From c7e3434b3e7d814c00e9609db4bb2a54d8eb8bab Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Fri, 16 Jul 2021 15:06:08 +0200
Subject: [PATCH 1/8] Added `stdout`, `stderr` argument to BmiClientSingularity
 constructor

---
 grpc4bmi/bmi_client_singularity.py | 45 ++++++++++++++++++++++++++----
 test/test_singularity.py           | 34 +++++++++++++++++++++-
 2 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index 8d852a7..48bb3a1 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -1,9 +1,9 @@
+import logging
 import os
+import subprocess
 import time
 from os.path import abspath
-import subprocess
-import logging
-from typing import Iterable
+from typing import Iterable, BinaryIO, TextIO, Union, Literal
 
 import semver
 from typeguard import check_argument_types, qualified_name
@@ -23,6 +23,21 @@ def check_singularity_version():
     return True
 
 
+class DeadSingularityContainerException(ChildProcessError):
+    """
+    Exception for when a Docker container has died.
+
+    Args:
+        message (str): Human readable error message
+        exitcode (int): The non-zero exit code of the container
+
+    """
+    def __init__(self, message, exitcode, *args):
+        super().__init__(message, *args)
+        #: Exit code of container
+        self.exitcode = exitcode
+
+
 class BmiClientSingularity(BmiClient):
     """BMI GRPC client for singularity server processes
     During initialization launches a singularity container with run-bmi-server as its command.
@@ -76,6 +91,19 @@ class BmiClientSingularity(BmiClient):
             By default will try forever to connect to gRPC server inside container.
             Set to low number to escape endless wait.
 
+        stderr (Union[None, BinaryIO, TextIO, int]): Redirect stderr of singularity container.
+
+            By default will inherit stderr file handle from current Python process.
+            Can be set to a file object to log stdout to a file.
+            Or can be set to `subprocess.DEVNULL` to redirect to null device never to be seen again.
+            Or can be set to `subprocess.STDOUT` to redirect the stderr to stdout.
+
+        stdout (Union[None, BinaryIO, TextIO, int]): Redirect stdout of singularity container.
+
+            By default will inherit stdout file handle from current Python process.
+            Can be set to a file object to log stdout to a file.
+            Or can be set to `subprocess.DEVNULL` to redirect to null device never to be seen again.
+
     **Example 1: Config file already inside image**
 
     MARRMoT has an `example config file <https://github.com/wknoben/MARRMoT/blob/master/BMI/Config/BMI_testcase_m01_BuffaloRiver_TN_USA.mat>`_ inside its Docker image.
@@ -176,7 +204,11 @@ class BmiClientSingularity(BmiClient):
         del client_rhine
 
     """
-    def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(), delay=0, timeout=None):
+
+    def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(), delay=0, timeout=None,
+                 stderr: Union[None, BinaryIO, TextIO, int] = None,
+                 stdout: Union[None, BinaryIO, TextIO, int] = None
+                 ):
         assert check_argument_types()
         if type(input_dirs) == str:
             msg = f'type of argument "input_dirs" must be collections.abc.Iterable; ' \
@@ -207,8 +239,11 @@ def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(
         args += ["--pwd", self.work_dir]
         args.append(image)
         logging.info(f'Running {image} singularity container on port {port}')
-        self.container = subprocess.Popen(args, preexec_fn=os.setsid)
+        self.container = subprocess.Popen(args, preexec_fn=os.setsid, stderr=stderr, stdout=stdout)
         time.sleep(delay)
+        returncode = self.container.poll()
+        if returncode is not None:
+            raise DeadSingularityContainerException(f'singularity container {image} prematurely exited with code {returncode}', returncode)
         super(BmiClientSingularity, self).__init__(BmiClient.create_grpc_channel(port=port, host=host), timeout=timeout)
 
     def __del__(self):
diff --git a/test/test_singularity.py b/test/test_singularity.py
index 4a42d04..ce05a38 100644
--- a/test/test_singularity.py
+++ b/test/test_singularity.py
@@ -1,3 +1,4 @@
+import os
 import subprocess
 from tempfile import TemporaryDirectory
 from textwrap import dedent
@@ -7,7 +8,7 @@
 from nbconvert.preprocessors import ExecutePreprocessor
 from nbformat.v4 import new_notebook, new_code_cell
 
-from grpc4bmi.bmi_client_singularity import BmiClientSingularity
+from grpc4bmi.bmi_client_singularity import BmiClientSingularity, DeadSingularityContainerException
 from test.conftest import write_config, write_datafile
 
 IMAGE_NAME = "docker://ewatercycle/walrus-grpc4bmi:v0.2.0"
@@ -175,6 +176,37 @@ def test_inputdirs_as_number(self, tmp_path):
             BmiClientSingularity(image=IMAGE_NAME, input_dirs=42, work_dir=some_dir)
 
 
+class TestRedirectOutput:
+    EXPECTED = 'Hello from Docker!'
+
+    @pytest.fixture
+    def image(self):
+        hello_image = 'docker://hello-world'
+        # Cache image, first test does not use delay time to build image
+        os.system(f'singularity run {hello_image}')
+        return hello_image
+
+    def test_default(self, image, tmp_path, capfd):
+        with pytest.raises(DeadSingularityContainerException):
+            BmiClientSingularity(image=image, work_dir=str(tmp_path), delay=2)
+
+        assert self.EXPECTED in capfd.readouterr().out
+
+    def test_textfile(self, image, tmp_path):
+        mylog = tmp_path / 'mylog.txt'
+
+        with mylog.open('w') as f, pytest.raises(DeadSingularityContainerException):
+            BmiClientSingularity(image=image, work_dir=str(tmp_path), stdout=f, delay=2)
+
+        assert self.EXPECTED in mylog.read_text()
+
+    def test_devnull(self, image, tmp_path, capfd):
+        with pytest.raises(DeadSingularityContainerException):
+            BmiClientSingularity(image=image, work_dir=str(tmp_path), stdout=subprocess.DEVNULL, delay=2)
+
+        assert self.EXPECTED not in capfd.readouterr().out
+
+
 @pytest.fixture
 def notebook(tmp_path):
     tmp_path.mkdir(exist_ok=True)

From 20f23fc0c4811d0d5abc7241d223417b2ba984b9 Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Fri, 16 Jul 2021 15:07:42 +0200
Subject: [PATCH 2/8] Use correct name

---
 grpc4bmi/bmi_client_singularity.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index 48bb3a1..aeb8239 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -25,7 +25,7 @@ def check_singularity_version():
 
 class DeadSingularityContainerException(ChildProcessError):
     """
-    Exception for when a Docker container has died.
+    Exception for when a Singularity container has died.
 
     Args:
         message (str): Human readable error message

From d6e632662f379c31e149f9ebdf76b6268a1a975c Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Fri, 16 Jul 2021 15:15:01 +0200
Subject: [PATCH 3/8] Unused import

---
 grpc4bmi/bmi_client_singularity.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index aeb8239..0ee0824 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -3,7 +3,7 @@
 import subprocess
 import time
 from os.path import abspath
-from typing import Iterable, BinaryIO, TextIO, Union, Literal
+from typing import Iterable, BinaryIO, TextIO, Union
 
 import semver
 from typeguard import check_argument_types, qualified_name

From bca8189dee626e90616defbbb50711ee341e1d93 Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Mon, 19 Jul 2021 15:43:14 +0200
Subject: [PATCH 4/8] Silence semver deprecation warning

---
 grpc4bmi/bmi_client_singularity.py | 8 +++++---
 setup.py                           | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index 0ee0824..3957b75 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -10,7 +10,7 @@
 
 from grpc4bmi.bmi_grpc_client import BmiClient
 
-REQUIRED_SINGULARITY_VERSION = '>=3.6.0'
+REQUIRED_SINGULARITY_VERSION = '3.6.0'
 
 
 def check_singularity_version():
@@ -18,8 +18,10 @@ def check_singularity_version():
     (stdout, _stderr) = p.communicate()
     if p.returncode != 0:
         raise Exception('Unable to determine singularity version')
-    if not semver.match(stdout.decode('utf-8').replace('_', '-'), REQUIRED_SINGULARITY_VERSION):
-        raise Exception(f'Wrong version of singularity found, require version {REQUIRED_SINGULARITY_VERSION}')
+    local_version = semver.VersionInfo.parse(stdout.decode('utf-8').replace('_', '-'))
+    if local_version < REQUIRED_SINGULARITY_VERSION:
+        raise Exception(f'Wrong version ({local_version}) of singularity found, '
+                        f'require version {REQUIRED_SINGULARITY_VERSION}')
     return True
 
 
diff --git a/setup.py b/setup.py
index 3342c21..266e5f3 100644
--- a/setup.py
+++ b/setup.py
@@ -31,7 +31,7 @@ def read(fname):
           "numpy",
           "docker",
           "basic-modeling-interface",
-          "semver",
+          "semver>=2.10.0",
           "typeguard",
       ],
       extras_require={

From e55e7dcfb07da6700ee5d9233ce390a3a992a8cf Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Mon, 19 Jul 2021 15:43:42 +0200
Subject: [PATCH 5/8] Add logs() to BmiClientSingularity and BmiClientDocker

In BmiClientSingularity:
Removed stderr+stdout passthrough in favor of grpc4bmi capturing everything by default
with option to disable log capture
---
 grpc4bmi/bmi_client_docker.py      |  9 +++++
 grpc4bmi/bmi_client_singularity.py | 63 +++++++++++++++++++++---------
 test/test_docker.py                |  6 +++
 test/test_singularity.py           | 18 +++------
 4 files changed, 66 insertions(+), 30 deletions(-)

diff --git a/grpc4bmi/bmi_client_docker.py b/grpc4bmi/bmi_client_docker.py
index 065f78f..a37c1b5 100644
--- a/grpc4bmi/bmi_client_docker.py
+++ b/grpc4bmi/bmi_client_docker.py
@@ -19,6 +19,7 @@ class DeadDockerContainerException(ChildProcessError):
         logs (str): Logs the container produced
 
     """
+
     def __init__(self, message, exitcode, logs, *args):
         super().__init__(message, *args)
         #: Exit code of container
@@ -62,6 +63,7 @@ class BmiClientDocker(BmiClient):
 
     See :py:class:`grpc4bmi.bmi_client_singularity.BmiClientSingularity` for examples using `input_dirs` and `work_dir`.
     """
+
     def __init__(self, image: str, work_dir: str, image_port=50051, host=None,
                  input_dirs: Iterable[str] = tuple(),
                  user=os.getuid(), remove=False, delay=5,
@@ -111,3 +113,10 @@ def __del__(self):
 
     def get_value_ref(self, var_name):
         raise NotImplementedError("Cannot exchange memory references across process boundary")
+
+    def logs(self) -> str:
+        """Returns complete combined stdout and stderr written by the Docker container.
+        """
+        if hasattr(self, "container"):
+            return self.container.logs().decode('utf8')
+        return ''
diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index 3957b75..673b17d 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -3,7 +3,8 @@
 import subprocess
 import time
 from os.path import abspath
-from typing import Iterable, BinaryIO, TextIO, Union
+from tempfile import SpooledTemporaryFile
+from typing import Iterable
 
 import semver
 from typeguard import check_argument_types, qualified_name
@@ -32,12 +33,15 @@ class DeadSingularityContainerException(ChildProcessError):
     Args:
         message (str): Human readable error message
         exitcode (int): The non-zero exit code of the container
+        logs (str): Logs the container produced
 
     """
-    def __init__(self, message, exitcode, *args):
+    def __init__(self, message, exitcode, logs, *args):
         super().__init__(message, *args)
         #: Exit code of container
         self.exitcode = exitcode
+        #: Stdout and stderr of container
+        self.logs = logs
 
 
 class BmiClientSingularity(BmiClient):
@@ -93,18 +97,11 @@ class BmiClientSingularity(BmiClient):
             By default will try forever to connect to gRPC server inside container.
             Set to low number to escape endless wait.
 
-        stderr (Union[None, BinaryIO, TextIO, int]): Redirect stderr of singularity container.
+        capture_logs (bool): Whether to capture stdout and stderr of container .
 
-            By default will inherit stderr file handle from current Python process.
-            Can be set to a file object to log stdout to a file.
-            Or can be set to `subprocess.DEVNULL` to redirect to null device never to be seen again.
-            Or can be set to `subprocess.STDOUT` to redirect the stderr to stdout.
-
-        stdout (Union[None, BinaryIO, TextIO, int]): Redirect stdout of singularity container.
-
-            By default will inherit stdout file handle from current Python process.
-            Can be set to a file object to log stdout to a file.
-            Or can be set to `subprocess.DEVNULL` to redirect to null device never to be seen again.
+            If false then redirects output to null device never to be seen again.
+            If true then redirects output to temporary file which can be read with :py:func:`BmiClientSingularity.logs()`.
+            The temporary file gets removed when this object is deleted.
 
     **Example 1: Config file already inside image**
 
@@ -208,8 +205,7 @@ class BmiClientSingularity(BmiClient):
     """
 
     def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(), delay=0, timeout=None,
-                 stderr: Union[None, BinaryIO, TextIO, int] = None,
-                 stdout: Union[None, BinaryIO, TextIO, int] = None
+                 capture_logs=True,
                  ):
         assert check_argument_types()
         if type(input_dirs) == str:
@@ -232,7 +228,7 @@ def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(
                 raise NotADirectoryError(input_dir)
             args += ["--bind", f'{input_dir}:{input_dir}:ro']
         self.work_dir = abspath(work_dir)
-        if self.work_dir in set([abspath(d) for d in input_dirs]):
+        if self.work_dir in {abspath(d) for d in input_dirs}:
             raise ValueError('Found work_dir equal to one of the input directories. Please drop that input dir.')
         if not os.path.isdir(self.work_dir):
             raise NotADirectoryError(self.work_dir)
@@ -241,17 +237,48 @@ def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(
         args += ["--pwd", self.work_dir]
         args.append(image)
         logging.info(f'Running {image} singularity container on port {port}')
-        self.container = subprocess.Popen(args, preexec_fn=os.setsid, stderr=stderr, stdout=stdout)
+        if capture_logs:
+            self.logfile = SpooledTemporaryFile(max_size=2**16,  # keep until 65Kb in memory if bigger write to disk
+                                                prefix='grpc4bmi-singularity-log',
+                                                mode='w+t',
+                                                encoding='utf8')
+            stdout = self.logfile
+        else:
+            stdout = subprocess.DEVNULL
+        self.container = subprocess.Popen(args, preexec_fn=os.setsid, stderr=subprocess.STDOUT, stdout=stdout)
         time.sleep(delay)
         returncode = self.container.poll()
         if returncode is not None:
-            raise DeadSingularityContainerException(f'singularity container {image} prematurely exited with code {returncode}', returncode)
+            raise DeadSingularityContainerException(
+                f'singularity container {image} prematurely exited with code {returncode}',
+                returncode,
+                self.logs()
+            )
         super(BmiClientSingularity, self).__init__(BmiClient.create_grpc_channel(port=port, host=host), timeout=timeout)
 
     def __del__(self):
         if hasattr(self, "container"):
             self.container.terminate()
             self.container.wait()
+        if hasattr(self, "logfile"):
+            # Force deletion of log file
+            self.logfile.close()
 
     def get_value_ref(self, var_name):
         raise NotImplementedError("Cannot exchange memory references across process boundary")
+
+    def logs(self) -> str:
+        """Returns complete combined stdout and stderr written by the Singularity container.
+
+        When object was created with `log_enable=False` argument then always returns empty string.
+        """
+        if not hasattr(self, "logfile"):
+            return ''
+
+        current_position = self.logfile.tell()
+        # Read from start
+        self.logfile.seek(0)
+        content = self.logfile.read()
+        # Write from last position
+        self.logfile.seek(current_position)
+        return content
diff --git a/test/test_docker.py b/test/test_docker.py
index 522d66a..9ba7bff 100644
--- a/test/test_docker.py
+++ b/test/test_docker.py
@@ -105,3 +105,9 @@ def test_inputdirs_as_number(self, tmp_path):
         some_dir = str(tmp_path)
         with pytest.raises(TypeError, match='must be collections.abc.Iterable; got int instead'):
             BmiClientDocker(image=walrus_docker_image, input_dirs=42, work_dir=some_dir)
+
+    def test_logs(self, walrus_model, capfd):
+        logs = walrus_model.logs()
+
+        assert 'R[write to console]' in logs
+        assert 'R[write to console]' not in capfd.readouterr().out
diff --git a/test/test_singularity.py b/test/test_singularity.py
index ce05a38..378c962 100644
--- a/test/test_singularity.py
+++ b/test/test_singularity.py
@@ -187,24 +187,18 @@ def image(self):
         return hello_image
 
     def test_default(self, image, tmp_path, capfd):
-        with pytest.raises(DeadSingularityContainerException):
+        with pytest.raises(DeadSingularityContainerException) as excinf:
             BmiClientSingularity(image=image, work_dir=str(tmp_path), delay=2)
 
-        assert self.EXPECTED in capfd.readouterr().out
-
-    def test_textfile(self, image, tmp_path):
-        mylog = tmp_path / 'mylog.txt'
-
-        with mylog.open('w') as f, pytest.raises(DeadSingularityContainerException):
-            BmiClientSingularity(image=image, work_dir=str(tmp_path), stdout=f, delay=2)
-
-        assert self.EXPECTED in mylog.read_text()
+        assert self.EXPECTED not in capfd.readouterr().out
+        assert self.EXPECTED in excinf.value.logs
 
     def test_devnull(self, image, tmp_path, capfd):
-        with pytest.raises(DeadSingularityContainerException):
-            BmiClientSingularity(image=image, work_dir=str(tmp_path), stdout=subprocess.DEVNULL, delay=2)
+        with pytest.raises(DeadSingularityContainerException) as excinf:
+            BmiClientSingularity(image=image, work_dir=str(tmp_path), capture_logs=False, delay=2)
 
         assert self.EXPECTED not in capfd.readouterr().out
+        assert self.EXPECTED not in excinf.value.logs
 
 
 @pytest.fixture

From 659721a46dc41e0c279b0ba9bfeb45f83bd93477 Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Tue, 20 Jul 2021 09:23:22 +0200
Subject: [PATCH 6/8] Prep for 0.2.13 release

---
 setup.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup.py b/setup.py
index 266e5f3..2cc1766 100644
--- a/setup.py
+++ b/setup.py
@@ -11,7 +11,7 @@ def read(fname):
 
 
 setup(name="grpc4bmi",
-      version="0.2.12",
+      version="0.2.13",
       author="Gijs van den Oord",
       author_email="g.vandenoord@esciencecenter.nl",
       description="Run your BMI implementation in a separate process and expose it as BMI-python with GRPC",

From e9a38b5390d7d5d5a8bce951635cc00f6b5a9a13 Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Tue, 20 Jul 2021 09:24:18 +0200
Subject: [PATCH 7/8] Use own method

---
 grpc4bmi/bmi_client_docker.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grpc4bmi/bmi_client_docker.py b/grpc4bmi/bmi_client_docker.py
index a37c1b5..f49b777 100644
--- a/grpc4bmi/bmi_client_docker.py
+++ b/grpc4bmi/bmi_client_docker.py
@@ -101,7 +101,7 @@ def __init__(self, image: str, work_dir: str, image_port=50051, host=None,
             self.container.reload()
             if self.container.status == 'exited':
                 exitcode = self.container.attrs["State"]["ExitCode"]
-                logs = self.container.logs()
+                logs = self.logs()
                 msg = f'Failed to start Docker container with image {image}, Container log: {logs}'
                 raise DeadDockerContainerException(msg, exitcode, logs)
 

From 6001693b17a303dba46d92219464eb6917b0aeee Mon Sep 17 00:00:00 2001
From: Stefan Verhoeven <stefan.verhoeven@gmail.com>
Date: Tue, 20 Jul 2021 09:36:17 +0200
Subject: [PATCH 8/8] Dedup container exception

---
 grpc4bmi/bmi_client_docker.py      | 22 ++--------------------
 grpc4bmi/bmi_client_singularity.py | 29 ++++++-----------------------
 grpc4bmi/exceptions.py             | 21 +++++++++++++++++++++
 test/test_docker.py                |  9 +++++----
 test/test_singularity.py           |  7 ++++---
 5 files changed, 38 insertions(+), 50 deletions(-)
 create mode 100644 grpc4bmi/exceptions.py

diff --git a/grpc4bmi/bmi_client_docker.py b/grpc4bmi/bmi_client_docker.py
index f49b777..8ccc23b 100644
--- a/grpc4bmi/bmi_client_docker.py
+++ b/grpc4bmi/bmi_client_docker.py
@@ -7,25 +7,7 @@
 from typeguard import check_argument_types, qualified_name
 
 from grpc4bmi.bmi_grpc_client import BmiClient
-
-
-class DeadDockerContainerException(ChildProcessError):
-    """
-    Exception for when a Docker container has died.
-
-    Args:
-        message (str): Human readable error message
-        exitcode (int): The non-zero exit code of the container
-        logs (str): Logs the container produced
-
-    """
-
-    def __init__(self, message, exitcode, logs, *args):
-        super().__init__(message, *args)
-        #: Exit code of container
-        self.exitcode = exitcode
-        #: Stdout and stderr of container
-        self.logs = logs
+from grpc4bmi.exceptions import DeadContainerException
 
 
 class BmiClientDocker(BmiClient):
@@ -103,7 +85,7 @@ def __init__(self, image: str, work_dir: str, image_port=50051, host=None,
                 exitcode = self.container.attrs["State"]["ExitCode"]
                 logs = self.logs()
                 msg = f'Failed to start Docker container with image {image}, Container log: {logs}'
-                raise DeadDockerContainerException(msg, exitcode, logs)
+                raise DeadContainerException(msg, exitcode, logs)
 
         super(BmiClientDocker, self).__init__(BmiClient.create_grpc_channel(port=port, host=host), timeout=timeout)
 
diff --git a/grpc4bmi/bmi_client_singularity.py b/grpc4bmi/bmi_client_singularity.py
index 673b17d..e0928c6 100644
--- a/grpc4bmi/bmi_client_singularity.py
+++ b/grpc4bmi/bmi_client_singularity.py
@@ -10,6 +10,7 @@
 from typeguard import check_argument_types, qualified_name
 
 from grpc4bmi.bmi_grpc_client import BmiClient
+from grpc4bmi.exceptions import DeadContainerException, SingularityVersionException
 
 REQUIRED_SINGULARITY_VERSION = '3.6.0'
 
@@ -18,32 +19,14 @@ def check_singularity_version():
     p = subprocess.Popen(['singularity', 'version'], stdout=subprocess.PIPE)
     (stdout, _stderr) = p.communicate()
     if p.returncode != 0:
-        raise Exception('Unable to determine singularity version')
+        raise SingularityVersionException('Unable to determine singularity version')
     local_version = semver.VersionInfo.parse(stdout.decode('utf-8').replace('_', '-'))
     if local_version < REQUIRED_SINGULARITY_VERSION:
-        raise Exception(f'Wrong version ({local_version}) of singularity found, '
-                        f'require version {REQUIRED_SINGULARITY_VERSION}')
+        raise SingularityVersionException(f'Wrong version ({local_version}) of singularity found, '
+                                          f'require version {REQUIRED_SINGULARITY_VERSION}')
     return True
 
 
-class DeadSingularityContainerException(ChildProcessError):
-    """
-    Exception for when a Singularity container has died.
-
-    Args:
-        message (str): Human readable error message
-        exitcode (int): The non-zero exit code of the container
-        logs (str): Logs the container produced
-
-    """
-    def __init__(self, message, exitcode, logs, *args):
-        super().__init__(message, *args)
-        #: Exit code of container
-        self.exitcode = exitcode
-        #: Stdout and stderr of container
-        self.logs = logs
-
-
 class BmiClientSingularity(BmiClient):
     """BMI GRPC client for singularity server processes
     During initialization launches a singularity container with run-bmi-server as its command.
@@ -238,7 +221,7 @@ def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(
         args.append(image)
         logging.info(f'Running {image} singularity container on port {port}')
         if capture_logs:
-            self.logfile = SpooledTemporaryFile(max_size=2**16,  # keep until 65Kb in memory if bigger write to disk
+            self.logfile = SpooledTemporaryFile(max_size=2 ** 16,  # keep until 65Kb in memory if bigger write to disk
                                                 prefix='grpc4bmi-singularity-log',
                                                 mode='w+t',
                                                 encoding='utf8')
@@ -249,7 +232,7 @@ def __init__(self, image: str, work_dir: str, input_dirs: Iterable[str] = tuple(
         time.sleep(delay)
         returncode = self.container.poll()
         if returncode is not None:
-            raise DeadSingularityContainerException(
+            raise DeadContainerException(
                 f'singularity container {image} prematurely exited with code {returncode}',
                 returncode,
                 self.logs()
diff --git a/grpc4bmi/exceptions.py b/grpc4bmi/exceptions.py
new file mode 100644
index 0000000..9d63cd9
--- /dev/null
+++ b/grpc4bmi/exceptions.py
@@ -0,0 +1,21 @@
+
+class DeadContainerException(ChildProcessError):
+    """
+    Exception for when a container has died.
+
+    Args:
+        message (str): Human readable error message
+        exitcode (int): The non-zero exit code of the container
+        logs (str): Logs the container produced
+
+    """
+    def __init__(self, message, exitcode, logs, *args):
+        super().__init__(message, *args)
+        #: Exit code of container
+        self.exitcode = exitcode
+        #: Stdout and stderr of container
+        self.logs = logs
+
+
+class SingularityVersionException(ValueError):
+    pass
diff --git a/test/test_docker.py b/test/test_docker.py
index 9ba7bff..ce79d6f 100644
--- a/test/test_docker.py
+++ b/test/test_docker.py
@@ -3,7 +3,8 @@
 import docker
 import pytest
 
-from grpc4bmi.bmi_client_docker import BmiClientDocker, DeadDockerContainerException
+from grpc4bmi.bmi_client_docker import BmiClientDocker
+from grpc4bmi.exceptions import DeadContainerException
 
 walrus_docker_image = 'ewatercycle/walrus-grpc4bmi:v0.2.0'
 
@@ -79,12 +80,12 @@ def test_workdir_absent(self, tmp_path):
 
     def test_container_start_failure(self, exit_container, tmp_path):
         expected = r"Failed to start Docker container with image"
-        with pytest.raises(DeadDockerContainerException, match=expected) as excinfo:
+        with pytest.raises(DeadContainerException, match=expected) as excinfo:
             BmiClientDocker(image=exit_container, work_dir=str(tmp_path))
 
         assert excinfo.value.exitcode == 25
-        assert b'my stderr' in excinfo.value.logs
-        assert b'my stdout' in excinfo.value.logs
+        assert 'my stderr' in excinfo.value.logs
+        assert 'my stdout' in excinfo.value.logs
 
     def test_same_inputdir_and_workdir(self, tmp_path):
         some_dir = str(tmp_path)
diff --git a/test/test_singularity.py b/test/test_singularity.py
index 378c962..b593a9c 100644
--- a/test/test_singularity.py
+++ b/test/test_singularity.py
@@ -8,7 +8,8 @@
 from nbconvert.preprocessors import ExecutePreprocessor
 from nbformat.v4 import new_notebook, new_code_cell
 
-from grpc4bmi.bmi_client_singularity import BmiClientSingularity, DeadSingularityContainerException
+from grpc4bmi.bmi_client_singularity import BmiClientSingularity
+from grpc4bmi.exceptions import DeadContainerException
 from test.conftest import write_config, write_datafile
 
 IMAGE_NAME = "docker://ewatercycle/walrus-grpc4bmi:v0.2.0"
@@ -187,14 +188,14 @@ def image(self):
         return hello_image
 
     def test_default(self, image, tmp_path, capfd):
-        with pytest.raises(DeadSingularityContainerException) as excinf:
+        with pytest.raises(DeadContainerException) as excinf:
             BmiClientSingularity(image=image, work_dir=str(tmp_path), delay=2)
 
         assert self.EXPECTED not in capfd.readouterr().out
         assert self.EXPECTED in excinf.value.logs
 
     def test_devnull(self, image, tmp_path, capfd):
-        with pytest.raises(DeadSingularityContainerException) as excinf:
+        with pytest.raises(DeadContainerException) as excinf:
             BmiClientSingularity(image=image, work_dir=str(tmp_path), capture_logs=False, delay=2)
 
         assert self.EXPECTED not in capfd.readouterr().out