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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    //! Snapshot and restoration commands.

    use std::time::Duration;
    use std::path::{Path, PathBuf};
    use std::sync::Arc;

    use ethcore::snapshot::{Progress, RestorationStatus, SnapshotService as SS};
    use ethcore::snapshot::io::{SnapshotReader, PackedReader, PackedWriter};
    use ethcore::snapshot::service::Service as SnapshotService;
    use ethcore::service::ClientService;
    use ethcore::client::{Mode, DatabaseCompactionProfile, VMType};
    use ethcore::miner::Miner;
    use ethcore::ids::BlockId;

    use cache::CacheConfig;
    use params::{SpecType, Pruning, Switch, tracing_switch_to_bool, fatdb_switch_to_bool};
    use helpers::{to_client_config, execute_upgrades};
    use dir::Directories;
    use user_defaults::UserDefaults;
    use fdlimit;

    use io::PanicHandler;

    /// Kinds of snapshot commands.
    #[derive(Debug, PartialEq, Clone, Copy)]
    pub enum Kind {
    	/// Take a snapshot.
    	Take,
    	/// Restore a snapshot.
    	Restore
    }

    /// Command for snapshot creation or restoration.
    #[derive(Debug, PartialEq)]
    pub struct SnapshotCommand {
    	pub cache_config: CacheConfig,
    	pub dirs: Directories,
    	pub spec: SpecType,
    	pub pruning: Pruning,
    	pub pruning_history: u64,
    	pub pruning_memory: usize,
    	pub tracing: Switch,
    	pub fat_db: Switch,
    	pub compaction: DatabaseCompactionProfile,
    	pub file_path: Option<String>,
    	pub wal: bool,
    	pub kind: Kind,
    	pub block_at: BlockId,
    }

    // helper for reading chunks from arbitrary reader and feeding them into the
    // service.
    fn restore_using<R: SnapshotReader>(snapshot: Arc<SnapshotService>, reader: &R, recover: bool) -> Result<(), String> {
    	use util::sha3::Hashable;

    	let manifest = reader.manifest();

    	info!("Restoring to block #{} (0x{:?})", manifest.block_number, manifest.block_hash);

    	snapshot.init_restore(manifest.clone(), recover).map_err(|e| {
    		format!("Failed to begin restoration: {}", e)
    	})?;

    	let (num_state, num_blocks) = (manifest.state_hashes.len(), manifest.block_hashes.len());

    	let informant_handle = snapshot.clone();
    	::std::thread::spawn(move || {
     		while let RestorationStatus::Ongoing { state_chunks_done, block_chunks_done, .. } = informant_handle.status() {
     			info!("Processed {}/{} state chunks and {}/{} block chunks.",
     				state_chunks_done, num_state, block_chunks_done, num_blocks);
     			::std::thread::sleep(Duration::from_secs(5));
     		}
     	});

     	info!("Restoring state");
     	for &state_hash in &manifest.state_hashes {
     		if snapshot.status() == RestorationStatus::Failed {
     			return Err("Restoration failed".into());
     		}

     		let chunk = reader.chunk(state_hash)
    			.map_err(|e| format!("Encountered error while reading chunk {:?}: {}", state_hash, e))?;

    		let hash = chunk.sha3();
    		if hash != state_hash {
    			return Err(format!("Mismatched chunk hash. Expected {:?}, got {:?}", state_hash, hash));
    		}

     		snapshot.feed_state_chunk(state_hash, &chunk);
     	}

    	info!("Restoring blocks");
    	for &block_hash in &manifest.block_hashes {
    		if snapshot.status() == RestorationStatus::Failed {
    			return Err("Restoration failed".into());
    		}

     		let chunk = reader.chunk(block_hash)
    			.map_err(|e| format!("Encountered error while reading chunk {:?}: {}", block_hash, e))?;

    		let hash = chunk.sha3();
    		if hash != block_hash {
    			return Err(format!("Mismatched chunk hash. Expected {:?}, got {:?}", block_hash, hash));
    		}
    		snapshot.feed_block_chunk(block_hash, &chunk);
    	}

    	match snapshot.status() {
    		RestorationStatus::Ongoing { .. } => Err("Snapshot file is incomplete and missing chunks.".into()),
    		RestorationStatus::Failed => Err("Snapshot restoration failed.".into()),
    		RestorationStatus::Inactive => {
    			info!("Restoration complete.");
    			Ok(())
    		}
    	}
    }

    impl SnapshotCommand {
    	// shared portion of snapshot commands: start the client service
    	fn start_service(self) -> Result<(ClientService, Arc<PanicHandler>), String> {
    		// Setup panic handler
    		let panic_handler = PanicHandler::new_in_arc();

    		// load spec file
    		let spec = self.spec.spec()?;

    		// load genesis hash
    		let genesis_hash = spec.genesis_header().hash();

    		// database paths
    		let db_dirs = self.dirs.database(genesis_hash, None, spec.data_dir.clone());

    		// user defaults path
    		let user_defaults_path = db_dirs.user_defaults_path();

    		// load user defaults
    		let user_defaults = UserDefaults::load(&user_defaults_path)?;

    		fdlimit::raise_fd_limit();

    		// select pruning algorithm
    		let algorithm = self.pruning.to_algorithm(&user_defaults);

    		// check if tracing is on
    		let tracing = tracing_switch_to_bool(self.tracing, &user_defaults)?;

    		// check if fatdb is on
    		let fat_db = fatdb_switch_to_bool(self.fat_db, &user_defaults, algorithm)?;

    		// prepare client and snapshot paths.
    		let client_path = db_dirs.client_path(algorithm);
    		let snapshot_path = db_dirs.snapshot_path();

    		// execute upgrades
    		execute_upgrades(&self.dirs.base, &db_dirs, algorithm, self.compaction.compaction_profile(db_dirs.db_root_path().as_path()))?;

    		// prepare client config
    		let client_config = to_client_config(
    			&self.cache_config,
    			Mode::Active,
    			tracing,
    			fat_db,
    			self.compaction,
    			self.wal,
    			VMType::default(),
    			"".into(),
    			algorithm,
    			self.pruning_history,
    			self.pruning_memory,
    			true
    		);

    		let service = ClientService::start(
    			client_config,
    			&spec,
    			&client_path,
    			&snapshot_path,
    			&self.dirs.ipc_path(),
    			Arc::new(Miner::with_spec(&spec))
    		).map_err(|e| format!("Client service error: {:?}", e))?;

    		Ok((service, panic_handler))
    	}
    	/// restore from a snapshot
    	pub fn restore(self) -> Result<(), String> {
    		let file = self.file_path.clone();
    		let (service, _panic_handler) = self.start_service()?;

    		warn!("Snapshot restoration is experimental and the format may be subject to change.");
    		warn!("On encountering an unexpected error, please ensure that you have a recent snapshot.");

    		let snapshot = service.snapshot_service();

    		if let Some(file) = file {
    			info!("Attempting to restore from snapshot at '{}'", file);

    			let reader = PackedReader::new(Path::new(&file))
    				.map_err(|e| format!("Couldn't open snapshot file: {}", e))
    				.and_then(|x| x.ok_or("Snapshot file has invalid format.".into()));

    			let reader = reader?;
    			restore_using(snapshot, &reader, true)?;
    		} else {
    			info!("Attempting to restore from local snapshot.");

    			// attempting restoration with recovery will lead to deadlock
    			// as we currently hold a read lock on the service's reader.
    			match *snapshot.reader() {
    				Some(ref reader) => restore_using(snapshot.clone(), reader, false)?,
    				None => return Err("No local snapshot found.".into()),
    			}
    		}

    		Ok(())
    	}

    	/// Take a snapshot from the head of the chain.
    	pub fn take_snapshot(self) -> Result<(), String> {
    		let file_path = self.file_path.clone().ok_or("No file path provided.".to_owned())?;
    		let file_path: PathBuf = file_path.into();
    		let block_at = self.block_at;
    		let (service, _panic_handler) = self.start_service()?;

    		warn!("Snapshots are currently experimental. File formats may be subject to change.");

    		let writer = PackedWriter::new(&file_path)
    			.map_err(|e| format!("Failed to open snapshot writer: {}", e))?;

    		let progress = Arc::new(Progress::default());
    		let p = progress.clone();
    		let informant_handle = ::std::thread::spawn(move || {
    			::std::thread::sleep(Duration::from_secs(5));

    			let mut last_size = 0;
    			while !p.done() {
    				let cur_size = p.size();
    				if cur_size != last_size {
    					last_size = cur_size;
    					let bytes = ::informant::format_bytes(p.size());
    					info!("Snapshot: {} accounts {} blocks {}", p.accounts(), p.blocks(), bytes);
    				}

    				::std::thread::sleep(Duration::from_secs(5));
    			}
     		});

    		if let Err(e) = service.client().take_snapshot(writer, block_at, &*progress) {
    			let _ = ::std::fs::remove_file(&file_path);
    			return Err(format!("Encountered fatal error while creating snapshot: {}", e));
    		}

    		info!("snapshot creation complete");

    		assert!(progress.done());
    		informant_handle.join().map_err(|_| "failed to join logger thread")?;

    		Ok(())
    	}
    }

    /// Execute this snapshot command.
    pub fn execute(cmd: SnapshotCommand) -> Result<String, String> {
    	match cmd.kind {
    		Kind::Take => cmd.take_snapshot()?,
    		Kind::Restore => cmd.restore()?,
    	}

    	Ok(String::new())
    }

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