> Attach to localhost:5005 and find out why a query is stuck.

connected localhost:5005
paused
24 threads, 2 blocked

Thread pool-3-thread-7 is waiting for a monitor lock:
#0 RolapResult.loadMembers:142
  monitor=@3f2a  state=BLOCKED
#1 RolapResult.execute:89

Lock is held by pool-3-thread-2, which is running:
#0 SqlStatement.execute:218
  sql="SELECT ... FROM fact_table"   -- full scan on 36M rows

Root cause: the query bypassed the aggregate table and fell back to
a full fact-table scan. Thread-7 is waiting for thread-2 to finish.

pip install jdwp-mcp

# Pre-built binary
curl -fsSL https://raw.githubusercontent.com/dronsv/jdwp-mcp/main/install.sh | sh

# Cargo (requires Rust)
cargo install --git https://github.com/dronsv/jdwp-mcp

# From source
git clone https://github.com/dronsv/jdwp-mcp && cd jdwp-mcp && cargo build --release

claude mcp add jdwp jdwp-mcp

{
  "mcpServers": {
    "jdwp": {
      "command": "jdwp-mcp"
    }
  }
}

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -jar app.jar

Attach to localhost:5005 and set a breakpoint at com.example.MyService line 42

# Allow all jdwp tools for this project
claude config set --project allowedTools 'mcp__jdwp__*'

claude config set allowedTools 'mcp__jdwp__*'

Attach to localhost:5005
Pause the JVM and find all blocked or waiting threads
Show the stack for the blocked thread with variables
Who holds the lock? Show their stack too

Attach to localhost:5005
Set an exception breakpoint for NullPointerException
Wait for the exception to fire
Show the stack and all local variables at the throw site

Attach to localhost:5005
Trace method calls on com.example.service
[send your HTTP request]
Show the trace result — which methods were called?

Attach to localhost:5005
Find classes matching UserService
List methods of UserService with line numbers
Set a breakpoint at UserService line 45
When it hits, show the stack with all variables
Step over to the next line

Agent  -->  MCP Server  -->  JDWP Client  -->  TCP  -->  JVM
              |
        Translates tool calls to JDWP,
        tracks session state, summarizes
        runtime objects for the agent.

cargo build --release
cargo test