6 files changed, 757 insertions, 0 deletions
diff --git a/tools/tryselect/util/__init__.py b/tools/tryselect/util/__init__.py
new file mode 100644
index 0000000000..c580d191c1
--- /dev/null
+++ b/tools/tryselect/util/__init__.py
@@ -0,0 +1,3 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
diff --git a/tools/tryselect/util/dicttools.py b/tools/tryselect/util/dicttools.py
new file mode 100644
index 0000000000..465e4a43de
--- /dev/null
+++ b/tools/tryselect/util/dicttools.py
@@ -0,0 +1,50 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import copy
+
+
+def merge_to(source, dest):
+    """
+    Merge dict and arrays (override scalar values)
+
+    Keys from source override keys from dest, and elements from lists in source
+    are appended to lists in dest.
+
+    :param dict source: to copy from
+    :param dict dest: to copy to (modified in place)
+    """
+
+    for key, value in source.items():
+        # Override mismatching or empty types
+        if type(value) != type(dest.get(key)):  # noqa
+            dest[key] = source[key]
+            continue
+
+        # Merge dict
+        if isinstance(value, dict):
+            merge_to(value, dest[key])
+            continue
+
+        if isinstance(value, list):
+            dest[key] = dest[key] + source[key]
+            continue
+
+        dest[key] = source[key]
+
+    return dest
+
+
+def merge(*objects):
+    """
+    Merge the given objects, using the semantics described for merge_to, with
+    objects later in the list taking precedence.  From an inheritance
+    perspective, "parents" should be listed before "children".
+
+    Returns the result without modifying any arguments.
+    """
+    if len(objects) == 1:
+        return copy.deepcopy(objects[0])
+    return merge_to(objects[-1], merge(*objects[:-1]))
diff --git a/tools/tryselect/util/estimates.py b/tools/tryselect/util/estimates.py
new file mode 100644
index 0000000000..a15ad72831
--- /dev/null
+++ b/tools/tryselect/util/estimates.py
@@ -0,0 +1,124 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import json
+import os
+from datetime import datetime, timedelta
+
+TASK_DURATION_CACHE = "task_duration_history.json"
+GRAPH_QUANTILE_CACHE = "graph_quantile_cache.csv"
+TASK_DURATION_TAG_FILE = "task_duration_tag.json"
+
+
+def find_all_dependencies(graph, tasklist):
+    all_dependencies = dict()
+
+    def find_dependencies(task):
+        dependencies = set()
+        if task in all_dependencies:
+            return all_dependencies[task]
+        if task not in graph:
+            # Don't add tasks (and so durations) for
+            # things optimised out.
+            return dependencies
+        dependencies.add(task)
+        for dep in graph.get(task, list()):
+            all_dependencies[dep] = find_dependencies(dep)
+            dependencies.update(all_dependencies[dep])
+        return dependencies
+
+    full_deps = set()
+    for task in tasklist:
+        full_deps.update(find_dependencies(task))
+
+    # Since these have been asked for, they're not inherited dependencies.
+    return sorted(full_deps - set(tasklist))
+
+
+def find_longest_path(graph, tasklist, duration_data):
+    dep_durations = dict()
+
+    def find_dependency_durations(task):
+        if task in dep_durations:
+            return dep_durations[task]
+
+        durations = [find_dependency_durations(dep) for dep in graph.get(task, list())]
+        durations.append(0.0)
+        md = max(durations) + duration_data.get(task, 0.0)
+        dep_durations[task] = md
+        return md
+
+    longest_paths = [find_dependency_durations(task) for task in tasklist]
+    # Default in case there are no tasks
+    if longest_paths:
+        return max(longest_paths)
+    else:
+        return 0
+
+
+def determine_percentile(quantiles_file, duration):
+    duration = duration.total_seconds()
+
+    with open(quantiles_file) as f:
+        f.readline()  # skip header
+        boundaries = [float(l.strip()) for l in f.readlines()]
+
+    boundaries.sort()
+    for i, v in enumerate(boundaries):
+        if duration < v:
+            break
+    # Estimate percentile from len(boundaries)-quantile
+    return int(100 * i / len(boundaries))
+
+
+def task_duration_data(cache_dir):
+    with open(os.path.join(cache_dir, TASK_DURATION_CACHE)) as f:
+        return json.load(f)
+
+
+def duration_summary(graph_cache_file, tasklist, cache_dir):
+    durations = task_duration_data(cache_dir)
+
+    graph = dict()
+    if graph_cache_file:
+        with open(graph_cache_file) as f:
+            graph = json.load(f)
+    dependencies = find_all_dependencies(graph, tasklist)
+    longest_path = find_longest_path(graph, tasklist, durations)
+    dependency_duration = 0.0
+    for task in dependencies:
+        dependency_duration += int(durations.get(task, 0.0))
+
+    total_requested_duration = 0.0
+    for task in tasklist:
+        duration = int(durations.get(task, 0.0))
+        total_requested_duration += duration
+    output = dict()
+
+    total_requested_duration = timedelta(seconds=total_requested_duration)
+    total_dependency_duration = timedelta(seconds=dependency_duration)
+
+    output["selected_duration"] = total_requested_duration
+    output["dependency_duration"] = total_dependency_duration
+    output["dependency_count"] = len(dependencies)
+    output["selected_count"] = len(tasklist)
+
+    percentile = None
+    graph_quantile_cache = os.path.join(cache_dir, GRAPH_QUANTILE_CACHE)
+    if os.path.isfile(graph_quantile_cache):
+        percentile = determine_percentile(
+            graph_quantile_cache, total_dependency_duration + total_requested_duration
+        )
+    if percentile:
+        output["percentile"] = percentile
+
+    output["wall_duration_seconds"] = timedelta(seconds=int(longest_path))
+    output["eta_datetime"] = datetime.now() + timedelta(seconds=longest_path)
+
+    output["task_durations"] = {
+        task: int(durations.get(task, 0.0)) for task in tasklist
+    }
+
+    return output
diff --git a/tools/tryselect/util/fzf.py b/tools/tryselect/util/fzf.py
new file mode 100644
index 0000000000..63318fce18
--- /dev/null
+++ b/tools/tryselect/util/fzf.py
@@ -0,0 +1,424 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import os
+import platform
+import shutil
+import subprocess
+import sys
+
+import mozfile
+import six
+from gecko_taskgraph.target_tasks import filter_by_uncommon_try_tasks
+from mach.util import get_state_dir
+from mozboot.util import http_download_and_save
+from mozbuild.base import MozbuildObject
+from mozterm import Terminal
+from packaging.version import Version
+
+from ..push import check_working_directory
+from ..tasks import generate_tasks
+from ..util.manage_estimates import (
+    download_task_history_data,
+    make_trimmed_taskgraph_cache,
+)
+
+terminal = Terminal()
+
+here = os.path.abspath(os.path.dirname(__file__))
+build = MozbuildObject.from_environment(cwd=here)
+
+PREVIEW_SCRIPT = os.path.join(build.topsrcdir, "tools/tryselect/selectors/preview.py")
+
+FZF_MIN_VERSION = "0.20.0"
+FZF_CURRENT_VERSION = "0.29.0"
+
+# It would make more sense to have the full filename be the key; but that makes
+# the line too long and ./mach lint and black can't agree about what to about that.
+# You can get these from the github release, e.g.
+#          https://github.com/junegunn/fzf/releases/download/0.24.1/fzf_0.24.1_checksums.txt
+# However the darwin releases may not be included, so double check you have everything
+FZF_CHECKSUMS = {
+    "linux_armv5.tar.gz": "61d3c2aa77b977ba694836fd1134da9272bd97ee490ececaf87959b985820111",
+    "linux_armv6.tar.gz": "db6b30fcbbd99ac4cf7e3ff6c5db1d3c0afcbe37d10ec3961bdc43e8c4f2e4f9",
+    "linux_armv7.tar.gz": "ed86f0e91e41d2cea7960a78e3eb175dc2a5fc1510380c195d0c3559bfdc701c",
+    "linux_arm64.tar.gz": "47988d8b68905541cbc26587db3ed1cfa8bc3aa8da535120abb4229b988f259e",
+    "linux_amd64.tar.gz": "0106f458b933be65edb0e8f0edb9a16291a79167836fd26a77ff5496269b5e9a",
+    "windows_armv5.zip": "08eaac45b3600d82608d292c23e7312696e7e11b6278b292feba25e8eb91c712",
+    "windows_armv6.zip": "8b6618726a9d591a45120fddebc29f4164e01ce6639ed9aa8fc79ab03eefcfed",
+    "windows_armv7.zip": "c167117b4c08f4f098446291115871ce5f14a8a8b22f0ca70e1b4342452ab5d7",
+    "windows_arm64.zip": "0cda7bf68850a3e867224a05949612405e63a4421d52396c1a6c9427d4304d72",
+    "windows_amd64.zip": "f0797ceee089017108c80b09086c71b8eec43d4af11ce939b78b1d5cfd202540",
+    "darwin_arm64.zip": "2571b4d381f1fc691e7603bbc8113a67116da2404751ebb844818d512dd62b4b",
+    "darwin_amd64.zip": "bc541e8ae0feb94efa96424bfe0b944f746db04e22f5cccfe00709925839a57f",
+    "openbsd_amd64.tar.gz": "b62343827ff83949c09d5e2c8ca0c1198d05f733c9a779ec37edd840541ccdab",
+    "freebsd_amd64.tar.gz": "f0367f2321c070d103589c7c7eb6a771bc7520820337a6c2fbb75be37ff783a9",
+}
+
+FZF_INSTALL_MANUALLY = """
+The `mach try fuzzy` command depends on fzf. Please install it following the
+appropriate instructions for your platform:
+
+    https://github.com/junegunn/fzf#installation
+
+Only the binary is required, if you do not wish to install the shell and
+editor integrations, download the appropriate binary and put it on your $PATH:
+
+    https://github.com/junegunn/fzf/releases
+""".lstrip()
+
+FZF_COULD_NOT_DETERMINE_PLATFORM = (
+    """
+Could not automatically obtain the `fzf` binary because we could not determine
+your Operating System.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_COULD_NOT_DETERMINE_MACHINE = (
+    """
+Could not automatically obtain the `fzf` binary because we could not determine
+your machine type.  It's reported as '%s' and we don't handle that case; but fzf
+may still be available as a prebuilt binary.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_NOT_SUPPORTED_X86 = (
+    """
+We don't believe that a prebuilt binary for `fzf` if available on %s, but we
+could be wrong.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_NOT_FOUND = (
+    """
+Could not find the `fzf` binary.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_VERSION_FAILED = (
+    """
+Could not obtain the 'fzf' version; we require version > 0.20.0 for some of
+the features.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_INSTALL_FAILED = (
+    """
+Failed to install fzf.
+
+""".lstrip()
+    + FZF_INSTALL_MANUALLY
+)
+
+FZF_HEADER = """
+For more shortcuts, see {t.italic_white}mach help try fuzzy{t.normal} and {t.italic_white}man fzf
+{shortcuts}
+""".strip()
+
+fzf_shortcuts = {
+    "ctrl-a": "select-all",
+    "ctrl-d": "deselect-all",
+    "ctrl-t": "toggle-all",
+    "alt-bspace": "beginning-of-line+kill-line",
+    "?": "toggle-preview",
+}
+
+fzf_header_shortcuts = [
+    ("select", "tab"),
+    ("accept", "enter"),
+    ("cancel", "ctrl-c"),
+    ("select-all", "ctrl-a"),
+    ("cursor-up", "up"),
+    ("cursor-down", "down"),
+]
+
+
+def get_fzf_platform():
+    if platform.machine() in ["i386", "i686"]:
+        print(FZF_NOT_SUPPORTED_X86 % platform.machine())
+        sys.exit(1)
+
+    if platform.system().lower() == "windows":
+        if platform.machine().lower() in ["x86_64", "amd64"]:
+            return "windows_amd64.zip"
+        elif platform.machine().lower() == "arm64":
+            return "windows_arm64.zip"
+        else:
+            print(FZF_COULD_NOT_DETERMINE_MACHINE % platform.machine())
+            sys.exit(1)
+    elif platform.system().lower() == "darwin":
+        if platform.machine().lower() in ["x86_64", "amd64"]:
+            return "darwin_amd64.zip"
+        elif platform.machine().lower() == "arm64":
+            return "darwin_arm64.zip"
+        else:
+            print(FZF_COULD_NOT_DETERMINE_MACHINE % platform.machine())
+            sys.exit(1)
+    elif platform.system().lower() == "linux":
+        if platform.machine().lower() in ["x86_64", "amd64"]:
+            return "linux_amd64.tar.gz"
+        elif platform.machine().lower() == "arm64":
+            return "linux_arm64.tar.gz"
+        else:
+            print(FZF_COULD_NOT_DETERMINE_MACHINE % platform.machine())
+            sys.exit(1)
+    else:
+        print(FZF_COULD_NOT_DETERMINE_PLATFORM)
+        sys.exit(1)
+
+
+def get_fzf_state_dir():
+    return os.path.join(get_state_dir(), "fzf")
+
+
+def get_fzf_filename():
+    return "fzf-%s-%s" % (FZF_CURRENT_VERSION, get_fzf_platform())
+
+
+def get_fzf_download_link():
+    return "https://github.com/junegunn/fzf/releases/download/%s/%s" % (
+        FZF_CURRENT_VERSION,
+        get_fzf_filename(),
+    )
+
+
+def clean_up_state_dir():
+    """
+    We used to have a checkout of fzf that we would update.
+    Now we only download the bin and cpin the hash; so if
+    we find the old git checkout, wipe it
+    """
+
+    fzf_path = os.path.join(get_state_dir(), "fzf")
+    git_path = os.path.join(fzf_path, ".git")
+    if os.path.isdir(git_path):
+        shutil.rmtree(fzf_path, ignore_errors=True)
+
+    # Also delete any existing fzf binary
+    fzf_bin = shutil.which("fzf", path=fzf_path)
+    if fzf_bin:
+        mozfile.remove(fzf_bin)
+
+    # Make sure the state dir is present
+    if not os.path.isdir(fzf_path):
+        os.makedirs(fzf_path)
+
+
+def download_and_install_fzf():
+    clean_up_state_dir()
+    download_link = get_fzf_download_link()
+    download_file = get_fzf_filename()
+    download_destination_path = get_fzf_state_dir()
+    download_destination_file = os.path.join(download_destination_path, download_file)
+    http_download_and_save(
+        download_link, download_destination_file, FZF_CHECKSUMS[get_fzf_platform()]
+    )
+
+    mozfile.extract(download_destination_file, download_destination_path)
+    mozfile.remove(download_destination_file)
+
+
+def get_fzf_version(fzf_bin):
+    cmd = [fzf_bin, "--version"]
+    try:
+        fzf_version = subprocess.check_output(cmd)
+    except subprocess.CalledProcessError:
+        print(FZF_VERSION_FAILED)
+        sys.exit(1)
+
+    # Some fzf versions have extra, e.g 0.18.0 (ff95134)
+    fzf_version = six.ensure_text(fzf_version.split()[0])
+
+    return fzf_version
+
+
+def should_force_fzf_update(fzf_bin):
+    fzf_version = get_fzf_version(fzf_bin)
+
+    # 0.20.0 introduced passing selections through a temporary file,
+    # which is good for large ctrl-a actions.
+    if Version(fzf_version) < Version(FZF_MIN_VERSION):
+        print("fzf version is old, you must update to use ./mach try fuzzy.")
+        return True
+    return False
+
+
+def fzf_bootstrap(update=False):
+    """
+    Bootstrap fzf if necessary and return path to the executable.
+
+    This function is a bit complicated. We fetch a new version of fzf if:
+    1) an existing fzf is too outdated
+    2) the user says --update and we are behind the recommended version
+    3) no fzf can be found and
+      3a) user passes --update
+      3b) user agrees to a prompt
+
+    """
+    fzf_path = get_fzf_state_dir()
+
+    fzf_bin = shutil.which("fzf")
+    if not fzf_bin:
+        fzf_bin = shutil.which("fzf", path=fzf_path)
+
+    if fzf_bin and should_force_fzf_update(fzf_bin):  # Case (1)
+        update = True
+
+    if fzf_bin and not update:
+        return fzf_bin
+
+    elif fzf_bin and update:
+        # Case 2
+        fzf_version = get_fzf_version(fzf_bin)
+        if Version(fzf_version) < Version(FZF_CURRENT_VERSION) and update:
+            # Bug 1623197: We only want to run fzf's `install` if it's not in the $PATH
+            # Swap to os.path.commonpath when we're not on Py2
+            if fzf_bin and update and not fzf_bin.startswith(fzf_path):
+                print(
+                    "fzf installed somewhere other than {}, please update manually".format(
+                        fzf_path
+                    )
+                )
+                sys.exit(1)
+
+            download_and_install_fzf()
+            print("Updated fzf to {}".format(FZF_CURRENT_VERSION))
+        else:
+            print("fzf is the recommended version and does not need an update")
+
+    else:  # not fzf_bin:
+        if not update:
+            # Case 3b
+            install = input("Could not detect fzf, install it now? [y/n]: ")
+            if install.lower() != "y":
+                return
+
+        # Case 3a and 3b-fall-through
+        download_and_install_fzf()
+        fzf_bin = shutil.which("fzf", path=fzf_path)
+        print("Installed fzf to {}".format(fzf_path))
+
+    return fzf_bin
+
+
+def format_header():
+    shortcuts = []
+    for action, key in fzf_header_shortcuts:
+        shortcuts.append(
+            "{t.white}{action}{t.normal}: {t.yellow}<{key}>{t.normal}".format(
+                t=terminal, action=action, key=key
+            )
+        )
+    return FZF_HEADER.format(shortcuts=", ".join(shortcuts), t=terminal)
+
+
+def run_fzf(cmd, tasks):
+    env = dict(os.environ)
+    env.update(
+        {"PYTHONPATH": os.pathsep.join([p for p in sys.path if "requests" in p])}
+    )
+    # Make sure fzf uses Windows' shell rather than MozillaBuild bash or
+    # whatever our caller uses, since it doesn't quote the arguments properly
+    # and thus windows paths like: C:\moz\foo end up as C:mozfoo...
+    if platform.system() == "Windows":
+        env["SHELL"] = env["COMSPEC"]
+    proc = subprocess.Popen(
+        cmd,
+        stdout=subprocess.PIPE,
+        stdin=subprocess.PIPE,
+        env=env,
+        universal_newlines=True,
+    )
+    out = proc.communicate("\n".join(tasks))[0].splitlines()
+
+    selected = []
+    query = None
+    if out:
+        query = out[0]
+        selected = out[1:]
+    return query, selected
+
+
+def setup_tasks_for_fzf(
+    push,
+    parameters,
+    full=False,
+    disable_target_task_filter=False,
+    show_estimates=True,
+):
+    check_working_directory(push)
+    tg = generate_tasks(
+        parameters, full=full, disable_target_task_filter=disable_target_task_filter
+    )
+    all_tasks = sorted(tg.tasks.keys())
+
+    # graph_Cache created by generate_tasks, recreate the path to that file.
+    cache_dir = os.path.join(
+        get_state_dir(specific_to_topsrcdir=True), "cache", "taskgraph"
+    )
+    if full:
+        graph_cache = os.path.join(cache_dir, "full_task_graph")
+        dep_cache = os.path.join(cache_dir, "full_task_dependencies")
+        target_set = os.path.join(cache_dir, "full_task_set")
+    else:
+        graph_cache = os.path.join(cache_dir, "target_task_graph")
+        dep_cache = os.path.join(cache_dir, "target_task_dependencies")
+        target_set = os.path.join(cache_dir, "target_task_set")
+
+    if show_estimates:
+        download_task_history_data(cache_dir=cache_dir)
+        make_trimmed_taskgraph_cache(graph_cache, dep_cache, target_file=target_set)
+
+    if not full and not disable_target_task_filter:
+        # Put all_tasks into a list because it's used multiple times, and "filter()"
+        # returns a consumable iterator.
+        all_tasks = list(filter(filter_by_uncommon_try_tasks, all_tasks))
+
+    return all_tasks, dep_cache, cache_dir
+
+
+def build_base_cmd(
+    fzf, dep_cache, cache_dir, show_estimates=True, preview_script=PREVIEW_SCRIPT
+):
+    key_shortcuts = [k + ":" + v for k, v in fzf_shortcuts.items()]
+    base_cmd = [
+        fzf,
+        "-m",
+        "--bind",
+        ",".join(key_shortcuts),
+        "--header",
+        format_header(),
+        "--preview-window=right:30%",
+        "--print-query",
+    ]
+
+    if show_estimates:
+        base_cmd.extend(
+            [
+                "--preview",
+                '{} {} -g {} -s -c {} -t "{{+f}}"'.format(
+                    sys.executable, preview_script, dep_cache, cache_dir
+                ),
+            ]
+        )
+    else:
+        base_cmd.extend(
+            [
+                "--preview",
+                '{} {} -t "{{+f}}"'.format(sys.executable, preview_script),
+            ]
+        )
+
+    return base_cmd
diff --git a/tools/tryselect/util/manage_estimates.py b/tools/tryselect/util/manage_estimates.py
new file mode 100644
index 0000000000..23fa481228
--- /dev/null
+++ b/tools/tryselect/util/manage_estimates.py
@@ -0,0 +1,132 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import json
+import os
+from datetime import datetime, timedelta
+
+import requests
+import six
+
+TASK_DURATION_URL = (
+    "https://storage.googleapis.com/mozilla-mach-data/task_duration_history.json"
+)
+GRAPH_QUANTILES_URL = (
+    "https://storage.googleapis.com/mozilla-mach-data/machtry_quantiles.csv"
+)
+from .estimates import GRAPH_QUANTILE_CACHE, TASK_DURATION_CACHE, TASK_DURATION_TAG_FILE
+
+
+def check_downloaded_history(tag_file, duration_cache, quantile_cache):
+    if not os.path.isfile(tag_file):
+        return False
+
+    try:
+        with open(tag_file) as f:
+            duration_tags = json.load(f)
+        download_date = datetime.strptime(
+            duration_tags.get("download_date"), "%Y-%M-%d"
+        )
+        if download_date < datetime.now() - timedelta(days=7):
+            return False
+    except (OSError, ValueError):
+        return False
+
+    if not os.path.isfile(duration_cache):
+        return False
+    # Check for old format version of file.
+    with open(duration_cache) as f:
+        data = json.load(f)
+        if isinstance(data, list):
+            return False
+    if not os.path.isfile(quantile_cache):
+        return False
+
+    return True
+
+
+def download_task_history_data(cache_dir):
+    """Fetch task duration data exported from BigQuery."""
+    task_duration_cache = os.path.join(cache_dir, TASK_DURATION_CACHE)
+    task_duration_tag_file = os.path.join(cache_dir, TASK_DURATION_TAG_FILE)
+    graph_quantile_cache = os.path.join(cache_dir, GRAPH_QUANTILE_CACHE)
+
+    if check_downloaded_history(
+        task_duration_tag_file, task_duration_cache, graph_quantile_cache
+    ):
+        return
+
+    try:
+        os.unlink(task_duration_tag_file)
+        os.unlink(task_duration_cache)
+        os.unlink(graph_quantile_cache)
+    except OSError:
+        print("No existing task history to clean up.")
+
+    try:
+        r = requests.get(TASK_DURATION_URL, stream=True)
+        r.raise_for_status()
+    except requests.exceptions.RequestException as exc:
+        # This is fine, the durations just won't be in the preview window.
+        print(
+            "Error fetching task duration cache from {}: {}".format(
+                TASK_DURATION_URL, exc
+            )
+        )
+        return
+
+    # The data retrieved from google storage is a newline-separated
+    # list of json entries, which Python's json module can't parse.
+    duration_data = list()
+    for line in r.text.splitlines():
+        duration_data.append(json.loads(line))
+
+    # Reformat duration data to avoid list of dicts, as this is slow in the preview window
+    duration_data = {d["name"]: d["mean_duration_seconds"] for d in duration_data}
+
+    with open(task_duration_cache, "w") as f:
+        json.dump(duration_data, f, indent=4)
+
+    try:
+        r = requests.get(GRAPH_QUANTILES_URL, stream=True)
+        r.raise_for_status()
+    except requests.exceptions.RequestException as exc:
+        # This is fine, the percentile just won't be in the preview window.
+        print(
+            "Error fetching task group percentiles from {}: {}".format(
+                GRAPH_QUANTILES_URL, exc
+            )
+        )
+        return
+
+    with open(graph_quantile_cache, "w") as f:
+        f.write(six.ensure_text(r.content))
+
+    with open(task_duration_tag_file, "w") as f:
+        json.dump({"download_date": datetime.now().strftime("%Y-%m-%d")}, f, indent=4)
+
+
+def make_trimmed_taskgraph_cache(graph_cache, dep_cache, target_file=None):
+    """Trim the taskgraph cache used for dependencies.
+
+    Speeds up the fzf preview window to less human-perceptible
+    ranges."""
+    if not os.path.isfile(graph_cache):
+        return
+
+    target_task_set = set()
+    if target_file and os.path.isfile(target_file):
+        with open(target_file) as f:
+            target_task_set = set(json.load(f).keys())
+
+    with open(graph_cache) as f:
+        graph = json.load(f)
+    graph = {
+        name: list(defn["dependencies"].values())
+        for name, defn in graph.items()
+        if name in target_task_set
+    }
+    with open(dep_cache, "w") as f:
+        json.dump(graph, f, indent=4)
diff --git a/tools/tryselect/util/ssh.py b/tools/tryselect/util/ssh.py
new file mode 100644
index 0000000000..7682306bc7
--- /dev/null
+++ b/tools/tryselect/util/ssh.py
@@ -0,0 +1,24 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import subprocess
+
+
+def get_ssh_user(host="hg.mozilla.org"):
+    ssh_config = subprocess.run(
+        ["ssh", "-G", host],
+        text=True,
+        check=True,
+        capture_output=True,
+    ).stdout
+
+    lines = [l.strip() for l in ssh_config.splitlines()]
+    for line in lines:
+        if not line:
+            continue
+        key, value = line.split(" ", 1)
+        if key.lower() == "user":
+            return value
+
+    raise Exception(f"Could not detect ssh user for '{host}'!")