{"record":{"id":"3e2a9836e3e9796e","repo":"nautechsystems/nautilus_trader","slug":"failed-to-start-blockchain-task-generation-e-3e2a98","errorCode":null,"errorMessage":"Failed to start blockchain task generation: {e}","messagePattern":"Failed to start blockchain task generation: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/adapters/blockchain/src/execution/client.rs","lineNumber":5852,"sourceCode":"            log::warn!(\"Blockchain execution client already connected\");\n            return Ok(());\n        }\n\n        log::info!(\n            \"Connecting to blockchain execution client on chain {}\",\n            self.chain.name\n        );\n\n        if !self.pending_tasks.is_open() || !self.pending_tasks.is_empty() {\n            self.pending_tasks.begin_shutdown();\n            self.pending_tasks\n                .finish_shutdown(Duration::from_secs(5), Duration::from_secs(2))\n                .await\n                .map_err(|e| anyhow::anyhow!(\"Failed to terminate blockchain submissions: {e}\"))?;\n            self.signer = None;\n            self.pending_tasks\n                .start_generation()\n                .map_err(|e| anyhow::anyhow!(\"Failed to start blockchain task generation: {e}\"))?;\n        }\n        release_preparing_slot(&self.in_flight);\n\n        let setup_guard = TaskGroupGuard::new(&[&self.pending_tasks], || {});\n\n        let payload_keys = PayloadKeySet::load(\n            self.config.payload_key_env.as_deref(),\n            &self.config.payload_key_retired_env,\n            self.config.payload_deployment_id.as_deref(),\n        )?\n        .map(Arc::new);\n\n        if self.cache.database.is_some() || self.config.postgres_cache_database_config.is_some() {\n            let keys = payload_keys.as_deref().ok_or_else(|| {\n                anyhow::anyhow!(\n                    \"Postgres execution requires an active payload key and deployment identity\"\n                )\n            })?;","sourceCodeStart":5834,"sourceCodeEnd":5870,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/18893faf8b356be3320add8de2f861b0b647cf06/crates/adapters/blockchain/src/execution/client.rs#L5834-L5870","documentation":"After terminating submissions during shutdown, the client restarts the pending_tasks generation via start_generation to reset the queue for a future reconnect. If the queue fails to start a new generation, the error is wrapped as \"Failed to start blockchain task generation\". This indicates the task queue could not be recycled and the client cannot safely accept new submissions.","triggerScenarios":"Calling the disconnect/restart path where, after finish_shutdown, pending_tasks.start_generation() fails (queue already closed or in an invalid internal state).","commonSituations":"Reconnect attempted while the queue was not fully torn down; concurrent shutdown/restart calls racing; a bug or prior failure left the queue in a bad state so subsequent generations cannot be opened.","solutions":["Read the inner error in {e}; if the queue is already closed or invalid, fully drop/recreate the client instead of reusing it","Ensure disconnect/restart is not invoked concurrently — serialize lifecycle calls behind a lock or lifecycle state machine","Wait for the finish_shutdown phase to complete (await its future) before attempting restart","Retry the reconnect from a fresh client instance if the queue remains wedged"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":"// ensure teardown completed before restart\nassert!(client.shutdown_complete(), \"cannot restart before finish_shutdown resolves\");","typeGuard":null,"tryCatchPattern":"match client.restart().await {\n    Err(e) if e.to_string().contains(\"Failed to start blockchain task generation\") => {\n        log::error!(\"task generation restart failed: {e}; recreating client\");\n        drop(client);\n        ExecutionClient::new(config).await // fresh queue\n    }\n    other => other,\n}","preventionTips":["Serialize lifecycle calls (disconnect/restart) behind a lifecycle state machine","Always await finish_shutdown to completion before starting a new generation","Never share a client instance across concurrent shutdown/restart callers","If a generation restart fails once, prefer recreating the client over retrying on a wedged queue"],"tags":["lifecycle","async-tasks","restart"],"backgroundTag":"invalid-state-transition","analyzedSha":"18893faf8b356be3320add8de2f861b0b647cf06","analyzedAt":"2026-09-08T20:49:34.690Z","contentChangedAt":"2026-09-08T20:49:34.690Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}