config.from_dict({'parameters': {}}))
-        self.assertEqual(
-            client.num_requests_per_key("reanalysis-era5-some-data"), 1)
+        self.assertEqual(FakeClient.num_requests_per_key("reanalysis-era5-some-data"), 1)
 
 
 if __name__ == '__main__':