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Merged
nileshsimaria merged 4 commits into from
Apr 27, 2026
Merged

Update render_and_apply_j2_template tool #30

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8a7d4bc
Fix: render_and_apply_j2_template auto-detect config format instead o…
jmizquierdo Apr 23, 2026
a8d9279
feat(jmcp): add explicit config_format parameter to render_and_apply_…
jmizquierdo Apr 23, 2026
abcd8f4
fix(jmcp): fix render_and_apply_j2_template tool description and schema
jmizquierdo Apr 24, 2026
bf23cfb
fix(jmcp): fix render_and_apply_j2_template tool description and schema
jmizquierdo Apr 24, 2026
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2 changes: 1 addition & 1 deletion .github/workflows/ci.yml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ jobs:
- name: Run Code Quality Tools
if: matrix.os == 'ubuntu-latest'
run: |
black --check .
black --check --fast .
pylint $(git ls-files '*.py' | grep -vE '^(docs/|build/|tests/|samples/|setup.py|versioneer.py)') --exit-zero

- name: Run Unit Tests
Expand Down
154 changes: 100 additions & 54 deletions jmcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1343,6 +1343,7 @@ async def handle_render_and_apply_j2_template(
- apply_config: Boolean to apply or just render (default: False)
- commit_comment: Optional commit comment
- dry_run: Boolean to show diff without committing (default: False)
- config_format: Override format detection ('set', 'text', 'xml'). Auto-detected if omitted.
context: MCP Context object

Returns:
Expand All @@ -1357,10 +1358,10 @@ async def handle_render_and_apply_j2_template(
"commit_comment", "Configuration applied via Jinja2 template"
)
dry_run = arguments.get("dry_run", False)
config_format_override = arguments.get("config_format", None)

results = []

# Step 1: Validate inputs
if not template_content:
return [
types.TextContent(
Expand All @@ -1373,11 +1374,20 @@ async def handle_render_and_apply_j2_template(
types.TextContent(type="text", text="❌ Error: vars_content is required")
]

# Handle single router_name or list of router_names
if config_format_override and config_format_override not in ("set", "text", "xml"):
return [
types.TextContent(
type="text",
text=(
f"❌ Error: invalid config_format '{config_format_override}'. "
"Must be 'set', 'text', or 'xml'."
),
)
]

if router_name and not router_names:
router_names = [router_name]

# Step 2: Load variables from YAML string
try:
await context.info("Parsing variables from YAML content...")
variables = yaml.safe_load(vars_content)
Expand All @@ -1398,7 +1408,6 @@ async def handle_render_and_apply_j2_template(
except Exception as e:
return [types.TextContent(type="text", text=f"❌ Error loading variables: {e}")]

# Step 3: Setup Jinja2 environment and render template
try:
await context.info("Rendering Jinja2 template...")

Expand All @@ -1420,18 +1429,14 @@ async def handle_render_and_apply_j2_template(
)
]

# Step 4: If not applying, just return the rendered config
if not apply_config:
result_text = f"""✅ Template rendered successfully!

**Rendered Configuration:**
```
{rendered_config}
```

To apply this configuration to devices, set apply_config=true and provide
router_name or router_names.
"""
result_text = (
"✅ Template rendered successfully!\n\n"
"**Rendered Configuration:**\n"
"```\n" + rendered_config + "\n```\n\n"
"To apply this configuration to devices, set apply_config=true and provide "
"router_name or router_names.\n"
)
return [
types.TextContent(
type="text",
Expand All @@ -1443,7 +1448,6 @@ async def handle_render_and_apply_j2_template(
)
]

# Step 5: Apply configuration to specified routers
if not router_names:
return [
types.TextContent(
Expand Down Expand Up @@ -1472,28 +1476,43 @@ async def handle_render_and_apply_j2_template(

device_info = devices[rtr_name]

# Use prepare_connection_params to get proper connection parameters
try:
connect_params = prepare_connection_params(device_info, rtr_name)
except ValueError as ve:
application_results.append(f"❌ {rtr_name}: {ve}")
await context.error(f"{rtr_name}: {ve}")
continue

# Connect to device
dev = Device(**connect_params)

try:
dev.open()
await context.info(f"Connected to {rtr_name}")

# Load configuration using exclusive mode
if config_format_override:
config_format = config_format_override
await context.info(f"Using explicit config format: {config_format}")
else:
config_format = "set"
for line in rendered_config.strip().splitlines():
stripped = line.strip()
if not stripped or stripped.startswith("#"):
continue
if not re.match(
r"^(set|delete|deactivate|activate)\s", stripped
):
config_format = "text"
break
await context.info(f"Auto-detected config format: {config_format}")

try:
with Config(dev, mode="exclusive") as cu:
await context.info(f"Loading configuration on {rtr_name}...")
cu.load(rendered_config, format="set")
await context.info(
f"Loading configuration on {rtr_name} "
f"(format={config_format})..."
)
cu.load(rendered_config, format=config_format)

# Get diff
diff = cu.diff()

if not diff:
Expand All @@ -1502,8 +1521,6 @@ async def handle_render_and_apply_j2_template(
await context.info(f"{rtr_name}: {result_msg}")
else:
if dry_run:
# DRY RUN: Perform commit check, show diff,
# and rollback without committing
await context.info(
f"Performing commit check on {rtr_name}..."
)
Expand Down Expand Up @@ -1539,17 +1556,11 @@ async def handle_render_and_apply_j2_template(
)
await context.error(f"{rtr_name}: {result_msg}")
finally:
# CRITICAL: Always rollback in dry-run mode
await context.info(
f"{rtr_name}: Rolling back changes (dry-run mode)"
)
try:
# Perform the rollback
cu.rollback()
# Verify rollback success by checking
# if there are pending changes.
# After a successful rollback, there
# should be no differences.
diff = cu.diff()

if diff:
Expand All @@ -1572,7 +1583,6 @@ async def handle_render_and_apply_j2_template(
f"error: {str(rollback_error)}"
)
else:
# REAL COMMIT: Perform commit check before committing
await context.info(
f"Performing commit check on {rtr_name}..."
)
Expand All @@ -1588,7 +1598,6 @@ async def handle_render_and_apply_j2_template(
await context.error(f"{rtr_name}: {result_msg}")
cu.rollback()
else:
# Apply the changes
await context.info(
f"Committing configuration on {rtr_name}..."
)
Expand All @@ -1614,7 +1623,6 @@ async def handle_render_and_apply_j2_template(
application_results.append(f"❌ {rtr_name}: {error_msg}")
await context.error(f"{rtr_name}: {error_msg}")
finally:
# Always close the device connection
try:
dev.close()
await context.info(f"Disconnected from {rtr_name}")
Expand All @@ -1630,23 +1638,18 @@ async def handle_render_and_apply_j2_template(
application_results.append(f"❌ {rtr_name}: {error_msg}")
await context.error(f"{rtr_name}: {error_msg}")

# Step 6: Format final results
summary = "\n".join(application_results)

mode_prefix = "🔍 DRY RUN - " if dry_run else ""
mode_name = "preview" if dry_run else "application"
final_text = f"""{mode_prefix}Configuration {mode_name} complete!

**Routers:** {', '.join(router_names)}

**Rendered Configuration:**
```
{rendered_config}
```

**Results:**
{summary}
"""
final_text = (
mode_prefix + "Configuration " + mode_name + " complete!\n\n"
"**Routers:** " + ", ".join(router_names) + "\n\n"
"**Rendered Configuration:**\n"
"```\n" + rendered_config + "\n```\n\n"
"**Results:**\n" + summary + "\n"
)

return [
types.TextContent(
Expand Down Expand Up @@ -2169,37 +2172,80 @@ async def list_tools() -> list[types.Tool]:
),
types.Tool(
name="render_and_apply_j2_template",
description="Render a Jinja2 template and apply it to the router",
description=(
"Render a Jinja2 template with YAML variables and optionally apply it "
"to one or more Junos routers. "
"When apply_config=false (default), the template is only rendered locally "
"— no device connection is made. "
"When apply_config=true, the tool connects to the device(s) and loads the "
"rendered configuration. "
"Combine apply_config=true with dry_run=true to perform a commit check "
"on the device and display the diff without committing — changes are "
"automatically rolled back after the check. "
"Use router_name for a single device or router_names (list) for multiple "
"devices; at least one must be provided when apply_config=true."
),
inputSchema={
"type": "object",
"properties": {
"router_name": {
"type": "string",
"description": "The name of the router",
"description": (
"Name of a single router to apply the configuration to. "
"Required when apply_config=true and router_names is not provided."
),
},
"router_names": {
"type": "array",
"items": {"type": "string"},
"description": (
"JSON array of router name strings to apply the configuration to "
"in sequence, e.g. ['pe1', 'pe2', 'pe3']. "
"Each element must exactly match a name in the device mapping. "
"Use this instead of router_name when targeting multiple devices. "
"Required when apply_config=true and router_name is not provided."
),
},
"template_content": {
"type": "string",
"description": "Jinja2 template to load",
"description": "Jinja2 template content as a string.",
},
"vars_content": {
"type": "string",
"description": "YAML variables to load",
"description": "YAML-formatted variables to render into the template.",
},
"apply_config": {
"type": "boolean",
"description": "Boolean to apply or just render (default: False)",
"description": (
"If false (default), only render the template locally without "
"connecting to any device. If true, connect to the device(s) "
"and load the rendered configuration."
),
},
"dry_run": {
"type": "boolean",
"description": (
"Boolean to show diff without committing "
"(default: False)"
"Only effective when apply_config=true. If true, perform a "
"commit check on the device and show the diff without committing. "
"Changes are automatically rolled back after the check. "
"If false (default), commit the configuration."
),
},
"commit_comment": {
"type": "string",
"description": "Commit comment",
"default": "Configuration loaded via MCP",
"description": "Commit comment recorded in the device commit log.",
"default": "Configuration applied via Jinja2 template",
},
"config_format": {
"type": "string",
"description": (
"Configuration format: 'set' (flat set commands), "
"'text' (stanza/hierarchical), or 'xml'. "
"If omitted, auto-detected from the rendered template content: "
"lines starting with set/delete/deactivate/activate → 'set', "
"otherwise → 'text'."
),
"enum": ["set", "text", "xml"],
},
},
"required": ["template_content", "vars_content"],
Expand Down
3 changes: 3 additions & 0 deletions pyproject.toml
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,9 @@ dependencies = [
[project.scripts]
junos-mcp-server = "jmcp:main"

[tool.black]
target-version = ["py310"]

[tool.setuptools]
py-modules = ["jmcp", "jmcp_token_manager"]

Expand Down
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